THE CHEMISTRY OF METAL ALKOXIDES THE CHEMISTRY OF METAL ALKOXIDES

by

Nataliya Ya. Turova Evgenia P. Turevskaya MV Lomonosov State University Moscow

Vadim G. Kessler Swedish University of Agricultural Sciences Uppsala, Sweden

Maria I. Yanovskaya L. Ya. Karpov Institute of Physical Chemistry Moscow

KLUWER ACADEMIC PUBLISHERS NEW YORK, BOSTON, DORDRECHT, LONDON, MOSCOW eBook ISBN: 0-306-47657-6 Print ISBN: 0-7923-7521-1

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Symbols and abbreviations ix PREFACE xi Chapter 1. INTRODUCTION 1 1.1. Classification. General characteristic of the metal alkoxides 1 1.2. Main steps in the development of the chemistry of metal alkoxides 3 1.3. Application of alkoxides in sol-gel processes 6 Chapter 2. GENERAL SYNTHETIC APPROACHES 11 2.1. Reactions of metals with (method 1) 11 2.2. Anodic oxidation of metals (method 2) 14 2.3. Reactions of metal oxides or with alcohols (method 3) 16 2.4. Alcoholysis of (method 4) 18 2.5. Metathesis reactions of with alkaline alkoxides or ammonia (method 5) 21 2.6. Reactions of interchange or (method 6) 26 2.7. Redox reactions of metal alkoxides: Oxidation of organometallic compounds (method 7) 28 Chapter 3. PHYSICOCHEMICAL PROPERTIES OF ALKOXIDES: REGULARITIES IN THE HOMOLOGOUS SERIES 31 Chapter 4. CRYSTAL AND MOLECULAR STRUCTURES OF METAL ALKOXIDES 37 4.1. Mononuclear complexes 38 4.2. Binuclear complexes 41 4.3. Trinuclear complexes 45 4.4. Tetranuclear complexes 48 4.5. Pentanuclear complexes 55 4.6. Hexanuclear complexes 56 4.7. Oligomeric alkoxides containing more than 6 nuclei 59 4.8. Polymers 65 Chapter 5. OXOALKOXIDES 69 Chapter 6. SPECIFIC FEATURES OF PHYSICO-CHEMICAL BEHAVIOR: COORDINATION POLYMERISM 77 Chapter 7. HETEROLEPTIC METAL ALKOXIDES CONTAINING CARBOXYLATO-, AND AMINOALKOXIDE 87 vi Contents

7.1. Synthesis 88 7.2. Molecular structures 92 7.3. Particular features of and thermolysis 94 Chapter 8. ADDUCTS AND HETEROMETALLIC ALKOXIDES 97 8.1. Solvate complexes 97 8.2. Heterometallic complexes 99 Chapter 9. HYDROLYSIS OF METAL ALKOXIDES AND SYNTHESIS OF SIMPLE OXIDES BY THE SOL-GEL METHOD 107 9.1. Alkoxides of the metals of groups I and II 112 9.2. Aluminum alkoxides 112 9.3. Alkoxides of rare earth elements 114 9.4. , tin, lead alkoxides 114 9.5. and alkoxides 115 9.6. Bismuth alkoxides 122 9.7. Vanadium alkoxides 123 9.8. and alkoxides 124 9.9. and alkoxides 125 9.10. ethoxide 125 Chapter 10. SYNTHESIS OF COMPLEX OXIDES FROM METAL ALKOXIDES 127 10.1. Barium titanate and solid solutions 129 10.2. Complex niobates and tantalates 137 10.3. Lead zirconate-titanate (PZT) and lead-lanthane zirconate-titanate (PLZT) solid solutions 141 10.4. Bismuth strontium tantalates and niobates 144 10.5. High-temperature superconductors 147 Chapter 11. HYBRID ORGANIC-INORGANIC MATERIALS 149 11.1. Systems with weak chemical interactions 150 11.2. Systems with strong chemical interactions between components 153 Chapter 12. THE OVERVIEW OF METAL ALKOXIDE DERIVATIVES ALONG THE GROUPS OF THE PERIODIC TABLE 159 12.1. Alkaline, alkaline earth, and magnesium alkoxides 160 12.2. Copper, silver, and gold alkoxides 199 12.3. Beryllium alkoxides 211 12.4. Zinc, cadmium, and mercury alkoxides 217 12.5. Aluminium alkoxides 224 Contents vii

12.6. , indium, and thallium alkoxides 245 12.7. Rare earth elements alkoxides 256 12.8. Germanium alkoxides 289 12.9. Tin alkoxides 297 12.10. Lead alkoxides 309 12.11. Titanium alkoxides 315 12.12. Zirconium and alkoxides 348 12.13. Thorium alkoxides 367 12.14. Bismuth alkoxides 372 12.15. Vanadium alkoxides 379 12.16. Niobium and tantalum alkoxides 383 12.17. Chromium alkoxides 399 12.18. Molybdenum and tungsten alkoxides 425 12.19. Uranium and transuranium elements alkoxides 434 12.20. Manganese alkoxides 468 12.21. Technetium and alkoxides 473 12.22. Iron alkoxides 475 12.23. and alkoxides 490 12.24. Alkoxide derivatives of platinum metals 497 REFERENCES 505 SUBJECT INDEX 563 SYMBOLS AND ABBREVIATIONS

Ac MeCO exp. explosive acac gl. glass Am gr. group amor. amorphous grn. green antiferr antiferro-magnetic at. atom hc. hydrocarbon. ax. axial hex. hexane b. boiling point Hmpa bipyr. bipyramid ins. insoluble bl. blue investig. investigated blk. black invol. involatile brn. brown isostr. isostructural bz. liq. liquid cat. cathode m. melting point CN coordinating number magn. magnetic Cod cyclooctadiene Mössb. Mössbauer sp. colrl. colorless m-s mass-spectra compl. complex oct. octahedron conduct. conductometry or. orange cr. crystalline org. organic diamagn. diamagnetic paramagn. paramagnetic d density pentag. pentagonal dec. decomposition powd. powder Dig diglyme prop. properties Diox dioxan ref. reference Dipy 2,2’dipyridil s. soluble, ~tion dist. distorted sld. solid Dme solv. solvent Dmfa sp. spectrum Dmpe stab. stable Dmso struc. structure, ~al, electr. electronic subl. sublimation En- synth. synthetic equ. equatorial t temperature, °C eth. tensim. tensimetry x

term. terminal vol. volatile tetrah. tetrahedron voltamet. voltammetry thd tetramethylheptanedione wh. white Tmeda yel. yellow tol. toluene effective magnetic trian. triangle moment, trig. trigonal molecular complexity unstab. unstable enthalpy, cal/mol v. very dielectric constant vac. vacuum dipol moment, D visc. viscous polyhedron one of which vlt. violet vertexes is occupied by a pair of electrons PREFACE

The study of the chemistry of metal alkoxides, which began more than 100 years ago, is now experiencing a renaissance connected with the broad application of these compounds as molecular precursors in the synthesis of materials of modern technology based on simple and complex oxides. The solution of this problem is occupying a wide circle of inorganic chemists, technologists specializing in fine synthesis in nonaqueous media, and those working on the production of films and coatings. The application of metal alkoxides in the first step of sol-gel technology (based on hydrolysis of alkox- ides with subsequent dehydration of the hydrated oxides formed) can benefit from this monograph covering the modern literature devoted to all the steps of this process. The information on chemistry of metal alkoxides has been reported in a number of reviews (devoted to the single groups of derivatives) and numerous original publications. The only other monograph — Metal Alkoxides by D. C. Bradley, R. C. Mehrotra and D. P. Gaur was published in 1978 (Aca- demic Press, London) and, unfortunately, does not reflect modern findings. The present book is devoted to the general questions of the chemistry of metal alkoxides — the synthetic routes to them (both laboratory and technol- ogy), physicochemical properties, structure, specific features of single groups of alkoxides, theoretical principles of their use for the preparation of simple and complex oxides by the sol-gel method, and major directions of the appli- cation of this method in the preparation of functional materials. Chapter 12 describes the derivatives of single elements of first throuth eighth Groups of the Periodic Table. The tables in this chapter contain the major data on the alkoxides, phenoxides, siloxides, derivatives of polyatomic alcohols, and phe- nols — their composition, structure, preparation techniques, and major phys- icochemical characteristics. Each table is accompainied by text that comments on it but is not a review in the classical sense of this word. These data allow this book to be used as a handbook permitting a quick and essentially complete acquaintance with the distinct compounds and the literature describing them. The book is intended for chemists and technologists who specialize in the area of functional materials, and who apply the metal alkoxides in their prac- tice. It also can be used as a textbook for students. xii

This book is written by a group of authors — Chapter 1 by N. Ya. Turova and M. I. Yanovskaya, Chapters 2 to 6 and 8 by N. Ya. Turova, Chapter 7 by V. G. Kessler, Chapter 9 and 10 by M. I. Yanovskaya, Chapter 11 by E. P. Turevskaya and Chapter 12 by E. P. Turevskaya, N. Ya. Turova, and V. G. Kessler. The general scientific editing of the book has been carried out by N. Ya. Turova and the English translation by V. G. Kessler. The authors express their sincerest gratitude to their colleagues — profes- sors L. G. Hubert-Pfalzgraf, K. G. Caulton, M. Veith, R. C. Mehrotra, W. E. Buhro, and G. Westin — who informed them about the publications of their works, Dr. A. I. Yanovsky for the continuous consultations on structural chemistry and tremendous help in the final editing of the text, Drs. D. E. Tchebukov and P. S. Berdonosov for assistance in the typing of the man- uscript. The special thanks are directed to Dr. T. J. Leedham, the president of the Inorgtech Corp. (Mildenhall, Suffolk, UK) for sponsoring the writing of this book and to Professor B. A. Popovkin for the moral support of this work. Inquiries can be sent by e-mail to [email protected] or [email protected].