Thermochemical study of the nickel–sulphur bond energy in bis(5-mercapto-2,2,6,6–tetramethylhept-4-en-3-onato-S)nickel(II)

Abstract

iL,I(g) --. ) Ni(g) 3. 2L.(g), AHf.r. = AHf"("iL23-

Standard molar enthalpies of formation of nickel(II) β-diketonates and monothio-β-diketonates

“…In the literature was only found an incomplete work reporting the study of the condensed phase thermochemistry of the bis(monothiodipivaloylmethanate)nickel(II), Ni(DPMS) 2 [18]. The authors have published the results in a form of the difference between the enthalpy of formation of the ligand and of the complex since the standard molar enthalpy of formation of the ligand (monothiodipivaloylmethane) was unavailable.…”

“…The authors have published the results in a form of the difference between the enthalpy of formation of the ligand and of the complex since the standard molar enthalpy of formation of the ligand (monothiodipivaloylmethane) was unavailable. Based on the previous work [20,40] the standard molar enthalpy of formation of the monothiodipivaloylmethane in the gas phase can be estimated as D f H m ðHdpmSÞ ¼ Àð299 AE 11Þ kJ Á mol À1 and, using the reported data [18], the standard molar enthalpy of formation of the bis(monothiodipivaloylmethanate)nickel(II), in the gas and solid phases, can be derived as D f H m ½NiðdpmSÞ 2 ; g ¼ Àð688 AE 24Þ kJ Á mol À1 , and as D f H m ½NiðdpmSÞ 2 ; cr ¼ Àð805 AE 24ÞkJ Á mol À1 . The standard molar enthalpies of formation of the crystalline bis(monothiodibenzoylmethanate)nickel(II), Ni(DBMS) 2 , was determined, independently, in the University of Porto and in the University of Wrocław, using two different reactions, yielding results that are in excellent agreement and so we consider the average of the two experimental determinations.…”

“…Experimental data concerning the molar bond dissociation enthalpy of the enolic hydrogen of b-diketones, D m (O-H, Hbdik, enol, g), are not available, and has been subject of several estimations [9,18,43]. In this paper, we assume for both b-diketones the value derived by Sharp and Richardson [44], (368 ± 25) kJ AE mol À1 , for the D m (O-H, Hbdik, enol, g) in order to derive the AED m ae(Ni-L) and, from that, the mean molar nickel to oxygen bond dissociation enthalpies.…”

“…Besides the extensive work done in the physical chemistry study involving monothio-b-diketonates complexes [2,5,8], so far, there is only one paper reporting the thermochemical study of the bis(monothiodipivaloylmethanate)-nickel(II), Ni(DPMS) 2 [18].…”

Standard enthalpy of formation of bis(diethyldithiocarbamato)nickel(II) at 298 K and the nickel–sulphur bond energy

“…For the octahedral complex [Ni(tu),lBr,, D(Ni-S), uncorrected for ligand-field stabilisation energy, is calculated as 363.4 kJ 38. Apart from the present work, the only square planar nickel(I1) complex containing nickel-sulphur bonds that has been studied calorimetrically is bis(5-mercapt o-2,2 ,6, 6-tetramethylhept-4-en-3-onato-.S)nickel(11) ,39 and D(Ni-S) is reported as 232 & 15 kJ. These data indicate that the thermochemical nickel-oxygen and nickel-sulphur coordinate bond energies are approximately equal and thus for square-planar nickel complexes it may be inferred that the groups NiS,O, _and NiS, are thermochemically equivalent and thus D(Ni-S) for the heptenonatocomplex should be approximately equal to D(N1-S) for bis(diethyldithiocarbamato)nickel(rI).…”