Thermochemistry of inorganic solids. 3. Enthalpies of formation of solid metal oxyhalide compounds

Abstract

Examination of available standard enthalpies of formation of solid oxyhalide compounds (total of 35) of various metals from main groups to actinide series shows that the standard enthalpies of formation of these compounds can be correlated quantitatively with the enthalpies of formation of the corresponding oxides and halides of the same oxidation states by the equation ..delta..H/sub f//sup 0/(MO/sub x/X/sub y/) = a((2x/z)..delta..H/sub f//sup 0/(MO/sub z/2/) + (y/z)..delta..H/sub f//sup 0/(MX/sub z/)) + C, where z = 2x +y = the formal oxidation state of the metal, MO/sub x/X/sub y/ is the oxychloride, and MO/sub z/2/ and MX/sub z/ are the corresponding oxide and halide of the same oxidation state z. C is a correction factor in kcal/mol. For main and first transition-metal compounds, a = 1 and C = 0. For trivalent-state lanthanides, a = 2.155 +/- 0.12 and C = 257.8 +/- 1.3 or 250.4 +/- 1.2 kcal/mol. For tetravalent oxychlorides, a = 1 and C = 5 kcal/mo. For penta- and hexavalent compounds, a = 1 and C = 0. 6 references, 2 figures, 6 tables.