Chromium complexes applications

Bis(arene)chromium complexes applications, 5, 345 in engineered materials, 5, 344 Bis(arene) complexes... 

Jan, D., Organometallic engineering of new ruthenium and chromium complexes. Applications to olefin polymerization, Ph.D. thesis. University of Liege (2000). 

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... 

Excellent diastereomeric ratios were achieved with terpene-derived auxiliaries. The pentacarbonyl[(-)-menthyloxycarbene]chromium complex 39 reacted with the sterically hindered 3,3-dimethylbut-l-yne to give tricarbonyl chromium naphthohydroquinone complex 40 in 81% de as the major diastereomer which was also characterised by X-ray analysis [41] (Scheme 25). Surprisingly, the application of other even more sterically demanding terpene auxiliaries or a variation of the alkyne did not improve the diastereomeric ratio [42]. 

Hg " complexes are common, but complexes of Na, Mg", or Al are rare. Chromium complexes are also common, but in such complexes the chromium is in a low or zero oxidation state (which softens it) or attached to other soft ligands. In another application, we may look at this reaction ... 

Recently, Lacour, Sauvage and coworkers were able to show that the association of chiral [CuL2] complexes (L=2-R-phen,6-R-bpy and2-iminopyridine) with TRISPHAT 8 leads to an NMR enantiodifferentiation, which allows the determination of the kinetics of racemization of the complexes (bpy=2,2 -bipyri-dine phen=l,10-phenanthroline) [119]. This type of application has recently been reported in conjunction with chiral sandwich-shaped trinuclear silver(l) complexes [122]. Several reports, independent from Lacour s group,have confirmed the efficiency of these chiral shift agents [123-127]. Finally, TRISPHAT can be used to determine the enantiomeric purity of (r] -arene)chromium complexes. These results broaden the field of application of 8 to chiral neutral, and not just cationic, species [114,128,129]. 

H. Kocaokutgen and S. Ozkinali, Characterisation and application of some o,o -dihydroxyazo dyes containing a 7-hydroxy group and their chromium complexes on nylon and wool. Dyes Pig., 63 (2004) 83-88. 

Substitution reactions also proceed well with cationic t/ -cycloheptadienyliron complexes such as 105 [81] and related chromium complexes [82], and have found applications in natural product synthesis (Scheme 2.38). 

Metal complexes of tetradentate azomethines, e.g. (199), are reported136 to have very high light-fastness but to be tinctorially weak and dull in hue. Despite this they are of technical interest as very fast yellow to brown pigments. They find no application as dyestuffs, however, because of these deficiencies for example, the chromium complex of (200) gives dull, tinctorially weak dyeings on wool possessing poor wet-fastness properties. 

A hexadentate chromium-complexed magenta dye (41) is described as being useful in image transfer applications.107 It is prepared by attaching an iminodiacetic acid residue to an o,o-dihydroxyazo dye in an appropriate position so that it is suitably disposed to coordinate to the chromium. 

The benzannulation technique is also applicable to the benzene homologation and functionalization of annulenes, as well to a quadruple arene modification of dendritic cores. The reaction of chromium carbene functionalized l,6-methano[10]annulene 82 with 3-hexyne under standard conditions afforded a fair yield of the benzannulation product 83 after protection and oxidative work-up (Scheme 32) [75]. The chromium complex 84 evidently partly survived the oxidation conditions using Feln a syn-stereochemistry with respect to the Cr(CO)3 fragment and the methano bridge was suggested on the basis of NMR data, which is in contrast to the preferred formation of anti-annulation products bearing cydophane skeletons [75b]. 

Acid dyes include metal-complexed azo structures, where the metals used are cobalt, chromium, and iron.10 Examples are 1 1 and 2 3 chromium complexes and 1 2 cobalt complexes, where the numbers employed represent the ratio of metal atoms to dye molecules. Metal-complexed dyes can be formed inside textile fibers by treating suitably dyed fibers with a solution containing metal ions.11 In this case, the metal-free forms of these azo dyes are known as mordant dyes and contain mainly ortho, ortho -bis-hydroxy or ortho-carboxy, ortho -hydroxy groups (e.g., C.I. Mordant Black 11, Mordant Yellow 8, and Mordant Orange 6). When the metal complexes are formed prior to the dye application process, the resultant dyes are known as... 

A further application of chromium complexes in aromatic chemistry allows the construction of a new aromatic ring. In the Dotz benzannu-lation, an alkyne adds to an unsaturated alkoxychromium carbene 11 to give a hydroquinone-chromium complex 12. Decomplexation yields the aromatic compound (Scheme 10.30). 

The same chiral auxiliary has also been used for the stereoselective synthesis of arene-chromium complexes treatment of an aromatic aminal with chromium hexacarbonyl gives the corresponding complex with high diastereomeric excess. This protocol was recently applied in a total synthesis of (—)-lasubine (eq 4). A successful application of 1,2-diaminocyclohexane (as its IR,2R enantiomer) as a chiral auxiliary is illustrated by the di-astereoselective alkylation of the potassium enolate of bis-amide (3) with electrophiles such as benzyl bromide to give bis-alkylated products with excellent diastereoselectivity (eq 5). Lower levels... 

Williams and Feist (149) described the application of electron ESCA techniques to evaluate wood and cellulose surfaces that had been modified by aqueous chromium trioxide treatment. ESCA data showed at least 80% Cr(VI) to Cr(III) reduction on all substrates. Leaching experiments confirmed this reduction to a highly water-insoluble or fixed chromium complex on both wood and on filter paper (cellulose). Similar oxidation products were observed with wood and filter paper. These experiments indicate that chromium-cellulose and chromium-lignin interactions are involved in the mechanism of chromium(VI) stabilization of wood surfaces. 

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