Enantioselective Epoxide Polymerization Using a Bimetallic Cobalt Catalyst

Abstract

A highly active enantiopure bimetallic cobalt complex was explored for the enantioselective polymerization of a variety of monosubstituted epoxides. The polymerizations were optimized for high rates and stereoselectivity, with s-factors (k(fast)/k(slow)) for most epoxides exceeding 50 and some exceeding 300, well above the threshold for preparative utility of enantiopure epoxides and isotactic polyethers. Values for mm triads of the resulting polymers are typically greater than 95%, with some even surpassing 98%. In addition, the use of a racemic catalyst allowed the preparation of isotactic polyethers in quantitative yields. The thermal properties of these isotactic polyethers are presented, with many polymers exhibiting high T(m) values. This is the first report of the rapid synthesis of a broad range of highly isotactic polyethers via the enantioselective polymerization of racemic epoxides.

Asymmetric Copolymerization of CO2 with meso‐Epoxides Mediated by Dinuclear Cobalt(III) Complexes: Unprecedented Enantioselectivity and Activity

“…[16] The dinuclear Co III complex 4 was also tested for the asymmetric copolymerization of CO 2 with CPO (Table 1, entries 17-19). Unfortunately, the binary catalyst systems based on complex 4 a or 4 b showed a very low activity, affording the copolymers with poor enantioselectivity (20-33 % ee).…”

Two cadmium(II) complexes with oxazoline-based ligands as effective catalysts for C–N cross-coupling reactions

“…However, the reaction with 10 mol% complex 1 gave 1a in 90% yield, and complex 2 provided 1a in 45% yield (Table 4, entries 2, 3). These results illustrate the importance of the ligand configuration and the cooperative bimetallic catalytic effect on this transformation [44,45]. Next, we chose complex 1 and subjected the catalyst to different solvent and base (Table 4, entries 4-7).…”

The role of CO2 in the Earth’s ecosystem and the possibility of controlling flows between subsystems

“…The company November, within the framework of a USDOE job order, developed a process using a cobalt catalyst (Thomas et al 2010) which allows CO 2 to be fixed during polymerisation of cyclic ethers (epoxides) to form thermoplastics with a 40-50% CO 2 content by weight.…”