Neutral Bimetallic Transition Metal Napthldioxydiiminato Catalysts and Related Polymerization Methods (28037)

New bimetallic Ni olefin polymerization catalyst system.

ADVANTAGE: Bimetallic olefin polymerization catalysts with increased activity, degree of and selectivity for methyl group branching, and comonomer incorporation versus mononuclear analogues under mild process conditions. The catalysts also produce highly branched polyethylenes in the absence of a cocatalyst.

SUMMARY: The remarkable cooperativity effects displayed by single-site group 4 bimetallic olefin polymerization catalysts include enhanced activity, chain branching, and comonomer enchainment selectivity. Cooperativity effects in systems other than group 4 now also prove valuable. Ni(II) complexes are active olefin polymerization catalysts, exemplified by the Ni phenoxyiminates which afford LDPEs having moderate molecular weights and 10-55 branches/1000 C atoms. This invention establishes the synthesis and polymerization characteristics of binuclear napthldioxydiiminato Ni(II) catalysts FI2-Ni2-A and FI2-Ni2-B (Figure) in which rigid ligation enforces close Ni⋅⋅⋅Ni distances. These catalysts exhibit significant cooperativity effects manifested in enhanced polymerization activity, increased methyl chain branching, and greater comonomer incorporation under mild reaction conditions, without requiring a cocatalyst.

Bimetallic FI2-Ni2-A and FI2-Ni2-B ethylene homopolymerizations carried out in the presence of the phosphine scavenger/cocatalyst Ni(cod)2. (10 µmol catalyst, 2 equiv cocatalyst/Ni, 7.0 atm ethylene, in toluene, 25°C) afford polyethylenes with molecular weights comparable to those produced by the mononuclear analogues with polydispersities consistent with single-site processes. However, the bimetallic catalysts exhibit a two-fold greater polymerization activity and with only methyl increased branching, ~ 2x that achieved by the mononuclear catalysts under identical reaction conditions (Table 1, entry 1,2,5,6). In the absence of a cocatalyst, mononuclear systems do not produce polyethylene, whereas these bimetallic catalysts produce polyethylenes with increased branching densities at somewhat reduced rates (Table 1, entry 8-11).

Ethylene - norbornene copolymerizations mediated by binuclear FI2-Ni2-A and FI2-Ni2-B proceed with 3-4x greater activity and achieve 3-4x greater selectivity for comonomer enchainment versus the mononuclear systems (Table 1, entry 12-15). The rigid bimetallic catalyst substantially increases selectivity for polar-functionalized norbornenes and methyl methacrylate, co-enchainment versus analogous mononuclear controls., The FI2-Ni2 catalysts exhibit 3-4x greater polar comonomer enchainment selectivity, regardless of the polar substituent. The binuclear catalysts also display enhanced activity in polar solvents (2.6x Et2O, 5x Me2CO, 3x H2O) versus the mononuclear analogues. These catalytic systems offer great potential for developing new polymer materials and properties.

STATUS: A patent application has been filed.

REFERENCE: Organometallics 2008, 27, 2166-2168

Type of Offer: Licensing



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