Bimetallic Anilido-Aldimine Zinc Complexes for Epoxide/CO_2 Copolymerization

摘要

Acyclic omicron-phenylene-bridged bis(anilido-aldimine)compounds,omicron-C_6H_4{C_6H_2R_2N venlence CH-C_6H_4-(H)N(C_6H_3R'2)}2 and related 30-membered macrocyclic compounds,omicron-C_6H_4{C_6H_2R'2N=CH-C_6H_4-(H)N-C_6H_2R2}2(omicron-Ce_6H_4)are prepared.Successive additions of Me_2Zn and SO_2 gas to the bis(anilido-aldimine)compounds afford quantitatively dinuclear mu-methylsulfinato zinc complexes,omicron-C_6H_4{(C_6H_2R2N=CH-C_6H_4-N(C_6H_3R'2)-kappa~2-N,N)Zn(mu-OS(O)Me)}_2(R = /Pr and R' = iPr,29;R = Et and R' = Et,30;R = Me and R' = Me,31;R = Me and R' =iPr,32;R = Et and R' = Me,33;R = Et and R' = iPr,34;R = iPr and R' = Et,35)and omicron-C_6H_4{C_6H_2R'_2N=CH-C_6H_4-N-C_6H_2R_2-kappa~2-N,N)Zn(mu-OS(O)Me)}_2(omicron-C_6H_4)(R = Et and R' = Et,36;R = Me and R' = Me,37;R = iPr and R' = Me,38;R = Et and R' = Me,39;R = Me and R' = iPr,40).Molecular structures of 34 and 40 are confirmed by X-ray crystallography.Complexes 30-35 show high activity for cyclohexene oxide/CO_2 copolymerization at low [Zn]/[monomer] ratio(1:5600),whereas the complex of mononucleating beta-diketiminate {[(C_6H_3Et_2)N=C(Me)CH=C(Me)N(C_6H_3Et_2)]Zn(mu-OS(O)Et)}_2 shows negligible activity in the same condition.Activity is sensitive to the N-aryl ortho substituents and the highest activity is observed with 32.Turnover number up to 2980 and molecular weight(M_n)up to 284 000 are attained with 32 at such a highly diluted condition as [Zn]/[monomer] = 1:17 400.Macrocyclic complexes 36-40 show negligible activity for copolymerization.