Thermochemistry of adducts of some bivalent transition metal bromides with triphenylphosphine

The compounds [MBrm(L)n] (where M is Mn(II), Fe(II), Co(II), Ni(II), Cu(I) or Zn(II); L = triphenyphosphine (tpp); m = 1 or 2; n = 1.5, 2 or 3) were synthesized and characterized by melting points, elemental analysis, thermal analysis and electronic and IR spectroscopy. The enthalpies of dissolution of the adducts, metal(II) bromides and triphenylphosphine in methanol or in a solution of 10% (v/v) triethanolamine, 40% (v/v) acetonitrile and 50% (v/v) methanol were measured and by using thermochemical cycles, the following thermochemical parameters for the adducts, have been determined: the standard enthalpies for the Lewis acid/base reaction (ΔrHθ), the standard enthalpies of formation (ΔfHθ), the standard enthalpies of decomposition (ΔDHθ), the lattice standard enthalpies (ΔMHθ) and the standard enthalpies of the Lewis acid/base reaction in the gaseous phase (ΔrHθ(g)). The mean bond dissociation enthalpies of the metal(II)-phosphorus bonds (D¯(M−P)) have been estimated.