Thermochemistry of some indium trihalide adducts

Abstract

The condensed-phase heats of formation (–ΔH_f) of the crystalline adducts InX₃,3py (X = Cl, Br, and I), InX₃,2Me₃N (X = Cl and Br) and InI₃,Me₃N from liquid donors and solid acceptors have been obtained by measuring the heats of solution of the donor, acceptor, and adduct in 2M-hydrochloric acid at 25°. The values obtained for –ΔH_f were: InCl₃,3py, 39·1(1); InBr₃,3py, 41·1(4); InI₃,3py, 40·3(2); InCl₃,2Me₃N, 33·3(6); InBr₃,2Me₃N, 37·8(7); InI₃,Me₃N, 22·6(4) kcal. mole^–1(1 kcal. = 4·183 kJ). There is insufficient structural and thermochemical information to calculate absolute values for the gas-phase heats of formation from these data, but it appears that the acceptor strength of the indium trihalides towards these nitrogen donors is relatively insensitive to the halogen atoms involved. This is similar to earlier results for the aluminium and gallium trihalides.