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.

New zinc complexes were prepared and tested for reactivity in phosphine dehydrocoupling. While the complexes were not active catalysts, some interesting zinc reactions like comproportionation were observed.Figure optionsDownload as PowerPoint slideHighlights
► (MesAI)ZnEt (1), (TolL)ZnEt (2), (dmpe)ZnEt2 (4) were synthesized, and 1 and 2 were structurally characterized.
► (TolL)2Zn was observed in a comproportionation reaction with phenylphosphine.
► (DippL)ZnPHPh was synthesized observed.