Cooperative Initiation in a Dinuclear Indium Complex for CO 2 Epoxide Copolymerization.

Dinuclear indium complexes have been synthesized and characterized. These include neutral and cationic indium complexes supported by a Schiff base ligand bearing a binaphthol linker. The new compounds were investigated for alternating copolymerization of CO 2 and cyclohexene oxide. In particular, the neutral indium chloride complex (±)-[(O Nap N i N)InCl 2 ] 2 ( 4 ) showed high conversion of cyclohexene oxide and selectivity for poly(cyclohexene carbonate) formation without cocatalysts at 80 °C under various CO 2 pressures (2-30 bar). Importantly, the reactivity of the dinuclear indium chloride complex 4 is drastically different from that of the mononuclear indium chloride complex (±)-(NN i O t Bu )InCl 2 ( 5 ), suggesting a cooperative initiation mechanism involving the two indium centers in 4 .