Solid-state phosphorus-31 NMR investigations of phosphido-bridged complexes: chemical shift bond angle correlations

Abstract

Solid-state CP/MAS {sup 31}P NMR spectra were measured for a series of phosphido-bridged diiron complexes Fe{sub 2}(CO){sub 6}({mu}-X)({mu}-PPh{sub 2}), where X is a three-electron-donor hydrocarbyl ligand, and for the isostructural series M{sub 2}(CO){sub 6}({mu}{sub 2}-{eta}{sup 2}-C{triple bond}CR)({mu}-PPh{sub 2}) (M = Fe, Ru, Os; R = Bu{sup t}, Pr{sup i}, Ph). The isotropic solid-state shifts correlate rather well with the corresponding shifts in solution, the largest difference being 8.9 ppM, indicating that there are no phase-dependent structural features. Analysis of the principal elements of the shielding tensor by the spinning-sideband method showed a good correlation between the individual tensor components {sigma}{sub 11}, {sigma}{sub 22}, and {sigma}{sub 33} or composite measures of these and the M-P-M bond angle. The increase of isotropic shift with M-P-M appears to reflect a large change in the {sigma}{sub 33} tensor component, and the correlations observed suggest that all of the compounds studied have common shift tensor orientations with respect to the molecular frame. Experimental techniques for optimizing the acquisition of solid-state {sup 31}P spectra are discussed. 15 refs., 7 figs., 4 tabs.