Bonding studies on zinc, cadmium, and mercury alkyls and amides, Zn(CH 2EMe 3) 2 (E  C or Si) and M[N(SiMe 3) 2] 2 (M  Zn, Cd, or Hg). Heats of Hydrolysis, standard heats of formation, and ZnC and MN (M  Zn, Cd, or Hg) bond energy terms

Abstract

Calorimetric measurements have been carried out on the heats of hydrolysis of the homoleptic zinc alkyls Zn(CH 2EMe 3) 2 (E  C or Si) and bis(trimethylsilyl)-amides M[N(SiMe 3) 2] 2 (M  Zn, Cd, or Hg) at 25 ± 0.01°C in aqueous hydrochloric (1 M; for the Zn compounds) or sulphyric (0.5 M; for the amides) acid. Using appropriate subsidiary data, values were derived for the standard enthalpies of formation Δ H f 0 of the following liquid compounds: Zn(CH 2CMe 3) 2, 175 ± 14; Zn(CH 2SiMe 3) 2, 410 ± 19; Zn[N(SiMe 3) 2] 2, 951 ± 9 (in eq. HCl) or 963 ± 9 (in aqueous H 2SO 4); Cd[N(SiMe 3) 2] 2, 85 ± 21; and Hg[N(SiMe 3) 2] 2, 834 ± 9 kJ mol -1. Using these data, and calculated enthalpies of vaporization, led (via Δ H f 0(g)) to the following relative MC and MN bond energy terms ( E − ): ZnC (CH 2CMe 3), 157; ZnC (CH 2SiMe 3), 195; ZnN, 203 (from HCl experiments); ZnN, 209 (from the H 2SO 4 experiments); CdN, 144; and HgN, 108 kJ mol -1.