A gas-phase kinetic study of the reaction of silylene with germane: absolute rate constants, temperature dependence and mechanism

Gas phase kinetic and theoretical studies of reactions of germylenes and dimethylstannylene

“…This is probably the case for the reaction of SiH 2 with SiH 4 , where the calculated barrier lies 48 kJ mol -1 below the initial reactant energy and, accord ing to the experimental data, the rates are virtually colli sion controlled. 54, 55 The secondary barriers are much closer to the threshold energy for the reaction of GeH 2 with GeH 4 and especially for the reaction GeH 2 + SiH 4 (Table 5), which result in slower rates for the GeH 2 inser tions compared to SiH 2 insertion. It seems likely that the second step, viz., rearrangement of the pre reaction com plex (only C1), is fully rate determining (i.e., k -1 >> k 2 , see Scheme 1) for reaction (9).…”

What have we learnt about heavy carbenes through laser flash photolysis studies?

“…It means that the reactions (generally) have negative activation energies. This is illustrated in Tables 5 and 6, containing the Arrhenius parameters for a variety of reactions of SiH 2 16,18,[39][40][41][42][43][44][45][46] and GeH 2 . 14,19,47,48 The values are discussed in more detail later but the key point is that the negative activation energies led to the idea that these reactions involve intermediate complexes.…”

Gas‐Phase Chemistry and Mass Spectrometry ofGe‐,Sn‐ andPb‐Containing Compounds

“…Reaction 46 has been found to be pressure-dependent, so that formation of Ge 2 H 6 is best described as a third body assisted association. The analogous reaction to 46, but using SiH 2 , reveals that silylene insertion in the Ge−H bond is faster than that of the corresponding germylene 237 . These fast insertion reactions display a negative activation energy 238 , and high level ab initio calculations 236 confirm the suggestion that these reactions proceed through a transition state where a hydrogen bridge between the two germanium atoms mediates formation of the final product in reaction 46.…”