SOLID-STATE INFRARED AND RAMAN-SPECTRA OF CARBONYL-TERT-BUTYL ISOCYANIDE COMPLEXES OF CHROMIUM(0), MOLYBDENUM(0) AND TUNGSTEN(0), M(CO)6-N(CNBU-T)N(N=1-3)

Vibrational assignments are reported for the room-temperature IR and Raman spectra of three series of solid group 6B metal(0) carbonyl-tert-butyl isocyanide complexes of the general formula M(CO)6-n(CNBu-t)n, where M = Cr, Mo, W and n = 1-3. Sequential replacement of the CO groups by CNBu-t leads to gradual shifts of the v(CN) bands to higher energies, while the v(CO) bands shift to lower energies. These results provide good evidence for the stronger sigma-donor and weaker pi-acceptor capacities of the CNBu-t ligand compared with those of CO.