An NMR study of some seven-coordinate organophosphine carbonyl iodide derivatives of molybdenum(II) and tungsten(II)

Abstract

The seven-coordinate complexes [MI 2(CO) 3L 2] (M = Mo, L = PMe 2Ph; M = W, L = PMe 2Ph, PMePh 2 or PPh 3) have been studied by variable temperature 31P-{ 1H} NMR spectroscopy; a fluxional process is observed and activation energies (Δ G ≠# = 52–57 kJ mol −1) have been calculated from coalescence temperatures. Low temperature 13C-{ 1H} and 31P-{ 1H} spectra suggest that the lowest energy configuration of [WI 2(CO) 3(PMe 2Ph) 2] is based on that of a carbonyl ligand face-capped octahedron with overall Cs symmetry with the PMe 2Ph ligands trans, and the two remaining carbonyl ligands presumably cis.