bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polyoxometalates
Authors: Pope Michael T. 
Published: December 2011

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.
Polyphosphazenes
Authors: Allcock Harry R. 
Published: December 2011

Abstract
Polyphosphazenes comprise the largest class of inorganic polymers. During the past 10 years, new synthetic developments have arisen that allow carefully tailored macromolecules to be assembled with precise chain lengths and with access to star geometries and a range of hybrid phosphazene‐organic polymer systems. This has stimulated research in the use of polyphosphazenes in biomedicine, optoelectronics (photonics), lithium battery technology, and fuel cell membranes, as well as in new elastomers and hydrogels.
Quasicrystals
Authors: King R. Bruce 
Published: December 2011

AbstractQuasicrystals are solid materials exhibiting diffraction patterns with apparently sharp spots containing symmetry axes such as fivefold or eightfold axes, which are incompatible with the three‐dimensional periodicity associated with crystal lattices. Many such materials are aluminum alloys that exhibit diffraction patterns with fivefold symmetry axes; such materials are called icosahedral quasicrystals. The location of atoms in quasicrystals requires the use of six‐dimensional crystallography. However, a polyhedral shell structure using a number of polyhedra of icosahedral symmetry provides a three‐dimensional model for the structure of many icosahedral quasicrystals.
Ruthenium: Organometallic ChemistryBased in part on the article Ruthenium: Organometallic Chemistry by Ulrich Koelle which appeared in the
Encyclopedia of Inorganic Chemistry, First Edition
.
Authors: White Rosemary E. , Hanusa Timothy P. 
Published: December 2011

Abstract

In the slightly more than half a century that the organometallic chemistry of ruthenium has had time to develop, it has become clear that the metal's position as the ‘middle child’ of the Group 8 metals is richly reflected in its organometallic derivatives. That is, despite many similarities in the compounds of the iron–ruthenium–osmium triad, addition and elimination reactions of ruthenium, for example, are slower than those of iron but are more facile than those of osmium. Similarly, complexes with hydride and alkyl bonds are generally more stable for ruthenium than for iron, but the ruthenium compounds are often unstable or highly fluxional compared to analogous osmium species. Carbonyl cluster complexes are an important feature of organoruthenium chemistry, and mixed‐ligand carbonyl species with high nuclearity are known, in some cases with more than 10 ruthenium atoms. Interstitial carbides and nitrides are often encountered in ruthenium clusters, and carbonyl hydrides are of interest as hydroformylation catalysts (conversion of alkenes to aldehydes). The cyclopentadienyl ligand is found extensively throughout organoruthenium chemistry, and with a decomposition temperature around 600°C, the sandwich complex ruthenocene Ru(C
5
H
5
)
2
is among the most stable organometallic compounds known. The stability of ruthenocene and its derivatives allow them to be incorporated as labels into biomolecules such as peptides. Ruthenocene derivatives have also been studied as potential second‐order nonlinear optical materials, and they have played a central role in the development of 30 valence electron triple‐decker cations of the iron group. The high ligand field stabilization of Ru
II
enables combinations of π‐acceptor ligands together with even the hardest σ‐donors, such as carbonate, sulfate, or nitrate, and hence Ru
II
carbonyl and phosphine complexes are known with myriad coligand combinations having O, N, or S binding functionalities. In particular, the ability of the (η‐arene)Ru moiety to bind N‐ and O‐ligands has been used to complex various amines, imines, Schiff bases, and amino acids to generate diastereomeric salts, which can serve as chiral catalysts; they are valuable in stereoselective organic syntheses and in the production of biologically active compounds.
Semiconductor Interfaces
Authors: Tan Ming X. , Bansal Ashish , Lauermann Iver , Shreve Gary A. , Lewis Nathan S. 
Published: December 2011

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.
Semiconductors
Authors: Stanton Colby E. , Nguyen SonBinh T. , Kesselman Janet M. , Laibinis Paul E. , Lewis Nathan S. 
Published: December 2011

AbstractThe structural, electronic, optical, and electrical properties of semiconductors are treated within a common framework. The bonding in the lattice determines the band structure of the solid, which is used to describe the chemical, optical, and electrical properties of the semiconductor. These concepts enable this process to be understood from a qualitative, chemically based viewpoint.
Short‐Lived Intermediates
Authors: Almond Matthew J. , Jenkins Samantha L. 
Published: December 2011

Abstract
Methods for the generation and detection of short‐lived intermediates are discussed. These include flow systems (where a steady‐state concentration of the intermediate is monitored), flash photolysis (where the intermediate is studied in real time using a very fast detection method), and matrix isolation (where the intermediate is preserved by trapping in a solid, inert host at low temperature and where conventional spectroscopic methods are used for detection). Many of the classical experiments utilizing these methods are described, but the relevance to modern chemical studies is also emphasized. The spectroscopic methods used to detect short‐lived intermediates are considered. These include nuclear magnetic resonance (NMR), electron spin resonance (ESR), microwave, infrared (IR), Raman, and ultraviolet‐visible absorption and emission spectroscopies. It is shown that IR remains the method of choice for matrix‐isolation experiments whereas flash photolysis work tends to rely mainly upon electronic spectroscopic techniques. The use of IR spectroscopy, using tunable lasers, for flash photolysis work (at least for slightly longer‐lived intermediates) is discussed. Finally two case studies are considered in detail. These are the photolysis of metal carbonyls and the formation of unusual main group compounds at high temperatures. These studies exemplify the procedures that have been used to investigate short‐lived intermediates in inorganic chemistry.
Silicon: Inorganic Chemistry
Authors: Lickiss Paul D. 
Published: December 2011

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: December 2011

AbstractAn 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: Inorganic & Coordination ChemistryBased in part on the article Silver: Inorganic & Coordination Chemistry by W. Ewen Smith which appeared in the
Encyclopedia of Inorganic Chemistry, First Edition
.
Authors: Mak Thomas C. W. , Zhao Xiao‐Li 
Published: December 2011

Abstract
The present review is a complete rewrite of the original article in the first edition. The new version provides concise and up‐to‐date information on the inorganic and coordination compounds of silver in oxidation states ranging from subvalent to Ag(IV). Literature coverage is extended to October 2004, and pertinent references are listed for the convenience of the interested reader.
The presentation is organized under the following headings: 1. Introduction; 2. Subvalent silver compounds; 3. Silver(I) compounds (under subheadings: 3.1 Halides and pseudohalides; 3.2 Phosphorus donor ligands; 3.3 Nitrogen donor ligands; 3.4 Oxygen donor ligands; 3.5 Chalcogen donor ligands; 3.6 Silver‐rich compounds); 4. Silver(II) compounds; 5. Silver(III) and silver(IV) compounds; 6. Catalysis. The structural features of the compounds are described, and specific examples are illustrated with five figures.

For the most important +1 oxidation state of silver, particular emphasis is placed on recent highlights and advances in new areas such as double and multiple salts of silver, silver(I) polyhedra with encapsulated acetylenediide (C
2
2−
) species (symbolized as C
2
@Ag

n

), argentophilic Ag(I)⋯Ag(I) interaction in supramolecular assembly, halide‐centered Ag

n

cages, mixed‐metal clusters, and silver‐rich chalcogenide supercluster complexes. Modern application of inorganic silver catalysts, of both achiral and chiral types, to organic synthesis is presented with selected examples from the recent literature.
Stereochemical Nonrigidity of Organometallic Complexes
Authors: Faller John W. 
Published: December 2011

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.
Sulfur: Organic PolysulfanesBased in part on the article Sulfur: Organic Polysulfanes by Ralf Steudel & Monika Kustos which appeared in theEncyclopedia of Inorganic Chemistry, First Edition.
Authors: Atwood David A. , Zaman M. Kamruz 
Published: December 2011

AbstractOrganic polysulfanes are compounds of the type RSnR with n > 2. They may be chain‐like or cyclic. The organic residues (alkyl or aryl) are linked to the sulfur atoms via carbon atoms. In the literature these compounds are often termed as organic polysulfides, but the IUPAC recommended nomenclature is polysulfanes. Sulfur‐rich organic polysulfanes can be viewed as intermediates between organic and inorganic compounds. On one hand, they are characterized by organic substituents R, which terminate the sulfur chain or close this chain to form a ring. On the other hand, compounds with sulfur chains of three or more sulfur atoms are ‘inorganic’ enough to attract the interest of inorganic chemists who have contributed much to this area. Organic polysulfanes with up to 16 sulfur atoms in the molecules have so far been obtained as pure substances, but species with up to 35 sulfur atoms in a chain or ring have been prepared in mixtures. Organic polysulfanes play an important role not only in basic research and industry, they are also found as natural products in organisms and occur in the inanimate nature. The main importance of organic polysulfanes comes, however, from their role in the large scale industrial vulcanization of natural and synthetic rubber. In this article, the preparation, structure, modern analysis, basic reactions, natural occurrence, biological activity, and practical importance of organic polysulfanes with three or more neighboring sulfur atoms in a chain or ring have been presented.
Technetium: Organometallic ChemistryBased in part on the article Technetium: Organometallic Chemistry by Ronald J. Clark which appeared in theEncyclopedia of Inorganic Chemistry, First Edition.
Authors: Rochon Fernande D. 
Published: December 2011

AbstractThe chemistry of organometallic technetium compounds is discussed along with its application in the field of nuclear medicine. Several99mTc radiopharmaceuticals are presently used in hospitals using a99Mo−99mTc generator to prepare the starting material [99mTcO4]−. The isotope99mTc is a γ‐ray emitter. The most common organometallic radiopharmaceutical is [Tc(MIBI)6]+, where MIBI is an isonitrile ligand.99mTc can be produced only at the tracer level and it disintegrates to the longer life isotope99Tc, which has a half‐life of 2.12 × 105years. The chemistry of technetium has been studied with the latter isotope, which is commercially available. But it emits weak β−particles and special precautions must be taken in the laboratories in order to avoid health problems.Most of the publications in the literature on organometallic Tc compounds contain the ligands CO, isonitriles or the cyclopentadienyl ion. These π‐accepting ligands usually bind to Tc in a low oxidation states. Tc‐CO compounds are the ones who have been most studied. Binary compounds and a great variety of mixed‐ligands complexes are discussed. The new complex ion [Tc(CO)3(H2O)3]+is particularly important, since a kit was recently developed for its preparation. It should open a new field for the development of99mTc radiopharmaceuticals. It can bind to biomolecules like proteins, peptides, and antibodies which have very specific targets.Several Tc‐cyclopentadienyl complexes have the sandwich or the piano stool structures. The arene compounds should have similar structures, but the latters have not been much studied yet. No Tc‐arene compound seem to have been characterized by crystallographic methods yet. But more recently, interest in the arene complexes has increased because of its potential use in nuclear medicine. Isonitriles or isocyanides and cyanide ligands are bonded to Tc through the C atom. A few crystal structures on mixed‐ligand isonitrile Tc complexes were determined and the segment TcCNC is linear. Fewer cyanide Tc compounds were studied. Finally a few Tc‐alkyl compounds have been reported.
Thallium: Organometallic ChemistryBased in part on the article Thallium: Organometallic Chemistry by William S. Rees, Jr. & Gertrud Kräuter which appeared in theEncyclopedia of Inorganic Chemistry, First Edition.
Authors: Pike Robert D. 
Published: December 2011

AbstractThe organometallic chemistry of thallium(I) is dominated by cyclopentadienyl complexes. These may be polymeric through bridging Cp arrangements or oligomeric as a result of Tl⋯Tl contacts. ThCp complexes are easily prepared and are highly useful Cp‐transfer agents. There are two known Tl(I) organometallics with direct TlC σ‐bonds; one is monomeric and the other is tetrameric due to Tl⋯Tl contact. A variety of Tl(I) π‐complexes are recognized. Bonding in the latter tends to be fairly weak.Two R2TlTlR2dimers (R = silyl group) are known, but no such Tl(II) complexes are known for carbon ligands. The chemistry of organothallium(III) compounds is more extensive, encompassing such species as R3Tl, R2TlX, RTlX2(X = anionic ligand), and complexes of these species with additional ligands. A wide array of X‐ray crystal structures for Tl(III) complexes reveals monomeric, oligomeric, and polymeric arrangements, with bridging ligands being very common.Thallium compounds are highly toxic and should be handled with great care. Volatile Tl species are of use in the chemical‐vapor deposition of superconducting phases. Finally, Tl(III) salts are fairly important reagents in organic syntheses, especially in oxidations and in ring expansion and contraction reactions.
Tin: Organometallic Chemistry
Authors: Wardell James L. , Spencer Gavin M. 
Published: December 2011

Abstract

Frankland produced the first organometallic tin compound, Et
2
SnI
2
, in 1849. Since that time a wide range of tin compounds containing SnC bonds have been prepared. This article will detail the synthesis and characterization of these compounds. This will include a description of tetraorganotin compounds, halides, pseudohalides, hydrides, tin‐tin bonded compounds, radicals, group 15, and group 16 derivatives. The industrial and environmental aspects of these compounds will also be discussed.
Transition Metal Carbonyls: Infrared Spectra
Authors: Timney John A. 
Published: December 2011

Abstract
The number, pattern, and position of the CO‐stretching absorptions (ν(CO)) of transition metal carbonyls gives considerable information about molecular structure, symmetry, and bonding. This article deals with the processing of the basic data (number, frequency, and intensity of ν(CO) bands) to give useful information about carbonyl‐containing organometallic compounds via an ‘energy factored force field’ (EFFF). The reasons why the EFFF works so well and the relationships between different types of force constant within the EFFF are examined. The application of these force constants in elucidating molecular structure is discussed, together with the very successful ligand effect model that enables chemists to predict ν(CO) frequencies with remarkable accuracy.