The complexes AsX(3) . nL(where L is triphenylamine (NPh(3)), triphenylphosphine (PPh(3)) or triphenylarsine (AsPh(3)); n = 1, 3/2, 2 or 3, and X is Cl, Br or I) were synthesized and characterized by melting points, elemental analysis, thermal studies, mass spectra and IR spectroscopy. From the enthalpies of dissolution in 25 or 50% diethylether in acetone, 10% ethanolamine in acetone or 20% cyclohexane in acetone, and using the appropriate thermochemical cycles, the following thermochemical parameters for the adducts have been determined: the standard enthalpies for the Lewis acid/base reaction (Delta(r)H(theta)), the standard enthalpies of formation (Delta(f)H(theta)), the standard enthalpies of decomposition (Delta(D)H(theta)), the lattice standard enthalpies (Delta(M)H(theta)) and the standard enthalpies of the Lewis acid/base reactions in the gaseous phase (Delta(r)H(theta)(g)). The mean standard enthalpies of arsenic-group-V element bonds have been estimated.279167175