Carbon-13 nuclear magnetic resonance spectra of tungsten and molybdenum carbonyl derivatives

Abstract

¹³ C N.m.r. data are presented for the series of complexes (CO)_6–nML_n(where M = Mo or W; L = alkylphosphine, alkyl phosphite, bisdiphenylphosphinoethane, bisdiphenylphosphinomethane, and n= 1 or 2) and for the corresponding free ligands. Chemical shifts and coupling constants for the co-ordinated carbon monoxide and ligand carbons are compared with results from other spectroscopic techniques. The chemical shift of co-ordinated carbon monoxide is found to reflect the charge donor ability of L. The phosphorus to carbon monoxide coupling constants vary in a similar way to phosphorus–phosphorus coupling constants in this class of compounds and a dependence of ¹J M–¹³CO on s-electron density at the metal atom is suggested.