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

Article abstract of DOI:10.1016/0022-328X(91)86147-I

The seven-coordinate complexes (M = Mo, L = PMe2Ph; M = W, L = PMe2Ph, PMePh2 or PPh3) have been studied by variable temperature 31P-<1H> NMR spectroscopy; a fluxional process is observed and activation energies (ΔG^* = 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 is based on that of a carbonyl ligand face-capped octahedron with overall Cs symmetry with the PMe2Ph ligands trans, and the two remaining carbonyl ligands presumably cis.