An investigation of C-S bond activation in transition metal crown thioether complexes using extended Huckel theory and electrospray mass spectrometry

Mullen, G.E.D. and Fassler, T.F. and Went, M.J. and Howland, K. and Stein, B. and Blower, P.J. (1999) An investigation of C-S bond activation in transition metal crown thioether complexes using extended Huckel theory and electrospray mass spectrometry. Journal of the Chemical Society-Dalton Transactions (21). pp. 3759-3766. ISSN 0300-9246. (The full text of this publication is not available from this repository)

The full text of this publication is not available from this repository. (Contact us about this Publication)

Abstract

Complexes of Re and Tc with 1,4,7-trithiacyclononane (9S3) differ from their later transition metal analogues in that their d(6) form ([M(9S3)(2)](+)) undergoes instantaneous C-S bond cleavage yielding ethene and [M(9S3)L](+) (L= SCH2CH2SCH2CH2S), a stable metal(III) thiolate complex, cleanly in aqueous solution. This contrast is interpreted as signifying increased pi-back donation by Re and Tc, compared to later metals, into ligand C-S sigma* orbitals. In order to validate this hypothesis within an established theoretical framework, and to compare the predicted relative C-S bond lability with relative experimental lability in a series of d(6) analogues, extended Huckel theory (EHT) was used to investigate the bonding (M=Mo, Tc, Ru, Rh or Pd) while electrospray mass spectrometry (ES-MS) was used to compare ethene loss, in a series of analogous complexes (M=Tc, Re, Ru or Os). The C-S overlap populations were smaller for M=Tc-II and Tc-I than for later metal(II) analogues, and were smaller for Tc-I than for Tc-II. Fragment molecular orbitals corresponding to C-S sigma* were more highly populated for M=Tc-II and Tc-I than for later analogues, and also more highly populated for Tc-I than for Tc-II. ES-MS showed that ethene loss from Tc/Re-I and Tc/Re-II complexes occurred at much lower energies than from the Ru/Os-II analogues. EHT supports the hypothesis that C-S activation is caused by pi-back donation into C-S sigma* orbitals, and correctly predicts that ethene loss occurs more readily from rhenium and technetium d(5) and especially d(6) complexes than from later transition metal analogues.

Item Type: Article
Subjects: Q Science
Divisions: Faculties > Science Technology and Medical Studies > School of Physical Sciences
Depositing User: I.T. Ekpo
Date Deposited: 30 Mar 2009 19:47
Last Modified: 30 Mar 2009 19:47
Resource URI: http://kar.kent.ac.uk/id/eprint/16952 (The current URI for this page, for reference purposes)
  • Depositors only (login required):