Some thermodynamic parameters for substituted ammonium salts of the tetramethoxyborate anion

Thermodynamic parameters for the formation of piperidinium tetramethoxyborate from piperidine, trimethoxyborane, and methanol are presented. The results show that the formation of the salt is due to a favourable enthalpy change, the standard entropy change being negative. The fact that similar salts with larger tetra-alkoxyborate anions are thermodynamically unstable is discussed. The derived enthalpy of formation of piperidinium tetramethoxyborate ΔHf° C5H12NB(OMe)4(s)=–1310·91 ± 1·72 kJ mol–1. The derived enthalpy of formation of 2-aminoethylammonium tetramethoxyborate ΔHf°enH B(OMe)4(s)=–1266·5 ± 1·5 kJ mol–1 and of ethylenediammonium ditetramethoxyborate ΔHf°enH2[B(OMe)4]2(s)=–2486·0 ± 2·0 kJ mol–1.