P-31 chemical shift anisotropies of trimethyl- and triphenylphosphine-substituted Group 6 metal pentacarbonyl complexes

The P-31 chemical shift tensor components and anisotropies of the trimethyl - and triphenylphosphine complexes of the group 6 metal pentacarbonyls, M(C O)(5)PR3 (M = Cr, Mo, W and R = Me, Ph), have been measured using solid-sta te CP-MAS P-31 NMR spectroscopy For the trimethylphosphine derivatives, the chemical shift tensors have near axial symmetry and the shift tensor compo nents are in reasonable agreement with the calculated values for the chromi um and molybdenum complexes. In the triphenylphosphine complexes, the tenso rs are asymmetric due to the different torsion angles of the phenyl rings. The trend to higher shielding of the isotropic P-31 chemical shifts on desc ending group 6 arises from changes in the perpendicular components of the s hift tensor. The one-bond coupling constants, (1)J(Mo-95/97-P-31), for the trimethyl- and triphenylphosphine complexes are 129 and 133 Hz, respectivel y.