Head of Discipline for Chemistry

Valeria Arrighi

 

Staff by Sections

Inorganic Chemistry

Alan Welch

Jan-Willem Bos

James Cameron

Scott Dalgarno

Gareth Lloyd

Stuart Macgregor

Stephen Mansell 

Ruaraidh McIntosh

Organic Chemistry

Dave Adams

Euan Brown

Graeme Barker

Magnus Bebbington

Nicola Howarth

Arno Kraft

Ai-Lan Lee

Nick Leslie

Kevin McCullough

Colin Rickman

Filipe Vilela

Physical Chemistry

Ken McKendrick

Valeria Arrighi

David Bucknall

Matt Costen

Stuart Greaves

Maciej Gutowski

Martin McCoustra

N Hendrik Nahler

Martin Paterson

Experimental Officers and Administrative Staff

Dave Ellis

Georgina Rosair

Placement Coordinators

Industrial:  Scott Dalgarno

Honorary and Emeritus Staff

John Parker

Joe Pfab

Alan Welch

BSc, PhD, CChem, FRSC, FRSE

Chair in Inorganic Chemistry

Telephone
+44 (0)131 451 3217
Email
a.j.welch@hw.ac.uk
Address
Room 2.23
William Perkin Building
Heriot-Watt University
Roles and responsibilities
  • Examinations Officer for Chemistry
Research

 

 

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 make. 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.

3. Structural Systematics in Heteroboranes

The characterisation of (hetero)carboranes by X-ray diffraction is challenging because of the similar X-ray scattering powers of C and B. We are developing methods (Vertex-to-Centroid Distance, VCD; B−H Distance, BHD) to help overcome this problem. This sometimes leads us to analyse structures already in the literature which may have been incorrectly reported and we have used Exo-polyhedral Ligand Orientation, ELO, to guide us here. Current work aims to extending VCD and ELO to other systems.

 

Figure 3. The original incorrect (left) and redetermined correct (right) structures of a rhodacarborane whose incorrect structure was suggested by ELO and confirmed by VCD methods. 

Selected publications

Up-to-date publications are listed on this research profile.