Chromium review

Chromium. The history of the investigations estabHshing the essentiaHty of chromium has been reviewed (136). An effect of brewer s yeast in preventing or curing impaired glucose tolerance in rats was revealed, and the active factor was identified as a Cr(III) organic complex, glucose tolerance... 

R. D. Harbison and W. E. Rinehart, eds.. Conclusions of the Expert Review Panel on Chromium Contaminated Soil in Hudson County, New Jersey, Industrial Health Foundation, Pittsburgh, Pa., 1990, p. 30. 

California Air Resources Board and Department of Health Services, Report to the Scientific Review Panel on Chromium, Sacramento, Calif., 1985. 

The topic of chromium oxdiations has been the subject of an excellent review by Wiberg. Discussions of the chemistry of chromium reagents have also been given by Stewart, Fieser, House, ° Neustaedter and Lee. ... 

Other potential poisons include zinc, manganese, chlorine, and bromine. A number of metals may be deposited on the catalysts from engine erosion and wear, including copper, chromium, nickel, and iron. The mechanism of poisoning has been reviewed by Maxted (134) and by Butt (135). 

Aryl- and alkenylcarbene complexes are known to react with alkynes through a [3C+2S+1C0] cycloaddition reaction to produce benzannulated compounds. This reaction, known as the Dotz reaction , is widely reviewed in Chap. Chromium-Templated Benzannulation Reactions , p. 123 of this book. However, simple alkyl-substituted carbene complexes react with excess of an alkyne (or with diynes) to produce a different benzannulated product which incorporates in its structure two molecules of the alkyne, a carbon monoxide ligand and the carbene carbon [128]. As referred to before, this [2S+2SH-1C+1C0] cycloaddition reaction can be carried out with diyne derivatives, showing these reactions give better yields than the corresponding intermolecular version (Scheme 80). 

Abstract Since its discovery the chromium-mediated benzannulation reaction has been developed into a unique and useful tool in organic synthesis. In this review, topical aspects of this reaction concerning its mechanism and the chemo-, regio- and stereoselectivity are summerised and discussed in detail. Special attention is paid to the asymmetric benzannulation reaction and, finally, the importance of this reaction as a key step in the total synthesis of natural products is outlined. 

For a review on chromium carbene complex photochemistry in organic syntheses see Hegedus LS (1997) Tetrahedron 53 4105... 

For reviews on chromium aminocarbenes see Schwindt MA, Miller JR, Hegedus LS (1991) J Organometal Chem 413 143 Grotjahn DB, Dotz KH (1991) Synlett 381... 

Chromium carbide has three phases Cr23Cg, Cr7C3, Cr3C2 (major). The latter phase is the one reviewed here. Chromium carbideis an important material because of its excellent resistance to corrosion. It is the most oxidation resistant of all metal carbides. Its characteristics and properties are summarized in Table 9.3. 

For a review, see Cainelli, G. Cardillo, G. Chromium Oxidations in Organic Chemistry, Springer NY, 1984, p. 8. 

The catalytically active material on the monolith also comes in many forms. Formulations based on iron, chromium, and vanadium as the active components supported on Ti02, AI2O3, Si02, and zeolites have been reported see the review by Bosch and Janssen [H. Bosch and F.J.J.G. Janssen, Catal. Today 2 (1988) 369]. 

Westheimer has also reviewed the induced oxidations by the Cr(VI)-As(III) couple of iodide, bromide and manganous ions vide supra). The induction factor of 0.5 for Mn(II) implies an intermediate tetravalent chromium species however, the factor of 2 for iodide points to a pentavalent chromium intermediate. Both... 

The Phillips catalyst has attracted a great deal of academic and industrial research over the last 50 years. Despite continuous efforts, however, the structure of active sites on the Phillips-type polymerization systems remains controversial and the same questions have been asked since their discovery. In the 1950s, Hogan and Banks [2] claimed that the Phillips catalyst is one of the most studied and yet controversial systems . In 1985 McDaniel, in a review entitled Chromium catalysts for ethylene polymerization [4], stated we seem to be debating the same questions posed over 30 years ago, being no nearer to a common view . Nowadays, it is interesting to underline that, despite the efforts of two decades of continuous research, no unifying picture has yet been achieved. 

L. Landner and R. Reuther (eds.) Metals in Society and in the Environment. A Critical Review of Current Knowledge on Fluxes, Speciation, Bioavailability and Risk for Adverse Effects of Copper, Chromium, Nickel and Zinc. 2004... 

The electron paramagnetic resonance spectrum of transition metal ions has been widely used to interpret the state of these ions in systems of catalytic interest. Major emphasis has been placed on supported chromia because of its catalytic importance in low-pressure ethylene polymerization and other commercial reactions. Earlier work on chromia-alumina catalysts has been reviewed by Poole and Maclver 146). On alumina it appears that the chromium is present in three general forms the S phase, which is isolated Cr3+ on the surface or in the lattice the 0 phase, which is clusters of Cr3+ and the y phase, which is isolated Cr5+ on the surface. The S and 0... 

Except for Prussian blue activity in hydrogen peroxide, reduction has been shown for a number of transition metal hexacyanoferrates. The latter were cobalt [151], nickel [152], chromium [150], titanium [153], copper [154], manganese [33], and vanadium [28] hexacyanoferrates. However, as was shown in review [117], catalytic activity of the mentioned inorganic materials in H202 reduction is either very low, or is provided by impurities of Prussian blue in the material. Nevertheless, a number of biosensors based on different transition metal hexacyanoferrates have been developed. 

Carvalho MF, Alves CCT, Ferreira MIM, De Marco P, Castro PML (2002) Isolation and initial characterization of a bacterial consortium able to mineralize fluorobenzene. Appl Environ Microbiol 68 102-105 Cheung KH, Gu J-D (2005) Reduction of chromate (Cr042 ) by a Bacillus mag-netarium isolated from marine. World J Microbiol Biotechnol 21 213-219 Cheung KH, Gu J-D (2007) Mechanism of hexavalent chromium detoxification by microorganisms and bioremediation application potential A review. Int Biodeter Biodegr 59 8-15... 

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