Molecular structure and binding energies of monosubstituted hexacarbonyls of chromium, molybdenum, and tungsten: Relativistic density functional study

Relativistic density functional calculations have been carried out for the group VI transition metal carbonyls M(CO)(5)L(M = Cr, Mo, W; L = OH2, NH3, PH3, PMe3, N-2, CO, OC (isocarbonyl), CS, CH2, CF2, CCl2, NO+). The optimized molecular structures and M-L bond dissociation energies, as well as the metal-carbonyl bond energy of the trans CO group, have been calculated. Besides the marked dependence of the trans M-CO bond length on the type of ligand L, such an effect on the that bond energy is also observed. For the chromium compounds, the trans Cr-CO bond length varies from 184 to 199 pm and its bond energy from 242 to 150 kJ/mol. For the molybdenum compounds, the range is 197 to 216 pm and 253 to 128 kJ/mol and, for tungsten, 198 to 214 pm and 293 to 159 kJ/mol. The observed trends can be explained with the pi acceptor strength of the L ligand. (C) 1997 John Wiley & Sons, Inc.