HIGHLY REDUCED ORGANOMETALLICS .33. CARBONYL HYDRIDES OF TITANIUM ANDCORRESPONDING CARBONYLTITANATES

Photopromoted substitution reactions of [(C5R5)Ti(CO)4]- (R = H, Me) w ith organophosphines have been examined for the first time and provide d new zerovalent titanium carbonyls of the general formula [(C5R5)Ti(C O)3(PR3)]-. Disubstituted phosphine derivatives of the formula [(C5R5) Ti(CO)2(dmpe)]- were obtained by the alkali metal naphthalenide promot ed reductive cleavages of titanocene dicarbonyls (C5R5)2Ti(CO)2 (R = H , Me) in the presence of dmpe, i.e., 1,2-bis(dimethylphosphino)ethane. The reductively promoted substitution reaction of (C5Me5)2Ti(CO)2 app ears to be the first report of such a reaction involving a bis(pentame thylcyclopentadienyl)metal complex although corresponding reactions in volving bis(cyclopentadienyl)metal complexes are well-known. Spectral studies on alkali metal salts of [(C5R5)Ti(CO)2(dmpe)]- established th at the cations interacted strongly with the carbonyl oxygens of the an ions and promoted anion decomposition. Alkali metal complexants substa ntially reduced this site-specific ion-pairing interaction and dramati cally improved the thermal stability of the anions in solution and in the solid state. Protonation of the carbonyltitanates provided the fir st examples of carbonyl hydrides of titanium. While hydrides of the mo nophosphine derivatives (C5R5)Ti(CO)3(PR'3)H (R' = Me, Ph) were found to be thermally unstable, the corresponding dmpe derivatives (C5R5)Ti( CO)2(dmpe)H were isolated as pure substances at room temperature. Thes e anions and hydrides have been characterized in solution by IR, H-1 N MR, and C-13 NMR spectroscopy. The carbonyl C-13 chemical shifts of th ese carbonyltitanates are of particular interest in that they represen t the most downfield values (delta 300-320) observed to date for coord inated terminal carbonyl groups in metal carbonyls.