Direct synthesis of organometallics V. Direct synthesis of isopropylcyclopentadienyl M(I) compounds of Ga, Tl, Mn and Cu via metal vapour cocondensation, and their spectroscopic characterization

Abstract

The cocondensation of metal atoms of Ga, Tl, Cu and Mn with 6,6-dimethylfulvene leads to the formation of Cp iM(I) derivatives (Cp i = C 5H 4CHMe 2) which need — in the case of Cu and Mn — trimethylphosphite as a co-ligand to fill up their coordination sphere. It is remarkable that the synthesis of the thermolabile Cp iGa(I) is possible by using the newly developed cocondensation vessel with a cooled internal drain. The species is stable in solution up to −30°C and is therefore characterized by its 71Ga NMR and MS spectrum and the following reactions. The reaction is believed to pass through a metal fulvene complex in a first step, which is characterized for Ga by quantum mechanical methods. For the gallium case a tucked-in η 6 bonding mode with formation of Ga(II), instead of coordination to an η 5 cylopentadienyl or η 4 fulvene, is observed. ▪ Following the formation of this first intermediate, a complete mechanism is developed by using semiempirical calculations. The resulting geometries and reaction enthalpies are discussed in comparison with the reaction of tin atoms with the fulvene, which ends in the formation of ansa-stannocene. In contrast to this reaction, the cocondensation of cobalt atoms with 6,6-dimethylfulvene in the presence of trimethylphosphite ends in the formation of CoH(P(OMe) 3) 4 instead of a half-sandwich complex.