bluuebunny/crossref_metadata_2025_split huggingface dataset:
Tellurium: Inorganic ChemistryBased in part on the article Tellurium: Inorganic Chemistry by William R. McWhinnie which appeared in theEncyclopedia of Inorganic Chemistry, First Edition.
Authors: Laitinen Risto S. , Oilunkaniemi Raija 
Published: March 2006

AbstractThe present chapter describes the main trends in the progress of inorganic tellurium chemistry during recent decades. The emphasis is on the synthesis and characterization of novel nonmetallic tellurium compounds and on transition metal compounds with tellurium‐containing ligands. Many inorganic tellurium compounds find use as single‐source precursors for the generation of binary telluride thin films for electronic applications, or as reagents in organic synthetic chemistry. The advent and progress in modern instrumental methods of analysis has shown that the structural features of tellurium compounds often differ from those of sulfur and selenium compounds.
Tin: Inorganic Chemistry
Authors: Wardell James L. 
Published: March 2006

AbstractThe alloying of copper with tin to produce bronze led to the formation of tools and weapons in what was later called the ‘Bronze Age’ from ≈2600–1500 BC. Since that time tin, in both the +2 and +4 oxidation states has figured prominently in inorganic compounds. This article will provide a summary of the types of inorganic compounds that tin forms, their spectroscopic characterization, and industrial uses.
Tin: Organometallic Chemistry
Authors: Wardell James L. , Spencer Gavin M. 
Published: March 2006

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.
Titanium: Inorganic & Coordination ChemistryBased in part on the article Titanium: Inorganic & Coordination Chemistry by Charles A. McAuliffe & Neil Bricklebank which appeared in the
Encyclopedia of Inorganic Chemistry, First Edition
.
Authors: Valentine Ann M. 
Published: March 2006

Abstract
This article describes the chemistry of titanium, with special focus on its inorganic coordination chemistry. This field has a rich history and has flourished in the years since the first industrial processes for isolation of titanium were introduced. Covered are the discovery of the metal, some of the physical properties of titanium and its complexes, and the unique coordination chemistry of titanium in its various oxidation states. The metal is commonly found in the +4 oxidation state, in which it behaves as a hard Lewis acid. Titanium complexes with formal oxidation states +3, and, much less commonly, +2, 0, and −1 are also known. The oxides, sulfides, halides, and complex halides are discussed. Complexes with carbon, nitrogen, oxygen, silicon, phosphorus, sulfur, and arsenic donor ligands are described. Structures and spectroscopic data are given for selected compounds. Interest in the coordination chemistry of titanium has been driven by important applications in materials chemistry and in catalysis.
Titanium: Organometallic Chemistry
Authors: Mintz Eric A. 
Published: March 2006

AbstractThe majority of titanium organometallic chemistry involves complexes in which the titanium is in its highest oxidation state (+4) with cyclopentadienyl derivatives as ancillary ligands. However, considerable chemistry has also been developed for complexes with titanium in the +3 and +2 oxidation state, with lesser amounts of chemistry developed for titanium in lower oxidation states (+1, 0). Since the early 1980s, chemists have placed considerable emphasis on the fine‐tuning of the structure and reactivity of titanium organometallic complexes. Particular emphasis has been devoted to tailoring the structure and reactivity of bis(cyclopentadienyl)titanium derivatives by incorporating electron‐donating, electron‐withdrawing, sterically demanding, or chiral substituents on the cyclopentadienyl ring. Considerable effort has gone into preparing ansa‐metallocenes with a wide variety of bridging groups and substituents to fine‐tune the reactivity catalysts prepared from them. In a similar manner, considerable effort has gone into the development of constrained geometry complexes. Several types of chiral substituted cyclopentadienyl, annulated cyclopentadienyl,ansa‐metallocenes, and constrained geometry complexes have been prepared and applied to olefin polymerization and organic synthesis. Additional efforts at modifying the structure and reactivity by focusing on varying the oxidation state or coordination geometry at the titanium center have expanded over the past decade.
Tungsten: Organometallic ChemistryBased in part on the article Tungsten: Organometallic Chemistry by Andreas Mayr which appeared in theEncyclopedia of Inorganic Chemistry, First Edition.
Authors: Pamplin Craig B. , Hayton Trevor W. , Legzdins Peter 
Published: March 2006

AbstractThis article surveys the organometallic chemistry of tungsten in a systematic manner according to the various types of complexes known to contain tungsten–carbon bonds. The first section deals with complexes having the inorganic ligands CO (carbonyl), CNR (isocyanide), and CN (cyanide) in the metal's coordination sphere. The second and by far the largest section considers tungsten complexes containing organic ligands. This section is divided into subsections dealing with compounds having η1‐hydrocarbyl ligands (i.e. alkyl and aryl complexes, vinyl and alkynyl complexes, carbene complexes, and carbyne complexes), η2‐hydrocarbon ligands (i.e. alkene complexes and alkyne complexes), η3‐hydrocarbon ligands (i.e. allyl complexes), η4‐hydrocarbon ligands (i.e. diene complexes), η5‐hydrocarbon ligands (i.e. cyclopentadienyl complexes), and η6‐hydrocarbon ligands (i.e. arene complexes). Within each category of complex, the material is generally presented in the following order: common methods of synthesis of these complexes, their characteristic physical properties, and their representative chemical properties. The latter are usually illustrated by examples taken from the literature published since 1992, the final year of coverage by the first edition of the Encyclopedia of Inorganic Chemistry. Other articles in the current encyclopedia also cover some aspects of this chemistry, most notably, alkene and alkyne metathesis reactions mediated by organotungsten complexes, the organometallic chemistry of di‐ and polynuclear tungsten complexes, and tungsten compounds containing main group element ligands. Consequently, these topics are not specifically discussed in this article.
Tungsten Proteins
Authors: Adams Michael W. W. , Roy Roopali 
Published: March 2006

AbstractTungsten (W, atomic number 74) and molybdenum (Mo, atomic number 42) are very similar metals chemically, and are equally abundant elements on this planet. Molybdenum has been known for decades to play an essential role in biology, and molybdenum‐containing enzymes are ubiquitous in both prokaryotes and eukaryotes. In contrast, tungsten appears to play a much more limited role in biological systems, and one that was established relatively recently. So far, tungsten‐containing enzymes have been found only in prokaryotes. The best‐characterized organisms with regard to their metabolism of tungsten are certain species of anaerobic archaea that grow at extreme temperatures (the hyperthermophiles) or produce methane gas (the methanogens), and anaerobic bacteria that produce acetate (the acetogens) or utilize acetylene. Of these, only the hyperthermophilic archaea appear to be obligately tungsten‐dependent. That is, they do not synthesize molybdenum‐containing homologs of key tungstoenzymes when grown on molybdenum rather than tungsten. Three fundamentally different types of tungstoenzyme have been characterized so far. The best characterized is the Aldehyde ferredoxin oxidoreductase (AOR) family, represented by aldehyde ferredoxin oxidoreductase. Hyperthermophilic archaea such asPyrococcus furiosuscontain at least four members of the AOR family of tungstoenzymes. These appear to play key roles in the metabolism of sugar and peptides. The second family, termed F(M)DH, contains two types of tungstoenzyme, formate dehydrogenase and formyl methanofuran dehydrogenase. These are involved in CO2metabolism in acetogens and methanogens, respectively. The F(M)DH members are much more complex enzymes than the AOR family and show no amino acid sequence similarity to them. The third family is represented by the enzyme acetylene hydratase (AH). It catalyzes the hydration of acetylene and is found in acetylene‐utilizing bacteria. Members of the AOR and F(M)DH family catalyze redox reactions of very low potential (≤−420 mV), in which tungsten undergoes a two‐electron redox reaction [W(IV) to W(VI)]. Crystal structures are available for two members of the AOR family and reveal that each subunit of the proteins contains a single W atom coordinated to two organic pterin molecules, which are bridged by a magnesium ion. An iron–sulfur cluster is situated near the W atom and is thought to be involved in electron transfer to it. The geochemical, ecological, and biochemical basis for tungsten‐ rather than molybdenum‐dependent organisms is discussed.
Vanadium in Biology
Authors: Wever Ron , Renirie Rokus , Hasan Zulfiqar 
Published: March 2006

AbstractIn this article, the role of vanadium in a number of biological systems will be discussed. The metal oxide (vanadate) is present as the prosthetic group in the haloperoxidases, enzymes that are able to oxidize halides in the presence of hydrogen peroxide to hypohalous acids. The bromoperoxidases seem to be involved in the production of the huge amounts of brominated compounds formed by several seaweeds. The enzymes have unusual properties in terms of stability and structural organization. X‐ray structures at high resolution are available now for four vanadium haloperoxidases and details of the events occurring at the active site during catalysis are known. The metal oxide binds peroxide in a side‐on fashion and seems to acts as a Lewis acid in polarizing the bound peroxide for further nucleophilic attack by an incoming halide. These enzymes are also able to mediate in the presence of hydrogen peroxide, the enantioselective sulfoxidation of organic sulfides yielding chiral sulfoxides with high enantiomeric excess. The active site of the haloperoxidases is very similar to that found in acid phosphatases that hydrolyze phosphate monoesters and there is some evidence that the haloperoxidases have evolved from the phosphatases. Vanadium is found in the vanadiumIIIstate in certain blood cells of tunicates (Ascidians) under very acidic conditions. Despite many studies, there is no clue as to the physiological role of the metal and there are many questions regarding the mechanism of accumulation and reduction of the metal in these organisms. The metal also seems to be used as an electron sink by certain bacteria under anaerobic conditions. Furthermore, vanadium is accumulated in Amanita species. These toadstools contain up to 10 mM of a vanadiumIVcompound with very special structure in which the vanadiumIVis eightfold coordinated in an unusual geometry. Although the compound has been reported to carry out redox reactions, the physiological function is elusive.
Vanadium: Inorganic & Coordination ChemistryBased in part on the article Vanadium: Inorganic & Coordination Chemistry by Elizabeth M. Page & Sherilyn A. Wass which appeared in the
Encyclopedia of Inorganic Chemistry, First Edition
.
Authors: Richards Raymond L. 
Published: March 2006

Abstract
The chemistry of vanadium and its complexes with various ligands is reviewed, following the format used in the corresponding article in the first edition of this Encyclopedia. The article begins with an update of the element itself. This is followed by a description of the binary compounds formed with hydride, halide, oxide, chalcogenide, nitride, and phosphide ligands. Compounds formed with carbide ligands are briefly mentioned, but thereafter carbon‐donor ligands are not included in this article.

Then follows a review of the coordination chemistry of vanadium, which, after a brief introduction, is grouped into sections according to the oxidation state of vanadium in the compounds under discussion. The first section describes compounds in low oxidation states, [vanadium(−1), vanadium(0), and vanadium(1)], in which nitrogen‐donor ligands such as N
2
and NO and tertiary phosphine ligands are prominent. The second section describes the coordination chemistry of vanadium(II). This section is subdivided according to the donor atom of the various ligands that bind the metal, that is, oxygen, nitrogen, and phosphorus ligands and other ligand types, such as halides. Vanadium(III) coordination complexes comprise the next section, which is subdivided according to oxygen ligands, nitrogen ligands, sulfur ligands, and halide and other ligands. It is to be noted that in general the compounds that have thus far been described tend to be oxidized rather easily to compounds of higher oxidation states.

The coordination chemistry of vanadium(IV), which comprises the next section, is dominated by the very stable VO
2+
(vanadyl) group and a separate subsection is devoted to coordination compounds that contain this grouping. The other subsections describe nonoxo complexes and halide, nitrogen, and sulfur and selenium ligands; the thiovanadyl group, VS
2+
is included in the last subsection. Oxygen‐donor ligands are also prominent in the chemistry of the highest oxidation state of vanadium(V), whose coordination chemistry is covered in the final section. Thus, separate subsections describe the coordination chemistry of the VO
3+
group, the VO
2
+
unit, and peroxo‐complexes. The remaining subsections describe nonoxo complexes, nitrogen, sulfur, and selenium ligands.

A feature of the development of vanadium chemistry during the years since the original article appeared has been the very large increase in the number of coordination complexes that have been prepared and structurally characterized. The content and relative sizes of the subsections of this article and the figures that are included reflect this trend.
ZeolitesBased in part on the article Zeolites by Alan Dyer which appeared in theEncyclopedia of Inorganic Chemistry, First Edition.
Authors: Williams Craig D. 
Published: March 2006

AbstractThis work looks at the natural formation of zeolites in our environment. It details the steps required in the laboratory to successfully manufacture zeolites, producing both novel and nature identical crystal forms. The classification of zeolites based on their aluminium content, pore/channel size is also covered in some detail. Finally the various physical and chemical properties that make zeolites so useful to everyday life are examined. These include their absorptive properties, ion‐exchange properties, desiccant properties, and catalytic properties.
Zinc: Inorganic & Coordination ChemistryBased in part on the article Zinc: Inorganic & Coordination Chemistry by Reg H. Prince which appeared in theEncyclopedia of Inorganic Chemistry, First Edition.
Authors: Burgess John , Prince Reg H. 
Published: March 2006

AbstractAlloys and salts of zinc have been known for many centuries; commercial production of the metal dates from early in the eighteenth century. Of the several million tons now produced annually, by electrolytic and smelting processes, much is used in alloys, in batteries, in corrosion prevention, and in the manufacture of a range of compounds with various uses. In particular, zinc oxide and zinc chloride have a large number of uses, detailed in this article. Zinc sulfide is both one of the main zinc ores and the archetype for the two main structural forms of 4:4‐coordinated structures (zinc blende and wurtzite). Many zinc compounds and complexes have interesting structural, spectroscopic, optical, magnetic, and conductivity properties, some of which are of actual or potential value in technical and industrial applications. Zinc‐containing species have also proved valuable in synthesis and self‐assembly of a range of supramolecular structures. Both in the solid state and in solution zinc exhibits a range of coordination numbers, though tetrahedral and, especially in solution, octahedral stereochemistries dominate. Zinc forms a variety of complexes, especially with nitrogen, oxygen, sulfur, and halide donor ligands. Many of these complexes show high stability, but they are generally labile in solution. Zinc plays an essential role in biology, being a key constituent of at least 200 metalloproteins. It is an essential element in human nutrition, but toxic in large quantities. Many zinc complexes have been synthesized as biochemical models; a few zinc salts are used in dietary supplements.
Zintl Compounds
Authors: Kauzlarich Susan M. 
Published: March 2006

AbstractThe term Zintl phases was originally used to recognize contributions to the field of solid‐state inorganic compounds by Eduard Zintl. They were defined as a subgroup of intermetallic phases where the anions or anionic network could be considered formally to be valence satisfied. These compounds are made up of electropositive elements from groups 1, 2 that, in a formal sense, donate their electrons to the electronegative elements from groups 13, 14, and 15, which use them to form the correct number of bonds such that each element has a filled shell. The historical definition has been expanded from binary to ternary phases and enlarged to include transition metals and rare earth elements in some cases. The compounds that make up this class are described along with the corresponding Zintl anions arising from solution chemistry. Recent results in the field such as the use of Zintl phases for novel materials is also described.
Zirconium & Hafnium: Organometallic ChemistryBased in part on the article Zirconium & Hafnium: Organometallic Chemistry by Bernard Gautheron, Roland Broussier, & Philippe Meunierk which appeared in the
Encyclopedia of Inorganic Chemistry, First Edition
.
Authors: Meunier Philippe , Pirio Nadine 
Published: March 2006

Abstract
This review considers the main aspects of organometallic chemistry of zirconium and hafnium during the last 10 years. It is complementary to the first edition of Encyclopedia of Inorganic Chemistry. The material is presented in two major parts divided in five and three sections respectively. The first part is devoted to syntheses: the first section, by far the largest, covers in a systematic manner bis and mono cyclopentadienyl complexes with +4, +3, and +2 oxidation states and more especially constrained‐geometry (CG) complexes, cationic complexes, and anionic or zwitterionic 18‐electron complexes; unusual coordination geometries at carbon stabilized by group 4 metallocenes are presented in the second section; other anionic π‐ligands complexes and also lacking π‐ligands complexes are considered in two different sections and bimetallics are developed in the last section. Applications in metal‐mediated organic synthesis and catalysis are reviewed in the second part: neutral organozirconium complexes in organic and organometallic syntheses (hydrozirconation and carbozirconation), cationic zirconocenes in organic synthesis and catalysis, and organozirconium complexes in asymmetric catalysis.
Bond Lengths in Inorganic Solids & Liquids
Authors: Brown I. David 
Published: March 2006

Abstract
The length of a chemical bond is determined by the number of valence electron pairs associated with it. In a simple electrostatic picture, this number is equal to the electrostatic flux linking the bonded atoms. The flux obeys a number of chemically useful theorems, and since it is independent of the ionic or covalent character of the bond, any bond can be transformed to the ionic limit where the flux can be calculated using Coulomb's law. Alternatively, by recognizing that a network of ionically bonded atoms is a capacitive electric circuit, the flux can be determined using the Kirchhoff equations. The correlation between the bond length and bond flux (or bond valence) allows the bond geometry to be predicted even for unknown compounds. A comparison of the observed bond lengths with those expected is useful in validating and analyzing an observed structure. Atomic radii can also be used to predict bond lengths in regular coordination spheres, but they are unable to predict the distortions from regularity typically found in low symmetry structures.
Hard & Soft Acids and Bases
Authors: Martin R. Bruce 
Published: March 2006

AbstractPractical metal ion hardness–softness scales applicable to aqueous solutions and corresponding to what most chemists probably imply when they use the terms hardness and softness are presented. The scales are derived from experimentally determined log stability constant differences for substitution reactions of one ligand for another on a metal ion. Correlations between scales for different ligand systems are high but not perfect. In an analogous ligand scale, all oxygen donors are hard and all nitrogen donors borderline. The principle of hard and soft acids and bases finds its most consistent application, not in direct stability constant comparisons, but rather in log stability constant differences of appropriate substitution reactions.
Metal‐Mediated Protein Modification
Authors: Whittaker James W. 
Published: March 2006

AbstractPosttranslational modification of proteins is a general mechanism for regulating biological activity and expanding the functionality in this family of biopolymers. Metal ions have been found to be intimately involved in many of these protein‐processing reactions, whether as cofactors of processing metalloenzymes, intrinsic cofactors for self‐processing proteins, or protein‐targeting solution complexes. A broad range of covalent modifications have been identified as the products of these metal‐mediated reactions. Novel amino acid residues resulting from oxygenation, oxidation, or cross‐linking side chains play important roles in the structure and reactivity of proteins. In a number of cases, the modified amino acids serve as built‐in catalytic cofactors. Reactions of certain metal complexes have been implicated in biomedically important protein modifications, and synthetic complexes have been developed as probes of macromolecular structure. These links underscore the close connections between inorganic and biological chemistry.