Jump to main content
Jump to site search

Issue 6, 1998
Previous Article Next Article

Density functional study of hydrogen exchange and methane elimination from bis(cyclopentadienyl)tungsten methyl hydrides and their ansa-bridged analogues

Abstract

Theoretical calculations have been carried out using density functional theory on the hydrogen exchange and methane elimination reactions of [W(η-C5H5)2(Me)H] and [W{(η-C5H4)2CH2}(Me)H]. In both cases the hydrogen exchange proceeds along a similar reaction path on which lies a η1-H σ complex. The midpoint of the exchange reaction is a η2-H,H σ complex. For [W(η-C5H5)2(Me)H] a transition state is proposed which is calculated to lie 81 kJ mol–1 above the ground state. This compares with an experimental free energy of activation of 106 kJ mol–1 for [W(η-C5H5)2(Me)D]. Elimination of methane is calculated to have an overall reaction energy of 19.6 kJ mol–1 for [W(η-C5H5)2(Me)H] and 78.3 kJ mol–1 for [W{(η-C5H4)2CH2}(Me)H]. The activation energy for elimination from the two compounds is estimated as around 80 and 85 kJ mol–1 respectively. The principal reason for the relative stability of the [W(η-C5H5)2] product is its relaxation to a parallel ring triplet state which is calculated to lie 67.9 kJ mol–1 below the lowest excited singlet state. For [W{(η-C5H4)2CH2}] the singlet and triplet states are separated by 13.3 kJ mol–1 with the rings inclined at an angle constrained by the ansa bridge.

Back to tab navigation

Article type: Paper
DOI: 10.1039/A708411K
Citation: J. Chem. Soc., Dalton Trans., 1998,0, 1057-1062
  •   Request permissions

    Density functional study of hydrogen exchange and methane elimination from bis(cyclopentadienyl)tungsten methyl hydrides and their ansa-bridged analogues

    J. C. Green and C. N. Jardine, J. Chem. Soc., Dalton Trans., 1998, 0, 1057
    DOI: 10.1039/A708411K

Search articles by author

Spotlight

Advertisements