π-Excess aromatic σ2-P ligands: synthesis and structure of an unprecedented μ2-P-1,3-benzazaphosphole bridged tetranuclear copper(i) acetate complex

Abstract

The –PCH–NR-heterocycle 1-neopentyl-1,3-benzazaphosphole (npBAP) reacts in THF with copper(I) acetate via labile soluble complexes (npBAP)_xCuOAc preferably to form the insoluble tetranuclear (npBAP)₂(CuOAc)₄ complex 1. The crystal structure analysis of 1·2CH₂Cl₂, grown from CH₂Cl₂–hexane, reveals two μ²-P coordinated ligands, folding the Cu₄ ring with each two short distances of the cyclic copper(I) acetate tetramer to a butterfly arrangement. AIM analysis of the ωB97-D/6-31+G* electron density, obtained at the crystal structure geometry, shows bond critical points between the copper atoms indicating covalent bonding interactions between the neighboring Cu atoms.