1. Sasol Technology Research Laboratory, St Andrews, Sasol Technology (UK) Limited, Purdie Building, North Haugh, St Andrews, Fife KY16 9ST, Scotland, U.K., School of Chemistry, University of St Andrews, Purdie Building, North Haugh, St Andrews, Fife KY16 9ST, Scotland, U.K., and Sasol Technology Research & Development, PO Box 1, Klasie Havenga Road, Sasolburg, 1947, South Africa