Combined quantum chemical and mass spectrometry study of [Ge,C,H](+) and its neutral counterpart

The cation [Ge,C,H](+) has been generated by the electron ionisation of tri chloromethylgermane. Collisional activation experiments were used to establ ish a Ge-C-H connectivity in this species, for which a significant fraction of the ion population was found to survive neutralisation-reionisation mas s spectrometry (NRMS) experiments. Thus, the neutral counterpart [Ge,C,H](0 ) is stable on a microsecond timescale, Becke's 3 parameter hybrid density functional (B3LYP) was used to map the ion and neutral potential-energy sur faces, in conjunction with double-zeta and triple-zeta basis sets. The comp utational results obtained using the triple-zeta basis sets suggest that, f or the cation, the global minimum is the high spin (3)Sigma GeCH+, with the first Ge-C-H excited state, (1)Sigma GeCH+, approximately 39 kcal mol(-1) less stable. The lowest energy ion structure with H-Ge-C connectivity is be nt ((3)A " HGeC+, angle H-Ge-C = 126.3) and 69 kcal mol(-1) less stable tha n the global minimum. For the neutral, a doublet ((2)pi) with Ge-C-H connec tivity is predicted to be the global minimum. The classical barrier for the neutral 1,2-hydrogen shift reaction on the doublet surface is negligible ( 0.1 kcal mol(-1)), while the smallest barrier for the cation is 13.0 kcal m ol(-1), corresponding to ((3)A ") HGeC+ --> ((3)Sigma) GeCH+. Natural bond order analysis has been used to establish the order of the metal-carbon bon d for selected states of both the neutral and the ion. Neutral and cationic isomers with Ge-C triple bonds were found to be high-energy excited states , with the metal-carbon bonds in the cation and neutral ground states of or der 2.0 and 2.5, respectively. The instability of Ge-C triple bonded specie s is attributed to the energy required for electronic promotion in the meta l in order to achieve a hybrid configuration suitable for the formation of such a bond.