Silicon bond enthalpy terms

Table 10.2 compares some bond enthalpy terms for single bonds in carbon compounds and in silicon compounds. 

A recent analysis of thermochemical data based on relationships between enthalpies of formation and the unshielded core potential of a moiety X, V ( ), throws some light into the behavior of silicon-hydrogen bonds in methyls lanes. Consider first the case of carbon-hydrogen bonds. The enthalpy of Reaction 12, which is shown to be a linear function of V iZ ) can be expressed in terms of bond dissociation enthalpies. Equation 13. 

The thermochemical correlations, the bond terms, and the unshielded core potential method all support a negligible effect of methyl groups on silicon-hydrogen bond dissociation enthalpies. This constancy is also in keeping with the hydridic nature of Si-H bonds in silanes (23). The effect of other substituents is, by comparison, poorly defined (19), although some results have recently become available. For example, it has been shown that silylation destabilizes Si-H bonds D(H SiSiH -H) = 361 8 kJ/mol (19),... 

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