Synthesis and molecular structure of tetranuclear Cu4P4 complexes with R2P-O-PR2 ligands

The reaction of secondary phosphine oxides R2P(O)H 1 with Cu(OAc)2 under nitrogen atmosphere produced complexes [(R2P)2O(CuOAc)2]22. A rapid ligand exchange took place when treating complexes 2 with NH4Cl to generate [(R2P)2O(CuCl)2]23 in good yields. The structures of 3 were determined by X-ray crystallography, showing that the geometries of these tetranuclear copper complexes vary with the R group of the phosphorus units. Compared to complexes 2 which are air sensitive, complexes 3 are stable under air.69