bluuebunny/crossref_metadata_2025_split huggingface dataset:
Boron: Inorganic Chemistry
Authors: Schubert David M. , Brotherton Robert J. 
Published: March 2006

AbstractBoron is unique among the elements and displays remarkable chemistry in all of its compounds. It is widely distributed at low concentrations on the Earth and is virtually always found bound to oxygen in its natural forms. Boron enters into the life cycle of and is an essential element for plants and animals. The vast majority of industrial uses of boron on a weight basis also involve boron–oxygen compounds, including important mineral sources, metal borates, boric acid, boric oxide, and boric acid esters. These find large‐scale applications in many industries, most notably in the manufacture of glass and other vitreous materials. Boric acid is a weak Lewis acid and does not display Brønsted acidity in aqueous solution. The condensation of B(OH)3and B(OH)4−species to form polyborates in relatively concentrated borate solutions has important implications for the solubilities and other solution properties of metal and nonmetal borate salts. Boric acid reacts with alcohols and other hydroxyl group‐bearing compounds to form esters, which find many industrial uses. Reversible borate ester crosslinking leads to polymer gel formation and provides the basis for the essential biological role of boron. Nonoxide boron compounds also have important industrial uses. These include refractory compounds, such as boron carbide, boron nitrides, boron phosphides, elemental boron, and metal–boron alloys, as well as nonrefractories, such as the boron halides. Nonrefractory boron–phosphorus and boron–sulfur compounds and the boron subhalides are yet to find significant industrial use, yet, nonetheless exhibit fascinating chemistries.
Boron: Metallacarbaboranes
Authors: Housecroft Catherine E. 
Published: March 2006

Abstract

Among cluster compounds of boron, the metallacarbaboranes form a well‐established family that has developed significantly over the last decade, for example, with regard to
f
‐block‐containing species and supramolecular systems. This article covers the basic principles of metallacarbaborane clusters: classification of clusters, structural, and bonding aspects. An attempt has been made to illustrate synthetic routes to metallacarbaboranes in a systematic manner, although it must be recognized that many other syntheses reported in the literature lack a strategic quality. Isomerism of the cluster skeleton is discussed with pertinent examples. Electrochemical properties of cluster and stacked metallacarbaboranes are summarized. An overview of typical patterns in reactivity is given, although, as with synthetic strategies, it is extremely difficult to generalize. Potential applications of metallacarboranes are covered in this article, but the discussion is selective in view of recent review articles.
Boron–Nitrogen CompoundsBased in part on the article Boron–Nitrogen Compounds by Robert T. Paine which appeared in the
Encyclopedia of Inorganic Chemistry, First Edition
.
Authors: Bakus Ronald C. , Atwood David A. 
Published: March 2006

Abstract
The majority of this article details the many synthetic routes and compounds that can be accessed in combinations of boron reagents with amines. Lewis acid‐base adducts are the simplest type of compounds, and lead into the more complex aminoboranes and iminoboranes. Owing to their widespread importance and usage, the borazines, pyrazaboles, and polypyrazaolyborates are covered in separate sections. The newly emerging fields of boron–nitrogen cations and boron nitride solid‐state materials are covered in detail.
Cadmium: Inorganic & Coordination Chemistry
Authors: Borsari Marco 
Published: March 2006

Abstract

This article provides an overview on the chemistry of cadmium. Cadmium is a naturally occurring metal elements, being the 67th most abundant element in the earth's crust, and it is found in several minerals. Occurrence, production and applications have been surveyed, also in the light of toxicological and environmental risks joined to uses of cadmium. The usual oxidation state of cadmium is 2+ and its chemistry closely resembles that of zinc. The versatile coordination ability allows a wide variety of structure. Therefore, emphasis is placed on stereochemical aspects of cadmium chemistry, in particular on 1D, 2D, and 3D architectures resulting from assembly of Cd
2+
–ligand(s) units. The main compounds and complexes, ordered by metal oxidation state and ligand donor atom, have been examined in their properties and structural aspects, both in solution and in solid state.
Cadmium: Organometallic ChemistryBased in part on the article Cadmium: Organometallic Chemistry by Gerard Parkin which appeared in the
Encyclopedia of Inorganic Chemistry, First Edition
.
Authors: Gupta Niladri Narayan , Atwood David A. 
Published: March 2006

Abstract
As a large, soft, heavy element, the chemistry of cadmium is marked by relatively weak bonding to carbon and other more electronegative atoms. Organocadmium compounds thus demonstrate diverse reaction chemistry. Furthermore, the large size and low valency of cadmium leads to interesting aggregated compounds. The reactivity and structural importance of organocadmium compounds and applications in solid‐state chemistry is offset by their high toxicity.
Carbides: Transition Metal Solid‐State ChemistryBased in part on the article Carbides: Transition Metal Solid State Chemistry by Peter Ettmayer & Walter Lengauer which appeared in the
Encyclopedia of Inorganic Chemistry, First Edition
.
Authors: Lengauer Walter , Eder Alexander 
Published: March 2006

Abstract
Basic properties and use of transition metal carbides and carbonitrides are presented in this article. Starting from crystal chemistry, bonding, and preparation, the article also briefly discusses analytical chemistry of chemical and physical carbon analysis as well as thermodynamics. Updated versions of phase diagrams of group 4, 5, and 6 transition metals with carbon as well as phase diagrams of FeC and MnC are presented together with those of the most important transition metal carbonitride systems TiCN and ZrCN. A large part is devoted to the solid‐state properties because they make carbides and carbonitrides interesting materials for application. The presentation of these properties includes hardness, thermal properties, conductivities, carbon diffusivity, and elastic properties. Some ternary and quaternary carbonitrides are also discussed. Several of these properties are given as a function of temperature and composition. Examples for application of carbides in modern hardmetal types such as recent development in fine‐grained hardmetals and functional gradient hardmetals are included. The topic is closely connected to the article Nitrides: Transition Metal Solid State Chemistry.
Carbonyl Complexes of the Transition Metals
Authors: Calderazzo Fausto 
Published: March 2006

AbstractCarbon monoxide is a versatile ligand as it forms compounds with both transition metals and main group elements. Transition d metals of electronic configuration dn(0 < n < 10) form the most numerous class of these compounds, although recent progress has been made in expanding the area of existence toward main group, lanthanide (4f) and actinide (5f) metals. The most extensively studied series of carbonyl derivatives have the general formula [M(CO)n]m, withnrepresenting the coordination number of the central metal atom M, andmbeing the nuclearity of the system. In these compounds, the central metal atom is in the zero oxidation state. Starting from readily available inorganic derivatives in a positive oxidation state, the synthesis of these compounds normally requires a reducing agent capable of acting in the presence of carbon monoxide: in fact, only nickel metal, as a finely divided activated powder, is reactive toward CO leading to the corresponding derivative Ni(CO)4. The selection of the reducing agent varies as a function of the position of the metal M within the periodic table. There is a general trend of an increase in the nuclearitymtoward the end of the transition d series, the nuclearity being related to the bonding arrangements of the CO ligand, which may act as terminal, doubly bridging or triply bridging. Metal carbonyls are characterized by IR‐active vibrations around 2000 cm−1associated with the carbonyl groups. Vibrational spectra in solution give important information about: (a) the electronic distribution within the M–CO bond in terminally bonded carbonyl groups; (b) the molecular structure associated with the number of bands observed; (c) the type of bonding in dinuclear or polynuclear compounds. X‐ray diffraction data have been extensively used in order to define the molecular structure in the solid state. The metal–CO combinations span a wide range of oxidation states, derivatives being known for oxidation states from +III to −IV. Metal carbonyls undergo three types of reaction: (a) substitution of the carbonyl groups, whereby the oxidation state of the central metal atom remains unchanged, (b) oxidation, and (c) reduction. Carbonyl derivatives of early‐ and late transition metals present specific bonding and spectroscopic properties. Concerning the transition elements of groups 6–9, the M–CO bond dissociation enthalpy increases down the group, and is normally greater than the metal–metal bond enthalpy, the latter being estimated from the heat of atomization. From a mechanistic viewpoint, substitution and redox reactions have been studied extensively. A special case of substitution is the migratory carbonyl insertion, by which an M–R bond to a carbyl group R is converted by CO into the M–(CO)R sequence.
Cation‐Activated Enzymes
Authors: Glusker Jenny P. 
Published: March 2006

AbstractCation‐activated enzymes are those that require a cation for maximal activity but which still have some activity in the absence of the cation, that is, the activating cation is not an essential part of the enzyme mechanism. The cations involved are generally metal or ammonium ions. The metal ions used are generally Na+, K+, Mg2+, or Ca2+, those that are abundant in nature. In the last 10 years, many crystal structures of cation‐activated enzymes have been determined and, in these studies, potassium is the most common activating cation. The geometry of binding and possible conclusions about this activity are the subject of this review. Chosen for description are thrombin (a sodium‐activated enzyme), pyruvate kinase, dialkylglycine decarboxylase, diol dehydrase, inosine monophosphate dehydrogenase, and tryptophanase (all potassium‐activated enzymes), and alkaline phosphatase (a magnesium‐activated enzyme). In some enzymes, the activating cation is near the active site, but in others it is distant. This implies that its function in these two possibilities involves the modification of the charge distribution in the reaction center or else stabilization of the enzyme conformation most suited to the reaction to be catalyzed. These studies provide information on one way in which nature controls enzyme activity, and hopefully further studies will help us learn more possibilities for utilizing these enzyme‐control strategies in medicine.
Chromium: Biological Relevance
Authors: Vincent John B. 
Published: March 2006

AbstractThe biochemistry of CrIIIhas been a poorly understood field of endeavor; studies of the biochemistry of none of the other transition metals have been as problematic. Despite four decades of investigation, only recently has a clear picture of the role of Cr been defined potentially. The biologically important form is the trivalent ion, although not in the form of the purported glucose tolerance factor. Apparently, CrIIIis required for proper carbohydrate and lipid metabolism in mammals, although Cr deficiency is difficult to achieve. Conditions that increase circulating glucose and insulin concentrations increase urinary chromium output. Cr is excreted after an insulin challenge, probably in the form of the oligopeptide chromodulin. Chromodulin may be the key to understanding the role of Cr at a molecular level as the molecule has been found to bind to the activated insulin receptor, stimulating its kinase activity. A mechanism for the action of chromodulin has been proposed recently. The popular nutritional supplement chromium picolinate has been associated with potentially deleterious effects. The mechanism of toxicity of chromate (CrVI) is still an area of intense investigation.
Chromium: Inorganic & Coordination Chemistry
Authors: Theopold Klaus H. 
Published: March 2006

Abstract

The element chromium (Cr, atomic number 24) belongs to the first row of the transition metals, the properties of which are marked by partial occupation of their 3d orbitals. Together with molybdenum (Mo), tungsten (W), and unstable seaborgium (Sg), it makes up group 6 of the periodic table. Chromium is relatively abundant, occurring naturally in various oxide minerals (notably chromite, FeCr
2
O
4
). Because of its resistance to reaction with air and water, thin coatings of chromium are used to protect other metals against corrosion. Chromium features a great variety of accessible oxidation states; among these the +VI, +III, and +II states are of prime importance. Octahedral coordination compounds of Cr(III) are very stable and numerous; they have played a prominent role in the development of coordination chemistry. Hexavalent chromium is a very strong oxidant. It has traditionally been used in organic synthesis, but the inevitable metal wastes have discouraged its use as a stoichiometric oxidant. Cr(VI) is a known carcinogen, but there are no indications of adverse health effects of Cr(III); the latter is indeed an essential trace mineral implicated in glucose metabolism. Heterogeneous chromium catalysts play an important role in the catalysis of ethylene polymerization.
Chromium: Organometallic Chemistry
Authors: Theopold Klaus H. , Kucharczyk Robin R. 
Published: March 2006

AbstractStarting with Hein's investigation of the reaction of CrCl3with PhMgBr in the beginning of the twentieth century, chromium organometallic chemistry is now marked by an ever increasing diversity of compound types and formal oxidation states. Organochromium compounds such as Cr(CO)6, (η6‐C6C6)2Cr, and (OC)5CrC(OMe)Ph represent milestones in the development of organometallic chemistry as a whole. The lower oxidation states (−IV to +II) are dominated by chromium carbonyl complexes with 18 electron configurations, while midvalent compounds (+II, +III) often feature cyclopentadienyl rings and exhibit unpaired electrons. Organometallic compounds of chromium in its highest oxidation states (+IV to +VI) are still relatively rare, but this has been a growing area of late. Much of the interest in chromium alkyls is due to the metal's important role in the catalysis of olefin polymerization. Homogeneous model systems for the Union Carbide catalyst (Cp2Cr/SiO2) and the Phillips catalyst (CrO3/SiO2) still motivate much synthetic work. Applications of organochromium chemistry in organic synthesis are also becoming more numerous and useful.
Cobalt:
B
12
Enzymes & Coenzymes
Authors: Kräutler Bernhard 
Published: March 2006

Abstract

The most prominent biological role associated with cobalt concerns vitamin B
12
, its natural variants, and its coenzyme forms. The B
12
‐derivatives are cobalt complexes of the unique and remarkably complex corrin ligand that belong to the larger class of the tetrapyrrolic natural compounds. The ‘antipernicious anemia factor’ vitamin B
12
and its cofactor forms are, first of all, required for human and animal health. However, except for the higher plants, all forms of life appear to depend upon the natural variants of vitamin B
12
. The main chemical reactivities of the corrinoids (needed to fulfill their essential biological roles) may reflect their possible corresponding chemical contributions to the development of the early stages of life on earth. Indeed, the corrinoids play a particularly basic role in carbon metabolism in microorganisms, which also are the only natural sources of the B
12
‐derivatives. Microorganisms have developed extraordinary means for the biosynthesis, and for the regulation of the biosynthesis of the B
12
‐derivatives, in order to cope with the structural and functional complexity of these tetrapyrrolic cobalt‐compounds, while most (other) forms of life have evolved intricate strategies for the economic and efficient uptake and transport of the corrinoids. The known cofactor functions of the cobalt‐corrinoids are due to their extraordinary organometallic chemistry and their redox chemistry under physiological conditions: Coenzyme B
12
, methylcorrinoids, and reduced corrinoids are the cofactors in various important and unique organometallic enzymes, whose intricate structural and mechanistic properties are the current focus of strong and broad research activities. The essential role of the corrinoids in the remarkable organometallic paths of carbon fixation and further carbon metabolism in anaerobic microorganisms has attracted particular attention. Vitamin B
12
and its derivatives thus hold an important position in all of the life sciences and are at the center of particular interdisciplinary interest from such diverse areas as medicine, biology, chemistry, and physics.
Cobalt: Inorganic & Coordination ChemistryBased in part on the article Cobalt: Inorganic & Coordination Chemistry by David A. Buckingham which appeared in theEncyclopedia of Inorganic Chemistry, First Edition.
Authors: Blackman Allan G. 
Published: March 2006

AbstractThis article provides a summary of the important and interesting aspects of the inorganic and coordination chemistry of cobalt. A brief history of the element, detailing its discovery and historical uses, is given, and some general information concerning the properties of elemental cobalt is detailed. The general chemistry of cobalt is then outlined, including an overview of the common oxidation states found in inorganic compounds and complexes, a discussion of the stereochemistry, spectra and magnetism of cobalt complexes, and an outline of some analytical methods used for cobalt. The inorganic chemistry of simple cobalt salts is then described, and the coordination chemistry of cobalt, which constitutes the majority of the article, is then outlined in some detail. Coordination complexes of cobalt are detailed according to the oxidation state of the metal ion, with complexes ranging from Co(−I) to Co(V) discussed. Brief descriptions of the chemistry of each oxidation state are given, and specific examples are then outlined according to the nature of the ligand donor atom(s), with extensive references to both the primary literature and to review articles given. Thus, Co(I), Co(0), and Co(−I) complexes containing aliphatic, aromatic, and macrocyclic amine ligands, as well as Schiff‐base, porphyrin, and P‐donor ligands are discussed, while Co(II) complexes of carboxylate, heterocyclic, and oxygen‐derived ligands are summarized. Co(III) ammine and amine complexes are described in detail, while Co(III) complexes containing O‐donor ligands are also discussed. The few known Co(IV) and Co(V) complexes are outlined.
Coordination & Organometallic Chemistry: Principles
Authors: Crabtree Robert H. 
Published: March 2006

Abstract
The title topic is reviewed. Under coordination chemistry, special attention is given to Werner complexes, the trans effect, soft and hard ligands, crystal and ligand field (LF) models, together with oxidation state and coordination number. Under organometallic chemistry, the main topics include electroneutrality, back bonding, the 18‐electron rule, and effects of complexation.
Copper: Hemocyanin/Tyrosinase ModelsBased in part on the article Copper: Hemocyanin/Tyrosinase Models by Nobumasa Kitajima which appeared in the
Encyclopedia of Inorganic Chemistry, First Edition
.
Authors: Shearer Jason , Karlin Kenneth D. 
Published: March 2006

Abstract

Coupled dinuclear copper(II) centers are found in metalloenzymes such as hemocyanin (Hc), tyrosinase (Tyr), and catechol oxidase (Co), and perform functions such as dioxygen transport,
o
‐phenol aromatic hydroxylations, and dehydrogenation of
o
‐catechols. These enzymes all contain two‐copper centers, each ligated by imidazole nitrogen ligands from histidine residues, and in their oxyforms are bridged by a μ‐η
2
:η
2
‐peroxo moiety. Synthetic model compounds have proven useful in elucidating a number of different aspects of the protein chemistry, such as spectroscopic and structural properties. Also, new coordination chemistry has been developed, such as a new and possibly important equilibrium form of the μ‐η
2
:η
2
‐peroxo‐

$\hbox{Cu}^{{\rm II}}_{2}$

species, namely, the

$\hbox{Cu}^{{\rm III}}_{2}$

‐bis‐μ‐oxo moiety. In conjunction with stopped‐flow kinetic studies, new fundamental reactions involving Cu
I
complexes and dioxygen have also been elucidated, such as the demonstration that an initial Cu
II
‐superoxo species is formed prior to

$\hbox{Cu}^{{\rm II}}_{2}$

‐peroxo formation. Both species are enthalpically favored at low temperatures, but an unfavorable entropy term precludes the isolation of many of these complexes near room temperature. Considerable efforts are directed towards elucidation of detailed mechanistic pictures for substrate oxidations with copper–dioxygen adducts.
Ortho
‐phenol hydroxylations proceed
via
an electrophilic aromatic substitution reaction. The mechanism of Co activity is still widely debated with evidence in model systems pointing towards both proton‐coupled electron transfer pathways, as well as direct hydrogen atom transfer reaction. Such mechanistic inquiries, and determining the differential reactivity of μ‐η
2
:η
2
‐peroxo‐

$\hbox{Cu}^{{\rm II}}_{2}$

and

$\hbox{Cu}^{{\rm III}}_{2}$

‐bis‐μ‐oxo complexes, are of continuing and future interest.
Copper: Organometallic ChemistryBased in part on the article Copper: Organometallic Chemistry by Bruce H. Lipshutz & Michael R. Wood which appeared in theEncyclopedia of Inorganic Chemistry, First Edition.
Authors: Lipshutz Bruce H. , Pfeiffer Steven S. 
Published: March 2006

AbstractMuch of copper chemistry over the past decade has transitioned toward catalysis, driven in large measure by environmental rather than economic concerns. Catalytic processes have appeared in large numbers, in particular due to the advances made in both the design of new ligands that effectively coordinate copper, but also due to their increased availability. Applications of copper‐catalyzed processes to bond formations have gone well‐beyond those of a CC nature, nowadays including CN, CO, CS, CP, and CH types. Asymmetric variants based on nonracemically ligated copper salts and copper hydride have led to highly valued entries to chiral products of great use in synthesis. Transmetalations from various metals (e.g. Zn, Zr, etc.) to copper also continue to play a vital role in organic synthesis, and are discussed herein as well.Considerable progress on many physical organic fronts relating to copper chemistry has been made. New advances in technologies that shed light on structural aspects of copper reagents are now available (extended X‐ray absorption fine structure, EXAFS, X‐ray absorption near edge structure, XANES) and are being used to accompany X‐ray analyses and highly sophisticated NMR techniques. High‐level computer calculations have led to theoretical ‘pictures’ illustrating the mechanistic pathways that may be followed by some of the most commonly used reactions in copper chemistry (e.g. 1,4‐additions). Taken in their entirety, these developments suggest that this past decade has been a most productive period in the continuing evolution of copper chemistry.