Ether Cleavage Following Insertion of Carbon Monoxide into the Tantalum-Silicon Bond of (Eta 5-C5Me5)Ta(SiMe3)Cl3

摘要

The tantalum silyl Cp*Ta(SiMe3)Cl3 (3, Cp* = eta 5 - C5Me5), prepared from Cp*TaCl4 and Al(SiMe3)3.OEt2, reacts with carbon monoxide (10-100 psi) to yield products which are determined by the reaction solvent. In ethers with Beta-CH3 groups (diethyl ether and 2-methyltetrahydrofuran), insertion of CO leads to cleavage of an ether carbon-oxygen bond to produce the cyclic complexes Cp*Cl3TaOCH(SiMe3)C(O)OR (4, R = Et and 6, R = (CH2)3CH=CH2). Compounds 4 and 6 have been characterized by elemental analysis, IR and NMR (1H and 13C) spectroscopy, labelling studies and derivative chemistry. These reactions are believed to involve addition of the ethers to an intermediate ketene complex derived from CO insertion. In tetrahydrofuran, the reaction of 3 with CO leads to reductive elimination of Me3Si-Cl with formation of Cp*TaCl2(CO)2(THF).