Catalysts - MDPI

1 downloads 0 Views 3MB Size Report
May 9, 2017 - Engineering, University of Science and Technology of China, Hefei 230026, China; ... In olefin polymerization, late transition metal catalysts have attracted ..... Cooper, C. Organic Chemist's Desk Reference, 2nd ed.; Chapman ...
polymers Article

Influence of Ligand Backbone Structure and Connectivity on the Properties of Phosphine-Sulfonate Pd(II)/Ni(II) Catalysts Zixia Wu, Changwen Hong, Hongxu Du, Wenmin Pang and Changle Chen * Chinese Academy of Sciences Key Laboratory of Soft Matter Chemistry, Department of Polymer Science and Engineering, University of Science and Technology of China, Hefei 230026, China; [email protected] (Z.W.); [email protected] (C.H.); [email protected] (H.D.); [email protected] (W.P.) * Correspondence: [email protected]; Tel.: +86-551-6360-1495 Academic Editor: Marinos Pitsikalis Received: 1 April 2017; Accepted: 3 May 2017; Published: 9 May 2017

Abstract: Phosphine-sulfonate based palladium and nickel catalysts have been extensively studied in ethylene polymerization and copolymerization reactions. Previously, the majority of the research works focused on the modifications of the substituents on the phosphorous atom. In this contribution, we systematically demonstrated that the change of the ligand backbone from benzene to naphthalene could greatly improve the properties of this class of catalysts. In the palladium system, this change could increase catalyst stability and polyethylene molecular weights. In the nickel system, this change could dramatically increase the polyethylene molecular weights. Most interestingly, the change in the connectivity of phosphine and sulfonate moieties to the naphthalene backbone could also significantly influence the catalyst properties. Keywords: phosphine-sulfonate; palladium; nickel; olefin polymerization; copolymerization

1. Introduction In olefin polymerization, late transition metal catalysts have attracted much attention because of their low oxophilicity, and correspondingly the potentials to incorporation polar functionalized monomers into polyolefins. Among the numerous late transition metal catalysts, the Brookhart type α-diimine Ni(II) and Pd(II) [1–14], phenoxyminato based Ni(II) [15–21] and the phosphine-sulfonate Pd(II) catalysts [22–35] are the most extensively studied systems. It has been demonstrated that the properties of these catalysts are very sensitive to the ligand sterics. Specifically, it has been well established that the steric bulk on the axial positions in α-diimine systems could decrease the chain transfer rate, and increase the polyolefin molecular weight (Scheme 1, I) [1,2,36–39]. Similarly, the steric bulk on the axial positions in phenoxyminato (Scheme 1, II) and phosphine-sulfonate (Scheme 1, III) systems is crucial to obtain high-performance catalysts [40–42]. The modulation of the steric effect on the axial positions directly affects the steric environment of the metal center. In addition, the ligand backbone structure could indirectly influence the steric environment of the metal center, and correspondingly affect the properties of the metal catalysts. For example, different substituents on the backbone R position could greatly alter the properties of the α-diimine Pd(II) and Ni(II) catalysts (Scheme 1, IV) [43–45]. Despite the various efforts to modify the phosphine-sulfonate ligands, there have been very few studies on the modifications of the ligand backbone structures [46]. Recently, our group showed that the catalyst stability and activity could be greatly enhanced by changing the phosphine-sulfonate backbone from a benzene bridge to a naphthalene one (Scheme 1, V) [47]. In this contribution, we hope to further improve the properties of

Polymers 2017, 9, 168; doi:10.3390/polym9050168

www.mdpi.com/journal/polymers

Polymers 2017, 9, 168 Polymers 2017, 9, 168

2 of 9 2 of 8

the naphthalene based phosphine-sulfonate Pd(II) and Ni(II) catalysts by: (1) changing the linking Polymers 2017, 9, 168 2 of 8 the linking position of the phosphine and the sulfonate on the naphthalene backbone; position of the phosphine and the sulfonate moieties onmoieties the naphthalene backbone; and (2)and using a (2) using a sterically very bulky bi-aryl substituent on the phosphorous atom. sterically very bulky bi-aryl on the phosphorous atom. the linking position of thesubstituent phosphine and the sulfonate moieties on the naphthalene backbone; and (2) using a sterically very bulky bi-aryl substituent on the phosphorous atom.

Scheme 1. The α-diimine, phenoxyminato based olefin polymerization catalysts. Scheme 1. The α-diimine, phenoxyminatoand and phosphine-sulfonate phosphine-sulfonate based olefin polymerization catalysts. Scheme 1. The α-diimine, phenoxyminato and phosphine-sulfonate based olefin polymerization catalysts.

2. Results Discussion 2. Results andand Discussion

2. Results and Discussion Literature procedure was employed to prepare the ligands [47]. First, the 2-naphthalenesulfonic Literature procedure was employed to prepare the ligands [47]. First, the 2-naphthalenesulfonic acid was converted to the toluidinium salt from the reaction with excess amount of p-toluidine procedure was employedsalt to prepare the ligands [47]. First, the 2-naphthalenesulfonic acid wasLiterature converted to the toluidinium from the reaction with excess amount of p-toluidine (Scheme 2, see Supplementary Materials, Experimental Sections). The corresponding lithium salt was acid was converted to the toluidinium salt from the reaction with excess amount of lithium p-toluidine (Scheme 2, see Supplementary Materials, Experimental Sections). The corresponding salt was generated from the reaction with 1 equivalent of nBuLi, and dehydrated using a dean-stark n (Scheme 2, see Supplementary Materials, Experimental Sections). The corresponding lithium saltapparatus was generated from the reaction with 1 equivalent of BuLi, and dehydrated using a dean-stark apparatus in refluxing toluene. Subsequently, ligands L1-L3 were obtained in 39–47% yields from generated from the reaction with 1 equivalent of nBuLi, and dehydrated using a dean-stark in refluxing toluene. Subsequently, ligands L1-L3 were in 39–47% yields from the the reaction of 1 equivalent of nBuLi with the lithium saltobtained in THF (tetrahydrofuran) followed by reaction the apparatus in refluxing toluene. Subsequently, ligands L1-L3 were obtained in 39–47% yields from n of 1 equivalent of2PCl. BuLi with then lithium salt in THFby (tetrahydrofuran) by the addition of addition of R These ligands were characterized by 1H, 13C, and 31P followed NMR (Nuclear Magnetic the reaction of 1 equivalent of BuLi with the lithium salt in THF (tetrahydrofuran) followed by the 1 H, 13 C,(see 31 P NMR (Nuclear Resonance) spectroscopycharacterized (Bruker, Karlsruhe, Germany) Supplementary Materials, Figures S1–S9), R2 PCl. Theseofligands by by and Magnetic Resonance) 1H, 13 addition R2PCl. were These ligands were characterized by by C, and 31P NMR (Nuclear Magnetic elemental analysis and Mass spectrometry (EI+, Bruker Daltonics Inc., Billerica, MA, USA). spectroscopy (Bruker, Karlsruhe, Germany) Supplementary Materials, FiguresFigures S1–S9), elemental Resonance) spectroscopy (Bruker, Karlsruhe,(see Germany) (see Supplementary Materials, S1–S9), analysis and Mass spectrometry (EI+, Bruker Inc., Billerica, MA,MA, USA). elemental analysis and Mass spectrometry (EI+,Daltonics Bruker Daltonics Inc., Billerica, USA).

Scheme 2. Synthesis of the phosphine-sulfonate ligands and the palladium and nickel complexes. Scheme 2. Synthesis of the phosphine-sulfonate ligands and the palladium and nickel complexes.

Scheme 2. Synthesis of the phosphine-sulfonate ligands 2and the palladium and nickel complexes. The reactions of ligands L1-L3 with (TMEDA)PdMe (TMEDA = tetramethylethylenediamine) in DMSO (dimethylsulfoxide) led to the formation of the Pd(II) complexes (Pd1-Pd3) at 41–48% The reactions of ligands L1-L3 with (TMEDA)PdMe2 (TMEDA = tetramethylethylenediamine) yields (Schemeof 2).ligands The reaction of ligands L1-L3 with Na2(TMEDA CO3 and trans-[(PPh 3)2Ni(Cl)Ph] afforded The reactions L1-L3 (TMEDA)PdMe = tetramethylethylenediamine) in in DMSO (dimethylsulfoxide) ledwith to the formation of the (Pd1-Pd3) at 41–48% 2 Pd(II) complexes the desired Ni(II) complexes (Ni1-Ni3) at 34–76% yields. These metal complexes were characterized yields (Scheme 2). The reaction ligands L1-L3 of with 2CO3 complexes and trans-[(PPh 3)2Ni(Cl)Ph] affordedyields DMSO (dimethylsulfoxide) led toofthe formation theNa Pd(II) (Pd1-Pd3) at 41–48% using 1H, 13C, and 31P NMR (see Supplementary Materials, Figures S10–S20), elemental analysis and the desired Ni(II) complexes (Ni1-Ni3) at 34–76% yields. complexes were characterized (Scheme 2). The reaction of ligands L1-L3 with Na COThese andmetal trans-[(PPh )2 Ni(Cl)Ph] afforded the 2 3 3 MALDI-TOF-MS (Matrix Assisted Laser Desorption Ionization-Time of Flight-Mass Spectrometry). 1H, 13C, and 31P NMR (see Supplementary Materials, Figures S10–S20), elemental analysis and using desired Ni(II) complexes (Ni1-Ni3) at 34–76% yields. These metal complexes were characterized For comparison purpose, the palladium complex Pd2′/Pd2″ and the nickel complex Ni2′/Ni1″ were Assisted Laser Desorption Ionization-Time of Flight-Mass Spectrometry). 1 H, 13 C, and 31(Matrix usingMALDI-TOF-MS P NMR (see Supplementary Materials, Figures S10–S20), elemental analysis and prepared according to literature procedures [48,49]. For comparison purpose, the palladium complex Pd2′/Pd2″ and the nickel complex Ni2′/Ni1″ were MALDI-TOF-MS (Matrix Assisted Laser Desorption Ionization-Time of Flight-Mass Spectrometry). prepared according to literature procedures [48,49]. 0 0

For comparison purpose, the palladium complex Pd2 /Pd2” and the nickel complex Ni2 /Ni1” were prepared according to literature procedures [48,49].

Polymers 2017, 9, 168 Polymers 2017, 9, 168

3 of 9 3 of 8

Themolecular molecularstructures structuresofofPd2 Pd2and andNi1 Ni1were weredetermined determinedby byX-ray X-raydiffraction diffractionanalysis analysis(Figure (Figure1;1; The see CIF files and Supplementary Materials, Tables S1 and S2). The geometry at both the palladium see CIF files and Supplementary Materials, Tables S1 and S2). The geometry at both the palladium and and the nickel is square with the methyl or phenyl substituent to the phosphine the nickel centercenter is square planarplanar with the methyl or phenyl substituent cis to thecisphosphine group. group. Clearly, the hydrogen atom on the C15 in Pd2 and C7 in Ni1 could exert some steric influence Clearly, the hydrogen atom on the C15 in Pd2 and C7 in Ni1 could exert some steric influence to the to the substituents the phosphorous Especially, steric effect could enhancedwhen whenthe the substituents on the on phosphorous atom.atom. Especially, this this steric effect could be be enhanced substituentsare arebulky. bulky. Most Most importantly, importantly, this interaction substituents interaction could couldpotentially potentiallyinfluence influencethe theproperties propertiesof these catalysts in ethylene polymerization and copolymerization reactions. of these catalysts in ethylene polymerization and copolymerization reactions.

(a)

(b)

Figure 1. Molecular structures of: (a) Pd2; and (b) Ni1. Hydrogen atoms have been omitted for Figure 1. Molecular structures of: (a) Pd2; and (b) Ni1. Hydrogen atoms have been omitted for clarity. Selected bond lengths (Å) and angles (°) for Pd2: Pd1-C23 = 2.067(11), Pd1-P1 = 2.211(2), Pd1-O3 = clarity. Selected bond lengths (Å) and angles (◦ ) for Pd2: Pd1-C23 = 2.067(11), Pd1-P1 = 2.211(2), 2.143(7), = 2.131(7), S1-O3 = 1.469(8), S1-O1= =1.469(8), 1.436(8), S1-O1 S1-C22== 1.436(8), 1.781(9), P1-C13 Pd1-O3Pd1-O4 = 2.143(7), Pd1-O4 = 2.131(7), S1-O3 S1-C22 ==1.864(3), 1.781(9), C13-C22 = 1.387(4), P1-Pd1-O32 = 91.3(1), P1-Pd1-O4 = 177.3(2), P1-Pd1-C23 = 94.7(3), Pd1-P1-C13 = P1-C13 = 1.864(3), C13-C22 = 1.387(4), P1-Pd1-O32 = 91.3(1), P1-Pd1-O4 = 177.3(2), P1-Pd1-C23 = 94.7(3), 115.5(3), S1-O3-Pd1 = 112.9(4); for Ni1: Ni1-C41 = 1.8873(15), Ni1-P1 = 2.2221(4), Ni1-P2 = 2.2100(4), Pd1-P1-C13 = 115.5(3), S1-O3-Pd1 = 112.9(4); for Ni1: Ni1-C41 = 1.8873(15), Ni1-P1 = 2.2221(4), Ni1-O1 1.9553(11),Ni1-O1 S1-O1 ==1.9553(11), 1.4352(13),S1-O1 P2-C23 = 1.8309(15), P2-C17 = 1.8118(17), P1-Ni1-O1 = Ni1-P2 == 2.2100(4), = 1.4352(13), P2-C23 = 1.8309(15), P2-C17 = 1.8118(17), 93.63(3), P1-Ni1-C41 = 88.18(5), P2-Ni1-O1 = 89.47(3),P2-Ni1-O1 P2-Ni1-C41== 89.62(5), P1-Ni1-O1 = 93.63(3), P1-Ni1-C41 = 88.18(5), 89.47(3),O1-Ni1-C41 P2-Ni1-C41= 174.92(6). = 89.62(5), O1-Ni1-C41 = 174.92(6).

The palladium catalysts are highly active in ethylene polymerization, with activities well above 105 g·mol−1·h−1 (Table 1, entries 1–6). Catalyst Pd3 with the biaryl substituent showed almost 10-fold The palladium catalysts are highly active in ethylene polymerization, with activities well above increase in polymer molecular weight comparing with catalyst Pd1. The nickel catalysts are also 105 g·mol−1 ·h−1 (Table 1, entries 1–6). Catalyst Pd3 with the biaryl substituent showed almost 10-fold highly active in ethylene polymerization, with activities comparable with those of the palladium increase in polymer molecular weight comparing with catalyst Pd1. The nickel catalysts are also catalysts (Table 1, entries 7–9). The palladium catalysts completely lost activity at 25 °C. However, highly active in ethylene polymerization, with activities comparable with those of the palladium the nickel catalysts could maintain high activity at 25 °C. Most importantly, the polyethylene catalysts (Table 1, entries 7–9). The palladium catalysts completely lost activity at 25 ◦ C. However, molecular weight could be dramatically increased at lower polymerization temperature. For the the nickel catalysts could maintain high activity at 25 ◦ C. Most importantly, the polyethylene molecular case of Ni3, molecular weight of up to 142,300 could be achieved (Table 1, entry 12). Similar with weight could be dramatically increased at lower polymerization temperature. For the case of Ni3, the palladium case, catalyst Ni3 with the biaryl substituent showed much higher polymer molecular weight of up to 142,300 could be achieved (Table 1, entry 12). Similar with the palladium molecular weight than catalysts Ni1 and Ni2. case, catalyst Ni3 with the biaryl substituent showed much higher polymer molecular weight than Some very interesting results were obtained from the comparisons between catalysts Pd2/Ni2 catalysts Ni1 and Ni2. and our previously reported catalysts Pd2′/Ni2′. Catalyst Pd2 showed similar activity and similar Some very interesting results were obtained from the comparisons between catalysts Pd2/Ni2 polymer molecular weight with catalyst 0Pd2′ 0(Table 1, entry 2 versus 13). The polyethylene and our previously reported catalysts Pd2 /Ni2 . Catalyst Pd2 showed similar activity and similar molecular weights for catalysts Pd2 and Pd2′0 are much higher than that of the conventional catalyst polymer molecular weight with catalyst Pd2 (Table 1, entry 2 versus 13). The polyethylene molecular Pd2″ with the benzene as ligand0 backbone. In terms of catalyst stability, catalyst Pd2 showed weights for catalysts Pd2 and Pd2 are much higher than that of the conventional catalyst Pd2” with the slightly better stability than catalyst Pd2′, both of which are much more stable than conventional benzene as ligand backbone. In terms of catalyst stability, catalyst Pd2 showed slightly better stability catalyst Pd2″ (Figure 2). Clearly, the change in the ligand backbone from benzene to naphthalene than catalyst Pd20 , both of which are much more stable than conventional catalyst Pd2” (Figure 2). could significantly improve the performance of phosphine-sulfonate palladium catalysts. However, Clearly, the change in the ligand backbone from benzene to naphthalene could significantly improve the change in the connectivity of the phosphine moiety and the sulfonate moiety to the naphthalene the performance of phosphine-sulfonate palladium catalysts. However, the change in the connectivity backbone does not influence the properties of these palladium catalysts. of the phosphine moiety and the sulfonate moiety to the naphthalene backbone does not influence the properties of these palladium catalysts.

Polymers 2017, 9, 168 Polymers 2017, 9, 168

4 of 8 4 of 9

Table 1. Ethylene polymerization catalyzed by Pd(II) and Ni(II) complexes a. b c d Entry Catalyst (μmol)polymerization T (°C) Yieldcatalyzed (g) Activity wc Polydispersity Table 1. [cat] Ethylene by Pd(II) M and Ni(II) complexes a . Tm (°C) Pd1 1 10 80 2 2.0 2100 1.15 109 Pd2 2 10 80 2.4 2.4 5100 c 2.36 117 ◦ d Entry Catalyst [cat] (µmol) T (◦ C) Yield (g) Mw Polydispersity c Activity b Tm ( C) Pd3 3 10 80 5 5.0 27,800 2.56 129 1 4 Pd1Pd1 10 2 8080 2 2.0 2100 1.15 0.5 2.5 3200 2.06 114 109 2 5 Pd2Pd2 10 2 8080 2.4 2.4 5100 2.36 0.4 2.0 5700 2.18 124 117 3 Pd3 10 80 5 5.0 27,800 2.56 129 Pd3 6 2 80 1.2 6.0 24,800 1.84 131 4 Pd1 2 80 0.5 2.5 3200 2.06 114 Ni1 7 10 80 1.9 1.9 3600 1.58 128 5 Pd2 2 80 0.4 2.0 5700 2.18 124 Ni2 2.2 2.2 9100 2.18 129 6 8 Pd3 2 10 8080 1.2 6.0 24,800 1.84 131 5.7 5.71.9 17,500 2.041.58 133 128 7 9 Ni1Ni3 10 10 8080 1.9 3600 0.7 1.72.2 37,200 3.642.18 134 129 8 10 Ni2Ni1 10 2 8025 2.2 9100 0.5 1.35.7 58,600 1.992.04 135 133 9 11 Ni3Ni2 10 2 8025 5.7 17,500 1.4 3.51.7 142,300 1.513.64 136 134 10 12 Ni1Ni3 2 2 2525 0.7 37,200 11 13 Ni2Pd2′ 2 10 2580 0.5 58,600 2.1 2.11.3 4200 2.281.99 123 135 12 14 Ni3Pd2″ 2 10 2580 1.4 142,300 1.4 1.43.5 1800 1.441.51 115 136 0 13 15 Pd2Ni2′ 10 10 8080 2.1 4200 1.5 1.52.1 4100 1.462.28 124 123 14 16 Pd2”Ni2′ 10 2 8025 1.4 1.4 1800 1.44 0.4 2.0 27,800 2.57 133 115 0 15 17 Ni2Ni1″ 10 10 8080 1.5 1.5 4100 1.46 trace - 124 16 Ni20 2 25 0.4 2.0 27,800 2.57 133 Ni1″ 18 2 25 trace 17 Ni1” 10 80 trace a Polymerization conditions: toluene = 22 mL, CH2Cl2 = 3 mL, ethylene = 9 atm, 80 °C, time = 1 h. 18 Ni1” 2 25 trace -

◦ C, time = 1 h. b Activity Activity is in unit of 10 toluene g·mol =·h . Determined byethylene Gel Permeation (GPC)isin Polymerization conditions: 22 mL, CH2 Cl2 = 3 mL, = 9 atm, 80Chromatograph in 5 g·mol−1 ·h−1 . c Determined by Gel Permeation Chromatograph (GPC) in trichlorobenzene d unit of 10 at 150 ◦ C trichlorobenzene at 150 °C (see Supplementary Materials, Figures S36–S49). Melting temperature d (see Supplementary Figures S36–S49). temperature was(see determined by differential scanning was determined Materials, by differential scanning Melting calorimetry (DSC) Supplementary Materials, calorimetry (DSC) (see Supplementary Materials, Figures S26–S35).

ba

5

−1

−1

c

Figures S26–S35).

◦ Cfor Figure Figure 2. 2. Polyethylene Polyethyleneyield yieldversus versus polymerization polymerization time time at at 80 80 °C forcatalysts catalystsPd2, Pd2,Pd2′ Pd20and andPd2″. Pd2”.

In the nickel system, catalyst Ni2 showed polyethylene molecular weight twice as much as that In the nickel system, catalyst Ni2 showed polyethylene molecular weight twice as much as that of catalyst Ni2′0 (Table 1, entry 8 versus 14, entry 11 versus 15). This suggested that the very small of catalyst Ni2 (Table 1, entry 8 versus 14, entry 11 versus 15). This suggested that the very small perturbations in ligand sterics could exert significant effect on the properties of the perturbations in ligand sterics could exert significant effect on the properties of the phosphine-sulfonate phosphine-sulfonate nickel catalysts. Most interestingly, more dramatically differences were nickel catalysts. Most interestingly, more dramatically differences were observed for the cases of observed for the cases of catalyst Ni1 versus catalyst Ni1″ bearing phenyl substituent on the catalyst Ni1 versus catalyst Ni1” bearing phenyl substituent on the phosphorous atom. No isolate phosphorous atom. No isolate solid polymer product was generated by catalyst Ni1″ in ethylene solid polymer product was generated by catalyst Ni1” in ethylene polymerization at either 80 or polymerization at either 80 or 25 °C. This agrees well with literature results [9]. In contrast, catalyst 25 ◦ C. This agrees well with literature results [9]. In contrast, catalyst Ni1 demonstrated high activity Ni1 demonstrated high activity (up to 1.9 × 105 g·mol−1·h−1), high polymer molecular weight (up to (up to 1.9 × 105 g·mol−1 ·h−1 ), high polymer molecular weight (up to 37,200) and high melting 37,200) and high ◦melting temperature (134 °C) in ethylene polymerization. Cleary, the ligand temperature (134 C) in ethylene polymerization. Cleary, the ligand backbone structure also plays an backbone structure also plays an important role in determining the catalyst properties. important role in determining the catalyst properties. The palladium catalysts Pd1-Pd3 can also initiate efficient ethylene/metal acrylate copolymerization, with comonomer incorporation ratios ranging between 3% and 27% (Table 2,

Polymers 2017, 9, 168

5 of 9

Polymers 2017, 9, 168 5 of 8 Polymers 2017, 9, 168 5 of 8 Polymers 2017, 9, 168 5 of 8 Polymers 168 polymer molecular weights were dramatically reduced comparing with those 5 ofin 8 entries 2017, 1–6).9, The Polymers 2017, 168 polymer molecular weights were dramatically reduced comparing with those 5 ofin8 entries 1–6).9,The ethylene homopolymerization. Because of the great performance of catalyst Ni3with in ethylene entries 1–6). weights were dramatically reduced comparing those Polymers 2017, 9,The 168 polymer molecular 5 ofin 8 ethylene homopolymerization. Because of the great performance of catalyst Ni3with in ethylene entries 1–6). weights were dramatically reduced comparing those Polymers 2017, 9,The 168 polymer 5also ofin8 homopolymerization, its molecular properties in ofethylene/polar monomer copolymerization ethylene homopolymerization. Because the great performance of catalyst Ni3with inwere ethylene entries 1–6). The polymer molecular weights were dramatically reduced comparing those in Polymers 2017, 9, 168 5 of homopolymerization, its properties in ofethylene/polar monomer copolymerization also8 ethylene homopolymerization. Because the great performance of catalyst inwere ethylene investigated. Recently, et al. that α-diimine nickel catalystNi3 could mediate entries 1–6). polymer molecular weights were dramatically reduced comparing with those Polymers 2017, 9,The 168 5also ofin 8 homopolymerization, itsCoates properties in showed ethylene/polar monomer copolymerization were ethylene homopolymerization. Because of the great performance of catalyst Ni3 in ethylene investigated. Recently, Coates et al. showed that α-diimine nickel catalyst could mediate entries 1–6). polymer molecular weights were dramatically reduced comparing with those Polymers 2017, 9,The 168 10-undecenoate 5also ofin 8 homopolymerization, itsCoates properties in showed ethylene/polar monomer copolymerization ethylene/methyl copolymerization in the α-diimine presence ofnickel MAO (methylaluminoxane) [50]. ethylene homopolymerization. Because of the great performance of catalyst inwere ethylene investigated. Recently, et al. that catalystNi3 could mediate entries 1–6). The polymer molecular weights were dramatically reduced comparing with those in homopolymerization, its properties in ethylene/polar monomer copolymerization were also Polymers 2017, 9, 168 5 of 8 ethylene/methyl 10-undecenoate copolymerization in the presence of MAO (methylaluminoxane) [50].

The palladium catalysts Pd1-Pd3 can also initiate efficient ethylene/metal acrylate copolymerization, with comonomer incorporation ratios ranging between 3% and 27% (Table 2, entries 1–6). The polymer molecular weights were dramatically reduced comparing with those in ethylene homopolymerization. Because of the great performance of catalyst Ni3 in ethylene homopolymerization, its properties in ethylene homopolymerization. Because ofethylene/polar the great performance of catalyst inwere ethylene investigated. Recently, et al. that α-diimine nickel catalyst could mediate entries 1–6). The polymer molecular weights were dramatically reduced comparing with those in Our groups showed that some sterically very bulky nickelNi3 catalysts could homopolymerization, itsCoates properties in showed monomer copolymerization also ethylene/methyl 10-undecenoate copolymerization in the phosphine-sulfonate presence of MAO (methylaluminoxane) [50]. ethylene/polar monomer copolymerization were also investigated. Coates et al. showed ethylene homopolymerization. Because ofvery the great performance of catalyst Ni3 in ethylene investigated. Recently, Coates et al. showed that α-diimine nickel catalyst could mediate Our groups showed that some sterically bulky phosphine-sulfonate nickelRecently, catalysts could entries 1–6). The polymer molecular weights were dramatically reduced comparing with those in homopolymerization, its properties in ethylene/polar monomer copolymerization were also ethylene/methyl 10-undecenoate copolymerization in the presence of MAO (methylaluminoxane) [50]. ethylene homopolymerization. Because of the great performance of catalyst Ni3 in ethylene copolymerize ethylene with various polar monomers [51]. Here,reduced Ni3 could also achieve moderate investigated. Recently, Coates et al. showed that α-diimine nickel catalyst could mediate Our groups showed that some sterically very bulky phosphine-sulfonate nickel catalysts could entries 1–6). The polymer molecular weights were dramatically comparing with those in homopolymerization, its properties in ethylene/polar monomer copolymerization were also ethylene/methyl 10-undecenoate copolymerization in the presence of MAO (methylaluminoxane) [50]. that α-diimine nickel catalyst could mediate ethylene/methyl 10-undecenoate copolymerization copolymerize ethylene with various polar [51]. Here, Ni3 could also achieve ethylene homopolymerization. Because ofmonomers the bulky great performance of catalyst Ni3 in moderate ethylene investigated. Recently, Coates et al. showed that α-diimine nickel catalyst could mediate Our groups showed that some sterically very phosphine-sulfonate nickel catalysts could homopolymerization, its properties incomonomer monomer copolymerization also catalytic activity, along with moderate incorporation and high copolymer molecular ethylene/methyl 10-undecenoate copolymerization in the presence MAO (methylaluminoxane) [50]. copolymerize ethylene with various polar monomers [51]. Here, of Ni3 could also achieve moderate ethylene homopolymerization. Because ofethylene/polar the bulky great performance of catalyst Ni3 inwere ethylene investigated. Recently, Coates et al. showed that α-diimine nickel catalyst could mediate Our groups showed that some sterically very phosphine-sulfonate nickel catalysts could catalytic activity, along with moderate incorporation and high copolymer molecular homopolymerization, its properties incomonomer ethylene/polar monomer copolymerization were also ethylene/methyl 10-undecenoate copolymerization in the presence of MAO (methylaluminoxane) [50]. copolymerize ethylene with various polar monomers [51]. Here, Ni3 could also achieve moderate in the homopolymerization, presence of MAO (methylaluminoxane) [50]. Our groups showed that investigated. Recently, Coates et al. showed that α-diimine nickel catalyst could mediate weights in ethylene copolymerization with methyl 10-undecenoate 6-chloro-1-hexene (Table 2, some sterically Our groups showed that some sterically very bulky phosphine-sulfonate nickel catalysts could catalytic activity, along with moderate incorporation and high copolymer molecular its properties incomonomer ethylene/polar monomer copolymerization were also ethylene/methyl 10-undecenoate copolymerization in the presence MAO (methylaluminoxane) [50]. copolymerize ethylene with various polar monomers [51]. Here, of Ni3 could also achieve moderate weights in ethylene copolymerization with methyl 10-undecenoate and 6-chloro-1-hexene (Table 2, investigated. Recently, Coates et al. showed that α-diimine nickel catalyst could mediate Our groups showed that some sterically very bulky phosphine-sulfonate nickel catalysts could catalytic activity, along with moderate comonomer incorporation and high copolymer molecular ethylene/methyl 10-undecenoate copolymerization in the presence of MAO (methylaluminoxane) [50]. entries 7 and 8). The palladium complex Pd2″ with benzene backbone showed much lower activity copolymerize ethylene with various polar monomers [51]. Here, Ni3 could also achieve moderate weights in ethylene copolymerization with methyl 10-undecenoate and 6-chloro-1-hexene (Table 2, very bulky phosphine-sulfonate nickel catalysts could copolymerize ethylene with various polar investigated. Recently, Coates et al. comonomer showed that α-diimine nickel catalyst could mediate Our groups showed that some sterically very bulky phosphine-sulfonate nickel catalysts could catalytic activity, along with moderate incorporation and high copolymer molecular entries 7in and 8). The palladium complex Pd2″ with benzene backbone showed much lower activity ethylene/methyl 10-undecenoate copolymerization in10-undecenoate the presence of MAO (methylaluminoxane) [50]. copolymerize ethylene with various polar monomers [51]. Here, Ni3 could also achieve moderate weights ethylene copolymerization with methyl and 6-chloro-1-hexene (Table 2, Our groups showed that some sterically very bulky phosphine-sulfonate nickel catalysts could and copolymer molecular weight than the corresponding complex Pd2 with the naphthalene catalytic activity, along with moderate comonomer incorporation and high copolymer molecular entries 7 in and 8). The palladium complex Pd2″ with benzene backbone showed much lower activity ethylene/methyl 10-undecenoate copolymerization in10-undecenoate the presence of MAO (methylaluminoxane) [50]. copolymerize ethylene with various polar monomers [51]. Here, Ni3 could also achieve moderate weights ethylene copolymerization with methyl and 6-chloro-1-hexene (Table 2, and copolymer molecular weight than the corresponding complex Pd2 with the naphthalene monomers [51]. Here, Ni3 could also achieve moderate catalytic activity, along with moderate Our groups showed that some sterically very bulky phosphine-sulfonate nickel catalysts could catalytic activity, along with moderate comonomer incorporation and high copolymer molecular entries 7 in and 8). The palladium complex Pd2″ with benzene backbone showed much lower activity copolymerize ethylene with various polar monomers [51]. Here, Ni3 could also achieve moderate backbone (Table 2, entries 9 weight and 10). Moreover, the nickel complex Ni1″ with benzene backbone is weights ethylene copolymerization with methyl 10-undecenoate and 6-chloro-1-hexene (Table 2, and copolymer molecular than the corresponding complex Pd2 with the naphthalene Our groups showed that sterically very bulky phosphine-sulfonate nickel catalysts could catalytic activity, with moderate comonomer incorporation and high copolymer molecular entries 7in and 8). The palladium complex Pd2″ with benzene backbone showed much lower activity backbone (Table 2,along entries 9some and 10). Moreover, the nickel complex Ni1″ with benzene backbone is copolymerization copolymerize ethylene with various polar monomers [51]. Here, Ni3 could also achieve moderate weights ethylene copolymerization with methyl 10-undecenoate and 6-chloro-1-hexene (Table 2, and copolymer molecular weight than the corresponding complex Pd2 with the naphthalene comonomer incorporation and high copolymer molecular weights in ethylene catalytic activity, with moderate comonomer incorporation and high copolymer molecular not active in the copolymerization (Table 2, monomers entry 11). entries 7in and 8). The palladium complex Pd2″ with benzene backbone showed much lower activity backbone (Table 2,along entries 9 weight and 10). Moreover, the nickel Ni1″ with benzene backbone is copolymerize ethylene with various polar [51].complex Here, Ni3 could also achieve moderate weights copolymerization with methyl 10-undecenoate and 6-chloro-1-hexene (Table 2, and copolymer molecular than corresponding complex Pd2 with thelower naphthalene not active inethylene the (Table 2,the entry 11). catalytic activity, with moderate comonomer incorporation and high copolymer molecular entries 7 in and 8). copolymerization The palladium complex Pd2″ with benzene backbone showed much activity backbone (Table 2,along entries 9 weight and 10). Moreover, the nickel complex Ni1″ withwith benzene backbone is weights copolymerization with methyl 10-undecenoate and 6-chloro-1-hexene (Table 2, and copolymer molecular than corresponding complex Pd2 the naphthalene not active inethylene the copolymerization (Table 2,the entry 11). with methyl 10-undecenoate and 6-chloro-1-hexene (Table 2, entries 7 and 8). The palladium complex catalytic activity, along with moderate comonomer incorporation and high copolymer molecular a. lower entries 7 and 8). The palladium complex Pd2″ with benzene backbone showed much activity backbone (Table 2, entries 9 and 10). Moreover, the nickel complex Ni1″ with benzene backbone is Table 2. Ethylene copolymerization catalyzed by Pd(II) and Ni(II) complexes weights in ethylene copolymerization with methyl 10-undecenoate and 6-chloro-1-hexene (Table 2, and copolymer molecular than corresponding complex Pd2 with the naphthalene a. lower not active in the copolymerization (Table 2,the entry 11). entries 7in and 8). The complex Pd2″ with benzene backbone showed much activity Table 2.palladium Ethylene copolymerization catalyzed by Pd(II) andand Ni(II) complexes backbone (Table 2, entries 9 weight and 10). Moreover, the nickel complex Ni1″ with benzene backbone is weights ethylene copolymerization with methyl 10-undecenoate 6-chloro-1-hexene (Table 2, and copolymer molecular weight than the corresponding complex Pd2 with the naphthalene not active in the copolymerization (Table 2, entry 11). a. Pd2” with benzene backbone showed much lower activity and copolymer molecular Table 2. Ethylene copolymerization catalyzed by Pd(II) and Ni(II) complexes entries 7 and 8). The palladium complex Pd2″ with benzene backbone showed much lower activity backbone (Table 2, entries 9 weight and 10). Moreover, the nickel complex Ni1″Pd2 with benzene backbone is weight than the Yield and copolymer molecular than corresponding complex naphthalene not active in the (Table 2,the entry 11). a. lower Entry Pcopolymerization (bar) T ( C) Comonomer [M] mol/L Activity X with (%)with M the Polydispersity entries 7Catalyst and 8). The complex Pd2″ with benzene backbone showed much activity Table 2.palladium Ethylene copolymerization catalyzed by Pd(II) and Ni1″ Ni(II) complexes backbone (Table 2, entries 9 weight and 10). Moreover, the nickel complex benzene backbone is Yield (mg) and copolymer molecular than the corresponding complex Pd2 with the naphthalene a. Polydispersity Entry Catalyst P (bar) T ( C) Comonomer [M] mol/L Activity X (%) M not active in the copolymerization (Table 2, entry 11). Table 2. Ethylene copolymerization catalyzed by Pd(II) and Ni(II) complexes corresponding complex Pd2 with the naphthalene backbone (Table 2, entries 9 andis10). Moreover, the Yield backbone (Table 2, entries 9weight and 10). Moreover, the nickel complex Ni1″ with benzene backbone (mg) and copolymer molecular than the corresponding complex Pd2 naphthalene a. Polydispersity not active in the (Table 2, entry 11). Entry Catalyst Pcopolymerization (bar)2. Ethylene T ( C) Comonomer [M] mol/L by Activity X complexes (%)with M the Table copolymerization catalyzed Pd(II) and Ni(II) Yield backbone (Table 2, entries 9 and 10). Moreover, the nickel complex Ni1″ with benzene backbone is (mg) not inNi1” the (Table 2, entry 11). Entry Catalyst P copolymerization (bar) T (80 C) Comonomer [M] mol/L X complexes M Pd1 1.2 500 25 3(%) 1000 a. Polydispersity 1.19 1active Yield Table 2. Ethylene copolymerization catalyzed by Pd(II)Activity and nickel complex benzene backbone isnickel not active inNi(II) the copolymerization backbone (Table 2,99with entries 9 and 10). Moreover, the complex backbone is(Table 2, entry 11). Pd1 1.2 500 25Ni1″X with 3(%) benzene 1000 1.19 1active Entry Catalyst (bar) T 80 ( C) Comonomer [M]11). mol/L (mg) Activity M a Polydispersity not in thePcopolymerization (Table 2, entry o o

b b

c c

o

b

c

o

b

c

o

b

c

wd wd wd

d d

wd wd

d

Table 2. Ethylene copolymerization catalyzed by Pd(II) and Ni(II) complexes . Yield

d

d

(mg) b X c3 Pd1 1.2 500 25 Ni(II) 1active 9 2. Ethylene Entry Catalyst Pcopolymerization (bar) T 80 (oC) Comonomer [M] mol/L by (%) 1000 Mw d a. not in the (Table 2, entry 11). Table copolymerization catalyzed Pd(II)Activity and complexes Yield (mg)

d 1.19 Polydispersity b X c3(%) d Pd1 1.2 500 25 1000 1.19 12 99 2. Ethylene Entry Catalyst P (bar) T 80 (oC) Comonomer [M] mol/L by M w d a. Polydispersity Pd2 Table 1.2 340 17 Ni(II) 5 4400 1.92 80 Yield copolymerization catalyzed Pd(II)Activity and complexes (mg) d o b c d a. Pd1 1.2 500 25 3 1000 1.19 1 9 80 Entry Catalyst P (bar) T ( C) Comonomer [M] mol/L X complexes Mw Pd2 a. Polydispersity 340 17 Ni(II) 5(%) 1.92 2 Table 2. Ethylene copolymerization catalyzed by Pd(II) and4400 Ni(II) complexes Table 2. Ethylene copolymerization catalyzed by Pd(II)Activity and Yield (mg) d Pd1 P (bar) 500 25 b X c53(%) 4400 1000 1.19 Pd2 340 17 1.92 21 9 Entry Catalyst T 80 (oC) Comonomer [M]1.2 mol/L Yield Activity Mw d Polydispersity (mg) oC) d Pd1 500 25 1000 1.19 Pd2 340 17 53(%) 4400 1.92 213 99 Entry Catalyst T 80 (80 Comonomer [M]1.2 mol/L Yield Activity M wd Polydispersity Pd3 P (bar) 1.2 950 47 b X c15 5500 1.55 d oC) d Pd1 1.2 500 25 35(%) M 1000 1.19 Pd2 P (bar) 340 17 b X c15 4400 1.92 Entry Catalyst T 80 (80 Comonomer [M] 1.2 mol/L (mg) Activity Polydispersity Pd3 950 47 5500 1.55 312 99 bw Entry T 80 (o C) Comonomer [M] X c (%)1.55 Activity Polydispersity d Pd1 P (bar) 1.2mol/L (mg) 500Yield (mg) 25 1000 1.19 Mw d 80 Pd2 340 17 53 4400 1.92 Pd3 1.2 950 47 15 5500 321Catalyst 99 Pd1 500 25 358 1000 1.19 Pd2 340 17 4400 1.92 Pd3 1.2 950 47 15 5500 1.55 3124 99 80 Pd1 2.5 200 10 1600 1.43 80 Pd2 1.2 500 385 25 1000 1423 Pd1 Pd1 80 340 17 4400 1.92 Pd3 950 500 25 47 15 5500 1.55 1000 1 999 80 1.2 3 1.19 1.19 Pd1 2.5 200 10 1600 1.43 80 Pd2 340 17 4400 1.92 80 Pd3 1.2 950 47 15 5500 1.55 Pd1 2.5 200 10 85 1600 1.43 432 99 80 Pd2 1.2 340 17 5 4400 1.92 2 9 80 Pd3 950 47 15 5500 1.55 1.2 5 1.43 1.92 2 99 80 2.5 200 8 17 1600 435 Pd2 Pd1 Pd2 2.5 300 340 10 15 12 2100 1.35 4400 80 Pd2 Pd3 1.2 340 17 58 4400 1.92 2534 99 80 950 47 15 5500 1.55 Pd1 200 10 1600 1.43 Pd2 2.5 300 15 12 2100 1.35 80 Pd3 1.2 950 950 15 47 15 5500 1.55 5500 80 Pd1 200 10 8 47 2100 1600 1.43 3 9 99 80 1.2 15 1.35 1.55 2.5 300 12 543 Pd3 Pd2 80 Pd3 1.2 950 47 15 5500 1.55 99 80 Pd1 200 10 8 1600 1.43 Pd2 2.5 300 15 12 2100 1.35 5346 Pd3 2.5 510 25 27 3600 1.58 80 Pd1 1.2 950 15 3645 Pd1 Pd3 80 2.5 200 10 8 10 5500 1600 1.43 Pd2 300 200 47 15 12 2100 1.35 1600 4 999 80 2.5 8 1.55 1.43 Pd3 2.5 510 25 27 3600 1.58 80 Pd1 2.5 200 10 8 1600 1.43 80 Pd2 300 15 12 2100 1.35 Pd3 2.5 510 25 27 3600 1.58 654 99 80 Pd1 2.5 200 10 8 1600 1.43 4 9 80 Pd2 300 15 12 15 61,500 2100 1.35 510 25 27 3600 657 Pd2 Pd3 5 99 80 2.5 12 1.58 1.35 Ni3 1.0 150 300 7.5 1.5 2.64 2100 25 Pd1 Pd2 2.5 200 10 8 1600 1.43 4756 99 80 300 15 12 2100 1.35 Pd3 510 25 27 3600 1.58 Ni3 1.0 150 7.5 1.5 61,500 2.64 25 Pd2 300 5107.5 15 12 25 61,500 2100 1.35 3600 2.5 510 25 27 3600 1.58 80 Ni3 1.0 150 1.5 765 Pd3 Pd3 25 6 9 99 80 2.5 27 2.64 1.58 Pd2 2.5 300 15 12 2100 1.35 99 80 Pd3 510 25 27 3600 1.58 Ni3 1.0 150 7.5 1.5 61,500 2.64 7568 25 Ni3 1.0 500 25 0.5 124,600 2.25 25 Pd3 2.5 300 15 12 2100 5867 Ni3 Pd2 80 510 25 277.5 124,600 3600 1.58 150 150 7.5 1.5 61,500 2.64 61,500 Ni3 1.0 500 25 0.5 2.25 25 1.0 1.5 1.35 2.64 7 999 25 Pd3 2.5 510 25 27 3600 1.58 80 150 7.5 1.5 61,500 2.64 Ni3 1.0 500 25 0.5 124,600 2.25 876 99 25 Pd3 2.5 510 25 27 3600 1.58 6 9 80 Ni3 1.0 150 7.5 1.5 61,500 2.64 7 25 500 0.5 89 Ni3 Pd2″ 8 99 25 1.0 0.5 2.25 2.25 1.2 110 500 5.5 2.525 124,600 1950 1.95 124,600 25 Pd3 Ni3 2.5 510 25 27 3600 1.58 6978 99 80 1.0 150 7.5 1.5 61,500 2.64 25 500 0.5 124,600 2.25 Pd2″ 1.2 110 5.5 2.5 1950 1.95 25 Ni3 150 1105.5 7.5 1.55.5 124,600 61,500 2.64 1950 25 1.0 500 25 0.5 2.25 1.2 110 2.5 1950 987 Pd2”Pd2″ 25 9 9 99 25 1.2 2.5 1.95 1.95 Ni3 1.0 150 7.5 1.5 61,500 2.64 500 25 0.5 124,600 2.25 Pd2″ 1.2 110 5.5 2.5 1950 1.95 978 99 25 Pd2″ 2.5 80 4 6 1100 1.63 10 25 Ni3 1.0 150 1.5 61,500 789 25 500 25 0.5 2.25 1.2 110 5.5 2.5 1950 1.95 1100 2.5 80 4 6 4 124,600 1100 1.63 10 25 10 Pd2”Pd2″ 999 25 2.5 80 7.5 6 2.64 1.63 Ni3 1.0 500 25 0.5 124,600 2.25 8 9 25 1.2 110 5.5 2.5 1950 1.95 9 Pd2″ 2.5 80 4 6 1100 1.63 10 9 25 Ni3 1.0 500 25 0.5 2.25 89 1.2 110 5.5 2.5 1950 1.95 Pd2″ 2.5 80 40 6- 0 124,600 1100 1.63 10 99 25 Ni1″ 1.0 0 11 25 1.0 0 11 Ni1” 9 25 Ni3 Pd2″ 1.0 500 25 0.5 124,600 2.25 89 99 25 1.2 110 5.5 2.5 1950 1.95 2.5 80 61100 1.63 10 Ni1″ 1.0 0 04 11 25 1.2 110 5.5 2.5 1950 1.95 9 Pd2″ 2.5 80 61100 1.63 10 9 25 Ni1″ 1.0 0 04 11 a Polymerization b a Polymerization conditions: total volume toluene + polar monomer = 25 mL, catalyst = 20 μmol. + polar110 monomer mL, catalyst = 201.95 Pd2″ 1.2 5.5 1950 9 a 2.5 80 61100 1.63 10 Ni1″ conditions: 0 04 = 252.5 -µmol. Activity in unit 11 9 25 total volume toluene 1.0 Polymerization conditions: total volume toluene1.2 25 mL, catalyst = 20 1μmol. −1 ·hin −1unit Pd2″ 110 5.5 2.5 1950 9gab·mol 2.5 80 40 =%), 6- (mol 1100 1.63 Ni1″ 1.0+ polar 0monomer - determined 11 −1 −1. c monomer Activity of 102533 g·mol ·h−1 Amount of polar monomer incorporated %), of 10310 .9 c Amount oftotal polar incorporated (mol H1.95 NMR spectroscopy (see Polymerization volume toluene + polar monomer = 25 determined mL, catalyst =by 20 μmol. −1 c Pd2″ 2.5 80 4 6 1100 1.63 10 ab Activity Ni1″ in unit 1.0 0 0 11 9 conditions: 25 of 10 g·moltotal ·h .volume Amount of polar monomer incorporated (mol %), determined dtoluene ◦ C (see Supplementary 1H NMR spectroscopy Polymerization conditions: + polar monomer =trichlorobenzene 25 dmL, catalyst =by 20 μmol. 3 g·mol −1Supplementary −1. c Amount (see Materials, Figures S21–S25). Determined GPC in Supplementary Materials, Figures S21–S25). Determined by GPC in at 150 Pd2″ 2.5 80 4 6 1100 1.63 10 9 25 Activity in unit of 10 ·h of polar monomer incorporated (mol %), determined Ni1″ 1.0 0 0 11 baby 1H NMR spectroscopy Polymerization conditions: volume toluene + polar monomer = 25 dmL, catalyst =by20GPC μmol. (seetotal Materials, Figures S21–S25). Determined 3 g·mol −1Supplementary −1. c Amount of Pd2″ Ni1″ in unit 2.5 80 40 6- (mol1100 1.63 10 9 at 1.0 monomer 0 - determined -in 11 bby Activity of 1025 ·h polar incorporated %), atrichlorobenzene 1H 150 °C(see (seetotal Supplementary Materials, Figures S49–S56). Materials, Figures S49–S56). Polymerization conditions: toluene + polar monomer = 25 dmL, catalyst =by20GPC μmol. NMR Materials, Figures S21–S25). Determined b Activity 3 g·mol −1Supplementary c Amount in spectroscopy unit of150 1025 ·h−1.volume of polar incorporated Ni1″ 1.0 monomer 0 0 - (mol %), - determined -in 11 aby 9 at trichlorobenzene °C(see (seetotal Supplementary Materials, Figures S49–S56). 1H NMR spectroscopy dmL, Polymerization conditions: volume toluene + polar monomer = 25 catalyst = 20 μmol. Supplementary Materials, Figures S21–S25). Determined by GPC by b Activity 3 −1 −1 c in spectroscopy unit of150 1025°C g·mol ·h .volume Amount of polar monomer incorporated %), Ni1″ 1.0+ polar 0monomer 0 = 25 dmL, - (mol - determined -in 11 trichlorobenzene 9 at (seetotal Supplementary Materials, Figures S49–S56). a Polymerization 1H conditions: toluene catalyst =by 20GPC μmol. NMR (see Supplementary Materials, Figures S21–S25). Determined in the by Clearly, great enhancement in the polymerization properties was achieved by changing b 3 −1 −1 c 1.0 monomer 0 0 was dachieved - (mol %), - by 11 trichlorobenzene 9 enhancement in unit of150 1025°C g·mol ·hin . the Amount of polar incorporated determined at (see Supplementary Materials, Figures S49–S56). a Activity 1 Ni1″ great Clearly, polymerization properties changing the

Polymerization conditions: toluene + polar monomer = 25 mL, catalyst =by20GPC μmol. H NMR (see Materials, Figures S21–S25). Determined in by −1Supplementary c Amount Activity in spectroscopy unit at of150 103 °C g·mol ·h−1.volume of polar monomer incorporated (mol %), determined trichlorobenzene (seetotal Supplementary Materials, Figures S49–S56).

b

ligand backbone from benzene toinnaphthalene (Scheme 3). Ligand electronic effect may play an aClearly, 1H NMR great enhancement the polymerization properties was achieved by=by changing conditions: total toluene + polar monomer = electronic 25 dmL, catalyst 20GPC μmol. spectroscopy (see Materials, Figures S21–S25). Determined inbythe by b Polymerization 3 °C −1Supplementary −1.volume c Amount Clearly, greatgreat in the polymerization properties was achieved changing the ligand ligand backbone from benzene to (Scheme 3). Ligand effect may play an Activity inenhancement unit of150 10 g·mol ·h of polar monomer incorporated (mol %), trichlorobenzene at (see Supplementary Materials, Figures S49–S56). 1H NMR aClearly, enhancement in−1naphthalene the polymerization properties was achieved bydetermined changing the spectroscopy (see Materials, Figures S21–S25). Determined GPC inacidic Polymerization conditions: total volume toluene + polar monomer = electronic 25 dmL, catalyst =by 20more μmol. important role. 1-Naphthalenesulfonic acid (pKa = 0.17 at 298 K in aqueous solution) is bby 3 g·mol −1Supplementary c Amount ligand backbone from benzene to naphthalene (Scheme 3). Ligand effect may play an Activity in unit of 10 ·h . of polar monomer incorporated (mol %), determined trichlorobenzene at 150 °C(see (see Supplementary Supplementary Materials, Figures S49–S56). 1H NMR Clearly, great enhancement in the polymerization properties was dachieved byby the important role. 1-Naphthalenesulfonic acid (pKa = 0.17monomer at 298Ligand Kincorporated in aqueous solution) ischanging more acidic spectroscopy Materials, Figures S21–S25). Determined GPCplay in by btrichlorobenzene 3 °C −1to −1naphthalene c Amount ligand backbone from benzene (Scheme 3). Ligand electronic effect may an backbone from benzene to naphthalene (Scheme 3). electronic effect may play an important at 150 (see Supplementary Materials, Figures S49–S56). Activity in unit of 10 g·mol ·h . of polar (mol %), determined than benzenesulfonic acid (pKa = 0.70 at 298 K in aqueous solution) [52], suggesting that Clearly, great enhancement in the polymerization properties was achieved by changing the 1 d important role. 1-Naphthalenesulfonic acid (pKa = 0.17 at 298 KS21–S25). in aqueous solution) ismay more H NMR spectroscopy (see Supplementary Materials, Figures Determined by GPCplay inacidic by ligand backbone from benzene to naphthalene (Scheme 3). Ligand electronic effect an trichlorobenzene at 150 °C(see (see Supplementary Materials, Figures S49–S56). than benzenesulfonic acid (pKa 0.70 at 298 K inat aqueous solution) [52], suggesting that 1H NMR dachieved Clearly, great enhancement in=naphthalene the polymerization properties was by changing the important role. 1-Naphthalenesulfonic acid (pKa = 0.17 298 KS21–S25). inthan aqueous solution) is more spectroscopy Supplementary Materials, Figures Determined by GPCplay inacidic by naphthalene based ligand is electronically more withdrawing the benzene based ligand. ligand backbone from benzene to (Scheme 3). Ligand electronic effect may an than benzenesulfonic acid (pKa = 0.70 at 298 K in aqueous solution) [52], suggesting that role. 1-Naphthalenesulfonic acid (pKa = 0.17 at 298 K in aqueous solution) is trichlorobenzene at 150 °C (see Supplementary Materials, Figures S49–S56). Clearly, great enhancement in theacid polymerization wasthe achieved by based the more acidic than important role. 1-Naphthalenesulfonic (pKa = 0.17 atproperties 298 K inthan aqueous solution) ischanging more acidic naphthalene based ligand is(pKa electronically more withdrawing benzene ligand. ligand backbone from benzene to (Scheme 3). electronic effect may play an than benzenesulfonic acid 0.70 at(pKa 298 inatFigures aqueous solution) [52], suggesting that trichlorobenzene at 150 °C Supplementary Materials, S49–S56). Clearly, enhancement in=naphthalene the polymerization properties was achieved by the Moreover, thegreat bigger size ofis(see the naphthalene backbone may help to prevent catalyst deactivation important role. 1-Naphthalenesulfonic acid =K 0.17 298Ligand K inthan aqueous solution) ischanging more acidic naphthalene based ligand electronically more withdrawing the benzene based ligand. ligand backbone from benzene to naphthalene (Scheme 3). Ligand electronic effect may play annaphthalene based than benzenesulfonic acid (pKa = 0.70 at 298 K in aqueous solution) [52], suggesting that benzenesulfonic acid (pKa 0.70 atnaphthalene 298 K(pKa in aqueous solution) [52], suggesting that Moreover, the bigger size=ofis the naphthalene backbone may help to prevent catalyst deactivation Clearly, great enhancement in the polymerization was achieved by based the important role. 1-Naphthalenesulfonic acid = 0.17 atproperties 298 K inthan aqueous solution) ischanging more acidic naphthalene based ligand electronically more withdrawing the benzene ligand. ligand backbone from benzene to (Scheme 3). Ligand electronic effect may play an reactions such as bis-ligation [53]. Furthermore, the potential interaction of the hydrogen atom on than benzenesulfonic acid (pKa = 0.70 at 298 K in aqueous solution) [52], suggesting that Moreover, the bigger size of the naphthalene backbone may help to prevent catalyst deactivation Clearly, great enhancement inFurthermore, theacid polymerization wasthe achieved by is changing the important role. 1-Naphthalenesulfonic (pKa = 0.17 atproperties 298Ligand K inthan aqueous solution) more acidic naphthalene based ligand is electronically more withdrawing benzene based ligand. reactions such as bis-ligation [53]. the potential interaction of the hydrogen atom on ligand backbone from benzene to naphthalene (Scheme 3). electronic effect may play an than acidofis (pKa = 0.70 298 Kwithdrawing in aqueous solution) [52], suggesting that the bigger size of Moreover, thebased bigger size the naphthalene backbone help tosulfonate prevent catalyst deactivation ligand is more withdrawing than the benzene based ligand. Moreover, important role. 1-Naphthalenesulfonic acidat (pKa =the 0.17 atmay 298Ligand K inor aqueous ismay more acidic theelectronically 8 benzenesulfonic position of the naphthalene backbone with phosphine substituent may also naphthalene ligand electronically more than theof solution) benzene based ligand. reactions such as bis-ligation [53]. Furthermore, the potential interaction the hydrogen atom on ligand backbone from benzene to naphthalene (Scheme 3). electronic effect play an than benzenesulfonic acid (pKa = 0.70 at 298 K in aqueous solution) [52], suggesting that Moreover, the bigger size of the naphthalene backbone may help to prevent catalyst deactivation the 8 position of the naphthalene backbone with phosphine sulfonate substituent may also important role. 1-Naphthalenesulfonic acidat (pKa =the 0.17 at aqueous 298 K inor aqueous solution) is more acidic naphthalene based ligand electronically more than the benzene based ligand. reactions such as bis-ligation [53]. Furthermore, the potential interaction the hydrogen atom onas bis-ligation [53]. than benzenesulfonic acid = 0.70 298 Kwithdrawing inat solution) [52], suggesting that influence the catalyst properties. This steric effect may bemay the help key factor inofthe differences between Moreover, the bigger size ofis(pKa the naphthalene backbone tosulfonate prevent catalyst deactivation the 8 position of the naphthalene backbone with phosphine substituent may also the naphthalene backbone may help to prevent catalyst deactivation reactions such important role. 1-Naphthalenesulfonic acid (pKa =the 0.17 298 inor aqueous solution) is more acidic naphthalene based ligand electronically more than the benzene based ligand. reactions such as bis-ligation [53]. Furthermore, the potential interaction the hydrogen atom on influence the catalyst properties. This steric may the K key factor inofthe differences between than benzenesulfonic acidofis (pKa = 0.70 ateffect 298 Kwithdrawing inbemay aqueous solution) [52], suggesting that Moreover, the bigger size the naphthalene backbone help to prevent catalyst deactivation the 8 position of the naphthalene backbone with the phosphine or sulfonate substituent may also naphthalene based ligand is electronically more withdrawing than the benzene based ligand. the two sets ofcatalyst catalysts with different connectivity topotential the naphthalene backbone. reactions such as the bis-ligation [53].This Furthermore, the interaction ofthe the hydrogen atomthat on influence the properties. steric effect may be the key factor in differences between than benzenesulfonic acid (pKa = 0.70 at 298 K in aqueous solution) [52], suggesting Moreover, the bigger size of the naphthalene backbone may help to prevent catalyst deactivation the 8 position of naphthalene backbone with the phosphine or sulfonate substituent may also Furthermore, the potential interaction of the hydrogen atom on the 8 position of the naphthalene the two sets of catalysts with different connectivity to the naphthalene backbone. naphthalene based ligand is electronically more withdrawing than the benzene based ligand. reactions such as bis-ligation [53]. Furthermore, the potential interaction of the hydrogen atom on influence the catalyst properties. This steric effect may bemay the key factor in thesubstituent differences between Moreover, the bigger size ofisdifferent the naphthalene backbone help tosulfonate prevent catalyst deactivation 8 position of the naphthalene backbone with the phosphine or may also the two sets ofbased catalysts with connectivity to the naphthalene backbone. naphthalene ligand electronically more withdrawing than the benzene based ligand. reactions such as bis-ligation [53]. Furthermore, the potential interaction the hydrogen atom on influence the catalyst properties. This steric effect may bemay the help key factor inofthe differences between Moreover, the bigger size of different the naphthalene backbone tosulfonate prevent catalyst deactivation 8 position of the naphthalene backbone with the phosphine or substituent may also the two sets of catalysts with connectivity to the naphthalene backbone. backbone with the phosphine or sulfonate substituent may also influence the catalyst properties. reactions such as bis-ligation [53]. Furthermore, the potential interaction of the hydrogen atom on influence the catalyst properties. steric effect may bemay the help keyorfactor in thesubstituent differences between Moreover, the bigger size of different the This naphthalene backbone tosulfonate prevent catalyst deactivation the two 8 position of naphthalene backbone with the phosphine also sets ofcatalyst catalysts with connectivity topotential the naphthalene backbone. reactions such as the bis-ligation [53].This Furthermore, the interaction the hydrogenmay atom on influence theof properties. steric effect may benaphthalene the key factor inofthe differences between 8 position of the naphthalene backbone with the phosphine or sulfonate substituent may also the two sets catalysts with different connectivity to the backbone. This steric effect be properties. the key factor in the differences between the sets may of catalysts with different reactions such as bis-ligation [53]. Furthermore, the potential interaction thetwo hydrogen atom on influence themay catalyst This steric effect may be the key inof the differences between the 8 position of the naphthalene backbone with the phosphine orfactor sulfonate substituent also two sets catalysts with different connectivity to the backbone. influence theof catalyst properties. This steric effect may benaphthalene the keyor factor in thesubstituent differencesmay between 8 position of the naphthalene backbone with the phosphine sulfonate also two sets ofcatalyst catalysts with different connectivity to the naphthalene backbone. connectivity to the naphthalene backbone. Polymersthe 2017, 9, 168 6 of 8 influence the properties. This steric effect may be the key factor in the differences between the two sets of catalysts with different connectivity to the naphthalene backbone. influence the catalyst properties. This steric effect may be the key factor in the differences between the two sets of catalysts with different connectivity to the naphthalene backbone. the two sets of catalysts with different connectivity to the naphthalene backbone.

Scheme 3. Comparison of the three ligand frameworks.

3. Conclusions To conclude, a series of phosphine-sulfonate based palladium and nickel catalysts were prepared and characterized. A naphthalene bridge was installed in the ligand framework. These palladium and nickel catalysts showed very high activities in ethylene polymerization. For the case

Polymers 2017, 9, 168

6 of 9

3. Conclusions To conclude, a series of phosphine-sulfonate based palladium and nickel catalysts were prepared and characterized. A naphthalene bridge was installed in the ligand framework. These palladium and nickel catalysts showed very high activities in ethylene polymerization. For the case of nickel system, very high polyethylene molecular weights could be achieved. Both the palladium and the nickel catalysts could initiate ethylene-polar monomer copolymerization. We clearly demonstrated the importance of ligand backbone structure and connectivity in determining the properties of these metal catalysts. This work provides an alternative strategy to modify/improve the properties of group 10 phosphine-sulfonate catalysts. Supplementary Materials: The following are available online at www.mdpi.com/2073-4360/9/5/168/s1. Experimental procedures, characterization for ligands, palladium complexes, nickel complexes (Figures S1–S20), polyethylene and copolymers (Figures S21–S56), and CIF files for complexes Pd2 and Ni1. Acknowledgments: This work was supported by National Natural Science Foundation of China (NSFC, 21690071, and 51522306), the Fundamental Research Funds for the Central Universities (WK3450000001), and the Recruitment Program of Global Experts. Author Contributions: Changle Chen conceived and designed the experiments; Zixia Wu, Changwen Hong, Hongxu Du, and Wenmin Pang performed the experiments; and Zixia Wu and Changle Chen analyzed the data and wrote the paper. Conflicts of Interest: The authors declare no conflict of interest.

References 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12.

13.

Guo, L.H.; Chen, C.L. (α-Diimine) palladium catalyzed ethylene polymerization and copolymerization with polar comonomers. Sci. China Chem. 2015, 58, 1663–1673. [CrossRef] Guo, L.H.; Dai, S.Y.; Sui, X.L.; Chen, C.L. Palladium and nickel catalyzed chain walking olefin polymerization and copolymerization. ACS Catal. 2016, 6, 428–441. [CrossRef] Guan, Z.; Cotts, P.M.; McCord, E.F.; McLain, S.J. Chain walking: A new strategy to control polymer topology. Science 1999, 283, 2059–2061. [CrossRef] [PubMed] Chen, C.; Luo, S.; Jordan, R.F. Multiple Insertion of a Silyl Vinyl Ether by (α-Diimine)PdMe+ Species. J. Am. Chem. Soc. 2008, 130, 12892–12893. [CrossRef] [PubMed] Chen, C.; Jordan, R.F. Palladium-catalyzed dimerization of vinyl ethers to acetals. J. Am. Chem. Soc. 2010, 132, 10254–10255. [CrossRef] [PubMed] Chen, C.; Luo, S.; Jordan, R.F. Cationic Polymerization and Insertion Chemistry in the Reactions of Vinyl Ethers with (α-Diimine)PdMe+ Species. J. Am. Chem. Soc. 2010, 132, 5273–5284. [CrossRef] [PubMed] Zhu, L.; Fu, Z.S.; Pan, H.J.; Feng, W.; Chen, C.L.; Fan, Z.Q. Synthesis and application of binuclear α-diimine nickel/palladium catalysts with a conjugated backbone. Dalton Trans. 2014, 43, 2900–2906. [CrossRef] [PubMed] Wang, R.K.; Sui, X.L.; Pang, W.M.; Chen, C.L. Ethylene polymerization by xanthene-bridged dinuclear α-diimine NiII complexes. ChemCatChem 2016, 8, 434–440. [CrossRef] Na, Y.N.; Wang, X.; Lian, K.; Zhu, Y.; Li, W.; Luo, Y.; Chen, C.L. Dinuclear α–diimine Ni(II) and Pd(II) Catalyzed Ethylene Polymerization and Copolymerization. ChemCatChem 2017, 9, 1062–1066. [CrossRef] Wang, R.K.; Zhao, M.H.; Chen, C.L. Influence of ligand second coordination sphere effects on the olefin (co)polymerization properties of α-diimine Pd(II) catalysts. Polym. Chem. 2016, 7, 3933–3938. [CrossRef] Guo, L.H.; Dai, S.Y.; Chen, C.L. Investigations of the ligand electronic effects on α-diimine nickel(II) catalyzed ethylene polymerization. Polymers 2016, 8, 37. [CrossRef] Takano, S.; Takeuchi, D.; Osakada, K.; Akamatsu, N.; Shishido, A. Dipalladium Catalyst for Olefin Polymerization: Introduction of Acrylate Units into the Main Chain of Branched Polyethylene. Angew. Chem. Int. Ed. 2014, 53, 9246–9250. [CrossRef] [PubMed] Allen, K.E.; Campos, J.; Daugulis, O.; Brookhart, M. Living Polymerization of Ethylene and Copolymerization of Ethylene/Methyl Acrylate Using “Sandwich” Diimine Palladium Catalysts. ACS Catal. 2015, 5, 456–464. [CrossRef]

Polymers 2017, 9, 168

14.

15.

16. 17.

18.

19.

20.

21. 22.

23.

24.

25. 26. 27. 28.

29. 30. 31. 32.

7 of 9

Zhou, C.; Liu, W.J.; Daugulis, O.; Brookhart, M. Mechanistic Studies of Pd(II)-Catalyzed Copolymerization of Ethylene and Vinylalkoxysilanes: Evidence for a β-Silyl Elimination Chain Transfer Mechanism. J. Am. Chem. Soc. 2016, 138, 16120–16129. Younkin, T.R.; Connor, E.F.; Henderson, J.I.; Friedrich, S.K.; Grubbs, R.H.; Bansleben, D.A. Neutral, Single-Component Nickel(II) Polyolefin Catalysts That Tolerate Heteroatoms. Science 2000, 287, 460–462. [CrossRef] [PubMed] Wang, C.; Friedrich, S.; Younkin, T.R.; Li, R.T.; Grubbs, R.H.; Bansleben, D.A.; Day, M.W. Neutral Nickel(II)-Based Catalysts for Ethylene Polymerization. Organometallics 1998, 17, 3149–3151. [CrossRef] Weberski, M.P.; Chen, C.; Delferro, M.; Zuccaccia, C.; Macchioni, A.; Marks, T.J. Suppression of β-hydride chain transfer in nickel(II)-catalyzed ethylene polymerization via weak fluorocarbon ligand–product interactions. Organometallics 2012, 31, 3773–3789. [CrossRef] Weberski, M.P.; Chen, C.; Delferro, M.; Marks, T.J. Ligand Steric and Fluoroalkyl Substituent Effects on Enchainment Cooperativity and Stability in Bimetallic Nickel(II) Polymerization Catalysts. Chem. Eur. J. 2012, 18, 10715–10732. [CrossRef] [PubMed] Stephenson, C.J.; McInnis, J.P.; Chen, C.; Weberski, M.P.; Motta, A.; Delferro, M.; Marks, T.J. Ni(II) Phenoxyiminato Olefin Polymerization Catalysis: Striking Coordinative Modulation of Hyperbranched Polymer Microstructure and Stability by a Proximate Sulfonyl Group. ACS Catal. 2014, 4, 999–1003. [CrossRef] Ölscher, F.; Göttker-Schnetmann, I.; Monteil, V.; Mecking, S. Role of Radical Species in Salicylaldiminato Ni(II) Mediated Polymer Chain Growth: A Case Study for the Migratory Insertion Polymerization of Ethylene in the Presence of Methyl Methacrylate. J. Am. Chem. Soc. 2015, 137, 14819–14828. [CrossRef] [PubMed] Godin, A.; Göttker-Schnetmann, I.; Mecking, S. Nanocrystal Formation in Aqueous Insertion Polymerization. Macromolecules 2016, 49, 8825–8837. [CrossRef] Nakamura, A.; Anselment, T.M.J.; Claverie, J.; Goodall, B.; Jordan, R.F.; Mecking, S.; Rieger, B.; Sen, A.; van Leeuwen, P.W.N.M.; Nozaki, K. Ortho-phosphinobenzenesulfonate: A superb ligand for palladium-catalyzed coordination–insertion copolymerization of polar vinyl monomers. Acc. Chem. Res. 2013, 46, 1438–1449. [CrossRef] [PubMed] Piche, L.; Daigle, J.C.; Rehse, G.; Claverie, J.P. Structure–Activity Relationship of Palladium Phosphanesulfonates: Toward Highly Active Palladium-Based Polymerization Catalysts. Chem. Eur. J. 2012, 18, 3277–3285. [CrossRef] [PubMed] Ota, Y.; Ito, S.; Kuroda, J.; Okumura, Y.; Nozaki, K. Quantification of the Steric Influence of Alkylphosphine–Sulfonate Ligands on Polymerization, Leading to High-Molecular-Weight Copolymers of Ethylene and Polar Monomers. J. Am. Chem. Soc. 2014, 136, 11898–11901. [CrossRef] [PubMed] Nakano, R.; Nozaki, K. Copolymerization of propylene and polar monomers using Pd/IzQO catalysts. J. Am. Chem. Soc. 2015, 137, 10934–10937. [CrossRef] [PubMed] Jian, Z.B.; Moritz, B.C.; Mecking, S. Suppression of Chain Transfer in Catalytic Acrylate Polymerization via Rapid and Selective Secondary Insertion. J. Am. Chem. Soc. 2015, 137, 2836–2839. [CrossRef] [PubMed] Jian, Z.B.; Mecking, S. Insertion Homo- and Copolymerization of Diallyl Ether. Angew. Chem. Int. Ed. 2015, 54, 15845–15849. [CrossRef] Zhang, Y.L.; Cao, Y.C.; Leng, X.B.; Chen, C.; Huang, Z. Cationic Palladium(II) Complexes of Phosphine–Sulfonamide Ligands: Synthesis, Characterization, and Catalytic Ethylene Oligomerization. Organometallics 2014, 33, 3738–3745. [CrossRef] Sui, X.L.; Dai, S.Y.; Chen, C.L. Ethylene polymerization and copolymerization with polar monomers by cationic phosphine phosphonic amide palladium complexes. ACS Catal. 2015, 5, 5932–5937. [CrossRef] Chen, M.; Zou, W.P.; Cai, Z.G. Norbornene homopolymerization and copolymerization with ethylene by phosphine-sulfonate nickel catalysts. Polym. Chem. 2015, 6, 2669–2676. [CrossRef] Chen, M.; Yang, B.P.; Chen, C.L. Redox-controlled olefin (co)polymerization catalyzed by ferrocene-bridged phosphine-sulfonate palladium complexes. Angew. Chem. Int. Ed. 2015, 54, 15520–15744. [CrossRef] [PubMed] Chen, M.; Yang, B.P.; Chen, C.L. Redox Control in Olefin Polymerization and Copolymerization. Synlett 2016, 27, 1297–1302. [CrossRef]

Polymers 2017, 9, 168

33. 34.

35. 36. 37.

38.

39. 40. 41. 42.

43.

44.

45. 46.

47.

48.

49. 50.

51.

8 of 9

Na, Y.N.; Zhang, D.; Chen, C.L. Modulating the Polyolefin Properties through the Incorporation of Nitrogen-Containing Polar Monomers. Polym. Chem. 2017, 8, 2405–2409. [CrossRef] Jian, Z.; Falivene, L.; Boffa, G.; Ortega Sánchez, S.; Caporaso, L.; Grassi, A.; Mecking, S. Direct Synthesis of Telechelic Polyethylene by Selective Insertion Polymerization. Angew. Chem. Int. Ed. 2016, 55, 14378–14595. [CrossRef] [PubMed] Wada, S.; Jordan, R.F. Olefin Insertion into a Pd–F Bond: Catalyst Reactivation Following β-F Elimination in Ethylene/Vinyl Fluoride Copolymerization. Angew. Chem. Int. Ed. 2017, 56, 1820–1824. [CrossRef] [PubMed] Rhinehart, J.L.; Brown, L.A.; Long, B.K. A robust Ni(II) α-diimine catalyst for high temperature ethylene polymerization. J. Am. Chem. Soc. 2013, 135, 16316–16319. [CrossRef] [PubMed] Dai, S.Y.; Sui, X.L.; Chen, C.L. Highly Robust Palladium(II) α-Diimine Catalysts for Slow-Chain-Walking Polymerization of Ethylene and Copolymerization with Methyl Acrylate. Angew. Chem. Int. Ed. 2015, 54, 9948–9953. [CrossRef] [PubMed] Dai, S.Y.; Chen, C.L. Direct Synthesis of Functionalized High-Molecular-Weight Polyethylene by Copolymerization of Ethylene with Polar Monomers. Angew. Chem. Int. Ed. 2016, 55, 13281–13285. [CrossRef] [PubMed] Dai, S.Y.; Zhou, S.X.; Zhang, W.; Chen, C.L. Systematic Investigations of Ligand Steric Effects on α-Diimine Palladium Catalyzed Olefin Polymerization and Copolymerization. Macromolecules 2016, 49, 8855–8862. [CrossRef] Hu, X.H.; Dai, S.Y.; Chen, C.L. Ethylene polymerization by salicylaldimine nickel(II) complexes containing a dibenzhydryl moiety. Dalton Trans. 2016, 45, 1496–1503. [CrossRef] [PubMed] Guironnet, D.; Roesle, P.; Runzi, T.; Gottker-Schnetmann, I.; Mecking, S. Insertion polymerization of acrylate. J. Am. Chem. Soc. 2009, 131, 422–423. [CrossRef] [PubMed] Perrotin, P.; McCahill, J.S.J.; Wu, G.; Scott, S.L. Linear, high molecular weight polyethylene from a discrete, mononuclear phosphinoarenesulfonate complex of nickel(II). Chem. Commun. 2011, 47, 6948–6950. [CrossRef] [PubMed] Liu, F.; Hu, H.; Xu, Y.; Guo, L.; Zai, S.; Song, K.; Gao, H.; Zhang, L.; Zhu, F.; Wu, Q. Thermostable α-Diimine Nickel(II) Catalyst for Ethylene Polymerization: Effects of the Substituted Backbone Structure on Catalytic Properties and Branching Structure of Polyethylene. Macromolecules 2009, 42, 7789–7796. [CrossRef] Guo, L.; Gao, H.; Guan, Q.; Hu, H.; Deng, J.; Liu, J.; Liu, F.; Wu, Q. Substituent effects of the backbone in α-diimine palladium catalysts on homo-and copolymerization of ethylene with methyl acrylate. Organometallics 2012, 31, 6054–6062. [CrossRef] Zou, W.P.; Chen, C.L. Influence of backbone substituents on the ethylene (co)polymerization properties of α-diimine Pd (II) and Ni (II) catalysts. Organometallics 2016, 35, 1794–1801. [CrossRef] Ota, Y.; Ito, S.; Kobayashi, M.; Kitade, S.; Sakata, K.; Tayano, T.; Nozaki, K. Crystalline Isotactic Polar Polypropylene from the Palladium-Catalyzed Copolymerization of Propylene and Polar Monomers. Angew. Chem. Int. Ed. 2016, 55, 7505–7509. [CrossRef] [PubMed] Wu, Z.X.; Chen, M.; Chen, C.L. Ethylene Polymerization and Copolymerization by Palladium and Nickel Catalysts Containing Naphthalene-Bridged Phosphine–Sulfonate Ligands. Organometallics 2016, 35, 1472–1479. [CrossRef] Nowack, R.J.; Hearley, A.K.; Rieger, B. New Phenylnickel-(2-phosphinobenzenesulfonate) Triphenylphosphine Complexes as Highly Active Ethylene Polymerization Catalysts. Anorg. Allg. Chem. 2005, 631, 2775–2781. [CrossRef] Ito, S.; Munakata, K.; Nakamura, A.; Nozaki, K. Copolymerization of Vinyl Acetate with Ethylene by Palladium/Alkylphosphine–Sulfonate Catalysts. J. Am. Chem. Soc. 2009, 131, 14606–14607. [CrossRef] [PubMed] Long, B.K.; Eagan, J.M.; Mulzer, M.; Coates, G.W. Semi-Crystalline Polar Polyethylene: Ester-Functionalized Linear Polyolefins Enabled by a Functional-Group-Tolerant, Cationic Nickel Catalyst. Z. Angew. Chem. Int. Ed. 2016, 55, 7222–7226. [CrossRef] Chen, M.; Chen, C.L. Rational Design of High-Performance Phosphine Sulfonate Nickel Catalysts for Ethylene Polymerization and Copolymerization with Polar Monomers. ACS Catal. 2017, 7, 1308. [CrossRef]

Polymers 2017, 9, 168

52. 53.

9 of 9

Cooper, C. Organic Chemist’s Desk Reference, 2nd ed.; Chapman and Hall/CRC: Boca Raton, FL, USA, 1995; p. 151. Runzi, T.; Tritschler, U.; Roesle, P.; Gottker-Schnetmann, I.; Moller, H.M.; Caporaso, L.; Poater, A.; Cavallo, L.; Mecking, S. Activation and Deactivation of Neutral Palladium(II) Phosphinesulfonato Polymerization Catalysts. Organometallics 2012, 31, 8388–8408. [CrossRef] © 2017 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).