Chromium complexes crystal structures

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 structures of these stannylene complexes closely resemble those of carbene complexes. In Fig. 12 the crystal structure of the stannylene complex 4 is displayed the tin atom, the two carbon and the chromium atoms are equi-planar 30). 

The crystal structures of (3a,4-8,8a-f/)-[5.7,8-trimethyl-8H-cyclohepta-(fe)-thiophen]- and (1—3,3a.8a-f7)-[5,7-dimethyl-4//-cyclohepta-(c)-thiophen]-chromium tricarbonyl complexes, (55) and (56). respectively, have been determined. ... 

The intermediate cyclooctene complex appears to be more reactive with respect to CS coordination and more sensitive to oxidation when the arene ring bears electron-withdrawing groups (e.g., C02CH3). Dicarbonyl(methyl rj6-benzoate)-thiocarbonyl)chromium is air stable in the solid state and reasonably stable in solution.9 The infrared spectrum exhibits metal carbonyl absorptions at 1980 and 1935 cm"1 and a metal thiocarbonyl stretch at 1215 cm"1 (Nujol) (these occur at 1978, 1932, and 1912 cm"1 in CH2C12 solution).10 Irradiation of the compound in the presence of phosphite or phosphine leads to slow substitution of CO by these ligands, whereas the CS ligand remains inert to substitution. The crystal structure has been published."... 

Wood, R. M., Aboud, K. A., Palenik, R. C., and Palenik, G. J. (2000). Bond valence sums in coordination chemistry. Calculation of the oxidation state of chromium complexes containing only Cr-O bonds and a redetermination of the crystal structure of potassium tetra(peroxo)chromate(V). Inorg. Chem. 

The crystal structure determination by Vahrenkamp and Noth proves the assumed structure of this new and interesting chromium-tricarbonyl complex 56 (Fig. 16). 

Chromium atoms provide a unique route to 7r-pyridine complexes. No simple product has been isolated from the reaction of pyridine and chromium atoms, but 2,6-dimethylpyridine and chromium atoms give a low yield of (i 8-2,6-dimethylpyridine)2chromium characterized by a crystal structure showing essentially planar pyridine rings (103). A mixture of pyridine with either PF3 or mesitylene gives a 7r-C5H5N complex ... 

Thermal deamination of tris(ethylenediamine)chromium(III) complexes is a standard preparative method for cis- and trans-diacidobis(ethylenediamine) complexes421,422 and the thermal behaviour of the starting materials has been related to their crystal structures.423 The cyano complex cis-[Cr(CN)2(en)2]C104 in DMSO undergoes stepwise reduction III— 11 — I at the DME. The standard redox potential for the Cr /Cr11 couple is -1.586 V (versus SCE). 

The tris and bis complexes of acetylacetone (2,4-pentanedione) (167) with chromium(III) have been known for many years (168,169).739 The tris compound is generally prepared by the reaction of an aqueous suspension of anhydrous chromium(III) chloride with acetylacetone, in the presence of urea.740 Recently a novel, efficient synthesis of tris(acetylacetonato)chromium-(III) from Cr03 in acetylacetone has been reported.741 The crystal structure of the tris complex has been determined.744 A large anisotropic motion was observed for one of the chelate rings, attributed to thermal motion, rather than a slight disorder in the molecular packing. 

Chromium is unusual in that it forms a stable hexakis O-bonded urea complex. The complex was first prepared as the chloride salt by Pfeiffer804 and a crystal structure of the complex salt [Cr OC(NH2)2 6][Cr(CN)6]-2DMSO>2EtOH has recently been reported.805 Coordination at chromium(IH) is octahedral r(Cr—O) is in the range 1.96-1.98 A. The reduction of the perchlorate salt of this complex to a chromium(II) species has been studied polarographically.806 Detailed studies of the luminescence spectra of several salts of the chromium urea complex have been reported.807,808... 

Crystallographic studies of the bis oxalates of chromium(III) are not abundant. However, the structure of both tarns904 and cis905 isomers has been confirmed crystallographically. Potassium tams-bis(oxalato)diaquachromate(III) is monoclinic (space group P2/c) the oxalates are strictly coplanar. The crystal structure of the complex salt [Cr(en)2(ox)][Cr(en)(ox)2] has been determined 905 this red salt is obtained as an intermediate in the preparation of salts of mixed ethylenediamine/oxalate chromium(III) complexes. The structure consists of discrete complex ions linked by H bonding to water molecules and neighbouring ions. 

Mixed dinuclear complexes of tartrates and 2,2 -bipyridyl or 1,10-phenanthroline and chromium(III) have been prepared 934,935 the typical structure is illustrated below (213). Stereochemical correlations have been carried out by oxidatively cleaving the tartrate bridge (214,215).936 The crystal structure of sodium hydrogen bis(//-meso-tartrato)bis(2,2 -bipyridyl)dichromate(III) heptahydrate has been reported.937... 

Complexes of simple amino adds with chromium(lll) were first prepared by Ley.1148 The isomers possible for tris chelated complexes of this type are illustrated below (248-251). The consequences of such isomerism were first seriously considered by Gillard.1149 Red complexes of the formulae [Cr(gly)3] and [Cr(L-ala)3] were prepared by neutralizing refluxed solutions of hexaaquachromium(Ill) and the amino add in ratios between 1 5 and 1 10. These complexes were shown to be isomorphous with 0-[Co(gly)3] and D- -[Co(L-ala)3] respectively. The crystal structure of red j8-[Cr(gly)3] has also been reported.1150... 

For tridentate amino acids with three non-equivalent donor atoms such as L-aspartic acid or L-cysteine, the isomers possible are illustrated below (252-254). There have been a number of reports of the preparation of L-aspartic acid complexes.1180,1181,1182. In the earlier work the isomers were not identified, however in the later study, the complexes were tentatively identified by comparison of their spectroscopic properties with those of the corresponding cobalt(III) complexes.1183 The order of elution of the complexes on HPLC was also similar to that observed for the corresponding cobalt(III) complexes. Mixed complexes containing l- or D-aspartate and L-histidine were also prepared.1182 A crystal structure of one salt obtained from this kind of system, bis(L-histidinato-0,Ar,Ar )chromium(III) nitrate, has been determined.1184... 

Sodium bis(L-cysteinato)chromate(III) dihydrate has been prepared by refluxing L-cysteine with chromium(III) nitrate and neutralizing the solution.1185. The product is a dark blue solid in which cysteine is coordinated with the sulfur atoms trans (see 252-254). A number of chloro and other complexes of cysteine and related amino acids have been studied.1186 A related complex L-histidinato-D-penicillaminatochromium(III) has been prepared11 7 and its crystal structure reported. 

The synthesis and characterization of materials showing biological activity similar to that of GTF isolated from yeast is a logical objective. As already mentioned, Mertz found aqua and similar complexes of chromium to be more active than chelates with strong ligands. An exception to this was an unspecified cysteine complex,1193 prepared by C. L. Rollinson, which showed marked, but erratic, behaviour in GTF tests. Further investigation of this observation would be interesting, particularly as the crystal structure of a cysteine complex is now known.1185... 

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