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

The standard (p0=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.