Enthalpies of formation of complexes [M(η-C5H5)2(SR)2](M = Mo, W, or Ti; R = C3H7, C4H9, or C6H5); metal–sulphur bond enthalpies

Abstract

Standard enthalpies of formation (kJ mol^–1) at 298.15 K were determined by reaction-solution calorimetry: ΔH_f^⊖{[Mo(η-C₅H₅)₂(SC₆H₅)₂],c}= 309.4 ± 4.8; ΔH_f^⊖{[W(η-C₅H₅)₂{SC₃H₇-n)₂],c}= 23.5 ± 5.6; ΔH_f^⊖{[Ti(η-C₅H₅)₂(SC₃H₇-n)₂],c}=–253.0 ± 9.7; ΔH_f^⊖{[Ti(η-C₅H₅)₂(SC₆H₅)₂],c}= 65.8 ± 7.9; and ΔH_f^⊖{[Ti(η-C₅H₅)₂(S₂C₆H₃CH₃)]}= 1.9 ± 9.4. From these data the metal–sulphur mean bond-dissociation enthalpies (D) and bond-enthalpy terms (E) have been derived, using extended-Hückel molecular-orbital calculations to take account of changes in structure upon dissociation.