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wells - structural inorganic chemistry 4e (clarendon, 1975)
Structural Inorganic Chemistry A.F. WELLS CLARENDON PRESS - OXFORD Oxford University Press Ely House, London W1 1975 4th Edition Fsfsdf Oxford University Press, Ely House, London W.1 GLASGOW NEW YORK TORONTO MELBOURNE WELLINGTON CAPE TOWN IBADAN NAIROBI DAR ES SALAAM LUSAKA ADDIS ABABA DELHl BOMBAY CALCUTTA MADRAS KARACHI LAHORE DACCA KUALA LUMPUR SINGAPORE HONG KONG TOKYO ISBN 0 19 855354 4 0 OXFORD UNIVERSITY PRESS 1975 All rights reserved. No part of this publication may be reproduced, storedin a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior permission of' Oxford University Press PRINTED IN GREAT BRITAIN BY WILLIAM CLOWES & SONS LIMITED LONDON, COLCHESTER AND BECCLES Fsfsdf Preface This book has been almosl entirely rewritten, but its purpose and general organization remain the same las those of previous editions. The Introduction to the first (1945) edition included dhe following paragraph: 'The reasons for writing this book were, firstly, the conviqtion that the structural side of inorganic chemistry cannot be put on a sound basls until the knowledge gained from the study of the solid state has been incorporated into chemistry as an integral part of that subject, and secondly, the equally strolng conviction that it is unsatisfactory merely to add information about the structures of solids to the descriptions of the elements and compounds as usually presented in a systematic treatment of inorganic chemistry.' Now, after a period of thirty years during which considerable advances have been made in solid state chemistry, it is still true to say that the structures and properties of solids receive very little atte~ntion in most treatments of inorganic chemistry, and this in spite of the fact that most elements and most inorganic compounds are solids at ordinary temperaturw. This state of affairs would seem to be sufficient justification for the appearance of yet another edition of this book. Since the results of structurkl studies of crystals are described in crystallographic language the first requirement is that these results be made available in a form intelligible to chemists. It was this challenge that first attracted the author, and it is hoped that this book will continue to provide teachers of chemistry with facts and ideas which can be incorporated into their teaching. However, while any addition of structural information to the donventional teaching of inorganic chemistry is to be welcomed the real need is a radical change of outlook and the recognition that not only is the structure of a substance in all states of aggregation an essential part of its full description (or characterization) but also that the structures and properties of solids form an integral part, pedhaps the major part, of the subject. The general plan of the boqk is as follows. Part I deals with a number of general topics and is intended as an introduction to the more detailed Part 11, which forms the larger part of the book. In Part I1 the structural chemistry of the elements is described systematically, and the arrangement of material is based on the groups of the Periodic Table. The advanlces made during the past decade have necessitated considerable changes in these latter chapters, but the major structural changes have been made in the content of Part I. Since a concise treatment of certain geometrical and topological topics is not readily available elsewhere mode space has been devoted to these than in previous editions at the expense of subjects such as the experimental methods of structural chemistry, which at best can receive only a sketchy treatment in a volume such as Preface this. Many students find difficulty in appreciating the three-dimensional geometry of crystal structures from two-dimensional illustrations (even stereoscopic photo- graphs). In order to acquire some facility in visualising the three-dimensional arrangements of atoms in crystals some acquaintance is necessary with symmetry, repeating patterns, sphere-packings, and related topics. Some of this material could be, and sometimes is, introduced into teaching at an early age. However, there is a tendency in some quarters to regard solid geometry as old-fashioned and to replace it in school curricula by more fashionable aspects of mathematics. This adds to the difficulties of those teachers of chemistry who wish to modernize their teaching by including information about the structures of solids. Unless the student has an adequate grounding in the topics noted above little is gained by adding diagrams of unit cells of crystal structures to conventional chemistry texts. The educational value of building models representing the arrangements of atoms in crystals cannot be over-emphasized; and by this we mean that the student actually assembles the model and does not simply look at a ready-made model, however much more elegant the latter may be. Some very tentative suggestions for model building have been offered in the author's Models in Structural Inorganic Chemistry, to which the abbreviation MSIC in the present volume refers. References. The present volume has never been intended as a reference work, though it may serve as a useful starting-point when information is required on a particular topic. As an essential part of the educational process the advanced student should be encouraged to adopt a critical attitude towards the written word (including the present text); he must learn where to find the original literature and to begin to form his own judgment of the validity of conclusions drawn from experimental data. It is becoming increasingly difficult to locate the original source of a particular item of information, and for this reason numerous references to the scientific literature are included in the systematic part of this book. These generally refer to the latest work, in which references to earlier work are usually included. To save space (and expense) the names of scientific journals have been abbreviated to the forms listed on pp. mi-xxiii. Indexes. There are two indexes. The arrangement of entries in the formula index is not entirely systematic for there is no wholly satisfactory way of indexing inorganic compounds which retains chemically acceptable groupings of atoms. The formulae have been arranged so as to emphasize the feature most likely to be of interest to the chemist. The subject index is largely restricted to names of minerals and organic compounds and to topics which are not readily located in the list of contents. Acknowledgments. During the writing of this book, which of necessity owes much to the work and ideas of other workers in this and related fields, I have had the benefit of helpful discussions with a number of colleagues, of whom I would particularly mention Dr. B. C. Chamberland. I wish to thank Dr. B. G. Bagley and the editor of Nature (London) for permission to use Fig. 4.3, Dr. H. T. Evans and Preface John Wiley and Sons for Figs Sc, 7, 10, 11, and 12b in Chapter 11, and Drs. G. T. Kokotailo and W. M. Meier for Fig. 23.27. It gives me great pleasure to acknowledge the debt that I owe to my wife for her support and encouragement over a period of many years. A. F. Wells Department of Chemhtry, University of Connecticut, Storrs, Connecticut, U.S.A. 1974 vii Fsfsdf Contents PART I 1. INTRODUCTION The importance of the solid state Structural formulae of inorganic compounds Geometrical and topological limitations on the structures of molecules and crystals The complete structural chemistry of an element or compound Structure in the solid state Structural changes on melting Structural changes in the liquid state Structural changes on boiling or sub- limation A classification of crystals Crystals consisting of infinite 3-dimen- sional complexes Layer structures Chain structures Crystals containing finite complexes Relations between crystal structures 2. SYMMETRY Symmetry elements Repeating patterns, unit cells, and lattices One- and two-dimensional lattices; point groups Three-dimensional lattices; space groups Point groups; crystal systems Equivalent positions in space groups Examples of 'anomalous' symmetry Isomerism Structural (topological) isomerism Geometrical isomerism Optical activity 3. POLYHEDRA AND NETS Introduction The basic systems of connected points Polyhedra Coordination polyhedra: polyhedral domains The regular solids Semi-regular polyhedra Polyhedra related to the pentagonal dodecahedron and icosahedron Some less-regular polyhedra Plane nets Derivation of plane nets Configurations of plane nets Three-dimensional nets Derivation of 3D nets Further characterization of 3D nets Nets with polyhedral cavities Interpenetrating nets Polyhedral molecules and ions Tetrahedral complexes Octahedral molecules and ions Cubic molecules and ions Miscellaneous polyhedral complexes Cyclic molecules and ions Infinite linear molecules and ions Crystal structures based on 3-connected nets Types of structural unit The plane hexagon net Structures based on other plane 3-con- nected nets Structures based on 3D 3-connected nets Contents Crystal structures based on 4-connected nets 99 Types of structural unit 99 Structures based on the plane 4-gon net 100 Layers of type A. Layers of type AX. Layers of type AX2. Layers of type AX4. 100-1 02 Structures based on the diamond net 102 AX2 structures. Structures based on 5 systems of interpenetrating diamond nets. 102-107 Structures based on more complex 4- connected nets 109 More complex tetrahedral nets. Nets with planar and tetrahedral co- ordination. Nets with polyhedral cavities or tunnels. 110-1 12 Space-filling arrangements of polyhedra Space-fillings of regular and Archi- medean solids Space-fillings of dodecahedra and related polyhedra 4. SPHERE PACKINGS Periodic packings of equal spheres Simple cubic packing The body-centred cubic packing The closest packing of equal spheres Icosahedral sphere packings. Sphere packings based on closest-packed layers Interstices between close-packed layers Structures with some pairs of adjacent layers of type A Hexagonal and cubic closest packing of equal spheres More complex types of closest packing Close-packed arrangements of atoms of two kinds Close-packed structures with atoms in tetra- hedral interstices Close-packed structures with atoms in octa- hedral interstices Some related MX2, MM'X~, and M2 M'X~ structures Close-packed structures with atoms in tetra- hedral and octahedral interstices An alternative representation of close-packed structures Structures built from close-packed AX3 layers ABX3 structures A3 B2 X9 structures A2 BX6 structures TETRAHEDRAL AND OCTAHEDRAL STRUCTURES Structures as assemblies of coordination poly- hedra Limitations on bond angles at shared X atoms The maximum number of polyhedra with a common vertex Tetrahedral structures Tetrahedra sharing vertices only Tetrahedra sharing edges only Tetrahedra sharing edges and vertices Octahedral structures Some finite groups of octahedra Infinite systems of linked octahedra Octahedra sharing only vertices Octahedra sharing only edges Octahedra sharing edges and vertices Octahedra sharing faces only Octahedra sharing faces and vertices Octahedra sharing faces and edges Octahedra sharing faces, edges, and vertices Structures built from tetrahedra and octa- hedra 6. SOME SIMPLE AX, STRUCTURES 130 The sodium chloride structure l3 The caesium chloride structure 135 The rutile structure Compounds ABX4, A2 BX6, etc, with 136 rutile-like structures Thefluorite(AX;)andantifluorite(A2 X)structures 204 140 Addition of anions to the fluorite structure: the Fe,Al structure 206 147 Defect fluorite structures 207 The pyrochlore structure 209 148 The Cd12 and related structures 209 . (X-H-X )- and (H20-H- OH2 1' Acids and acid salts Acids Acid salts The structures of acid salts and crystal- line oxy-acids Compounds of the noble gases Fluorides of xenon Fluoro-ions. halides-simple and com- plex. Oxychlorides and related compounds. Mercuric oxide and sulphide. Mercury-nitrogen com- pounds. 92 0-6 The structural chemistry of gallium and indium 926 The structural. crystal structures of basic salts 530 Finite hydroxy-metal complexes 532 1-dimensional hydroxy-metal com- plexes 532 2-dimensional hydroxy-metal com- plexes 535 15. WATER AND HYDRATES 537 The