Thermochemistry of adducts of some bivalent transition metal bromides with aniline

The compounds [MBr 2(an) 2] (where M is Mn(II), Fe(II), Co(II), Ni(II), Cu(II) or Zn(II); an = aniline) were synthesized and characterized by melting points, elemental analysis, thermal studies, and electronic and IR spectroscopy. The enthalpies of dissolution of the adducts, metal(II) bromides and aniline in methanol, aqueous 1.2 M HCl or 25% (v/v) aqueous 1.2 M HCl in methanol were measured. The following thermochemical parameters for the adducts have been determined by thermochemical cycles: the standard enthalpies for the Lewis acid/base reactions (Δ r H°), the standard enthalpies of formation (Δ f H°), the standard enthalpies of decomposition (Δ D H°), the lattice standard enthalpies (Δ M H°) and the standard enthalpies of the Lewis acid/base reactions in the gaseous phase (Δ r H°(g)). The mean bond dissociation enthalpies of the M(II)–nitrogen bonds ( D ¯ ( M N ) ) and the enthalpies of formation of the adducts from the ions in the gaseous phase: M 2+ (g) + Br − (g) + an (g) → [MBr 2(an) 2] (g), (Δ fi H°) have been estimated.