Physical Inorganic Chemistry

Transcription

1 Physical Inorganic Chemistry

2 Physica Inorganic Chemistry A Coordination Chemistry Approach S. F. A. KETTLE Professorial Fellow, University of East Anglia, and Adjunct Professor, Royal Military College, Kingston, Ontario Springer-Verlag Berlin Heidelberg GmbH

3 In memory of Doreen,

4 British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library. ISBN ISBN (ebook) DOI / Library of Congress Cataloging-in-Publication Data Kettle, S. F. A. (Sidney Francis Alan) Physical inorganic chemistry: a coordination chemistry approach I Sidney F. A. Kettle p. em. Includes bibliographical references and index 1. Physical inorganic chemistry 2. Coordination compounds. I. Title. QD475.K '242-dc CIP Copyright 1996 S. F. A. Kettle Originally published by Spektrum Academic Publishers in 1996 No part of this publication may be reproduced by any mechanical, photographic, or electronic process, or in the form of phonographic recording, nor may it be stored in a retrieval system, transmitted, or otherwise copied for public or private use without written permission of the publisher. Set by KEYWORD Publishing Services, London

5 Contents Foreword xiii 3.3 What determines coordination number and geometry? 42 Preface 'IN 3.4 Isomerism in coordination compounds Conformation isomerism 43 Introduction Geometrical isomerism Coordination position isqmerism Coordination isomerism 44 Typical ligands, typical complexes Ionization isomerism Classical ligands, classical complexes Hydrate isomerism Novel ligands, novel complexes Some final comments Linkage isomerism Polymerization isomerism Ligand isomerism Optical isomerism 46 Nomenclature, geometrical structure Structural and fluxional isomerism 47 and isomerism of coordination Spin isomerism 48 compounds Nomenclature 24 4 Preparation of coordination 3.2 Coordination numbers 31 compounds Complexes with coordination numbers one, two or three Complexes with coordination number 4.1 Introduction 51 four Preparative methods Complexes with coordination number five Simple addition reactions Complexes with coordination number Substitution reactions 54 six Oxidation-reduction reactions Complexes with coordination number seven Thermal dissociation reactions Complexes with coordination number Preparations in the absence of oxygen 62 eight Reactions of coordinated ligands Complexes with coordination number nine The trans effect Complexes of higher coordination Other methods of preparing number 41 coordination compounds 69

6 viii 1 Contents Tetrahedral complexes 148 Stability of coordination 7.9 Square planar complexes 150 compounds Other stereochemistries Introduction Stability constants Ligand field theory Determination of stability constants 75 Electronic spectra of transition 5.4 Stability correlations 80 metal complexes Statistical and chelate effects Introduction Solid complexes The electronic spectra of ym and Ni Steric effects Conclusions 92 complexes Spin-forbidden transitions Effect of spin-orbit coupling Jahn-Teller effect 166 Molecular orbital theory of transition 8.6 Band contours 170 metal complexes Band intensities 171 Introduction Octahedral complexes Metal-ligand ri interactions Metal-ligand 7t interactions Tetrahedral complexes Tetrahedral complexes Complexes of other geometries Charge-transfer spectra Intervalence charge-transfer bands Conclusions Complexes of other geometries Formal oxidation states 115 Magnetic properties of transition 6.6 Experimental 117 metal complexes Introduction Classical magnetism 187 Crystal field theory of transition metal complexes 121 moment Orbital contribution to a magnetic 7.1 Introduction Spin contribution to a magnetic Symmetry and crystal field theory Crystal field splittings Weak field complexes Strong field complexes 136 moment Spin-orbit coupling Low symmetry ligand fields 192 Experimental results Orbital contribution reduction 7.6 Intermediate field complexes 143 factor Non-octahedral complexes An example 195

7 Contents 1 ix Spin-only equation Magnetically non-dilute compounds Spin equilibria 208 compounds 269 Other methods of studying coordination Introduction 269 Beyond ligand field theory Vibrational spectroscopy Bonding in transition metal 12.3 Resonance Raman spectroscopy 275 organometallic complexes Spectroscopic methods unique to 10.2 Metal-fullerene complexes 215 optically active molecules Ab initio and XIX methods Nuclear spectroscopies Semiempirical methods Nuclear magnetic resonance (NMR) Extended Hiickel method Nuclear quadrupole resonance 10.6 Angular overlap model 226 (NQR) Mossbauer spectroscopy Three examples: ferrocene, hexacarbonylchromium and 12.6 Electron paramagnetic (spin) ethenetetracarbonyliron 227 resonance spectroscopy (EPR, ESR) Ferrocene Hexacarbonylchromium Photoelectron spectroscopy (PES) Ethenetetracarbonyliron Evidence for covalency in transition 10.8 Final comments 235 metal complexes Molar conductivities Cyclic voltammetry 297 f electron systems: the lanthanides and actinides X-ray crystallography 299 Introduction Conclusion Shapes off orbitals Electronic structure of the lanthanide and actinide ions Spin-orbit coupling Spin-orbit coupling in pictures Introduction Excited states of f electron systems Ionic radii Thermodynamic and related aspects of ligand fields Electronic spectra of f electron 13.3 Heats of ligation 305 systems Lattice energies Crystal fields and f -+ f intensities Site preference energies f-+ d and charge-transfer transitions Stability constants Lanthanide luminescence 13.7 Lanthanides Magnetism of lanthanide and actinide ions Molecular mechanics f orbital involvement in bonding Conclusions 315

8 x I Contents Search for reaction intermediates 391 Reaction kinetics of coordination 16.4 Peroxidases 393 compounds Blue copper proteins Introduction Nitrogen fixation Electron-transfer reactions Protonation equilibria in bioinorganic 14.3 Mechanisms of ligand substitution systems 403 reactions: general considerations Substitution reactions of square 17 planar complexes 328 Introduction to the theory of the 14.5 Substitution reactions of octahedral solid state 407 complexes Base-catalysed hydrolysis of 17.1 Introduction 407 cobalt(iii) ammine complexes Nodes, nodes and more nodes Mechanisms of ligand substitution reactions: postscript Fluxional molecules Photokinetics of inorganic Travelling waves and the Brillouin zone Band structure 417 complexes Fermi surface 422 Bonding in cluster compounds Introduction Bonding in P 4 (and B 4Cl 4 ) 346 Appendix Solid state and coordination compounds Spectra of crystalline materials 'Simple ammonia' model for P4 346 Conformation of chelate 'Twisted ammonia' model for P4 348 rings Atomic orbital model for P Unity of the three models of P4 Appendix 2 bonding 352 Valence shell electron pair 15.3 Wade's rules 353 repulsion (VSEPR) model Topological models Free-electron models 362 Appendix Detailed calculations 375 Introduction to group theory Clusters and catalysis, a comment 379 Appendix 4 16 Equivalence of dz2 and dx -y in an Some aspects of bioinorganic chemistry 381 octahedral ligand field 445 Appendix Introduction 381 Russell-Saunders coupling 16.2 Myoglobin and hemoglobin 384 scheme 446

9 Contents 1 xi Appendix 6 Ligand tt group orbitals of an octahedral complex 449 Appendix 7 Tanabe-Sugano diagrams and some illustrative spectra 455 Appendix 8 Group theoretical aspects of band intensities in octahedral complexes 459 Appendix 9 Determination of magnetic susceptibilities Appendix 10 Magnetic susceptibility of a tetragonally distorted dg ion Appendix 11 High temperature superconductors 472 Appendix 12 Combining spin and orbital angular momenta 477 Appendix 13 Bonding between a transition metal atom and a en Rn ring, n = 4, 5 and Appendix 14 Hole-electron relationship in spin-orbit coupling Index

10 Foreword GEORGE CHRISTOU Indiana University, Bloomington I am no doubt representative of a large number of current inorganic chemists in having obtained my undergraduate and postgraduate degrees in the 1970s. It was during this period that I began my continuing love affair with this subject, and the fact that it happened while I was a student in an organic laboratory is beside the point. I was always enchanted by the more physical aspects of inorganic chemistry; while being captivated from an early stage by the synthetic side, and the measure of creation with a small c that it entails, I nevertheless found the application of various theoretical, spectroscopic and physicochemical techniques to inorganic compounds to be fascinating, stimulating, educational and downright exciting. The various bonding theories, for example, and their use to explain or interpret spectroscopic observations were more or less universally accepted as belonging within the realm of inorganic chemistry, and textbooks of the day had whole sections on bonding theories, magnetism, kinetics, electron-transfer mechanisms and so on. However, things changed, and subsequent inorganic chemistry teaching texts tended to emphasize the more synthetic and descriptive side of the field. There are a number of reasons for this, and they no doubt include the rise of diamagnetic organometallic chemistry as the dominant subdiscipline within inorganic chemistry and its relative narrowness vis-d-vis physical methods required for its prosecution. These days inorganic chemistry is again changing dramatically with the resurgence of coordination chemistry, fuelled by the increasing importance of metals in biology and medicine and the new and explosive thrusts into inorganic materials encompassing a wide variety of types and areas of application, of which high-temperature superconductors, molecular ferromagnets and metallomesogens are merely the tip-of-theiceberg. Modern-day, nco-coordination chemistry is thus a much broader discipline and one that now demands greater knowledge and expertise in a much larger range of theoretical or spectroscopic techniques and physicochemical methods, and to a higher level of sophistication. At Indiana University, as at most universities I am sure, we have assigned a high priority to modifying our inorganic chemistry curriculum to accurately reflect the changing nature of the field and to better prepare our students for the demands on them of the new century. The general paucity of suitable texts directed towards the inorganic chemistry student is a problem. There are, of course, many advanced texts available for consultation but, on the theoretical/physical side at least, these are frequently directed at the more quantum mechanically and mathematically competent reader. In my experience as an instructor, the average student of inorganic chemistry

11 xiv 1 Foreword picking up an advanced text on magnetochemistry, for example, will probably not survive the initial jump into the deep waters of quantum mechanics. This present work by Sid Kettle represents a wonderful bridge for the student. It is designed as an intermediate-level text that can serve both as a user-friendly introduction to a large number of topics and techniques of importance to the student of coordination and physical inorganic chemistry, and also as a springboard to more advanced texts and studies. It is written in a style that is appropriate for a teaching text, anticipating and answering the questions that students will typically have on encountering the topic for the first time, and introduces a large number of theoretical, spectroscopic and physicochemical techniques without sacrificing the more classical content of a coordination chemistry text. In this regard, it is a wonderful hybrid of the classic and modern aspects of coordination and physical inorganic chemistry and is consequently an admirable text for the student of this area.

12 Preface Some twenty years ago, theoretical aspects of inorganic chemistry formed a major component of any inorganic textbook. Today, this component is much less evident. No doubt, this shift in emphasis is a proper response both to the undue weight then given to theoretical aspects and to the developments that have taken place elsewhere in the subject. However, in the interval there have been theoretical developments that deserve a place; further, it has probably become more difficult for the interested student to access the older work. There seemed to me to be a real need for an easy-to-read, and so largely non-mathematical, text that would bridge the gap between the relatively low-level treatments currently available and the research level paper, review, monograph or text. The present book was written with the object of providing a bridge for this gap. Although the motivation for writing it is seen in its theoretical content, it was recognized that there are advantages in placing this in a broader context. So, what has resulted is a book which contains an overview of the relatively traditional and elementary along with contemporary research areas, wherever possible viewed from an integrated theoretical perspective. Because a text on physical inorganic chemistry can easily become a series of apparently disconnected topics, I have given the subject a focus, that of coordination chemistry, and have included chapters which should enable the book to double as a text in that area. To keep the size of the book manageable, to recognize that it is aimed at the intermediate stage reader, and because the topic is covered so extensively elsewhere, I have assumed a knowledge of the most elementary aspects of bonding theory. In a book such as this it is impossible to avoid cross-references between chapters. However, it is equally difficult to ensure that such cross-references supply the answers expected of them. I have therefore attempted to make each chapter as free-standing as possible and have used the resulting duplications as a mechanism for deepening the discussion. This strategy can produce its own problems as well as benefits; I hope that the index will provide direction to sufficient additional material to deal with the problems! I am indebted to many institutions which provided the hospitality that enabled most of the book to be written-chalmers University and the University of Gothenburg, Sweden; the Royal Military College, Kingston, Canada; the University of Turin, Italy; the University of Nairobi, Kenya; Tokyo Institute of Technology, Japan; the University of Szeged, Hungary and Northwestern University, USA. Of the numerous individuals who have provided helpful comments on sections of the book, and often offered material for inclusion, I am grateful to Professor R. Archer and his students at the University of Massachusetts, Amherst, USA, who made many detailed comments on an early edition of the text, to Professor K. Burger of the University of Szeged, Hungary-his contributions were very helpful-and to Dr. S. Cotton, who was a constant fund of

13 xvi I Preface comment and information. I am particularly indebted to the Rev. Dr. lain Paul who, in his own inimitable manner, worked through every sentence and made a multitude of suggestions for improvement and clarification. Defects, errors and omissions, of course, are my own responsibility. S.F.A.K.