Thermochemistry of adducts of tin(IV) bromide with amide and thioamide ligands

The compounds SnBr4. nL (where L is urea (u), 1,1-dimethylurea (1,1-dmu). 1 ,3-dimethylurea (1,3-dmu), tetramethylurea (tmu), thiourea (tu), tetramethy lthiourea (tmu) or 1-allyl-2-thiourea (atu) and n = 2, 3 or 4) were synthes ized and characterized by melting points, elemental analysis, thermal analy sis and IR spectroscopy. The enthalpies of dissolution of the adducts, tin( IV) bromide and ligands in methanol were measured and by using thermochemic al cycles the following thermochemical parameters for the adducts have been determined: the standard enthalpies for the Lewis acid/base reaction (Delt a H-r(0)); the standard enthalpies of formation (Delta H-f(0)) the standard enthalpies of decomposition (Delta H-D(0)); the lattice standard enthalpie s (Delta H-M(0)) and the standard enthalpies of the Lewis acid/base reactio n in the gaseous phase (Delta H-r(0)(g)). The mean standard enthalpies of t he tin-oxygen ((D) over bar ((Sn-O))) and tin-sulphur ((D) over bar ((Sn-S) )) bonds have been estimated. (C) 2001 Elsevier Science B.V. All rights res erved.