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

Abstract

The standard ( p ∘ = 0.1 MPa) molar enthalpies of formation of the crystalline diaquobis(dibenzoylmethanate)nickel(II), Ni( dbm) 2(H 2O) 2, diaquobis(thenoyltrifluoroacetonate)nickel(II), Ni( ttfa) 2(H 2O) 2 bis(monothiodibenzoylmethanate)nickel(II), Ni( dbmS) 2 and bis(monothiothenoyltrifluoroacetonate)nickel(II), Ni(H ttfaS) 2 were determined, at T = 298.15 K, by high precision solution-reaction calorimetry. The standard molar enthalpy of sublimation of the monothiothenoyltrifluoroacetone (H ttfaS) complex was measured by high-temperature Calvet microcalorimetry. From the standard molar enthalpies of formation of the complexes in the gaseous state, the mean nickel(II)-ligand molar dissociation enthalpies, 〈 D m〉(Ni–L), were derived. Δ f H m ∘ (cr) / ( kJ · mol - 1 ) Diaquobis(dibenzoylmethanate)nickel(II), Ni( dbm) 2(H 2O) 2 −993.3 ± 3.8 Diaquobis(thenoyltrifluoroacetonate)nickel(II), Ni( ttfa) 2(H 2O) 2 −2452.0 ± 8.3 Bis(monothiodibenzoylmethanate)nickel(II), Ni( dbmS) 2 −42.1 ± 5.9 Bis(monothiothenoyltrifluoroacetonate)nickel(II), Ni( ttfaS) 2 −1473.5 ± 8.1