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Department of Chemistry

Dr Keith B. Dillon

Emeritus Reader in the Department of Chemistry
Telephone: +44 (0) 191 33 42122

(email at k.b.dillon@durham.ac.uk)

Research Interests

Principal research interests are the coordination chemistry of main-group elements, particularly phosphorus, tin, boron, zinc and their analogues, both as acceptors (Lewis acids) and as donors (Lewis bases) towards other metal centres, together with the application of radio-frequency (NMR and NQR) spectroscopic techniques to inorganic systems. Since many of the compounds studied are air- and/or moisture-sensitive, these have to be handled using glove-box, vacuum line or Schlenk line techniques. We rely extensively on multinuclear NMR spectroscopy, including 31P,19F,11B and 119Sn nuclei as appropriate, for characterisation of materials, supported by excellent Departmental services for X-ray crystallography, elemental analysis and sometimes mass spectrometry. Current emphasis is on:

Cyclic triphosphenium ions and related species

Several new cyclic triphosphenium ions, and some arsenic analogues, have been synthesised, a number of which have been characterised by X-ray crystallography.1 Their reactions with protonating and alkylating agents are currently under investigation2, as well as their donor properties to transition metal fragments such as platinum(II) species. Part of this work on novel four-membered rings is being carried out in collaboration with a research group at the Technical University of Munich.3

Low-coordinate main-group species and their metal complexes

The stabilisation by bulky electron-withdrawing ligands, usually aromatic groups with CF3 substituents, of novel and unusually-coordinated main group and transition metal species. These include derivatives of Groups 154, 145 and 13.6 Very recently we have extended these studies to zinc(II) compounds, where a very interesting tetrameric cubane structure has been established for the first example to be isolated. We are particularly interested in derivatives containing multiple bonds, suchasdiphosphenes, phosphaalkenes and phosphaalkynes An air-stable diphosphene and various phosphaalkenes have already been synthesised. Their coordination chemistry towards transition metal fragments is then of interest, since they may bond in η1 (via the lone pair on P) or η2 (via the π system of the multiple bond) modes, or by a combination of these. The synthesis of new platinum(II) complexes, to be screened for possible anti-cancer activity, is an integral part of this work. Tests on a diphosphene complex prepared here have shown anti-tumour properties against various types of cancer. We have established a novel high-yield route to the synthesis of unsymmetrical diphosphenes, and hope to extend this to analogous hetero- and homo-nuclear species. Part of this work is being carried out in collaboration with a research group at the University of Sussex.

Phosphoranides and Six-coordinate Phosphorus(V) Derivatives

We are interested in the synthesis and structural characterisation of novel hypervalent phosphorus(III) anionic species (phosphoranides), which are important models for the intermediates in nucleophilic substitution reactions at phosphorus(III) centres. In addition, structure and isomerism in anionic six-coordinate phosphorus(V) species have been investigated, and many configurations have been successfully assigned from analysis of NMR data.

References

  1. R. J. Barnham, R. M. K. Deng, K. B. Dillon, A. E. Goeta, J. A. K. Howard and H. Puschmann, Heteroatom Chem., 2001, 12, 501
  2. K. B. Dillon and R. J. Olivey, Heteroat. Chem., 2004, 15, 150.
  3. K. B. Dillon, P. K. Monks, R. J. Olivey and H. H. Karsch, Heteroat. Chem., 2004, 15, (in press).
  4. A. S Batsanov, S. M. Cornet, K. B. Dillon, A. E. Goeta, P. Hazendonk and A. L. Thompson, J. Chem. Soc., Dalton Trans., 2002, 4622.
  5. A. S Batsanov, S. M. Cornet, K. B. Dillon, A. E. Goeta,, A. L. Thompson and B. Y. Xue, Dalton Trans., 2003, 2492.
  6. S. M. Cornet, K. B. Dillon, C. D. Entwistle, M. A. Fox, A. E. Goeta, H. P. Goodwin, T. B. Marder and A. L. Thompson, Dalton Trans., 2003, 4395.