Download Alkanes and xenon as ligands: NMR studies of photolytically

Alkanes and xenon as ligands:
NMR studies of photolytically generated, short-lived complexes.
Graham E. Ball
School of Chemistry, University of New South Wales, Sydney 2052, AUSTRALIA
We have been studying the binding of unusual ligands, namely alkanes and xenon, to
transition metal centres using NMR spectroscopy.1-5 Complexes containing intact
alkane and xenon ligands have long been seen as key reactive intermediates in
organometallic chemistry. Owing to the poor nature of these ligands, such complexes
are highly unstable and usually have only fleeting existences even at low
temperatures. Hence, the observation of alkane and xenon complexes has been
mostly restricted to using “fast” spectroscopies such as UV and IR.
This talk will describe our studies on complexes of the type Cp’Re(CO)(L)(alkane)
(1) and Cp’Re(CO)(PF3)(Xe) (2) (Cp’ = Cp, iPrCp; L = CO, PF3), the first
organometallic alkane and xenon complexes observed
using NMR. These complexes are formed
photolytically inside the spectrometer at low
temperatures to stabilize them sufficiently to allow their characterization. Bonding in
these molecules, stability, ligand exchange processes, binding preferences amongst
different alkane sites, oxidative cleavage of bound alkanes and NMR techniques
employed will be discussed.
1. Lawes, D.J.; Geftakis, S.; Ball, G.E. J. Am. Chem. Soc. 2005, 127, 4134.
2. Geftakis, S.; Ball, G. E. J. Am. Chem. Soc. 1998, 120, 9953.
3. Lawes, D.J.; Darwish, T.A.; Clark, T.; Harper, J.B.; Ball, G.E. Angew. Chem. Int. Ed. Engl. 2006,
45, 4486.
4. Ball, G.E.; Brookes, C.M.; Cowan, A.J.; Darwish, T.A; George, M.W.; Kawanami, H.K.; Portius,
P.; Rourke, J.P. Proc. Natl. Acad. Sci. USA., 2007, 104, 6927.
5. Ball, G.E.; Darwish, T.A; Geftakis, S.; George, M.W.; Lawes, D.J.; Portius, P.; Rourke, J.P. Proc.
Natl. Acad. Sci. USA. 2005, 102, 1853.