Chromium, tris racemization

A number of substituted benzenes, naphthalenes, indans, pyridmes, and indoles form arene(tricarbonyl)chromium complexes upon thermolysis under an inert atmosphere, usually in a high boiling ether, or by irradiation of the arenes in the presence of chromium hexacarbonyl. The complexes are relatively air-stable and can usually be stored for long periods in the absence of light. Somewhat milder conditions can be used by transfer of the chromium tricarbonyl group from preformed naphthalene(tricarbonyl)chromium, tris(L)tricarbonyl chromium (L = acetonitrile, ammonia, pyridine), or tricarbonyl( -l-methylpyrrole)chromium. Enan-tiomerically pure arene(tricarbonyl)chromium complexes having two different substituents, either ortho or meta can be prepared conveniently by classical resolution of racemic... 

It must be concluded, therefore, that the ligands do not become completely detached from the metal ion in isomerization reactions. Comparable results have been observed in the isomerization of potassium diaquodioxalatochromium(III) and the racemization of optically active potassium tris(oxalato)chromium(III) when no exchange with free ligand in solution occurs. Thus, although it is not practicable to take advantage of the desirable properties of individual isomers of 2 1 chromium and cobalt complexes of tridentate azo compounds because of the facility with which such compounds isomerize in solution, the technically important unsymmetrical 2 1 complexes are capable of practical application because they show little or no tendency to disproportionate in solution. 

Chromate, tetrakis(dioxygen)-stereochemistry, 94 Chromate, tricyanodiperoxy-structure, 78 Chromate, tris(oxalato)-racemization solid state, 466 strychnine salt racemization, 466 Chromatography optical resolution, 26 Chrome azurol S metallochromic indicator, 556 Chromium... 

One of the simplest bidentate ligands is the oxalate anion. Racemization of its tris-chelates of cobalt(iii) and chromium(m) have already been mentioned racemization of its rhodium(m) tris-chelate has also been studied recently. The similarity of the kinetic parameters for racemization and for inner-oxygen exchange of [Rh(ox)3l suggests a close similarity of mechanism. A common five-co-ordinate intermediate is proposed, whose lifetime is sufficient for inner router oxygen exchange or for racemization to take place. 

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