Reaction Mechanisms of Inorganic and Organometallic Systems TOPICS IN INORGANIC CHEMISTRY A Series of Advanced Textbooks in Inorganic Chemistry Series Editor Peter C. Ford, University of California, Santa Barbara Chemical Bonding in Solids, J. Burdett Reaction Mechanisms of Inorganic and Organometallic Systems, 3rd Edition, R. Jordan Reaction Mechanisms of Inorganic and Organometallic Systems Third Edition Robert B. Jordan OXFORD UNIVERSITY PRESS 2007 OXPORD UNIVERSITY PRESS Oxford University Press, Inc., publishes works that further Oxford University's objective of excellence in research, scholarship, and education. Oxford New York Auckland Cape Town Dar es Salaam Hong Kong Karachi Kuala Lumpur Madrid Melbourne Mexico City Nairobi New Delhi Shanghai Taipei Toronto With offices in Argentina Austria Brazil Chile Czech Republic France Greece Guatemala Hungary Italy Japan Poland Portugal Singapore South Korea Switzerland Thailand Turkey Ukraine Vietnam Copyright © 2007 by Oxford University Press, Inc. Published by Oxford University Press, Inc. 198 Madison Avenue, New York, New York 10016 www.oup.com Oxford is a registered trademark of Oxford University Press All rights reserved. No part of this publication may be reproduced, stored in 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. Library of Congress Cataloging-in-Publication Data Jordan, Robert B. Reaction mechanisms of inorganic and organometallic systems / Robert B. Jordan.—3rd ed p. cm. Includes bibliographical references and index. ISBN 978-0-19-530100-7 1. Reaction mechanisms (Chemistry) 2. Organometallic compounds. 3. Inorganic compounds. I. Title. QD502J67 2006 41'.39—dc25 2006052498 987654321 Printed in the United States of America on acid-free paper Preface This book evolved from the lecture notes of the author for a one- semester course given to senior undergraduates and graduate students over the past 20 years. This third edition presents an updating of the material to cover the literature through to the end of 2005, with occasional excursions to early 2006. As a result, the total number of references has increased from about 660 in the second edition to over 1570 in the present one, and 140 pages of text have been added; this seems to be a clear testament to the vitality of the subject area. A new Chapter 9 on kinetics in heterogeneous systems has been added. This area has long been the domain of chemical engineers, but it is of increasing relevance to inorganic kineticists who are studying catalytic processes, such as hydrogenation and carbonylation reactions, where gas/liquid mass transfer is involved. This chapter also covers the kinetic aspects of adsorption and reaction of species on solids, and the question of whether the reaction is really homogeneous or heterogeneous. The overall organization of the first edition has been retained. The first two chapters cover basic kinetic and mechanistic terminology and methodology. This material includes new sections on the analysis of data under second-order conditions, Curtin-Hammett conditions and an expanded discussion of pressure effects. New material has been added at various points throughout Chapters 3 and 4. The coverage of organometallic systems in Chapter 5 has been increased substantially, primarily with material on metal hydrides, catalytic hydrogenation and asymmetric hydrogenation. The inverted region and activation parameters for electron-transfer reactions predicted by Marcus theory have been added to Chapter 6, along with an expanded discussion of intervalence electron transfer. The recently revised assignment of the electronic spectra of metal carbonyls has resulted in substantial revisions to photochemical interpretations in Chapter 7. The coverage of selected bioinorganic systems in Chapter 8 has been extended to include methylcobalamin as a methyl transferase and the chemistry of nitric oxide synthase. Chapter 10 on experimental methods and their applications is largely unchanged. Some new problems for each chapter have been added. There is more material than can be covered in depth in one semester, but the organization allows the lecturer to omit or give less coverage to certain areas without jeopardizing an understanding of other areas. It is assumed that the students are familiar with elementary crystal field v vi Preface theory and its applications to electronic spectroscopy and energetics, and concepts of organometallic chemistry, such as the 18-electron rule, 71 bonding and coordinative unsaturation. For the material in the first two chapters, some background from a physical chemistry course would be useful, and familiarity with simple differential and integral calculus is assumed. It is expected that students will consult the original literature to obtain further information and to gain a feeling for the excitement in the field. This experience also should enhance their ability to critically evaluate such work. Many of the problems at the end of the book are taken from the literature, and original references are given; outlines of answers to the problems will be supplied to instructors who request them from the author. The issue of units continues to be a vexing one in this area. A major goal of this course has been to provide students with sufficient background so that they can read and analyze current research papers. To do this and be able to compare results, the reader must be vigilant about the units used by different authors. Energy units are a special problem, since both joules and calories are in common usage. Both units have been retained in the text, with the choice made on the basis of the units in the original work as much as possible. However, within individual sections the text uses one energy unit. Bond lengths are given in angstroms, which are still commonly quoted for crystal structures. The formulas for various calculations are given in the original or most common format, and units for the various quantities are always specified. The author is greatly indebted to all of those whose research efforts have provided the core of the material for this book. The author is pleased to acknowledge those who have provided the inspiration for this book: first, my parents, who contributed the early atmosphere and encouragement; second, Henry Taube, whose intellectual stimulation and experimental guidance ensured my continuing enthusiasm for mechanistic studies. I am only sorry that I did not finish this edition soon enough for Henry to see that I did make the changes he suggested. Finally and foremost, Anna has been a vital force in the creation of this book through her understanding of the time commitment, her comments, criticisms and invaluable editorial assistance in producing the camera-ready manuscript. However, the inevitable remaining errors and oversights are entirely the responsibility of the author. R.B.J. Edmonton, Alberta June 2006 Contents 1 Tools of the Trade, 1 1.1 Basic Terminology, 1 1.2 Analysis of Rate Data, 3 1.3 Concentration Variables and Rate Constants, 12 1.4 Complex Rate Laws, 15 1.5 Complex Kinetic Systems, 15 1.6 Temperature Dependence of Rate Constants, 17 1.7 Pressure Dependence of Rate Constants, 21 1.8 Ionic Strength Dependence of Rate Constants, 24 1.9 Diffusion-Controlled Rate Constants, 25 1.10 Molecular Modeling and Theory, 28 2 Rate Law and Mechanism, 31 2.1 Qualitative Guidelines, 31 2.2 Steady-State Approximation, 32 2.3 Rapid-Equilibrium Assumption, 34 2.4 Curtin-Hammett Conditions, 36 2.5 Rapid-Equilibrium or Steady-State?, 37 2.6 Numerical Integration Methods, 3 8 2.7 Principle of Detailed Balancing, 39 2.8 Principle of Microscopic Reversibility, 40 3 Ligand Substitution Reactions, 43 3.1 Operational Approach to Classification of Substitution Mechanisms, 43 3.2 Operational Tests for the Stoichiometric Mechanism, 44 3.3 Examples of Tests for a Dissociative Mechanism, 49 3.4 Operational Test for an Associative Mechanism, 54 3.5 Operational Tests for the Intimate Mechanism, 57 3.6 Some Special Effects, 73 3.7 Variation of Substitution Rates with Metal Ion, 83 3.8 Ligand Substitution on Labile Transition-Metal Ions, 94 3.9 Kinetics of Chelate Formation, 100 4 Stereochemical Change, 114 4.1 Types of Ligand Rearrangements, 114 4.2 Geometrical and Optical Isomerism in Octahedral Systems, 119 4.3 Stereochemical Change in Five-Coordinate Systems, 128 4.4 Isomerism in Square-Planar Systems, 130 4.5 Fluxional Organometallic Compounds, 130 5 Reaction Mechanisms of Organometallic Systems, 150 5.1 Ligand Substitution Reactions, 150 5.2 Insertion Reactions, 168 5.3 Oxidative Addition Reactions, 177 vii viii Contents 5.4 Reductive Elimination Reactions, 188 5.5 Reactions of Alkenes, 188 5.6 Catalytic Hydrogenation of Alkenes, 195 5.7 Homogeneous Catalysis by Organometallic Compounds, 225 6 Oxidation-Reduction Reactions, 253 6.1 Classification of Reactions, 253 6.2 Outer-Sphere Electron-Transfer Theory, 256 6.3 Differentiation of Inner-Sphere and Outer-Sphere Mechanisms, 273 6.4 Bridging Ligand Effects in Inner-Sphere Reactions, 274 6.5 Intervalence Electron Transfer, 281 6.6 Electron Transfer in Metalloproteins, 285 7 Inorganic Photochemistry, 292 7.1 Basic Terminology, 292 7.2 Kinetic Factors Affecting Quantum Yields, 294 7.3 Photochemistry of Cobalt(III) Complexes, 295 7.4 Photochemistry of Rhodium(III) Complexes, 301 7.5 Photochemistry of Chromium(III) Complexes, 304 7.6 Photochemistry of Ruthenium(II) Complexes, 310 7.7 Organometallic Photochemistry, 313 7.8 Photochemical Generation of Reaction Intermediates, 327 8 Bioinorganic Systems, 337 8.1. Basic Terminology, 337 8.2 Terms and Methods of Enzyme Kinetics, 338 8.3 Vitamin B , 341 12 8.4 A Zinc(II) Enzyme: Carbonic Anhydrase, 356 8.5 Enzymic Reactions of Dioxygen, 361 8.6 Enzymic Reactions of Nitric Oxide, 373 9 Kinetics in Heterogeneous Systems, 391 9.1 Gas/Liquid Heterogeneous Systems, 391 9.2 Gas/Liquid/Solid Heterogeneous Systems, 400 9.3 Where is the Catalyst?, 409 10 Experimental Methods, 422 10.1 Flow Methods, 423 10.2 Relaxation Methods, 428 10.3 Electrochemical Methods, 431 10.4 Nuclear Magnetic Resonance Methods, 435 10.5 Electron Paramagnetic Resonance Methods, 446 10.6 Pulse Radiolysis Methods, 448 10.7 Flash Photolysis Methods, 451 Problems, 457 Chemical Abbreviations, 488 Index, 491 Reaction Mechanisms of Inorganic and Organometallic Systems