Dr Andrew Hughes, (Director of Education)
(email at email@example.com)
Research interests focus on synthesis, characterisation and stoichiometric and catalytic reactivity studies of early transition metal coordination and organometallic complexes. The common theme that runs through much of our chemistry is the use of a number of early transition-metal amide complexes as starting materials, and exploring their reactions with a variety of different ligands, including bulky cyclopentadienyls, amidines, and other nitrogen donors, and carboranyls.
Much of our chemistry involves working with air- and moisture-sensitive materials using inert-atmosphere glove-box and Schlenk-line techniques. Characterisation involves the use of multinuclear NMR (1H, 13C, and 11B) spectroscopy, as well as mass spectrometry and single crystal X-ray diffraction, in collaboration with Prof. J A K Howard and Dr A E Goeta.
Most published work on metallacarboranes has explored the chemistry of middle and late transition metals in low oxidation states, yet the nido carborane dianion, C2B9H112- and its derivatives, are ligands able to stabilise early transition metal organometallic complexes in high oxidation states, providing a contrast in electronic properties with cyclopentadienyl complexes; indeed there is a relationship with metal imido chemistry. The (C2B9H11)Ta fragment has the same electron count as the (η-C5H5)Zr fragment and the tungsten complex (C2B9H11)(RN)W(NHR)2 is iso-numeral with (C5H5)2ZrX2; we are investigating several series of such related compounds, exploring differences and similarities in their synthesis, reactivity and structures.
In addition to exploring novel coordination chemistry of known carborane ligands, we are also interested in the development of novel carboranes to use as ligands. Our main focus here has been to develop routes to amine functionalised nido-carboranes and to coordinated these to early transition metals as carborane analogues of the “constrained-geometry” Cp-linked-amide type complexes.
We have developed a synthesis of cyclopentadienyl ligands bearing alkyl chains terminated with amines, C5H5(CH2)3NHR. These ligands coordinate metals at two sites and their electronic and steric properties provide a contrast with well-established ansa-bis(cyclopentadienyl) complexes. In a separate study we have developed a flexible synthesis of bulky per-alkylated cyclopentadienyl ligands, and we continue to develop this chemistry towards the synthesis of chiral group 3 metallocenes.
Nitrogen donor ligands
The amine elimination reactions of metal amides, such as Zr(NMe2)4, Ta(NMe2)5 and W(NtBu)2(NHtBu)2 with acidic cyclopentadienes and carboranes have been exploited by us and others, and are useful since they avoid difficulties associated with some salt elimination methods of synthesis. Although known since the 1960s these homoleptic metal amides were little exploited until the mid 1990s and several are now commercially available. We are interested in the wider range of elimination and insertion reactions of metal amides leading to the synthesis of novel early transition metal complexes of amidinates, guanadinates, dithiodiphosphinylimides and other N-, O- and S-donor ligands. The organometallic chemistry of these complexes provides a further contrast with metallocene chemistry of the early transition metals.
- A. K. Hughes, J. Organomet. Chem., 2002, 657, 9.
- A. S. Batsanov, M. A. Fox, A. E. Goeta, J. A. K. Howard, A. K. Hughes and J. M. Malget, J. Chem. Soc., Dalton Trans., 2002, 2624.
- M. A. Fox, A. K. Hughes and J. M. Malget, J. Chem. Soc., Dalton Trans., 2002, 3505.
- A.S. Batsanov, B.M. Bridgewater, J.A.K. Howard, A.K. Hughes and C. Wilson, J. Organomet. Chem., 1999, 590, 169.
- H. L. Nguyen, L. E. M. Howard, G. W. Stinton, S. R. Giblin, B. K. Tanner, I. Terry, A. K. Hughes, I. M. Ross, A. Serres & J. S. O. Evans (2006). Synthesis of size controlled fcc and fct FePt nanoparticles. Chemistry of Materials 18(26): 6414-6418.