bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hypervalent CompoundsBased in part on the article Indium: Inorganic Chemistry by Dennis G. Tuck which appeared in the
Encyclopedia of Inorganic Chemistry, First Edition
.
Authors: Sean McGrady G. , Steed Jonathan W. 
Published: December 2011

Abstract
The chemistry of compounds formally exhibiting more than eight valence electrons is introduced and surveyed. The review covers the definition and representation of hypervalent bonding and its orbital description, including recent developments in electron localization function calculations. The synthesis and reactivity of hypervalent compounds is examined including their use in organic synthesis, along with the factors contributing to their stability. Techniques for determining the structures of hypervalent species are described, including gas‐phase electron diffraction and vibrational and NMR spectroscopic methods. Novel hypervalent intermediates and transition states are also surveyed, including recently appreciated inter‐ligand hypervalent interactions. Particular emphasis is placed on the important topic of pentacoordination. The review includes chemistry of the halogens, chalcogens, pnictides, noble gases, tin, silicon, and a variety of transition metals.
Indium: Inorganic ChemistryBased in part on the article Indium: Inorganic Chemistry by Dennis G. Tuck which appeared in the
Encyclopedia of Inorganic Chemistry, First Edition
.
Authors: Zhao Yanbao , Zhang Zhijun 
Published: December 2011

Abstract

This review highlights the development in inorganic chemistry of indium made in the last ten years. The first parts of this article describe the preparation of new low‐valence indium complexes and organoindium (III) compounds, and the use of these compounds as starting materials for further synthesis. A special highlight is the compounds R
4
In
4
and R
4
In
2
, which show the lively development and the current trends in this field. The following parts present the development of organoindium compounds with group 15 or 16 ligands as single‐source molecular precursors for the deposition of indium‐containing semiconductors by MOCVD; the preparation and characterization of nanoparticles, nanowires, and nanotubes of indium metal, alloys, oxides, and indium‐V/VI semiconductors, which play a sizable role in the new generation of nanoscale electronic and optical devices; and the preparation of new indium intermetallic compounds, which present large structural variety and peculiar magnetic and electrical properties. The last part advances the applications of indium and indium halides in organic synthesis with particular reference to regio‐, stereo‐, and chemoselectivity. These reactions include the regioselective allylation of unsaturated functional groups, the acylation of alcohols and amines, the rearrangement of epoxides, the stereoselective debromination, and other reactions.
Ionic Conductors
Authors: Greenblatt Martha 
Published: December 2011

AbstractThe fundamental structural and physical properties of ionic conductors in the solid state are briefly discussed. Recent developments in ionically conducting solids are reviewed. Materials discussed include: crystalline cation conductors with Na+, Li+, and H+ion motion; crystalline anion conductors, primarily with the fluorite‐type structure and with oxide‐ and fluoride ion mobilities; mixed ionic/electronic conductors; amorphous glass electrolytes and polymer solid electrolytes. Applications of some of these solid‐state ionic conductors in electrochemical devices such as sodium and lithium rechargeable batteries, sensors, fuel cells and electrochromic smart windows are presented.
Iron: Heme Proteins & Electron Transport
Authors: Durham Bill , Millett Francis S. 
Published: December 2011

AbstractThis chapter discusses the structure and function of cytochromes, which are a class of iron‐containing heme proteins primarily involved in biological electron‐transfer reactions. Subcellular organelles called mitochondria are responsible for carrying out oxidative phosphorylation, the major energy‐transduction process in eukaryotic cells. Enormous progress has been made in our understanding of the molecular mechanism of the mitochondrial electron‐transport chain over the past decade. X‐ray crystal structures have been determined for three of the four electron‐transfer complexes: succinate–ubiquinone reductase, cytochromebc1, and cytochromecoxidase (CcO). Cytochromec(Cc) is a small heme protein with a molecular weight of 12 500 Da that transports electrons from cytochromebc1to CcO. It is a very positively charged protein, and is known to bind to both cytochromebc1and CcO by means of electrostatic interactions. Extensive chemical modification studies have demonstrated that the binding domain on Cc for both proteins involves lysines immediately surrounding the heme crevice, and Cc functions as a mobile shuttle during electron transport. The reactions of Cc with its redox partners are too fast to resolve by conventional techniques such as stopped‐flow spectroscopy. A new method to study biological electron transfer has been introduced that utilizes a photoactive tris(bipyridine)ruthenium complex, Ru(II), which is covalently attached to a protein such as Cc. Photoexcitation of Ru(II) to the metal‐to‐ligand charge‐transfer state, Ru(II*), a strong reductant, leads to rapid electron transfer to the ferric heme group in Cc. Subsequent electron transfer from photoreduced heme c to redox center(s) in another protein can be measured on a timescale as short as 50 ns. This technique has been used to measure intracomplex electron transfer between Cc and its physiological partners, CcO, cytochromebc1, cytochromecperoxidase (CcP), and cytochromeb5. The ruthenium technique was used to characterize sequential electron transfer in cytochromebc1from ubiquinol to the Rieske iron–sulfur protein (2Fe2S), cytochromec1, and finally to Cc. Cytochrome oxidase contains four redox centers, CuA, heme a, heme a3, and CuB. A ruthenium Cc derivative was used to demonstrate that the initial site of electron entry into CcO is CuA, followed by electron transfer to heme a, and then heme a3.
Iron: Inorganic & Coordination ChemistryBased in part on the article Iron: Inorganic & Coordination Chemistry by Pelham N. Hawker & Martyn V. Twigg which appeared in theEncyclopedia of Inorganic Chemistry, First Edition.
Authors: Burgess John , Twigg Martyn V. 
Published: December 2011

AbstractIron, the most abundant transition element in the biosphere, is essential in higher forms of life and its compounds have numerous industrial applications. The element has catalytic properties. Several simple iron compounds are industrially important, for example, large amounts of iron oxides are produced for pigment and magnetic recording media applications. Oxidation states ranging from −2 to +6 are known, the most familiar are +2 (ferrous iron) and +3 (ferric iron). Most common complexes are octahedral, although examples of higher (e.g. seven coordinate) and lower (e.g. tetrahedral and square planar) geometries are well known, as are a variety of mixed oxidation state compounds. Depending on ligands involved high‐ and low‐spin complexes can be formed, and temperature‐dependent spin‐state crossover complexes are well documented. The thermodynamics and kinetics of reactions of low‐spin iron(II) complexes with ligands such as 1,4‐diimines and CN−have been extensively studied. While low‐spin iron(II) is present in biological systems such as oxygenated heme centered oxygen carriers and thiolate clusters, iron(III) is more common. Thiolate‐containing iron clusters form readily, and here mixed oxidation states are a prominent feature that is exploited in some important electron transfer proteins. Microorganism iron uptake is facilitated by tris‐catecholate and tris‐hydroxamate ligands like enterobactin that have an extraordinarily high affinity for iron(III) that results in a dramatic enhancement of the 3+ relative to the 2+ state in terms of redox potential.
Iron: Organometallic ChemistryBased in part on the article Iron: Organometallic Chemistry by James R. Green which appeared in theEncyclopedia of Inorganic Chemistry, First Edition.
Authors: Paley Robert S. 
Published: December 2011

AbstractStudies involving the preparation, reactivity, and properties of the organometallic complexes of iron (compounds possessing a FeC bond) have played a central role in the growth of organometallics as a major subdiscipline with chemistry. From the discovery of ferrocene in the 1950s to the present day, interest and research activity remain high. This entry provides a survey of this large and diverse area of organometallic chemistry, and is arranged by increasing hapticity of the organic ligand of interest that is bound to iron. Included are discussions of the chemistry of iron σ‐alkyl, acyl, alkynyl, and vinyl complexes, iron carbenes, η1‐ and η3‐allyl iron complexes, η2‐alkene and η4‐diene iron complexes, trimethylenemethane and cyclobutadiene complexes of iron, cationic iron pentadienyl, cyclohexadienyl, and arene complexes, and ferrocenes and heteroferrocenes.
Lead: Organometallic ChemistryBased in part on the article Lead: Organometallic Chemistry by R. Bruce King which appeared in theEncyclopedia of Inorganic Chemistry, First Edition.
Authors: Sharma Hemant K. , Pannell Keith H. 
Published: December 2011

AbstractAn update on the organometallic chemistry of lead since 1995 is presented. In particular the exciting chemistry associated with the synthesis, structure and reactivity plumbylenes, diplumbynes and related species are presented. In addition an extensive section on organolead transition metal complexes of is presented, an area not previously covered.
Manganese Proteins with Mono‐ & Dinuclear Sites
Authors: Penner‐Hahn James E. 
Published: December 2011

AbstractAlthough manganese is not as widely recognized as iron and copper, it nevertheless plays an essential role in several key biological processes. Consequently, manganese concentrations are tightly regulated in most cells. Several Mn‐specific transporters have been identified and a novel Mn‐regulatory protein has been characterized. Manganese‐activated enzymes are proteins that have relatively weak affinities for Mn; in many cases these are isolated without any metal bound. Manganese‐activated enzymes are especially important in hydrolytic reactions, and appear, in at least some cases, to have physiologically significant changes in activity that respond to changes in Mn concentration. The best characterized Mn proteins are redox‐active enzymes, where Mn typically cycles between the MnIIand MnIIIoxidation states, although some MnIV‐containing species are known.
Mercury: Inorganic & Coordination ChemistryBased in part on the article Mercury: Inorganic & Coordination Chemistry by Gregory J. Grant which appeared in the
Encyclopedia of Inorganic Chemistry, First Edition
.
Authors: Bebout Deborah C. 
Published: December 2011

Abstract

Mercury is one of the oldest known elements. The element exhibits surprisingly different chemistry from its congeners zinc and cadmium, and it is the only group 12 member without a known beneficial biological role. Unique properties associated with the element and its compounds have led to diverse applications. However, many of these are being phased out to minimize further increases in the environmental and atmospheric burden with this toxic heavy metal. Motivations to study the compounds and complexes of mercury include potential for discovery of novel properties such as high‐temperature superconductivity and improved understanding of its interactions in physiological systems. Valuable characterization of mercury‐containing compounds is possible with
199
Hg NMR techniques.

Mercury is the only group 12 member to have a stable monovalent state. Observed primarily in the oldest known and most common of all metal polycations, Hg
2
2+
, this metal–metal bonded species readily disproportionates into Hg
2+
and Hg
0
. Mercury(I) compounds, typically, have a linear structure of type XHgHgX. Halides, oxy salts, oxides, and coordination compounds with oxygen and weakly basic nitrogen‐donor ligands are best known for Hg
2
2+
.

The most prevalent ionization state of mercury, Hg
2+
, is a d
10
metal ion, which lacks strong coordination number and geometry preferences. As a result, structural characterization of its compounds by X‐ray crystallography is particularly critical. A wide range of halides, pseudohalides, and chalcogenides of Hg
2+
are known. The softness of Hg
2+
has led to an investigation of coordination, with a wide variety of sulfur ligands and physiological sulfur donors being assumed to be the most important. Mercury(II) typically has a stronger affinity for S‐, N‐, and P‐donors than any other divalent metal ion. However, Hg
2+
also has a tendency to undergo incredibly rapid ligand exchange. Recent studies have shown that sterically demanding multidentate ligand systems can suppress ligand exchange processes.
Metal Vapor Synthesis of Transition Metal Compounds
Authors: Schmidt Eckhardt , Klabunde Kenneth J. , Ponce Aldo , Smetana Alexander , Heroux David 
Published: December 2011

Abstract
The title topic is reviewed with special reference to the reactivity of metal atoms, their energetics of vaporization, vaporization techniques, and some detailed examples of reaction products. Recent advances in nanoparticle work are also discussed.
MetalloregulationBased in part on the article Metalloregulation by Robert P. Hausinger which appeared in theEncyclopedia of Inorganic Chemistry, First Edition.
Authors: Rouault Tracey A. , Philpott Caroline C. 
Published: December 2011

AbstractMetalloregulation refers to the concept that living organisms from bacteria to mammals must orchestrate the processes of metal import, utilization, sequestration, and export to optimize availability of metals for use in metabolism. Metals are required for the function of many proteins, but metals can also be toxic because free metal ions may react with protein, nucleic acid, and lipid contents of cells. In general, metals are transported across membranes by specific unidirectional transporters, and cells and organisms regulate the abundance of specific transporters and metal sequestration proteins to meet their needs. Changes in abundance result mainly from changes in either the rate of transcription, the stability of mRNA, the translation rate, or the stability of the metal protein. Complex regulatory frameworks exist to govern metal homeostasis in virtually all cells and organisms. Usually a central component of a successful regulatory network is a protein that registers metal availability by directly binding the metal ion that requires regulation. Metal binding then drives a change in function of the central regulatory protein, which usually has multiple regulatory targets that include transporters, chaperone proteins, sequestration molecules, and others. In this chapter, we focus on the main regulatory proteins of iron homeostasis in bacteria, yeast, plants, and mammals, and those involved with regulation of zinc homeostasis in bacteria and yeast. We describe the sensing mechanism and targets of the bacterial transcription factor, fur, and the yeast transcription factors known as Aft 1 and 2. In mammals, we focus on the sensing and regulatory mechanisms utilized by iron regulatory proteins (IRPs) and on the role of the peptide hormone hepcidin in physiologic regulation of iron metabolism. In zinc homeostasis, we focus on the bacterial transcription factors Zur and Znt 1, and the yeast transcription factor, Zap1. References for regulation of copper, manganese, and nickel metabolism are cited for further reading. Nature has produced a wide variety of solutions to the important question of how cells and organisms can ‘sense’ their metal status and modify gene expression to ensure that metals are appropriately available for use in metabolism.
Metathesis Polymerization Processes by Homogeneous Catalysis
Authors: Wagener Kenneth B. , Boncella James M. , Smith Dennis W. 
Published: December 2011

AbstractAlkene polymerization reactions proceeding by homogeneous metathesis catalysis are reviewed. Fundamental mechanistic aspects of these reactions are discussed with special emphasis on ring opening metathesis polymerization and acyclic diene metathesis polymerization chemistry.
Mixed Donor LigandsBased in part on the article Mixed Donor Ligands by Nikolay N. Gerasimchuk & Kristin Bowman‐James which appeared in theEncyclopedia of Inorganic Chemistry, First Edition.
Authors: Lawrance Geoffrey A. 
Published: December 2011

AbstractMixed donor ligands are extremely common and are linear, branched, or cyclic molecules that contain at least two different donor groups capable of chelation to metal ions by those groups as polydentate ligands. The most common donor atoms met are N, O, S, and P, although other donors such as group 14 elements (including C) are known. Whereas mixed donor ligands are considered classically to involve groups with different donor atoms (such as N from an amine and O from a carboxylate), different classes of donor groups of one type of donor atom (such as pyridine and amine groups) also effectively produce mixed donor ligands. The coordination chemistry of mixed donor ligands is very extensive; all metal ions form mixed donor complexes, and the number of isomers possible for complexes with mixed donors is usually greater than with symmetrical ligands of comparable denticity.
Molybdenum: Inorganic & Coordination Chemistry
Authors: McCleverty Jon A. 
Published: December 2011

Abstract
The inorganic and coordination chemistry of molybdenum is described, being presented according to ligands and/or donor atom set (halides, cyanides, ligands containing O, S, Se, Te, N, P, or As‐donor atoms) and are discussed in relation to oxidation state. Special mention is made of metal–metal bonded dinuclear species, a brief description of polyoxoanionic species is given, and tri‐ and tetranuclear cluster compounds and some species of higher nuclearity containing chalcogenide atoms are described.
Molybdenum:MPT‐Containing Enzymes
Authors: Young Charles G. 
Published: December 2011

AbstractMolybdenum, an essential trace element for all forms of life, is found in a wide range of Mo‐MPT enzymes important in the metabolism of small molecules and anions of nitrogen, sulfur, carbon, chlorine, selenium, and arsenic, and in the global biogeochemical cycles of these elements. These enzymes feature active sites composed of a single (mononuclear) Mo atom coordinated by one or two MPT‐based ligands, L (MPT = ‘molybdopterin′ orMetal‐bindingPterin ene‐1,2‐diThiolate). These ligands contain a pyranopterin or simple pterin nucleus, an ene‐1,2‐dithiolate (dithiolene) unit, and a pendant phosphate group; in enzymes from prokaryotes, the phosphate is generally attached to a nucleotide, giving ‘dinucleotide’ forms of MPT. The dithiolene moiety functions as a bidentate S2‐donor ligand to Mo. The Mo‐MPT enzymes are classified into two broad functional types: oxotransferases and hydroxylases. The oxotransferases generally catalyze oxygen atom transfer reactions and fall into two families: the sulfite oxidase and dimethyl sulfoxide (DMSO) reductase families. Enzymes from these families contain square‐pyramidalcis‐[MoVIO2L(cysteinate)]−and distorted trigonal prismatic [MoVIO(AA)L2]−(AA = serinate, cysteinate, selenocysteinate, etc.) oxidized active sites, respectively. The hydroxylases all belong to the xanthine oxidase family and generally catalyze net insertion of oxygen into the CH bonds of heterocyclic aromatic compounds and aldehydes. They contain biologically unique, square‐pyramidal [MoVIOS(OH)L]−oxidized active sites featuring a catalytically essential terminal sulfido ligand. The sulfido ligand can act in a bridging capacity to Cu, as recently demonstrated for CO dehydrogenase. In most reactions catalyzed by Mo‐MPT enzymes, an oxygen atom is exchanged between substrate and water with concomitant consumption (for reductases) or production (for oxidases) of reducing equivalents (2e−, 2H+). Synthetic analogue (model) studies have produced complexes replicating or informing the composition, structures, spectroscopy, and chemistry of the enzymes. This account focuses on the Mo bioinorganic chemistry of the Mo‐MPT enzymes and selected synthetic analogues. It is divided into two main parts. Part 1 provides an overview of the enzyme systems, their distribution, roles, and essential chemistry, as well as a discussion of consensus structures and likely mechanisms. The genes and proteins involved in Mo trafficking and Mo‐cofactor biosynthesis are also briefly described. Part 2 summarizes important developments in the production of synthetic analogues, with a focus on new dithiolene, scorpionate, and other complexes sharing the structural, spectroscopic, or chemical attributes of the enzymes.
Nickel: Models of Protein Active SitesBased in part on the article Nickel: Models of Protein Active Sites by Michael J. Maroney which appeared in theEncyclopedia of Inorganic Chemistry, First Edition.
Authors: Liaw Wen‐Feng 
Published: December 2011

AbstractDuring the past decade, structures and functions of the active sites have been established for the nickel‐based metalloenzymes present in the hydrogenases, ureases, carbon monoxide dehydrogenases/acetyl coenzyme A synthase, and methyl coenzyme M reductase. Roles of nickel in these Ni‐containing enzymes serve as catalytic or redox centers. Model compounds and various biophysical techniques have been lent to elucidate aspects of the structure and function (catalytic mechanism) of the Ni sites in these enzymes. Structures/functions of these Ni‐containing enzymes, biomimetic model compound studies, and the proposed catalytic mechanisms are presented.