Abstract
Catalyst systems of MX2(η5-C5R5)(η 4-diene) (M = Nb and Ta; R = H and CH3; X = Cl and CH3) in a combination of methylaluminoxane (MAO) are the precursors of the living polymerization of ethylene. Mono-diene complexes MCl2(η5-C5R5)(η 4-diene) [M = Nb, R = CH3 (1); M = Ta, R = CH3 (2); M = Ta, R = H (3); M = Nb, R = H (4); diene = buta-1,3-diene (a), isoprene (b), 2,3-dimethylbuta-1,3-diene (c)] were prepared by the reaction of MCl4-(η5-C5R5) with 2 equiv of the methylated allyl Grignard reagents in THF. Reaction of 2 and 3 with MeMgI afforded dimethyl complexes, Ta(η5-C5R5)(η 4-1,3-butadiene)Me2 [R = CH3 (5); R = H (6)], respectively. The polymerization of ethylene catalyzed by 1/MAO, 2/MAO, and 5/MAO at low temperature (-20°C) gave polyethylene with very narrow polydispersities (Mw/Mn as low as 1.05). The niobium complexes are superior to the tantalum complexes in terms of the catalyst activity and the polydispersity. When the ligand was Cp instead of Cp*, the catalyst activity of 3 for the polymerization of ethylene at -20°C increased but the polydispersity of the obtained polyethylene broadened (Mw/Mn = 1.40). Protolytic reaction of 5b with 1 equiv of TfOH produces TaCp*(η4-isoprene)(CH3)(OSO2CF 3) (7), whose structure is determined by single-crystal X-ray diffractometry. Compound 7 crystallizes in the orthorhombic space group P212121 (No. 19) with a = 13.388(6) Å, b = 16.196(4) Å, c = 9.214(4) Å, Z = 4, V = 1998(1) Å3, Dcalcd = 1.823 g/mL, and R = 0.041 based on 2191 reflections. The molecular structure shows that 7 is not a cationic complex. The tantalum atom is in a chiral center surrounded by four different ligands: η1-triflate, η5-Cp*, η4-isoprene, and methyl. A cationic species derived from 5b and B(C6F5)3 was detected by 1H NMR spectroscopy and found to be active in ethylene polymerization. A system of one of the bis-diene complexes of the type M(η5-C5R5)(η 4-2,3-dimethyl-1,3-butadiene)2 [M = Nb, R = H (8); M = Nb, R = CH3 (9); M = Ta, R = CH3 (10)] in the presence of a large excess of MAO was also found to be an active catalyst for the polymerization of ethylene.
| Original language | English |
|---|---|
| Pages (from-to) | 2633-2640 |
| Number of pages | 8 |
| Journal | Organometallics |
| Volume | 14 |
| Issue number | 6 |
| Publication status | Published - 1995 |
| Externally published | Yes |
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ASJC Scopus subject areas
- Inorganic Chemistry
- Organic Chemistry
Cite this
Living polymerization of ethylene catalyzed by diene complexes of niobium and tantalum, M(η5-C5Me5)(η4-diene)X 2 and M(η5-C5Me5)(η4-diene) 2 (M = Nb and Ta), in the presence of methylaluminoxane. / Mashima, Kazushi; Oshiki, Toshiyuki; Tanaka, Yoshiyuki; Urata, Hisao; Oshiki, Toshiyuki; Tanaka, Eiji; Nakamura, Akira.
In: Organometallics, Vol. 14, No. 6, 1995, p. 2633-2640.Research output: Contribution to journal › Article
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TY - JOUR
T1 - Living polymerization of ethylene catalyzed by diene complexes of niobium and tantalum, M(η5-C5Me5)(η4-diene)X 2 and M(η5-C5Me5)(η4-diene) 2 (M = Nb and Ta), in the presence of methylaluminoxane
AU - Mashima, Kazushi
AU - Oshiki, Toshiyuki
AU - Tanaka, Yoshiyuki
AU - Urata, Hisao
AU - Oshiki, Toshiyuki
AU - Tanaka, Eiji
AU - Nakamura, Akira
PY - 1995
Y1 - 1995
N2 - Catalyst systems of MX2(η5-C5R5)(η 4-diene) (M = Nb and Ta; R = H and CH3; X = Cl and CH3) in a combination of methylaluminoxane (MAO) are the precursors of the living polymerization of ethylene. Mono-diene complexes MCl2(η5-C5R5)(η 4-diene) [M = Nb, R = CH3 (1); M = Ta, R = CH3 (2); M = Ta, R = H (3); M = Nb, R = H (4); diene = buta-1,3-diene (a), isoprene (b), 2,3-dimethylbuta-1,3-diene (c)] were prepared by the reaction of MCl4-(η5-C5R5) with 2 equiv of the methylated allyl Grignard reagents in THF. Reaction of 2 and 3 with MeMgI afforded dimethyl complexes, Ta(η5-C5R5)(η 4-1,3-butadiene)Me2 [R = CH3 (5); R = H (6)], respectively. The polymerization of ethylene catalyzed by 1/MAO, 2/MAO, and 5/MAO at low temperature (-20°C) gave polyethylene with very narrow polydispersities (Mw/Mn as low as 1.05). The niobium complexes are superior to the tantalum complexes in terms of the catalyst activity and the polydispersity. When the ligand was Cp instead of Cp*, the catalyst activity of 3 for the polymerization of ethylene at -20°C increased but the polydispersity of the obtained polyethylene broadened (Mw/Mn = 1.40). Protolytic reaction of 5b with 1 equiv of TfOH produces TaCp*(η4-isoprene)(CH3)(OSO2CF 3) (7), whose structure is determined by single-crystal X-ray diffractometry. Compound 7 crystallizes in the orthorhombic space group P212121 (No. 19) with a = 13.388(6) Å, b = 16.196(4) Å, c = 9.214(4) Å, Z = 4, V = 1998(1) Å3, Dcalcd = 1.823 g/mL, and R = 0.041 based on 2191 reflections. The molecular structure shows that 7 is not a cationic complex. The tantalum atom is in a chiral center surrounded by four different ligands: η1-triflate, η5-Cp*, η4-isoprene, and methyl. A cationic species derived from 5b and B(C6F5)3 was detected by 1H NMR spectroscopy and found to be active in ethylene polymerization. A system of one of the bis-diene complexes of the type M(η5-C5R5)(η 4-2,3-dimethyl-1,3-butadiene)2 [M = Nb, R = H (8); M = Nb, R = CH3 (9); M = Ta, R = CH3 (10)] in the presence of a large excess of MAO was also found to be an active catalyst for the polymerization of ethylene.
AB - Catalyst systems of MX2(η5-C5R5)(η 4-diene) (M = Nb and Ta; R = H and CH3; X = Cl and CH3) in a combination of methylaluminoxane (MAO) are the precursors of the living polymerization of ethylene. Mono-diene complexes MCl2(η5-C5R5)(η 4-diene) [M = Nb, R = CH3 (1); M = Ta, R = CH3 (2); M = Ta, R = H (3); M = Nb, R = H (4); diene = buta-1,3-diene (a), isoprene (b), 2,3-dimethylbuta-1,3-diene (c)] were prepared by the reaction of MCl4-(η5-C5R5) with 2 equiv of the methylated allyl Grignard reagents in THF. Reaction of 2 and 3 with MeMgI afforded dimethyl complexes, Ta(η5-C5R5)(η 4-1,3-butadiene)Me2 [R = CH3 (5); R = H (6)], respectively. The polymerization of ethylene catalyzed by 1/MAO, 2/MAO, and 5/MAO at low temperature (-20°C) gave polyethylene with very narrow polydispersities (Mw/Mn as low as 1.05). The niobium complexes are superior to the tantalum complexes in terms of the catalyst activity and the polydispersity. When the ligand was Cp instead of Cp*, the catalyst activity of 3 for the polymerization of ethylene at -20°C increased but the polydispersity of the obtained polyethylene broadened (Mw/Mn = 1.40). Protolytic reaction of 5b with 1 equiv of TfOH produces TaCp*(η4-isoprene)(CH3)(OSO2CF 3) (7), whose structure is determined by single-crystal X-ray diffractometry. Compound 7 crystallizes in the orthorhombic space group P212121 (No. 19) with a = 13.388(6) Å, b = 16.196(4) Å, c = 9.214(4) Å, Z = 4, V = 1998(1) Å3, Dcalcd = 1.823 g/mL, and R = 0.041 based on 2191 reflections. The molecular structure shows that 7 is not a cationic complex. The tantalum atom is in a chiral center surrounded by four different ligands: η1-triflate, η5-Cp*, η4-isoprene, and methyl. A cationic species derived from 5b and B(C6F5)3 was detected by 1H NMR spectroscopy and found to be active in ethylene polymerization. A system of one of the bis-diene complexes of the type M(η5-C5R5)(η 4-2,3-dimethyl-1,3-butadiene)2 [M = Nb, R = H (8); M = Nb, R = CH3 (9); M = Ta, R = CH3 (10)] in the presence of a large excess of MAO was also found to be an active catalyst for the polymerization of ethylene.
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M3 - Article
AN - SCOPUS:0000341645
VL - 14
SP - 2633
EP - 2640
JO - Organometallics
JF - Organometallics
SN - 0276-7333
IS - 6
ER -