Organochromium complexes

Homolytic and free radical pathways in reactions of organochromium complexes. J. H. Espenson, Prog. Inorg. Chem., 1983, 30,189-212 (85). 

Mercury(II) reacts with organochromium complexes by electrophilic substitution. Rate constants have been reported for Hg2+ attack at a series of alkylchromium complexes with the macrocyclic ligand 1,4,8,11-tetrazacyclotetradecane, CrR(H20)([14]aneN4). The Hammett relationship established for a series of meta and para substituted benzyl analogues is consistent with attack of the Hg2+ at a-carbon (89). 

The observation that reaction (13) is the slowest step, and that the organochromium complexes are highly colored with peak maxima at 300 (2500) and —400 (—300), provides a means of determining rate constants for (13) (18). 

Supported organochromium complexes exhibit catalytic behavior very similar to that of the traditional Phillips catalyst, and both systems are very sensitive to minute experimental variables.322 Modification of the catalyst allows for control of... 

Once formed in reaction 8.52, CH3 will be captured quantitatively by Craq2+ to form the organochromium complex ... 

In the first stage, the organochromium complexes were generated in a Fenton-type scheme, Eqs. 13-15. 

The organochromium complex disappears in two parallel processes irreversible acidolysis (ka) and reversible homolysis (kh). The kinetics, Eq. 56, are determined by ka and the competition for the organic radical between Co(NH3)5py + and a... 

Espenson, James H., Homolytic and Free Radical Pathways in the Reactions of Organochromium Complexes. 30 189... 

The electronic effects in energy and electron transfer reactions, including excited state systems, have been discussed in a review by Endicott. The trends observed in the rate constants for the quenching of the doublet E) excited state of [Cr(bpy)3] by a series of organochromium complexes, [Cr(H20)5R], indicate an outer-sphere electron transfer mechanism. The different reactivity patterns found for the oxidations of [(H20)Co([14]aneN4)R] complexes by [Ru(Bpy)3] and [ Cr(bpy)3] point to electron and energy transfer mechanisms, respectively. The reductive quenching of [ Cr(bpy)3] by Fe produces [Cr(bpy)3], which also quenches the excited state in the absence of added... 

Reviews with relevance material include those on organochromium complexes 3 and cyclopentadienyl molybdenum and tungsten dihalides. 1 ... 

Treatment of chromium(III) chloride with phenylmagnesium bromide under an atmosphere of carbon monoxide provided a route to chromium hexacarbonyl (Job-Cassels reaction). When this reaction was carried out under nitrogen it was possible to isolate organochromium complexes, but these are now known to be rj -arene compounds, formed via unstable chromium phenyls (see p. 314). 

Organochromium Complexes with Nitrogen-Containing Ligands for Ethylene Polymerization... 

The formation of organochromium complexes, e.g. in the above case [CrMe] +, is thought to result from fragmentation of the alko,xy radicals produced and subsequent reaction with Cr +, equation (3). 

Light-induced homolysis of some organochromium complexes produces low concentrations of Cr used to study the reaction of Cr " and H202. The first and rate-determining step of the reaction shown in equation (32),... 

A. Petrou, E. Vrachnou-Astra, and D. Katakis, Inorg. Chim. Acta, 1980, 39, 161. A new series of organochromium complexes formed in aqueous solutions. 

The formation of unstable organochromium complexes was first observed in 1903 [85], but it was not until 1919 that Hein successfully isolated a polyphenyl du-omhun complex , firom the reaction between phenyl-magnesium bromide and dhromium(III) chloride in anhydrous ether [86]... 

The organochromium complex 47 provides a good example of remote addition to an j " complex (Scheme 14.18) with stereocontrolled reaction with the nucleophile and trapping the anion [198]. Similar examples have been reported by Uemura s group [199], establishing the general principles of remote nucleophile addition to tf Cr(CO)3 complexes. An example from Muller in Munich has used this effect to add PrS" to an allenylbenzene ligand [200]. 

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