Stephen Mansell

Assistant Professor

Telephone
+44 (0)131 451 4299
Email
s.mansell@hw.ac.uk
Address
Room 2.07
William Perkin Building
Heriot-Watt University
Roles and responsibilities
  • BSc 4th year Coordinator
  • ICS Induction Coordinator
  • ICS Representative, EPS Early Career Network and Athena SWAN self-assessment team
  • ICS Seminar Coordinator
  • ICS Schools Outreach Coordinator (joint Prof. Martin McCoustra)
     
Research

Catalysis

My group's research focuses on the synthesis and development of new homogeneous catalysts. We use skills in synthetic main group chemistry to construct ligands with new properties, such as cooperative reaction sites.  Synthetic organometallic chemistry is then exploited to form transition metal and f-element complexes for testing in catalysis.

1. Unconventional ligands

In order to access unusual reactivity, new classes of ligand are required, so we target the synthesis of unconventional ligands.  Examples include the synthesis and exploration of the chemistry of N-heterocyclic stannylenes (NHSns), the tin analogues of extensively used N-heterocyclic carbenes (NHCs).  Low-coordinate phosphorus compounds also show very different ligand behaviour compared to conventional phosphine ligands, and we have been exploring the properties of phosphines, the phosphorous analogue of pyridine, particularly with a phosphine substituent.  These can be used as small bite-angle ligands in catalysis, a field of growing importance.

S. M. Mansell, Catalytic applications of small bite-angle diphosphorous ligands with single-atom linkers Dalton Transactions, 2017, 46, 15157

S. M. Mansell, R. H. Herber, I. Nowik, D. H. Ross, C. A. Russell and D. F. Wass, Coordination Chemistry of N-Heterocyclic Stannylenes: A Combined Synthetic and Mossbauer Spectroscopy Study Inorg. Chem.2011, 50, 2252

 

Figure 1. An anionic indenide N-heterocyclic stannylene ligand (left) and a bis(phosphino) phosphinine (right).

2. H-atom catalysis

Transfer hydrogenation holds great potential in chemical synthesis because it replaces hazardous reducing agents, such as hydrogen gas or metal hydrides, with more convenient chemical sources of hydrogen, commonly isopropanol or formic acid/formate. Related to this are hydrogen-borrowing processes that involve the oxidation of a saturated substrate by transfer of an equivalent of dihydrogen to a metal centre, thereby facilitating new reactivity, before the borrowed hydrogen is then returned. We are developing catalysts that incorporate unconventional ligands, and these have shown excellent activity for room temperature transfer hydrogenation as well as the hydrogen borrowing upgrading of MeOH / EtOH to isobutanol. Isobutanol has great promise as an ‘advanced biofuel’ because it is much more compatible with current engine and infrastructure technologies.

R. J. Newland, M. F. Wyatt, R. Wingad and S. M. Mansell, A Ruthenium (ll) Bis(Phosphinophosphinine) Complex as a Precatalyst for Transfer-Hydrogenation and Hydrogen-Borrowing Reactions Dalton Trans.2017, 46, 6172

  

 Figure 2. Transfer hydrogenation and hydrogen borrowing catalysis.

3. Dinitrogen and hydrocarbon activation

We are also interested in functionalising conventionally inert small molecules, such as dinitrogen and hydrocarbons. These compounds are often very cheap and abundant but difficult to convert selectively into useful and valuable products. C-H activation has the potential to revolutionise chemical synthesis enabling direct routes from simple, inexpensive starting materials. To this end, we have been exploring tethered NHC and NHSn ligands and their applications in Rh chemistry. We are working on the synthesis of tethered Rh compounds, and their comparison to non-tethered analogues will allow us to identify how geometric constraint changes the reactivity of these complexes.

M. Roselló-Merino and S. M. Mansell, Synthesis and Reactivity of Fluorenyl-Tethered N-heterocyclic Stannylenes Dalton Trans., 2016, 45, 6282

Figure 3. A multi-metallic Rh-NHSn complex.

Selected publications

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

 

Further information

http://www.mansellresearch.org.uk

3-D Laboratory tour of the Mansell Lab