Chromium complexes phase chemistry

Chromium(III) complexes, 701 acetates, 869 acetylacetonates, 861 phase chemistry, 863 physical studies, 862 alcoholates, 860 alkoxides, 860 alkyl, 779... 

The incentive for synthesis of molecular cluster complexes with the cluster cores M6E8 (M = Cr, Mo, W E = S, Se, ) has been to solve some of the structural problems in the Chevrel phases (40) and to find solution chemistry to prepare chromium or tungsten Chevrels (28, 77). 

Rhodotorulic acid (RA), a dihydroxamate siderophore, forms dimeric complexes with iron, aluminium and chromium of the stoichiometry M2(RA)3 at neutral pH 36 188). The coordination chemistry of this siderophore is probably the most complicated of the siderophores. The combination of cis-trans, A and A configurations of two iron miters, connected by three RA molecules, makes 42 non-redundant isomers theoretically possible each can be simulated by molecular models. Recently three different isomers or mixtures of isomers of Cr2RA3 were separated by reversed phase HPLC-chromatography177). The visible spectrum of the most abundant fraction corresponds to the cis isomer the two other fractions are very similar to the visible spectrum of the trans Cr(men)3 isomer. The CD spectra, in comparison with the Cr(men)3 model complex, show two different optical isomers, assigned as A -trans and A -trans. The A isomer preparation seems also to contain a certain amount of the A configuration. This is the first time that two different, kinetically stable optical isomers have been isolated from the metal complexes of a siderophore 177). 

All phases of coordination chemistry are encompassed by the complex chromium(III) azides. A yellow, crystalline salt of the composition [Cr (NH3)6] (N3)3, for example, is not a true azido complex but the azide salt of the hexammmechromium(III) cation. It is soluble in water the heated solution aquates over a red intermediate, aquopentamminechromium, to chromium hydroxide. The dry salt explodes in the match test. Similarly explosive is the neutral complex triamminetriazidochromium(III), [(NH3)3Cr (N3)3]°, an olive-green, crystalline solid which is, expectedly, insoluble in water and organic solvents it explodes thermally within 25 sec at 250°, and within 1 sec at 300°C, and also on impact [145]. The compound was made by heating a solution of 10 g hexamminechromium perchlorate, 10 g ammonium sulfate, and 50 g sodium azide in 300 ml water for 90 min. 

As carbene complexes have become proficient catalysts, their incorporation into recyclable catalyst systems has grown into a field of its own. The most common strategy for recovering a catalyst for subsequent use is to append it to a heterogeneous support (e.g., a PS bead), and both Fischer carbenes and NHCs have been incorporated into polymers for this purpose. The first polymer-bound Fischer carbene complexes were reported by Mariorana and Seneci in 1999 [51], for use in soHd-phase organic synthesis for combinatorial chemistry. These materials were prepared via the attachment of chromium carbene complexes to a polymer resin... 

An overview of the effect of catalyst in the reaction of arenes with chromium hexacarbrmyl has been published. The reactivity of 17-, 18-, and 19-etectron catkMis generated electrochemically from mesitylene-tungsten tricarbonyl has been examined. The gas phase ion chemistry of a range of arene tricarbonylchromium complexes has been investigated by F.T. mass spectrometry. An improved synthesis of substituted naphthalene chromium carbonyls has appeared. ... 

The effect of materials chemistry and microstructure of materials in SCC and the interrelationship between the two is highly complex. The composition of the alloy has a significant bearing on the properties of the passive films and phase distribution. For example, a high amount of carbon in steels tends to form chromium carbide which causes sensitization of steel and leads to intergranular corrosion. Similarly, impinity elements in steels segregates and affects the corrosion dissolution process. 

Cr, Mo and W - The gas-phase ion chemistry of the chromium cycloheptatriene complexes [Cr(T -C7H8)(CO)3] was studied272 by Fourier Transform Ion Cyclotron Resonance Spectroscopy. The presence of a fragment ion [C5H6Cr]+ with the hydrido-ri -cyclopentadienyl structure was detected. Reaction of the same complex [Cr(Ti -C7H8)(CO)3] with the carbene complex [Cr(CO)5(=C(OMe)Me)] afforded273 an isomeric mixture of bicyclo[4.2.1]nonanone products. 

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