The Group 13 Metals – Aluminium, Gallium, Indium and Thallium

Simon Aldridge is a Lecturer and Tony Downs is Emeritus Professor at the University of Oxford.

Chapter 1 Introduction to the Chemistry of the Group 13 Metals: Context and Current Perspectives (30 pages): Tony Downs. Reminder of the essential chemical characteristics of the metals, and how they differ from boron. General issues of redox chemistry, metal-metal bonding, and structure and bonding at large. Areas of greatest current interest and developments in methodology, leading to a (brief) preview of subsequent chapters. Chapter 2 Formal Oxidation State +3: Binary and Other Simple Inorganic Compounds (50 pages): Simon Aldridge. This will concentrate on recent advances in synthesis, physical and chemical characterisation, and applications organised on a ligand-by-ligand basis, viz. (i) hydrides; (ii) halides; (iii) oxygen-bound derivatives; (iv) chalcogen-bound derivatives; (v) derivatives with bonds to Group 15 atoms; (vi) derivatives with bonds to boron or heavier Group 14 elements; (vii) pseudohalides. The approach will be similar to that successfully used by Taylor and Brothers in Chapter 3 of the earlier Chemistry of Aluminium, Gallium, Indium and Thallium (edited by Downs, published by Blackie in 1993); cross-referencing to this and other texts, and judicious use of tables will aim to put new developments in context, while reducing undue repetition of what is now well established material. . Chapter 3 Formal Oxidation State +3: Organometallic Chemistry (50 pages): Professor A. H. Cowley, The University of Texas at Austin, U.S.A. Much the same approach as in Chapter 2 to be adopted here, with the main emphasis being on recent advances, but not modelled on the rather idiosyncratic Chapter 6 (by Starowieyski) in Chemistry of Aluminium, Gallium, Indium and Thallium . Synthesis and characterisation to be organised systematically according to organic group and to other ligands attached to the metal centre, e.g. H, halogen, Group 16-bound ligands, and Group 15-bound ligands. Structures, primary and secondary bonding, metathesis, complexation, and transition metal complexes to be treated as major issues. Role of organo-Group 13 metal compounds in catalysis. There is a pressing need for a readable, concise, yet authoritative and up-to-date review of organo-Group 13 metal derivatives, giving due weight to their role as mediators of important organic reactions. Chapter 4 Formal Oxidation State +2: Mononuclear vs. Metal-Metal Bonded Derivatives (30 pages): Prof W. Uhl, Universitat Munster, Germany. Here we compare and contrast mononuclear MII-centred species (identified, for example, by matrix-isolation or gas-phase studies or implied by kinetic studies of redox reactions) with compounds featuring an MII MII bond, e.g. M2X62 and M2R4 (M = Al, Ga, In or Tl; X = halogen; R = bulky organic or pseudo-organic ligand). The approach will be modelled on that adopted for indium(II) in a very recent review of low-valent indium compounds written by Pardoe and Downs (Chem. Rev. 2007, 107, #-#). Particular attention to be paid to the formation and properties of the metal-metal bond. Chapter 5 Formal Oxidation State +1: From Molecular to Ionic Compounds (50 pages): Prof Philip Power, UC Davis, USA. The review by Pardoe and Downs (see above) includes a section on indium(I) which will be used as a template for a more general treatment of Group 13 metals in the +1 oxidation state. Sub-sections would then be: (i) general characteristics and subdivision; (ii) molecular M(I) compounds (M = Al, Ga, In or Tl) aggregation, structures and reactions; (iii) M(I) compounds with appreciable ionic character, e.g. halides, oxysalts, salts of fluoroanions, etc. synthesis, properties, and role as synthons. Chapter 6 Mixed or Intermediate Valence Group 13 Metal Compounds (40 pages): Prof C L B Macdonald, University of Windsor, Canada. Here we are concerned with the formation and properties of compounds each incorporating Group 13 metal atoms M in two or more different oxidation states and environments. As noted in part of Section V of the Pardoe/Downs review (see above), these are generally Class A mixed valence compounds according to the Robin-Day classification. Sub-sections might then be: (i) preamble outlining the scope of this class of compound; and (ii) compounds with discrete M or M2 centres, e.g. MIMIIIX4, MI2MII2X6 (X = halogen), and MIMIIIS2. Chapter 7 From Metal Atoms via Metal Clusters to the Bulk Metal (50 pages): Prof H Schnockel, University of Karlsruhe, Germany. In this chapter we would aim to follow the transition from the free metal atom, through the formation of increasingly large metal clusters subject to varying degrees of oxidation, to the bulk metal. Chapter 8 Simple and Mixed Metal Oxides and Hydroxides: Solids with Extended Structures of Different Dimensionalities and Porosities (50 pages): Dr A Fogg, University of Liverpool, UK. Here the aim will be to review the role of the Group 13 metals in solid binary, ternary or multicomponent oxides characterised by 1-, 2- or 3-dimensional solid frameworks and varying degrees of openness. Hence we would hope to provide a manageable but authoritative overview of a huge and highly topical subject embracing microporous and macroporous, and layered materials, of which zeolites, clays, phosphates and phosphonates are among the best known representatives, and their applications in catalysis, separation, ion exchange, etc. More or less open and/or defect structures may give rise to solids with significant electrical and/or optical properties, e.g. normal or doped In2O3, yttrium aluminium garnet, etc. The chapter should seek to answer the questions: why a Group 13 metal, and why this particular Group 13 metal?. The synthesis, properties and applications of such compounds will be discussed. Chapter 9 Coordination and Solution Chemistry of the Metals: Biological, Medical and Environmental Relevance (50 pages): Prof P Brothers, University of Auckland, New Zealand. In this case, the obvious starting points of reference would be Chapter 8 (by Tuck) in Chemistry of Aluminium, Gallium, Indium and Thallium (q.v.) and Chapters 3.4 and 3.5 (by Robinson and Rasika Dias, respectively) in Comprehensive Coordination Chemistry II , Vol. 3, Elsevier, 2004. In earlier treatments, however, the distinction between normal compounds of the metals and genuine coordination compounds formed by addition to such compounds has not always been clear, leading to repetition and unnecessary overlap. Here we would want to make it clear that the focus of the chapter is on the natural Lewis acidity of most Group 13 metal compounds, while allowing for the possibility of Lewis basicity in the case of M(I) species (M = Al, Ga, In or Tl), and on the neutral or charged complexes they form through partial charge transfer with an appropriate partner. Organisation will be by ligand type, and for each ligand type the metals will generally be treated in turn, with a further sub-division, as necessary, by oxidation state. Rather than having separate chapters on the biological, environmental and medical roles of the metals (cf. Chapter 9 in Chemistry of Aluminium, Gallium, Indium and Thallium), the plan would be to use this chapter as a vehicle for such (important and sometimes controversial) aspects, which reflect mainly the Lewis acidity of the M3+ ions and their derivatives. Chapter 10 III-V and Related Semiconductor Materials (30 pages): Prof P O Brien, University of Manchester, UK. An account seeking to enlarge upon, and update, Chapter 5 (by Grant) in Chemistry of Aluminium, Gallium, Indium and Thallium . The plan would be to give rather more weight than in this earlier review to the synthesis of the materials, to multicomponent phases, e.g. AlGaInAs, to superlattice structures, low-dimensional and quantum dot structures, and the devices that are currently or potentially important. Chapter 11 Group 13 Metal Compounds as Reagents or Mediators in Organic Reactions (50 pages): Dr J A Miller, Exxon Chemical Co., Texas, USA. Finally, we would aim to update the good, well organised chapter on this topic by Miller (Chapter 7) in Chemistry of Aluminium, Gallium, Indium and Thallium . Significant advances in the past 15-20 years include (i) use of heavier Group 13 metal hydrides as selective reducing agents, (ii) increasing use of indium and its compounds as reagents or mediators in organic and organometallic synthesis, including the ability to bring about a variety of changes in environmentally friendly aqueous media, and (iii) the use of ionic liquids that incorporate Group 13 metals as reaction media. Organisation to be by Group 13 metal, with subdivisions generally to be by reaction type.