Tetra-nuclear copper complex having P–N–P ligand to P–O–P ligand – synthesis, structural, and mechanistic studies

Abstract

We report the synthesis and structures of three copper(I) complexes, [Cu4(μ3-Cl)2(μ2-Cl)2{μ2-(2,6-Me2C6H3N(PPh2)2)}2] (2), [Cu4(μ3-Cl)2(μ2-Cl)2{μ2-(Ph2POPPh2)}2] (4), and [Cu2(μ2-Cl)2(μ2-PPh2OPPh2)(η1-Ph2PP(=O)Ph2)(PPh3)] (5), and one cobalt complex, [(CoCl2){μ2-2,6-Me2C6H3N(PPh2)2}2][CoCl3NH2(2,6-Me2Ph)] (3). Tetra-nuclear copper complex 2 was prepared in good yield by the reaction of bis(diphenylphosphino)-2,6-dimethylaniline [2,6-Me2C6H3N(PPh2)2] (1) with copper(I) chloride along with triphenylphosphine in methanol. Adding a calculated amount of water and dichloromethane mixture (1 : 10) to 2 produced a second tetra-nuclear copper(I) complex, 4, with a P–O–P backbone, along with a small amount of the unsymmetrical copper(I) complex 5. The cobalt complex 3 was obtained by reaction of 1 with cobalt(II) chloride. The solid-state structures of 2–5 were established by single-crystal X-ray diffraction analysis. In the solid state, both 2 and 4 form a tetra-nuclear copper core. In the 31P{1H} NMR study, we observed the conversion of 2, with P–N–P backbone, to 4, with P–O–P backbone.