Synthesis and Properties of Dicyclopentadienyltantalum(III) Carbonyl Compounds

Reaction of Cp2Ta(H)L (L = C3H6, C4H8, C5H10 and C5H8) with CO under mild conditions gives alkyltantalum carbonyl complexes Cp2Ta(CO)R (R = C3H7, C4H9, C5H11 and C5H9, respectively). Depending upon the position of the olefin relative to the hydride ligand in the hydride-olefin complex, Cp2Ta(CO)H is also formed during the carbonylation reaction. Reduction of Cp2TaCl2 by potassium or t-BuMgCl under one atmosphere of CO affords the very stable compound Cp2Ta(CO)Cl in moderate yields. Reaction of Cp2Ta(CO)Cl with RLi or RMgX does not give the Cp2Ta(CO)R complex

Preparation of (η5-C5H5)2Ti Alkyl Compounds and Reactions with Unsaturated Substrates

Reaction of Cp2TiCl with RLi (R = —CH3, —C2H5, —n-C4H9, —s-C4H9, —t-C4H9) yields the thermally instable TiIII compounds Cp2TiR. Reaction of these compounds with 2,6-xylylisocyanide, phenylisocyanate or carbon dioxide results in insertion of these ligands into the Ti—alkyl bond with formation of iminoacyl, amido and carboxylato derivatives, respectively. In the reaction with ketones a pinacol-type dimerisation is observed