A DFT study of germane activation in ruthenium complexes. σ-coordination versus oxidative addition
Abstract
The coordination of GeH4 to the ruthenium complex RuH2(η2-H2)2(PH3)2 can lead to oxidative addition or σ-bond coordination of the germane. The corresponding germyl or σ-isomers have been optimized by DFT using the B3LYP hybrid functional. The most stable isomer corresponds to a germyl bis(dihydrogen) complex RuH(GeH3)(η2-H2)2(PH3)2 (1T-b1) with trans phosphines. It is only 2 kcal mol−1 below the σ-isomer RuH2(η2-H2)(η2-H–GeH3)(PH3)2 (1C-a1). This is in contrast to what has been previously observed in the corresponding silane chemistry, in which σ-coordination was favoured. However, calculated binding energies for GeH4 or SiH4 to the RuH2(H2)(PH3)2 fragment are very similar (−21.3 and −22.2 kcal mol−1, respectively). The nature of the metal–germane interaction is analysed by natural bond orbital (NBO) calculations.