bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polonium: Inorganic Chemistry
Authors: Zingaro Ralph A. 
Published: March 2006

AbstractThe chemistry of polonium is quite limited. Because all of the isotopes of this element are radioactive, and because it is available in such limited quantities, research with polonium is difficult. The metal has been isolated and characterized. Although a number of polonium compounds, such as PoO2 have been well characterized, the evidence for many is insubstantial. Among the halide derivatives, PoCl4 has been studied in greatest detail. A number of other halides, and their complex ions such as PoBr6‐2, have been studied with considerable success. A simple binary nitride has never been prepared, and only indirect evidence for the existence of H2Po has been reported.
Polyhedra
Authors: King R. Bruce 
Published: March 2006

Abstract

The concept of a polyhedron is a useful way of describing diverse chemical structures, including those of coordination compounds and metal clusters. In this context, a polyhedron may be regarded as a set consisting of vertices, edges, and faces. Familiar examples of polyhedra are the five regular (Platonic) polyhedra, that is, the tetrahedron, cube, octahedron, dodecahedron, and icosahedron. The relationship between the numbers of vertices (
v
), edges (
e
), and faces (
f
) in a polyhedron can be described by Euler's theorem, that is,
v
−
e
+
f
= 2. A given polyhedron can be converted to larger polyhedra by capping one or more of its faces. Interchanging the vertices and faces of a polyhedron leads to its dual, which has the same symmetry as the original polyhedron. A projection of a polyhedron onto a plane, known as a Schlegel diagram, is often a useful way of visualizing polyhedra, which supplements the usual perspective drawings. There are no formulas, direct or recursive, for which the number of distinct polyhedra having a given number of vertices, edges, or faces can be calculated.
Polynuclear Organometallic Cluster Complexes
Authors: Keister Jerome B. 
Published: March 2006

Abstract
The title refers to molecular compounds containing three or more transition metal atoms and hydrocarbyl ligands as a part of the metal–carbon cluster core. Because the chemistry of trimetallic clusters is the most well developed, these examples are to be stressed. Selected examples are presented to illustrate the principles of structure and bonding of organometallic clusters, synthetic approaches, and chemical reactions, including ligand substitution, oxidative addition, intramolecular insertion, protonation of metal–metal bonds and coordinated ligands, nucleophilic attack on coordinated ligands, and ligand fluxionality. The chemistry of these clusters is exemplified by trimetallic clusters containing hydrocarbon fragments of one, two, or three carbon atoms. While, many of the features of cluster chemistry are common with those of organometallic complexes containing a single metal atom, there are notable differences in structures and reactivities owing to the tendencies of ligands to bridge between two or more metal atoms and for ligands bound to only a single metal atom to undergo facile intramolecular migrations between metal atoms. These distinctions give rise to the ‘metal‐cluster‐metal surface analogy’ in which structural and spectroscopic features of organometallic clusters are used as models for hydrocarbons chemisorbed on metal surfaces.
Polyoxometalates
Authors: Pope Michael T. 
Published: March 2006

AbstractThe elements of groups 5 and 6, especially vanadium, molybdenum, and tungsten in their highest oxidation states, form a vast range of polyoxoanions that can incorporate most other positive‐valent elements of the periodic table. The first examples of these complexes were discovered in the latter half of the nineteenth century, but it is only within the last few decades that the extraordinary variety and numbers of polyoxoanion structures, properties, and applications have begun to be recognized. The field has historically been divided into isopoly‐ and heteropolyanions according to whether one or more than one type of positive‐valent element is incorporated, respectively. The largest variety of isopolyanions is found with V, Mo, and W, and the results of speciation studies in aqueous solution are summarized. The structures of heteropolyanions are dependent upon the coordination demands of the heteroatom, and the major types based on 4‐, 6‐, 8‐, and 12‐coordination are described. In virtually every case, the V, Mo, and W atoms (addenda atoms) occupy MO6octahedra with one or two (cis) unshared oxygen atoms. Such octahedra share vertices and edges with their neighbors. Structures in which one or more (adjacent) MO6octahedra have been ‘removed’ can be prepared by the control of solution pH, and the resulting lacunary anions are used as precursors to generate new, larger structures and derivatives. Since the addenda atoms are in their highest oxidation states (d0), many polyoxoanions can reversibly accept variable numbers of electrons to yield mixed‐valence heteropoly ‘blues’ (d0,d1) with delocalized hopping electrons and ‘browns’ (d0,d2) with metal–metal bonds. Several strategies for the synthesis of derivatized and functionalized polyoxoanions with organic and organometallic groups are reviewed since this has been a major thrust in the field in recent years. Also, a recent development has been the discovery of extremely large polyoxoanions with 100 + metal atoms that are readily prepared and are stable in aqueous solution. Examples are the mixed‐valence polymolybdate wheels (Mo154and Mo176) and tungstate(VI) assemblies (W184Ln16). Polyoxoanions have long been used in analytical chemistry, and their use as heterogeneous and homogeneous acid and oxidation catalysts continues to be developed. Other applications, especially in structural biology (imaging, crystallographic phasing) and medicine (antiviral and antitumoral agents) are also important.
Polysiloxanes & PolysilanesBased in part on the article Polysiloxanes & Polysilanes by Robert West which appeared in theEncyclopedia of Inorganic Chemistry, First Edition.
Authors: Mitra Amitabha , Atwood David A. 
Published: March 2006

AbstractSilicon‐containing polymers, of which polysiloxanes and polysilanes are the most important ones, are becoming more and more important industrially because of their unique properties. Polysiloxanes that contain SiOSi linkage in their structure are most commonly prepared by ring‐opening polymerization of cyclic siloxanes. The monomer for this process is prepared by the ‘Direct Process’. The polysiloxanes are hydrophobic despite having polar SiO bonds in their structures. They possess highly flexible structures with large SiOSi bond angles. They are chemically inert and have good thermal stability, low viscosity, and good gas permeability. These polymers and related copolymers find use in a variety of fields as silicone fluids, elastomers, and resins. Polysilanes consisting of chains exclusively made up of silicon atoms are most commonly prepared by Wurtz coupling reaction. through sodium condensation of dichlorosilanes. The most interesting aspect of their properties is σ‐electron delocalization, which gives rise to many interesting photochemical and photophysical effects like thermochromism, solvatochromism, and ionochromism. These polymers find use in preparation of silicon carbide and as photoresists, photoinitiators, and hole conductors in electrophotography. In this article, the history, synthesis, properties, and application of polysiloxane and polysilane polymers have been reviewed.
Rhodium: Organometallic Chemistry
Authors: Mague Joel T. 
Published: March 2006

AbstractA review of the major advances in the organometallic chemistry of rhodium covering the period 1993–2003 is presented. Highlighted are complexes containing N‐donor ligands such as triazacyclononanes and tris‐(pyrazolyl)borates, those containing vinylidene and allenylidene ligands, and the formation of metallamacrocyclic complexes. Also featured are results of detailed computational studies on the activation of CH bonds and the course of olefin hydroformylation and hydrogenation processes. Classes of organorhodium compounds covered include alkyl, aryl, vinylidene, allenylidene, alkynyl, and carbene complexes. Also reviewed are alkene, alkyne, isocyanide, and arene complexes, as well as carbonyl cluster compounds together with significant coverage of dinuclear complexes stabilized by bis(diphenylphosphino)methane ligands.
Ruthenium: Inorganic & Coordination ChemistryBased in part on the article Ruthenium: Inorganic & Coordination Chemistry by Bruno Chaudret & Sylviane Sabo‐Etienne which appeared in theEncyclopedia of Inorganic Chemistry, First Edition.
Authors: Sabo‐Etienne Sylviane , Grellier Mary 
Published: March 2006

AbstractThis article presents an overview of the inorganic and coordination chemistry of ruthenium. Since the first edition of the encyclopedia in 1994, the field has seen a huge growth. We have attempted to select the most useful data for the readers not familiar with this topic and to detail the most promising systems for future developments. Key data and recent highlights are thus presented for seven classes of compounds incorporating the following ligands: (1) Halides: RuCl3·xH2O is by far the most useful starting material in ruthenium chemistry. (2) Oxygen‐donor ligands: this area is dominated by the chemistry of oxo complexes, with many applications in catalysis. (3) Sulfur‐donor ligands: potential applications are found in medicinal chemistry as antitumor agents and as radiosensitizers. (4) Nitrogen‐donor ligands: they represent the most important class of compounds in ruthenium chemistry. Supramolecular chemistry dominates, with photo‐redox processes and a wide range of applications being investigated from solar energy conversion to bioapplications. Ammines and bipyridines (and related ligands) are key ligands in this area. A great variety of inorganic architectures have been designed to assemble molecular machines and to favor interactions with DNA. (5) Phosphorus‐donor ligands: this class of compounds is at the origin of a rich organometallic chemistry, and the resulting complexes are often used as precursors in homogeneous catalysis. The design of new ligands for the improvement of catalytic performances is an active area of research. (6) Group 14 ligands: this field is dominated by the reactivity with silanes. New bonding modes, concepts, and applications have been disclosed. (7) Hydride ligands: the most recent developments concern the chemistry of dihydrogen complexes. The formation of dihydrogen bonds should have important consequences on the selectivity and stereochemistry in many catalytic processes. Finally, the last section is devoted to polynuclear complexes, with the new developments in the field of nanoparticles.
S
‐Donor Ligands
Authors: Collinson Simon R. , Schröder Martin 
Published: March 2006

Abstract
The chemistry of S‐donor ligands with metal centres is reviewed with emphasis placed on the structures and redox activity of the resultant complexes. Sulfides and thiolates bind to a wide range of metal ions. The oxidation of thiolates to sulfones and sulfoxides and the structures and chemistry of metal‐thiolene complexes are detailed. Thioethers are generally poor ligands for transition metal ions but macrocylic ligands afford stable complexes. Many metalloproteins contain metal–sulfur bonds and the structures of many of these have now been elucidated. This has sparked a renaissance in the synthesis of low‐molecular weight metal complex mimics.
Scandium, Yttrium & The Lanthanides: Organometallic ChemistryBased in part on the article Scandium, Yttrium & The Lanthanides: Organometallic Chemistry by R. D. Köhn, G. Kociok‐Köhn, & H. Schumann which appeared in theEncyclopedia of Inorganic Chemistry, First Edition.
Authors: Schumann Herbert , Fedushkin Igor L. 
Published: March 2006

AbstractThe group 3 metals scandium and yttrium and the 4f elements lanthanum to lutetium build up a big variety of organometallic compounds, in general with the metal in the oxidation state +3. Most of them are sandwich complexes Cp3Ln, Cp2LnX, and CpLnX2containing unsubstituted or substituted cyclopentadienyl ligands. In addition, cyclopentadienyl‐free organo rare earth compounds, like alkyl or aryl derivatives, alkenyl, allyl, alkynyl, hydrido, and carbene complexes, and organolanthanide compounds with indenyl, fluorenyl, cyclooctatetraenyl, or with heterocyclic ligands are described. Samarium, europium, and ytterbium form reasonable stable organic compounds in the oxidation state +2, whereas only a few rare earth organometallics with the metal in the oxidation state 0, +1, and +4 are known. All organo rare earth complexes are extremely sensitive to oxygen and water. The development of various synthetic methods as well as intensive single‐crystal X‐ray structure investigations made these highly reactive organometallic compounds available for use as organic synthons, efficient catalysts for polymerization, hydrogenation, hydroamination, and hydrosilylation as well as precursors for Metal Organic Chemical Vapor Deposition (MOCVD) and other material science applications.
Semiconductor Interfaces
Authors: Tan Ming X. , Bansal Ashish , Lauermann Iver , Shreve Gary A. , Lewis Nathan S. 
Published: March 2006

AbstractThis article describes the properties of semiconductors that are responsible for the operation of rectifiers, transistors, photovoltaic devices, and light emitting. The penetration of the electric field and the electric potential into a bulk semiconductor phase yields a nonuniform carrier concentration in the sample, and produces contacts that either attract or repel specific types of charge carriers. Chemical control over these electric fields is crucial to the technology of semiconductor contacts. In principle, such control can be established through a simple variation in the electrochemical potential of the contacting phase. In practice, this ideal model often does not apply, and other factors influence or completely determine the interfacial electric field strength. The application of these principles is described for semiconductor/semiconductor, semiconductor/metal, semiconductor/liquid, and semiconductor/polymer contacts, making the approach valuable for understanding the operational principles of a variety of technologically important semiconductor devices.
Silicon: Inorganic Chemistry
Authors: Lickiss Paul D. 
Published: March 2006

AbstractSilicon is an element of vital importance in many areas of modern synthetic chemistry, the electronics industry and in materials science. This article attempts to summarize the many types of important inorganic derivatives of silicon but excludes the chemistry of silicates and zeolites, which are covered in separate articles. The isolation of elemental silicon from sand is described together with the various methods of purification of the element for use in the semiconductor industry. A brief description of the occurrence of silicon in biology is also given. The bulk of the article deals with compounds of silicon organized according to coordination number. One‐coordinate compounds are short‐lived intermediates and are described briefly. Two‐coordinate compounds, silylenes, have become increasingly important in recent years as are transition metal complexes in which they act as ligands. The use of bulky substituents has allowed stable silylenes to be isolated and their chemistry is described. Three‐coordinate compounds comprise radicals, cations, anions, and silanes (compounds containing a double bond to Si). These species are also generally short‐lived and reactive. The bulk of the article deals with four‐coordinate compounds and is organized according to the substituents at silicon. The industrially important hydrosilanes and halosilanes are described together with the mixed halohydrosilanes and the less common pseudohalosilanes. Alkoxysilanes are also industrially important and these are discussed with other oxygen derivatives such as esters and silanols. Compounds containing SiN bonds are also common and have interesting structural features. The preparation and structures of transition metal complexes containing silyl ligands is described. This is followed by a description of compounds containing silicon with coordination number five or six. The final section describes the analytical methods for the determination of the composition and structure of inorganic silicon compounds. Compounds containing SiC bonds are excluded throughout.
Silicon: Organosilicon Chemistry
Authors: Sakurai Hideki 
Published: March 2006

Abstract
An overview of the chemistry of organosilicon compounds from the first synthesis in 1863 to the latest results is presented. After an introduction, classes of compounds and nomenclature are briefly described. Synthesis of organosilicon compounds is then disucssed systematically. Characteristic points of structure and bonding of organosilicon compounds, including tetrahedral and polyhedral compounds are described. Important σ–π conjugation (sigma‐pi conjugation) and σ*–π conjugation (sigma*‐pi conjugation) in organosilicon compounds are discussed in relation to structure and reactions. Reactions of organosilicon compounds are classifed into ionic and hemolytic (nonionic) reactions and various reactive intermediates including silyl radicals, silylium ions (silyl cations), silyl anions, and silylenes are described. Recent developments in kinetic stablization of these reactive intermediates are then summarized. In relation to kinetic stablization, silicon‐containing multiple bonds, silaaromatics, and silicon polyhedranes are described. Lastly, two important applications of organosilicon compounds, namely polymers and organic synthesis, are described briefly.
Silver: Organometallic Chemistry
Authors: Fackler John P. 
Published: March 2006

Abstract

The organometallic chemistry of silver and copper are in many ways similar. Simple alkyls are not thermally stable but fluorination of the hydrocarbon imparts considerable stability to the silver(I) products. Except for the special anion, [Ag(CF
3
)
4
]
−
, and derivatives such as Ag(CF
3
)
3
L, L = phosphine, which are stable, the fluorocarbon products generally are light and air sensitive, but less so than the nonfluorinated alkyls. Organometallic stability is increased when the silver is bonded to alkenes, alkynes, and other unsaturated species. Alkynylsilver compounds are generally polymeric solids. Alkenes π‐bond to the silver in Ag(I) salts. This feature has led to the well‐established use of silver catalysts for olefin epoxidation.
Sol–Gel Synthesis of Solids
Authors: Coradin Thibaud , Livage Jacques 
Published: March 2006

Abstract
The synthesis of glasses and ceramics via the sol–gel route is based on the inorganic polymerization of molecular precursors such as metal alkoxides. Precursor structure and reactivity can be chemically controlled via complexation or acid–base catalysis. Sol‐gel chemistry allows the powderless processing of glasses and ceramics, at much lower temperatures than usual solid‐state reactions. It provides a convenient and flexible access to nanoparticles, films, and fibres. Moreover, precursors are mixed at the molecular level and multicomponent materials can be formed. Thus, hybrid organic–inorganic materials have been made via the sol–gel route. The organic component can be used as a network modifier during the sol–gel synthesis and then withdrawn, allowing the formation of structured porous materials. It can also remain entrapped in the mineral matrix via weak interactions. Alternatively, organoalkoxysilanes allow covalent binding of organic moieties to silica networks. Such composites fill the gap between polymers and glasses and open new fields in materials science such as ‘sol–gel optics’ or bioencapsulation in mineral hosts.
Solids: Computer Modeling
Authors: Catlow Richard 
Published: March 2006

Abstract
We review the role of computer modeling techniques in solid state chemistry. The basic aims and objectives of the field are summarised. We then describe basic aspects of the methodologies both of techniques based on interatomic potentials and electronic structure methods. We consider the range of applicability of each technique. Later sections of the chapter describe recent topical examples including modeling and prediction of crystal structures, simulation of nano‐cluster structures and energies and modeling of reaction mechanisms in heterogeneously catalysed reactions.
Stereochemical Nonrigidity of Organometallic Complexes
Authors: Faller John W. 
Published: March 2006

AbstractCompounds that undergo intramolecular rearrangements at rates that affect the NMR line shapes in generally accessible temperature ranges are described as stereochemically nonrigid. Analysis of 1D and 2D NMR spectra as a function of temperature often allow the rates, as well as the mechanisms of interconversion of conformers or isomers, to be determined. Examples were selected to illustrate the importance of stereochemical nonrigidity in reactivity and the potential for affecting stereochemistry in the products of reactions.
Supported Organotransition Metal Compounds
Authors: Hanson Brian E. 
Published: March 2006

Abstract
Supported transition metal complexes were first prepared in the 1960s as a potential method for the immobilization of homogeneous catalysts. Although this goal is yet to be commercially realized, the chemistry of supported complexes has given insight to the preparation of heterogeneous catalysts as, for example, in the use of discrete metal complexes as precursors to heterogeneous polymerization catalysts. The purpose of this article is to review the general methods for the immobilization of transition metals with examples of each type of immobilization technique.
Technetium & Rhenium: Inorganic & Coordination Chemistry
Authors: Pombeiro Armando J. L. , Guedes da Silva M. Fátima C. , Crabtree Robert H. 
Published: March 2006

Abstract
The inorganic and coordination chemistry of both rhenium and technetium is described in a condensed way with presentation of significant and typical compounds and reactions and applications in nuclear medicine and catalysis. After an Introduction, with properties of those elements and their sources, a description of binary compounds (for example oxides, sulfides, halides, and nitrides), their syntheses, structures, and selected reactions are given. This is followed by a treatment of the coordination chemistry of those metals, comprising hydrides, metal–metal bonded species and complexes with ligands coordinated by donor‐atoms mainly of the following periodic groups: 15 (commonly nitrogen and phosphorus, including dinitrogen, nitrile, nitric oxide and related ligands, hydrazides, diazenides, nitride, imides, pyrazolylborates, and phosphine ligands), 16 (mainly oxo, thio, and other O‐ or S‐ligands), and 17 (halide ligands); the metal–carbon (group 14) bond complexes are usually not covered since they are dealt with separately. Preparative methods, structures, and reactivities are illustrated for those types of complexes.

Selected complexes of
99 m
Tc and
186
Re (or
188
Re) are described and their applications in nuclear medicine illustrated, as radiopharmaceuticals normally for clinical diagnosis. The application of inorganic rhenium complexes in catalysis constitutes a currently expanding area of high potential and their use as catalysts for the following reactions is reviewed: oxygen atom transfer (OAT) and related reactions; isomerization or etherification of allylic or propargylic alcohols; Beckmann rearrangement of oximes; dehydration of primary amides and aldoximes; dehydrogenation of alkanes, unconventional reduction of aldehydes and ketones; aldol‐type reactions; and photo‐ and electrocatalytic reduction of carbon dioxide. A few catalytic applications of technetium compounds are also indicated.