Synthesis and X-ray crystal structures of dimeric nickel(0) and tetrameric copper(I) iodide complexes of 2-diphenylphosphino-3-methylphosphinine

Article abstract of DOI:10.1016/S0022-328X(97)00071-5

The dimer [Ni₂(μ-CO)(CO)₂(μ-1)₂] 2 has been prepared by two different procedures which involve the reaction of the 2-diphenylphosphino-3-methylphosphinine ligand 1 with either Ni(COD)₂ or NiBr₂ · DME/Zn under CO atmosphere. The crystal structure of 2 has been determined by X-ray crystallography. As the analogous dppm complex, 2 adopts a W-frame structure with two bridging ligands 1, two terminal carbonyl ligands and one bridging carbonyl ligand. An electrochemical study reveals that the electron density in the Ni₂ core is considerably reduced in 2 compared to the dppm complex. The reaction of 1 with two equivalents of copper iodide yields the tetranuclear complex [Cu₄(μ-1)₂(μ₄-1)₂(μ-1)₂] 3 which has been identified by an X-ray diffraction study. The structure of 3 consists of an octahedron having a square planar Cu₄ base bridged by two ligands 1 and two μ²-iodo atoms. The most surprising feature of this structure concerns the coordination of the two other iodide atoms respectively located at each apex of the octahedron, which display a face μ⁴-face-bridging bonding mode.