Microcalorimetric studies. Enthalpies of formation of Cr(PF3)6 and Ni(PF3)4

Abstract

Measurements of the heats of iodination of hexakis(trifluorophosphine)chromium(0) and of tetrakis(trifluorophosphine)nickel(0) were carried out by high temperature microcalorimetry. Standard enthalpies of formation were derived: ΔH^°_f(Ni(PF₃)₄, liq)=–961.9 ± 3 kcal mol^–1(–4025 ± 12 kJ mol^–1), ΔH^°_f(Cr(PF₃)₆, c)=–1446.4 ± 4 kcal mol^–1(–6052 ± 17 kJ mol^–1).

The mean bond dissociation energies, D(Ni—PF₃) and D(Cr—PF₃) were evaluated as 35.2 ± 0.8 and 25.5 ± 1 kcal mol^–1 respectively; these values compare very closely with the values D(Ni—CO) and D(Cr—CO) in Ni(CO)₄ and Cr(CO)₆.