关键词: 过渡金属钨有机化合物, 氢转移反应, 超共轭效应

The theoretical studies on a series of α-hydrogen shift reactions of the organometallic tungsten complexes were carried out with the density functional theory B3LYP method.The optimal structures of the reactants, transition states and the products were determined.Calculated results indicate that in all of the 12 transition states studied in this work the sp² hybridization has been adopted by the central carbon atoms, from which the hydrogen atom has shifted.Both electron donating group and electron withdrawing group, that delocalize the unpair electron in p_z orbital of the carbon atom in some way, will lead to a lower reaction barrier.There exists the highest barrier when the substituent in the position R¹ or R² is a hydrogen atom, because the 1s orbital of hydrogen atom cannot lead to an effective match with the p_z orbital of the central carbon atom.The most preferable substituents are methyl groups for positions R¹ and R², due to the existence of a hyperconjugation effect between the p_z orbital of the central carbon atom and one of the C—H bond in methyl group.For the positions R³ and R³ the most favorite substituents are silyl groups SiH 3, which stablize the unpair electron of the central carbon atom by the orbital interaction through the metal atom.

Key words: organometallic tungsten complex, α-hydrogen shift reaction, hyperconjugation effect