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

• Published in: Inorganica Chimica Acta 2003-12, Vol.356, p.95-102
• Main Authors: Ribeiro da Silva, Manuel A.V, Ribeiro da Silva, Maria D.M.C, da Silva, Luı́s C.M, Gomes, José R.B, Damas, Ana M, Dietze, Frank, Hoyer, Eberhard
• Format: Article
• Language: English
• Subjects: bis( N, N-Diethyl- N′-pivaloylthioureato)copper(II); bis( N, N-Diethyl- N′-pivaloylthioureato)nickel(II); Dissociation enthalpy; Enthalpy of formation; Enthalpy of sublimation; Thermochemistry
• ISSN: 0020-1693; 1873-3255
• DOI: 10.1016/S0020-1693(03)00268-8

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. The enthalpy of the hydrogen binding to the nitrogen atom of N, N-diethyl- N′-pivaloylthiourea and the mean metal–ligand dissociation enthalpy of bis( N, N-diethyl- N′-pivaloylthioureato) M(II), M=Cu or Ni, were measured by combination of experimental and computational approaches. The crystal and molecular structures of these complexes were determined by X-ray diffraction.