The Chemistry Of Macrocyclic Ligand Complexes (cambridge Texts In Chemistry And Biochemistry)

The chemistry of macrocyclic ligand complexes The chemistry of macrocyclic ligand complexes LEONARD F. LINDOY Department of Chemistry and Biochemistry, James Cook University, Townsville, Australia The right of the University of Cambridge to print and sell all manner of books was granted by Henry Vlll in 1534. The University has printed and published continuously since 1584. CAMBRIDGE UNIVERSITY PRESS Cambridge New York Port Chester Melbourne Sydney Published by the Press Syndicate of the University of Cambridge The Pitt Building, Trumpington Street, Cambridge CB2 1RP 40 West 20th Street, New York, NY 10011, USA 10 Stamford Road, Oakleigh, Melbourne 3166, Australia © Cambridge University Press 1989 First published 1989 First paperback edition 1990 British Library cataloguing in publication data Lindoy, Leonard F. The chemistry of macrocyclic ligand complexes. 1. Macrocyclic ligands I. Title 547'. 5 Library of Congress cataloguing in publication data Lindoy, Leonard F. The chemistry of macrocyclic ligand complexes/Leonard F. Lindoy. p. cm. Bibliography: p. Includes index. 1. Ligands. 2. Cyclic compounds. I. Title. QD474.L54 1989 541.2'242-—CH, CH. (4) 4 What is different about macrocyclic ligand complexes? model compounds for the natural macrocycles. Although these efforts have not always met with spectacular success, the resultant development of new macrocyclic ligand chemistry has provided a valuable background against which the natural systems can often be seen in clearer perspective. Apart from the biological implications, aspects of the chemistry of macrocyclic ligands are of relevance to a diverse number of other areas. Indeed, there has been a remarkable expansion of research involving these other areas during recent times. Many of the developments impinge on topics such as metal-ion catalysis, organic synthesis, metal-ion discrimination, and analytical methods, as well as on a number of potential industrial, medical and other applications. 1.2 Steric and electronic considerations The macrocyclic cavity Macrocyclic rings and chelate rings. As with simple polydentate ligands, the donor atoms in macrocyclic ligands are normally spaced so that on coordination five-, six-, (and occasionally) seven-membered chelate rings are formed with the metal ion. This requirement results in macrocycles incorporating three donor atoms usually containing between nine and 13 atoms in their inner macrocyclic ring. Thus, ring sizes of between 12 and 17 members most commonly occur when the macrocycle contains four donor atoms, 15-21 members when there are five donor atoms, and 18-25 members for six donor atoms. Examples of different chelate ring patterns for metal complexes of 14-membered macrocycles are given by (6)-(8). (6) Factors influencing the macrocyclic hole size. The hole size of a macrocyclic ligand is a fundamental structural parameter which will usually influence, to a large degree, the properties of resultant metal complexes relative to those of the corresponding non-cyclic ligands. The large number of X-ray diffraction studies now complete for macrocyclic systems makes it possible to define many of the parameters which affect hole size Steric