Scandium alkyl and amide complexes containing a cyclen-derived (NNNN) macrocyclic ligand: Synthesis, structure and ring-opening polymerization activity toward lactide monomers

摘要

Cyclic polyamine 1,4,7-trimethyl-1,4,7,10-tetraazacyclododecane, (Me _3TACD)H (= Me_3[12]aneN_4), reacted with [K{N(SiHMe_2)_2}] in benzene-d_6 to give [K{(Me_3TACD)SiMe_2N(SiHMe_2)}] (1) under hydrogen evolution. Single-crystal X-ray diffraction of 1 shows a dinuclear structure in the solid state, featuring a bridging μ-amido and a weak β-agostic Si-H bond. 1,7-Dimethyl-1,4,7,10-tetraazacyclododecane (Me_2TACD)H _2 (= Me_2[12]aneN_4) and (Me_3TACD)H were reacted with [Sc{N(SiHMe_2)_2}_3(thf)] in benzene-d_6 to give [{(Me_2TACD)SiMe_2N(SiHMe _2)}Sc{N(SiHMe_2)_2}] (2) and [(Me _3TACD)Sc{N(SiHMe_2)_2}_2SiMe _2] (3), respectively. Both compounds are monomeric in solution and X-ray diffraction studies showed the scandium metal centers to be six-coordinate. The scandium alkyl complex [Sc(Me_3TACD)(CH _2SiMe_3)_2] (4) was obtained by reacting (Me _3TACD)H with [Sc(CH_2SiMe_3)_3(thf)] in benzene-d_6. The scandium amide complexes 2 and 3 catalyzed the ring-opening polymerization (ROP) of meso-lactide to give syndiotactic polylactides.