Chromium diketonate ligands

Figure 5-10. A reaction sequence involving a 2,4-diketonate ligand co-ordinated to chromium(m) which allows the introduction of a fluoro substituent.

It was found that octahedral iron(lll), manganese(III) or chromium(lll) ions produced mesomorphic complexes when complexed with three -diketonate ligands, presumably with the molecules associating as in Figure 88 [167],... 

Chromium, (ri6-benzene)tricarbonyl-stereochemistry nomenclature, 1,131 Chromium complexes, 3,699-948 acetylacetone complex formation, 2,386 exchange reactions, 2,380 amidines, 2,276 bridging ligands, 2,198 chelating ligands, 2,203 anionic oxo halides, 3,944 applications, 6,1014 azo dyes, 6,41 biological effects, 3,947 carbamic acid, 2,450 paddlewheel structure, 2, 451 carboxylic acids, 2,438 trinuclear, 2, 441 carcinogenicity, 3, 947 corroles, 2, 874 crystal structures, 3, 702 cyanides, 3, 703 1,4-diaza-1,3-butadiene, 2,209 1,3-diketones... 

The octahedral complex Cr[CH3C(0)CHC(0)Fc]3 displays a single ferrocenyl oxidation at -1-0.58 V, vs. SCE (CH2CI2 solution), which is lower by about 60 mV than that of the free l-ferrocenyl-l,3-butanedionato ligand, thus suggesting that the chromium(III) diketonate donates electron density to the ferrocenyl appendices . As a consequence, the Cr(in) Cr(II) reduction, which is partially overlapped by the solvent discharge in Cr(acac)3, cannot be detected. The simultaneous oxidation of the three ferrocenyl units means that they are electronically isolated from each other. 

One of the most versatile classes of ligands in coordination chemistry is that of the /3-diketonates, of which the most common is the acetylacetonate, (acac), Figure 9.1. The coordination chemistry of this ligand first appears in the literature in work by Combes in 1887-1894. Alfred Werner also published on the chemistry of the acac ligand in 1901. The acac ligand is remarkable in that it forms complexes with virtually any metal, including beryllium, lead, aluminum, chromium, platinum, and gadolinium. 

PC. Uden, I.E. Bigley, and EH. Walters. The separation of geometrical isomers and mixed ligand forms of cobaltdil) and chromium(III) beta-diketonates by high pressure liquid chromatography. Anal. Chim. Acta, 100, 555 (1978). 

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