CHEMICAL REVIEWS Registered in U.S. Patent and Trademark Office; Copyright 1995 by the American Chemical Society Department
of Chemistry
J O S E F MICHL, Editor and Biochemistry, University of Colorado,
J o h n A . G l a d y s z , Associate
Editor,
University
Boulder, of
Colorado
80309-0215
Utah
Editorial Advisory Board Anthony J. Arduengo, III, DuPont Central Research and Development James K. Bashkin, Washington University Athel L. J. Beckwith, Australian National University Guy Bertrand, Paul Sabatier University Friedrich Bickelhaupt, Free University, Amsterdam Edwin A. Chandross, AT&T Bell Laboratories Robert Crabtree, Yale University Ernest R. Davidson, Indiana University Francois Diederich, University of California, Los Angeles David A. Evans, Harvard University Marye Anne Fox, University of Texas at Austin Donald Hilvert, Scripps Research Institute Chemical Reviews (ISSN 0009-2665) is p u b l i s h e d e i g h t t i m e s p e r y e a r (January/February, March/April, May, J u n e , July/August, September/ October, November, a n d December) by t h e American Chemical Society at 1155 16th St., N.W., Washington, DC 20036. Second-class postage paid a t Washington, DC, and additional maili n g offices. P O S T M A S T E R : S e n d address changes to Chemical Reviews, Member & Subscriber Services, P.O. Box 3337, Columbus, OH 43210. C a n a d i a n GST Reg. No. R127571347. Printed in t h e USA. P U B L I C A T I O N S DIVISION Robert H. Marks, Director Journals Department: C h a r l e s R. Bertsch, H e a d Editorial Office: Mary E. Scanlan, Manager; Anne C. O'Melia, J o u r n a l s Editing Manager; M a r g a r e t A. Winship, Assist a n t Editor Advertising Office: Centcom, Ltd., 1599 Post Road East, P.O. Box 231, Westport, CT 06881. © Copyright 1995 American Chemical Society. Copyright permission: Reprographic copying beyond t h a t permitted by Section 107 or 108 of the US Copyright Act is allowed, provided t h a t the appropriate per-copy fee is paid directly to the Copyright Clearance Center (CCC), 222 Rosewood Dr., Danvers, MA 01923, USA. Anyone may excerpt up to 200 words per article for noncommercial, scholarly purposes w i t h a p p r o p r i a t e credit to t h e source. Direct other reprint permission requests to ACS Copyright Office, Publications Division, 1155 S i x t e e n t h St., N.W., Washington DC 20036. For quotes a n d i n f o r m a t i o n on o r d e r i n g b u l k reprints, call (202) 872-4539 or write to Distribution Office at the ACS Washington address. The paper used in t h i s publication m e e t s t h e m i n i m u m r e q u i r e m e n t s of American National Standard for InformaAmerican Chemical Society 1155 16th St., N.W. Washington, DC 20036 (202) 872-4600 TDD (202) 872-8733 FAX (202) 872-4615
Richard H. Holm, Harvard University István T. Horváth, Exxon Research and Engineering Hiizu Iwamura, University of Tokyo Irving M. Klotz, Northwestern University Fred W. McLafferty, Cornell University Robert D. Miller, IBM Almaden Research Center Ryoji Noyori, Nagoya University Thomas B. Rauchfuss, University of Illinois Edward I. Solomon, Stanford University Joan S. Valentine, University of California, Los Angeles John T. Yates, Jr., University of Pittsburgh Rudolf Zahradnik, Czechoslovak Academy of Sciences, Prague
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