Cyclopentadienylmetal group 6 metal carbonyl derivatives with 2-propanoneoximato and related ligands

The structures and energetics of species with the stoichiometries (Me2CNO)M(CO)nCp (M = Cr, Mo, W; n = 3, 2, 1; Cp = η5-C5H5) have been studied by density functional theory. The experimental structure Mo2-1S with an NO-dihapto Me2CNO ligand found by X-ray crystallography for (Me2CNO)Mo(CO)2Cp is shown to be the lowest energy isomer by a substantial margin. The expected initial Me2CNOMo(CO)3Cp product from the reaction of NaMo(CO)3Cp with Me2C(NO)Br used to synthesize (Me2CNO)Mo(CO)2Cp is predicted to undergo facile CO dissociation based on ΔH and ΔG values. The energetics of the currently unknown analogous chromium and tungsten systems appear to be similar to that of the molybdenum system. The structures Me2NC(CO)OM(CO)2Cp (M = Cr, Mo, W) with a dimethylcarbamate ligand are much lower energy (Me2CNO)M(CO)3Cp isomers but are clearly not accessible from reactions of the anions CpM(CO)3− with Me2C(NO)Br. The lowest energy structures for the monocarbonyl (Me2CNO)M(CO)Cp are of the type (Me2CN)M(O)(CO)Cp with separate dimethylimino and oxo ligands formed by oxidative addition of the Me2CNO unit to the central metal atom.