A binuclear lithium complex based on an ansa -bis(1-azaallyl) ligand: synthesis, structure and catalysis for ring-opening polymerization of ɛ-caprolactone

Deprotonation of the Schiff base 2,6-dimethyl- N -(1-phenylethylidene)aniline, C 16 H 17 N or [MeC(Ph)=N(2,6-Me 2 C 6 H 3 )], 1 , with one equivalent of lithium diisopropylamide (LDA) and subsequent reaction with half an equivalent of SiPh 2 Cl 2 gave a new diimine, N -[2-({2-[(2,6-dimethylphenyl)imino]-2-phenylethyl}diphenylsilyl)-1-phenylethylidene]-2,6-dimethylaniline, C 44 H 42 N 2 Si, 2 . Further treatment of 2 with LDA in the presence of tetrahydrofuran (THF) yielded the target binuclear ansa -bis(1-azaallyl) lithium compound {μ- N -[2-({2-[(2,6-dimethylphenyl)azanidyl]-2-phenylethyl}diphenylsilyl)-1-phenylethylidene]-2,6-dimethylanilinido}bis[(tetrahydrofuran)lithium], [Li 2 (C 44 H 40 N 2 Si)(C 4 H 8 O) 2 ], 3 . Both 2 and 3 were characterized by 1 H and 13 C NMR spectroscopy and elemental analysis, and the structures of 1 , 2 and 3 were confirmed by X-ray crystallography. Density functional theory (DFT) calculations were carried out for compounds 1 – 3 . In addition, the catalytic properties of 3 towards the ring-opening polymerization of ɛ-caprolactone were investigated and the compound showed good catalytic activity.