GAS-PHASE REACTIONS OF C+(P-2) AND SI+(P-2) WITH OXYGEN BASES - A G2 AB-INITIO MOLECULAR-ORBITAL STUDY

G2 ab initio molecular orbital theory has been used to study the relative stabilities of the different products of the reactions of C+(2P) and Si+(2P) with several oxygen bases in the gas phase. The reactions of Si+ and C+ with formaldehyde and methanol as well as those of C+ with silanone and silanol were considered. Significant differences in C+ and Si+ reactivity have been found in all cases, as a consequence of the greater electronegativity of carbon with respect to silicon and to the enhanced stability of the Si-O linkages, owing to their sizeable Si+-O- polarity. Consistent with this, methyl substitution, for instance, considerably stabilizes these oxygen-containing cations when the substituted center is the silicon rather than the oxygen atom. On the contrary, silyl substitution is more stabilizing when the substituted center is the oxygen atom.