Bonding studies of organometallic compounds of boron and the group IV elements. Part I. Heats of hydrolysis and bond energies for some trimethylsilyl derivatives

Abstract

The heats of hydrolysis, in aqueous 1M-hydrochloric acid, of nine trimethylsilyl compounds of type (Me₃Si)_nX to give hexamethyldisiloxane and XH_n, have been measured. By use of separately measured or known heats of formation of (Me₃Si)₂O and XH_n in 1M-HCl, standard heats of formation were calculated as follows: ΔH_f°(Me₃SiCl, liq.)=–91·8 ± 0·8; ΔH_f°(Me₃SiBr,liq.)=–77·9 ± 0·8; ΔH_f°(Me₃SiOH, liq.)=–130·3 ± 0·8; ΔH_f°(Me₃Si·SBuⁿ, liq.)=–91·0 ± 0·8; ΔH_f°(Me₃Si·NHMe, liq.)=–62·5 ± 0·8; ΔH_f°[(Me₃Si)·NMe₂, liq.]=–66·6 ± 0·8; ΔH_f°[(Me₃Si)₂NH, liq.]=–123·9 ± 1·6; ΔH_f°[(Me₃Si)₂NMe, liq.]=–116·1 ± 1·6; and ΔH_f°[(Me₃Si)₃N, solid]=–173·2 ± 2·2 kcal./mole. Si–X relative bond energies [with respect to E(Si–Cl)= 96·6 kcal./mole] are derived; and it is noteworthy that E(Si–N) does not vary greatly with environment. A Zahn-type interaction scheme was applied to series of CN and SiN compounds.