Alan Welch BSc, PhD, CChem, FRSC, FRSE

Profile

• Director of Studies, Year 1
• Programme Director, Chemistry with a Year in North America
• Director of Postgraduate Research in EPS

Heteroborane Chemistry

We are involved with the synthesis of new heteroborane species, their characterisation and an exploration of their chemistry. The research is principally curiosity-driven but we are always aware of any potential applications of the compounds we produce. Species are characterised by mass spectrometry, NMR spectroscopy and X-ray diffraction. Structures and reactivity are probed by DFT calculations with SA Macgregor and (spectro)electrochemistry studied with P Zanello in Siena, Italy.

1. Supraicosahedral Heteroboranes

The logical, high-yielding, synthesis of supraicosahedral heteroboranes remains a considerable challenge and a number of projects are devoted to surmounting this challenge. We are also interested in understanding the bonding within supraicosahedral species and are investigating a number of approaches to help us here, including analysis of exopolyhedral ligand orientation exemplified by the indenyl ligand orientation in Figure 1.

 

Figure 1. Experimental (left) and computed (right) orientation of the indenyl ligand in a supraicosahedral cobaltacarborane. The two orientations agree within 14°.

2. Bis(carborane) Chemistry

The chemistry of bis(carboranes), two carborane units joined by a 2c-2e bond, is severely underdeveloped. What is clear, however, from the few studies that have been done is that in many cases the chemistry observed is significantly different to that of the parent carboranes, particularly when the two cages operate in concert. This is dramatically illustrated by the formation of the fly-over ruthenacarborane shown in Figure 2, which results from room temperature cleavage of an aromatic C–C bond.

Figure 2. Whole molecule (left) and central part (right) of a fly-over ruthenacarborane, resulting from the reductive cleavage of a C–C bond of an arene associated with one (ruthena)carborane by the other carborane.

 

 

1. 'Exopolyhedral ligand flipping on isomerisation of novel supraicosahedral stannacarboranes', P. D. Abram, D. Ellis, G. M. Rosair and A. J. Welch, Chem. Commun., 2009, 5403.
2. 'Supraicosahedral indenyl cobaltacarboranes', G. Scott, A. McAnaw, D. McKay, A. S. F. Boyd, D. Ellis, G. M. Rosair, S. A. Macgregor, A. J. Welch, F. Laschi, F. Rossi and P. Zanello, Dalton Trans., 2010, 39, 5286.
3. 'Room temperature C-C bond cleavage in an arene by a metallacarborane', D. Ellis, D. McKay, S. A. Macgregor, G. M. Rosair and A. J. Welch, Angew. Chem. Int. Ed., 2010, 49, 4943.
4. 'The first supraicosahedral bis(heteroborane)', D. Ellis, G. M. Rosair and A. J. Welch, Chem. Commun., 2010, 46, 7394.
5. 'Spectroscopic, structural, computational and (spectro)electrochemical studies of icosahedral carboranes bearing fluorinated aryl groups', H. Tricas, M. Colon, D. Ellis, S. A. Macgregor, D. McKay, G. M. Rosair, A. J. Welch, I. V. Glukhov, F. Rossi, F. Laschi and P. Zanello, Dalton Trans., 2011, 40, 4200.