Thermochemical and structural studies of Cu(II) and Ni(II) complexes with N, N-diethyl- N′-pivaloylthiourea

Abstract

The standard ( p 0=0.1 MPa) molar enthalpies of formation of crystalline bis( N, N-diethyl- N′-pivaloylthioureato)copper(II), Cu(PVET) 2, and bis( N, N-diethyl- N′-pivaloylthioureato)nickel(II), Ni(PVET) 2, were measured, at T=298.15 K, by solution–reaction isoperibol calorimetry. The standard molar enthalpies of sublimation, at T=298.15 K, of both complexes were obtained using a Knudsen effusion technique. These values were used to derive the standard molar enthalpy of formation of Cu(PVET) 2 and Ni(PVET) 2 in gaseous phase, and to evaluate the difference between the mean metal–ligand and the hydrogen–ligand bond dissociation enthalpies, in these compounds. The NH homolytic bond dissociation enthalpy in N, N-diethyl- N′-pivaloylthiourea ligand (HPVET) was calculated by high-level density functional theory based calculations. The three-dimensional structures of Cu(PVET) 2 and Ni(PVET) 2 are presented and show a planar coordination around the metal in both molecules.