Ethylene Polymerization Using (Imino)vanadium(V) Dichloride Complexes Containing (Anilido)methyl-pyridine, -quinoline Ligands–Halogenated Al Alkyls Catalyst Systems
1
Department of Chemistry, Tokyo Metropolitan University, 1-1 Minami Osawa, Hachioji, Tokyo 192-0397, Japan
2
Institute of Chemistry, Chinese Academy of Sciences, Zhongguancun, Beijing 100190, China
*
Author to whom correspondence should be addressed.
Catalysts 2013, 3(1), 148-156; https://doi.org/10.3390/catal3010148
Submission received: 25 December 2012
/
Revised: 29 January 2013
/
Accepted: 30 January 2013
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Published: 7 February 2013
(This article belongs to the Special Issue Molecular Catalysis for Precise Olefin Polymerization)
Abstract
:The effect of ligand and Al cocatalysts in ethylene polymerization, using V(N-1-adamantyl)Cl2(L) [L = 2-(2,6-Me2C6H3)NCH2(C9H6N), 8-(2,6-Me2C6H3)NCH2(C9H6N)] and V(N-2-MeC6H3)Cl2[2-(2,6-R'2C6H3)NCH2(C5H4N)] (R' = Me, iPr), has been explored. The reaction products in the presence of Et2AlCl or Me2AlCl cocatalyst were polyethylene whereas the reaction product of the 2-methylphenylimido analogues in the presence of MAO cocatalyst was 1-butene with high selectivity, suggesting that the catalyst/cocatalyst nuclearity effect plays a role in this catalysis.
1. Introduction
Designing vanadium complex catalysts for olefin polymerization/oligomerization has been considered as a promising subjects, because the classical Ziegler-type catalyst systems [V(acac)3, VOCl3, etc. and Et2AlCl, EtAlCl2, nBuLi, etc.] display unique high reactivity toward olefins in olefin coordination/insertion polymerization [1,2,3,4,5]. We previously reported that (arylimido)vanadium(V) complexes, containing anionic donor ligands (L), V(N-2,6-Me2C6H3)Cl2(L) (L = aryloxo, ketimide, phenoxyimine etc.), exhibited remarkable catalytic activities for ethylene polymerization in the presence of Al cocatalysts [3,4,5,6,7,8,9,10]. The activity by the aryloxo analogue was strongly affected by the Al cocatalyst; the activities in the presence of halogenated Al alkyls (iBu2AlCl, EtAlCl2, Me2AlCl, Et2AlCl) were higher than those in the presence of methylaluminoxane (MAO) [7,8]. Both the activity, and the norbornene incorporation, in the ethylene/norbornene copolymerization were also affected by the Al cocatalyst employed [7,8]. We thus speculated that a reason for the observed difference would be due to a formation of the different catalytically-active species, catalyst/cocatalyst nuclearity effect (assumed in Scheme 1) [5,11,12,13]. The activity decreased upon addition of CCl3CO2Et (for example, [14]), which can be commonly used as effective additives to improve the catalyst stability [8], clearly suggesting that the active species were, thus, different from those prepared from vanadium(III), (IV) complexes [1,2,3,4,5,14].
Scheme 1.
Proposed catalytically-active species formed by different Al cocatalysts.
More recently, we demonstrated that the (adamantylimido)vanadium(V) complexes containing (2-anilidomethyl)pyridine ligand, V(NAd)Cl2[2-ArNCH2(C5H4N)] [Ad = 1-adamantyl; Ar = 2,6-Me2C6H3 (1a), 2,6-iPr2C6H3 (1b)], efficiently dimerize ethylene with both notable catalytic activities, and high selectivity in the presence of MAO [15,16], whereas the reaction products by 1a,b in the presence of Me2AlCl or Et2AlCl cocatalyst were ultrahigh molecular weight polyethylene (PE) (runs 1–5, Table 1) [16]. Moreover, we prepared the adamantylimido complexes containing 2- or 8-(anilidomethyl)-quinoline ligands, V(NAd)Cl2[(2,6-Me2C6H3)NCH2(C9H6N)] (2a,3a, Scheme 2), and V(N-2-MeC6H4)Cl2[2-ArNCH2(C5H4N)] complexes (4a,b) and explored reactions with ethylene in the presence of MAO (Table 1) [17]: remarkable effect of the imido ligand toward the selectivity (oligomer, polymer) was observed in the presence of MAO (Table 1, runs 9–12), whereas the reaction products by the quinoline analogues were a mixture of PE and oligomers. Since the reaction products by 1a,b in presence of Et2AlCl or Me2AlCl were PE, in this paper, we thus explored reactions with ethylene in the presence of halogenated Al alkyls to confirm our hypothesis outlined in Scheme 1, for example in ethylene polymerization by the other vanadium complex catalysts, [18,19,20,21,22,23,24].
Table 1.
Reaction of ethylene with V(NR)Cl2(L) [R = Ad, L = 2-(2,6-R'2C6H3)NCH2(C5H4N) [R' = Me (1a), iPr (1b)], 2-(2,6-Me2C6H3)NCH2(C9H6N) (2a), 8-(2,6-Me2C6H3)NCH2(C9H6N) (3a); R = 2-MeC6H4 (4a,b), 2,6-Me2C6H3 (5a,b), L = 2-(2,6-R'2C6H3)NCH2(C5H4N)]–MAO or R''2AlCl (R'' = Me, Et) catalysts a.
| Run | V complex | Al cocat. | Al/V b | C4',C6' | Polyethylene (PE) | ||||
|---|---|---|---|---|---|---|---|---|---|
| (μmol) | Activity c | C4'/% d | C6'/% d | Activity e | Mw f | Mw/Mn f | |||
| 1 | 1a (0.2) g | MAO | 500 | 57800 | 96.8 | 3.2 | |||
| 2 | 1a (0.1) g | MAO | 1500 | 76500 | 97.0 | 3.0 | |||
| 3 | 1b (0.5) g | MAO | 1000 | 35700 | 92.1 | 7.9 | |||
| 4 | 1a (5.0) h | Et2AlCl | 100 | 137 | 5.92 i | ||||
| 5 | 1a (5.0) h | Me2AlCl | 200 | 704 | 6.76 i | ||||
| 6 | 2a (5.0) j | MAO | 1000 | 43 | 71.6 | 28.4 | 53 | ||
| 7 | 3a (2.0) j | MAO | 1000 | 201 | 92.4 | 7.6 | 30 | ||
| 8 | 3a (2.0) j | MAO | 1500 | 249 | 92 | 8 | 45 | ||
| 9 | 4a (0.2) j | MAO | 600 | 50300 | 95.2 | 4.8 | |||
| 10 | 4b (0.2) j | MAO | 700 | 41500 | 97.1 | 2.9 | |||
| 11 | 5a (2.0) k | MAO | 3000 | 78 | 2.98 | 2.0 | |||
| 12 | 5b (2.0) k | MAO | 3000 | 189 | 2.93 | 2.6 | |||
a Conditions: toluene 30 mL, ethylene 8 atm., 25 °C, 10 min MAO or R"2AlCl (R" = Me, Et). b Al/V molar ratio. c Activity in (kg of ethylene reacted)/mol-V·h. d Determined by GC analysis. e Activity in kg-PE/mol-V·h. fGPC data in O-dichlorobenzene versus polystyrene standards. g Data cited from reference [15]. h Data cited from reference [16] and 0 °C. iMν value measured by viscosity. j Data cited from reference [17]. k Data cited from reference [10].
Scheme 2.
List of complexes employed in this study.
2. Results and Discussion
2.1. Ethylene Polymerization Using V(NAd)Cl2[2-ArNCH2(C9H6N)], V(NAd)Cl2[8-ArNCH2(C9H6N)]–Me2AlCl Catalyst Systems
Reactions of ethylene with V(NAd)Cl2[2-(2,6-Me2C6H3)NCH2(C9H6N)] (2a), V(NAd)Cl2[8-(2,6-Me2C6H3)NCH2(C9H6N)] (3a) in the presence of Me2AlCl were conducted in toluene and the results are summarized in Table 2. The results with V(NAd)Cl2[2-(2,6-Me2C6H3)NCH2(C5H4N)] (1a) [16], are also shown for comparison. Me2AlCl was chosen, because Me2AlCl showed higher catalytic activity than Et2AlCl in ethylene polymerization using 1a,b [16].
It turned out that the quinoline analogues 2a,3a showed the higher catalytic activities than the pyridine analogue (1a) especially under the optimized Al/V molar ratios: the activities were affected by the Al/V molar ratios. The reaction products were polyethylene that are insoluble in hot O-dichlorobenzene for measurement of their molecular weight(s) by GPC in the ordinary analysis procedure, suggesting formations of ultrahigh molecular weight polymers as observed previously [8,16,17]. The activity by 2a showed higher than 3a, probably due to a stability of catalytically active species (formed five membered ring around vanadium and L in 2a vs. six membered ring in 3a). The facts observed should be promising, because the reaction products were a mixture of PE and 1-butene (major) when the reactions by 2a,3a were conducted in the presence of MAO. Moreover, the observed activities in the presence of Me2AlCl were higher than those in the presence of MAO.
Table 2.
Ethylene polymerization with V(NAd)Cl2(L) [L = 2-ArNCH2(C5H4N) (1a), 2-ArNCH2(C9H6N) (2a), 8-ArNCH2(C9H6N) (3a), Ar = 2,6-Me2C6H3]–Me2AlCl catalysts a.
| Run | Vanadium complex | Al/V b | Yield | Activity c | |
|---|---|---|---|---|---|
| L (V cat.) | /μmol | /mg | |||
| 5 d | 2-ArNCH2(C5H4N) (1a) e | 0.5 | 200 | 58.7 | 704 |
| 13 d | 2-ArNCH2(C5H4N) (1a) f | 1.0 | 500 | 116 | 696 |
| 14 | 2-ArNCH2(C9H6N) (2a) | 0.2 | 2500 | 70.2 | 2110 |
| 15 | 2-ArNCH2(C9H6N) (2a) | 0.2 | 5000 | 122 | 3670 |
| 16 | 2-ArNCH2(C9H6N) (2a) | 0.2 | 7500 | 152 | 4560 |
| 17 | 2-ArNCH2(C9H6N) (2a) | 0.2 | 10000 | 120 | 3600 |
| 18 | 8-ArNCH2(C9H6N) (3a) | 0.2 | 1000 | 79.6 | 2390 |
| 19 | 8-ArNCH2(C9H6N) (3a) | 0.2 | 2000 | 73.6 | 2210 |
| 20 | 8-ArNCH2(C9H6N) (3a) | 0.2 | 5000 | 58.7 | 1760 |
a Conditions: toluene 30 mL, ethylene 8 atm, 0 °C, 10 min. b Molar ratio of Al/V. c Activity in kg-PE/mol-V·h.; d Data cited from reference [16]. e Mν = 6.76×106 measured by viscosity. f Mν = 8.96×106 measured by viscosity.
2.2. Ethylene Polymerization Using V(N-2-MeC6H4)Cl2[2-(2,6-R'2C6H3)NCH2(C5H4N)]–Halogenated Al Alkyls Catalyst Systems
We recently reported [17] that the 2-methylphenylimido analogues, V(N-2-MeC6H4)Cl2[2-(2,6-R2C6H3)NCH2(C5H4N)] [R' = Me (4a), iPr (4b)], exhibited remarkable catalytic activities for ethylene dimerization in the presence of MAO [17], whereas the reaction by 2,6-dimethylphenylimido analogues (5a,b) afforded polyethylene (Table 1, runs 11–12) [10]. Since the reaction product by the adamantylimido analogues (1a,b) in the presence of halogenated Al alkyls (in place of MAO) afforded ultrahigh molecular weight polyethylene, we thus conducted the reaction with ethylene in the presence of Et2AlCl, Me2AlCl (Table 2). The results by the 2,6-dimethylphenylimido analogues (5a,b) [10] are also shown for comparison.
Although reaction with ethylene by 4a,b afforded 1-butene exclusively in the presence of MAO, and the activities are similar to those by 1a,b, the activities by 4a,b in the presence of Me2AlCl, Et2AlCl were low in all cases. The reaction products were polyethylene that were insoluble in hot O-dichlorobenzene for measurement of their molecular weight(s) by GPC in the ordinary analysis procedure, suggesting formations of ultrahigh molecular weight polymers [8,16,17]. The activities were affected by the Al/V molar ratios employed, but the activities by 4a showed higher than those by 4b [ex. activity: 382 kg-PE/mol-V·h by 4a (run 25) vs. 165 kg-PE/mol-V·h by 4b (run 30)] and the activities in the presence of Me2AlCl were higher than those in the presence of Et2AlCl [ex. activity by 4a: 382 kg-PE/mol-V·h (run 25, Me2AlCl) vs. 148 kg-PE/mol-V·h (run 30)]. It also seems likely that the activities were affected by the amount Al employed rather than the Al/V molar ratios in this catalysis (Figure 1). Exclusive formation of polyethylene by 4a,b should be noteworthy, because, as described above, these complexes afforded 1-butene exclusively in the reaction with ethylene in the presence of MAO [17].
Table 3.
Reaction of ethylene with V(NR)Cl2[2-ArNCH2(C5H4N)] [R = 1-adamantyl (Ad, 1), 2-MeC6H4 (4), 2,6-Me2C6H3 (5): Ar = 2,6-Me2C6H3 (a), 2,6-iPr2C6H3 (b)]–Me2AlCl, Et2AlCl catalysts a.
| Run | Vanadium complex | Al cocat. | Al/V b | Yield | Activity c | |
|---|---|---|---|---|---|---|
| R (V cat.) | /μmol | (mmol) | /mg | |||
| 5d | 1-adamantyl (1a) e | 0.5 | Me2AlCl (0.10) | 200 | 58.7 | 704 |
| 13d | 1-adamantyl (1a) f | 1.0 | Me2AlCl (0.50) | 500 | 116 | 696 |
| 21 | 2-MeC6H4 (4a) | 1.0 | Me2AlCl (1.0) | 1000 | 16.7 | 100 |
| 22 | 2-MeC6H4 (4a) | 1.0 | Me2AlCl (2.0) | 2000 | 46.4 | 278 |
| 23 | 2-MeC6H4 (4a) | 1.0 | Me2AlCl (3.0) | 3000 | 51.0 | 306 |
| 25 | 2-MeC6H4 (4a) | 1.0 | Me2AlCl (4.0) | 4000 | 63.7 | 382 |
| 26 | 2-MeC6H4 (4a) | 1.0 | Me2AlCl (5.0) | 5000 | 57.8 | 347 |
| 27 | 2-MeC6H4 (4b) | 2.0 | Me2AlCl (1.5) | 750 | 11.9 | 36 |
| 28 | 2-MeC6H4 (4b) | 2.0 | Me2AlCl (2.0) | 1000 | 17.8 | 53 |
| 29 | 2-MeC6H4 (4b) | 2.0 | Me2AlCl (2.5) | 1250 | 18.2 | 55 |
| 30 | 2-MeC6H4 (4b) | 2.0 | Me2AlCl (3.0) | 1500 | 55.1 | 165 |
| 31 | 2-MeC6H4 (4b) | 2.0 | Me2AlCl (4.0) | 2000 | 54.1 | 162 |
| 32 | 2-MeC6H4 (4a) | 1.0 | Et2AlCl (0.20) | 200 | 8.1 | 49 |
| 33 | 2-MeC6H4 (4a) | 1.0 | Et2AlCl (0.50 | 500 | 11.7 | 70 |
| 34 | 2-MeC6H4 (4a) | 1.0 | Et2AlCl (1.0) | 1000 | 11.6 | 70 |
| 35 | 2-MeC6H4 (4a) | 1.0 | Et2AlCl (1.5) | 1500 | 24.6 | 148 |
| 36 | 2-MeC6H4 (4a) | 1.0 | Et2AlCl (2.0) | 2000 | 15.9 | 95 |
| 37 | 2-MeC6H4 (4b) | 1.0 | Et2AlCl (0.20) | 200 | 5.5 | 33 |
| 38 | 2-MeC6H4 (4b) | 1.0 | Et2AlCl (0.50) | 500 | 5.1 | 31 |
| 39 | 2-MeC6H4 (4b) | 1.0 | Et2AlCl (1.0) | 1000 | 10.1 | 61 |
| 40 | 2-MeC6H4 (4b) | 1.0 | Et2AlCl (1.5) | 1500 | 4.0 | 24 |
| 41 | 2-MeC6H4 (4b) | 1.0 | Et2AlCl (2.0) | 2000 | 3.2 | 19 |
| 42 | 2,6-Me2C6H3 (5a) g | 1.0 | Et2AlCl (0.10) | 100 | 140 | 840 |
| 43 | 2,6-Me2C6H3 (5b) g | 0.2 | Et2AlCl (0.04) | 200 | 200 | 6000 |
Figure 1.
Effect of R2AlCl (R = Me, Et) toward the activity in ethylene polymerization by V(N-2-MeC6H4)Cl2[2-(2,6-R'2C6H3)NCH2(C5H4N)] [R' = Me (4a), iPr (4b)]. Details are shown in Table 3.
Figure 1.
Effect of R2AlCl (R = Me, Et) toward the activity in ethylene polymerization by V(N-2-MeC6H4)Cl2[2-(2,6-R'2C6H3)NCH2(C5H4N)] [R' = Me (4a), iPr (4b)]. Details are shown in Table 3.
3. Experimental Section
3.1. General Procedure
All experiments were carried out under a nitrogen atmosphere in a Vacuum Atmospheres drybox. Anhydrous grade toluene, n-hexane (Kanto Kagaku Co., Ltd. Tokyo, Japan) was transferred into a bottle containing molecular sieves (a mixture of 3A 1/16, 4A 1/8, and 13 × 1/16) in the drybox under nitrogen stream, and were passed through an alumina short column under N2 stream prior to use. Complexes employed here were prepared according to our previous reports [10,15,16,17]. Polymerization grade ethylene (purity > 99.9%, Sumitomo Seika Co. Ltd., Hyogo, Japan) was used as received. Toluene and AlMe3 in the commercially available methylaluminoxane (PMAO-S, 9.5 wt% (Al) toluene solution, Tosoh Finechem Co., Yamaguchi, Japan) were removed under reduced pressure (at ca. 50 °C for removing toluene, AlMe3, and then heated at >100 °C for 1 h for completion) in the drybox to give white solids.
3.2. Ethylene Polymerization
Ethylene polymerizations were conducted in a 100 mL scale stainless steel autoclave. The typical reaction procedure is as follows. Toluene (29 mL) and a prescribed amount of Et2AlCl or Me2AlCl (1 M in n-hexane) were added into the autoclave in the drybox. The reaction apparatus was then filled with ethylene (1 atm.), and catalyst in toluene (1.0 mL) was then added into the autoclave, the reaction apparatus was then immediately pressurized to 7 atm. (total 8 atm.), and the mixture was magnetically stirred for a prescribed time. After the above procedure, ethylene that remained was purged upon cooling, and the mixture was then poured into MeOH containing HCl. The resultant polymer (white precipitate) was collected on a filter paper through filtration, and was adequately washed with MeOH. The resultant polymer was then dried in vacuo at 60 °C for 2 h.
4. Conclusions
In summary, in this paper, we explored ethylene polymerization using V(NR)Cl2(L) [R = 1-adamantyl, L = 2-(2,6-R'2C6H3)NCH2(C5H4N) {1a,b, R' = Me (a), iPr (b)}, 2-(2,6-Me2C6H3)NCH2(C9H6N) (2a), 8-(2,6-Me2C6H3)NCH2(C9H6N) (3a); R = 2-MeC6H4 (4a,b), 2,6-Me2C6H3 (5a,b), L = 2-(2,6-R'2C6H3)NCH2(C5H4N)] in the presence of halogenated Al alkyls. The reaction products were polyethylene that were insoluble in hot O-dichlorobenzene for measurement of molecular weights by GPC in ordinary analysis procedure, suggesting formation of ultrahigh molecular weight polymers as reported previously [8,16]. Moreover, we demonstrated by 1a,b, that the anionic chelate donor ligand plays an essential role for stabilization of catalytically-active species and proposed an assumption that cationic vanadium(V) species play a key role in this catalysis, the facts observed here should be promising and important for designing efficient catalysts for olefin polymerization/dimerization, including the effect of catalyst/cocatalyst nuclearity that would play an important role in this catalysis.
Acknowledgments
This project was partly supported by Bilateral Joint Projects between Japan Society of Promotion of Sciences (JSPS) and National Natural Science Foundation of China (NSFC). Kotohiro Nomura and Atsushi Igarashi express their heartfelt thanks to Tosoh Finechem Co. for donating MAO.
Conflict of Interest
The authors declare no conflict of interest.
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Igarashi, A.; Zhang, W.; Sun, W.-H.; Nomura, K. Ethylene Polymerization Using (Imino)vanadium(V) Dichloride Complexes Containing (Anilido)methyl-pyridine, -quinoline Ligands–Halogenated Al Alkyls Catalyst Systems. Catalysts 2013, 3, 148-156. https://doi.org/10.3390/catal3010148
AMA Style
Igarashi A, Zhang W, Sun W-H, Nomura K. Ethylene Polymerization Using (Imino)vanadium(V) Dichloride Complexes Containing (Anilido)methyl-pyridine, -quinoline Ligands–Halogenated Al Alkyls Catalyst Systems. Catalysts. 2013; 3(1):148-156. https://doi.org/10.3390/catal3010148
Chicago/Turabian StyleIgarashi, Atsushi, Wenjuan Zhang, Wen-Hua Sun, and Kotohiro Nomura. 2013. "Ethylene Polymerization Using (Imino)vanadium(V) Dichloride Complexes Containing (Anilido)methyl-pyridine, -quinoline Ligands–Halogenated Al Alkyls Catalyst Systems" Catalysts 3, no. 1: 148-156. https://doi.org/10.3390/catal3010148
APA StyleIgarashi, A., Zhang, W., Sun, W. -H., & Nomura, K. (2013). Ethylene Polymerization Using (Imino)vanadium(V) Dichloride Complexes Containing (Anilido)methyl-pyridine, -quinoline Ligands–Halogenated Al Alkyls Catalyst Systems. Catalysts, 3(1), 148-156. https://doi.org/10.3390/catal3010148
