Salicylaldehyde compound containing an ammonium salt unit, [2-(HO)-3-tBu-5-{Bu₃N+(CH₂)₃Si(Me₂)}C_(6)H₂C(=O)H][BF4-] is prepared from which a Salen-type ligand and its cobalt(III) complex, (Salen-1)CoX (1: Salen-1 = [trans-N,N'-bis(3-tBu-5-(Bu3N+(CH₂)₃Si(Me₂)-salicylidene)-1,2-cyclohexanediamine)] X=2,4-dinitrophenolate) is prepared. Complex 1 shows high activity for CO₂/(propylene oxide) copolymerization even at a condition of high [propylene oxide]/[catalyst] ratio and high temperature up to 90 ℃, at which conditions a typical binary system of [(Salen)CoX]/[PPNCl] does not yield any copolymer. A very high TOF (up to 3500 h^(-1)) and TON (up to 14,500) are achieved, which have never been attained with other catalytic systems. The high selectivity (>90%) for the formation of copolymer over cyclic carbonate and the high molecular weight of the obtained polymers (Mn = 53,000 - 80,000) are the other merits of the catalyst.1
