Synthesis and characterization of zinc complexes and reactivity with primary phosphines

Zinc complexes of chelating monoanionic N-donors and neutral diphosphine ligands were synthesized by reaction of diethylzinc with 1,3-diketimine, diazabutadiene, and diphosphine ligand precursors. These complexes were reacted with primary phosphines in an attempt to solicit phosphine dehydrocoupling reactivity. In most cases, insoluble zinc-containing precipitates were formed and ligands were liberated. For the most sterically encumbered complex, (DippL)ZnEt (3, DippL = [(2,6-iPrC6H3)NC(CH3)]2CH−), a product assigned as the zinc-phosphide (DippL)ZnPHPh (6) was observed but could not be isolated as a pure compound. A new, less bulky β-diketiminate complex (TolL)ZnEt (2, TolL = [(p-CH3C6H4)NC(CH3)]2CH−) was reacted with primary phosphines to give a precipitate and the bis(β-diketiminate)zinc complex (TolL)2Zn (5), an apparent product of comproportionation. (MesAI)ZnEt (1, MesAI = MesNC(Me)(Et)C(Me) = NMes) and 2 were structurally characterized.