THERMOCHEMISTRY OF COMPLEXES OF PYRIDINE AND PICOLINES WITH PHENYLDIHALOARSINES

The complexes PhAsX2.L, where L = pyridine (py), beta- or gamma-picoline (beta- or gamma-pico) and X = Cl, Br or I, were synthesized and characterized by melting point, elemental analysis, thermogravimetric studies and infrared spectroscopy. The standard enthalpies (DELTA(r)H-kelvin) for the Lewis acid/base reactions were determined from the enthalpies of dissolution in 25% ethanolamine in ethanol of the complexes, phenyldihaloarsines and ligands at 298.15 K. The following thermochemical parameters for the complexes were calculated from DELTA(r)H-kelvin values and thermochemical cycles: the standard enthalpies of formation (DELTA(f)H-kelvin), the standard enthalpies of decomposition (DELTA(D)H-kelvin), the lattice standard enthalpies (DELTA(M)H-kelvin) and the standard enthalpies of the Lewis acid/base reactions in the gaseous phase (DELTA(r)H-kelvin(g)). The mean standard enthalpies of arsenic-nitrogen bonds (DBAR(As-N)) were estimated.