The Homogeneous Hydrogenation of Acetylenes by Dicyclopentadienyltitaniumdicarbonyl

Abstract

The homogeneous hydrogenation of acetylenes and olefins in the presence of dicyclopentadienyltitaniumdicarbonyl (I) was studied. The results of the hydrogenation varied with the acetylene substituent. The relative activating effects of the substituents on the hydrogenation of such acetylenes as RC≡CH and R′C≡CR′ are as follows: R: Ph>t-butyl>n-alkyl, R′ : Ph>n-alkyl. The order is the reverse of that observed with the usual metal catalysts of the VIII group. In order to elucidate the mechanism of hydrogenation, the reaction of the dicarbonyl (I) with various acetylenes was studied, and the structures of the products were discussed.