Thermochemistry of alkaline-earth phenoxides

The standard molar enthalpies of formation of some alkaline-earth metal phenoxides were determined by reaction-solution calorimetry. The results obtained at T = 298.15 K were as follows: Delta H-f(m)o [M(OR)(2), cr]/kJ . mol(-1) (837.9 +/- 7.3) [Mg(OPh)(2)]; -(837.4 +/- 7.2) [Ca(OPh)(2)]; -(888.1 +/- 7.2) [Ca(O-2,6-MePh)(2)], -(828.8 +/- 7.3) [Sr(OPh)(2)]; -(808.6 +/- 7.3) [Ba(OPh)(2)]; -(880.7 +/- 7.3) [Ba(O-2, 6-Me2Ph)(2)]. Together with an appropriate Born-Haber cycle, these results allow the calculation of lattice energies for the [M(OR)(2)] compounds. The thermochemical radii of the anions OR- were obtained using the Kapustinskii equation and the lattice energies previously determined. A set of lattice energies and standard molar enthalpies of formation for alkaline-earth metal phenoxides [M(OR)(2), M = Mg, Ca, Sr, Ba; R = OPh, 2,6-Me2OPh], was presented. Estimates for these properties for unmeasured compounds were made based on a model first applied to aliphatic alkaline metal alkoxides. (C) 2005 Elsevier Ltd. All rights reserved.