Bonding Studies of Compounds of Boron and the Group IV Elements. VIII. Heats of Hydrolysis and Bond Energies for some Trimethylmetalyl Derivatives Me 3M-X (M = Si, Ge, and Sn).

摘要

The heats of hydrolysis, in aqueous 1M-hydrochloric acid, of one silicon, five germanium, and eight tin(IV) compounds of type (Me3M)nX (where M = Si, Ge, or Sn, n = 1-3, and X is a univalent ligand in which the donor atom adjacent to M is N, O, S, Cl, Br, or I) to give (Me3Si)2O. (Me3Ge)2O, and (Me3SnOH)2 have been measured. From these, standard heats of formation have been calculated. Gas-phase enthalpies of formation of these compounds and thermochemical bond energy terms E(M-X) have been calculated. Group trends show that, for constant X, E(C-X) < E(Si-X) > E(Ge-X) > E(Sn-X), whereas E(C-Y) > E(Si-Y) (Y = H or Me). Another conclusion is that the 'softness' (in terms of heats of formation of reactions) of the acids Me3M(+) increase in the order C < Si < Ge < Sn; several chemical reaction types are examined in this light. (Modified author abstract)