ALKANEDIYL AND RELATED DERIVATIVES OF PERMETHYLHAFNOCENE

The reactions of Cp*2HfH2 (Cp* = (eta(5)-C5Me5)) with alpha,omega-dienes (1,3-butadiene, 1,4-pentadiene, 1,5-hexadiene and 1,6-heptadiene) in a 2:1 molar ratio yield the new binuclear alkanediyl derivatives Cp*2-(H)Hf(CH2)nHf(H)Cp*2 (n = 4-7). The reactions of Cp*2HfH2 with the same dienes in a 1:1 molar ratio lead to the mononuclear compounds Cp*2(H)Hf(eta(3)-CH2CHCHCH3), Cp*2HfCH2(CH2)2CH(CH3), Cp*2- activated HfCH2(CH2)3CH(CH3), and the alpha-hafna-omega-alkene Cp*2(H)HfCH2(CH2)4CH = CH2, respectively. Allene reacts with Cp*2HfH2 (1:1) to cleanly afford the allyl hydride derivative, Cp*2(H)Hf(eta(3)-CH2CHCH2); reaction with a 1:2 ratio yields a mixture of products, one of which appears to be Cp*2(H)Hf(CH2)3Hf(H)Cp*2. Reaction of Cp*2HfH2 with acetylene yields Cp*2(H)HfCH = CH2, which does not react with excess Cp*2HfH2 to yield the ethanediyl derivative. 1,3-Pentadiene and Cp*2HfH2 cleanly yield Cp*2(H)Hf(eta(3)-CH2CHCHCH2CH3). The thermal stabilities and reactions of some of these derivatives with excess diene, ethylene, CO, H2, and H2O have been investigated. The possibility of extending this chemistry to the permethyltitanocene and permethylzirconocene systems has also been explored.