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

The P=CH-NR-heterocycle 1-neopentyl-1,3-benzazaphosphole (npBAP) reacts in THF with copper(I) acetate via labile soluble complexes (npBAP)(x)CuOAc preferably to form the insoluble tetranuclear (npBAP)(2)(CuOAc)(4) complex 1. The crystal structure analysis of 1 center dot 2CH(2)Cl(2), grown from CH2Cl2-hexane, reveals two mu(2)-P coordinated ligands, folding the Cu-4 ring with each two short distances of the cyclic copper(I) acetate tetramer to a butterfly arrangement. AIM analysis of the omega B97-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.