Triketiminate bis(borohydride) complexes of rare-earth metals [(2,6-Me2C6H3N=CMe)2C(2,6-Me2C6H3N=CBut)]Ln(BH4)2(THF)2 (Ln = Y, Nd): synthesis, structure, and catalytic activity in polymerization of rac-lactide, ε-caprolactone, and isoprene

A new triketimine (2,6-Me 2 C 6 H 3 N=CMe) 2 CH(2,6-Me 2 C 6 H 3 N=CBu t ) ( 1 ) was synthesized by the reaction of imidoyl chloride 2,6-Me 2 C 6 H 3 N=CClBu t with lithium diketiminate (2,6-Me 2 C 6 H 3 N=CMe) 2 CHLi. In the crystalline state, compound 1 exists in the diimineenamine form; in solution, in the triimine form. The metalation of triketimine 1 with n -butyllithium in THF at 0 °C produced lithium triketiminate [(2,6-Me 2 C 6 H 3 N=CMe) 2 C(2,6-Me 2 C 6 H 3 N=CBu t )]Li(THF) 2 ( 2 ). The metathesis reactions of Ln(BH 4 ) 3 (THF) 3 (Ln = Y, Nd) with compound 2 (1: 1 molar ratio, THF) gave the neutral triketiminate bis(borohydride) complexes [(2,6-Me 2 C 6 H 3 N=CMe) 2 C(2,6-Me 2 C 6 H 3 N=CBu t )]Ln(BH 4 ) 2 (THF) 2 (Ln = Y ( 3 ), Nd ( 4 )). As opposed to the complexes with neutral triketimine, the monoanionic triketiminate ligand is coordinated to Li and Y or Nd cations in a bidentate fashion. Complexes 3 and 4 catalyze the polymerization of rac -lactide and ε-caprolactone; in combination with [Ph 3 C][B(C 6 F 5 ) 4 ] and AlBu 3 i (1 : 1 : 10 molar ratio), these compounds exhibit catalytic activity in the polymerization of isoprene.