Chromium complexes trinuclear

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... 

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]. 

Chromium complexes acetylacetone complex formation, 386 exchange reactions, 380 amidines, 276 bridging ligands, 198 chelating ligands, 203 carbamic add, 450 paddlewheel structure, 451 carboxylic adds, 438 trinuclear, 441 oorroles, 874... 

Aza[3]ferrocenophanes, synthesis, 6, 187 Azaheterocycles, alkynylation with Ir catalysts, 7, 340 7-Azaindole, in trinuclear Ru and Os clusters, 6, 725 Azametallacyclobutane, tantalum complexes, 5, 168 Azametallacyclopropane, with niobium, 5, 87 Aza-oxo ligands, chromium complexes, 5, 353 Azaphosphirenes, with tungsten carbonyls, 5, 623 2H-Azaphosphirenes, with tungsten carbonyls, 5, 679 Aza-titanacyclopentenes, synthesis, 4, 407-408 Azavinylidenes... 

An intercalation process under reflux conditions for 4 days has been performed by Ma et al. to prepare chromium oxide-pillared manganese oxides [38]. In this reaction chromium hydroxyl acetate clusters, Cr3(OAc)7(OH)2, are used as the pillaring species. Cr + self-polymerizes under reflux to form polynuclear clusters between the manganese oxide layers. Intercalation of this trinuclear chromium complex constitutes a challenge because redox reactions may occur between manganese oxide and the transition metal oxide during the process, which could destroy the layer structure. 

Further condensation of the dinuclear species may occur either by continuing the edge-to-edge condensation, which leads to linear trinuclear structures such as 4a and 4b, or by condensation of a third chromium ion to each of the two chromium(III) centers in structure 2, yielding the cyclic structure 5. The (NH3)4Co(OH)2Co(CN)2(OH)2-Co(NH3)43+ cation (49) possesses structure 4a, and there is good evidence that the trinuclear amine complex Cr3(en)5(OH)45+ has the same structure (42). The linear trinuclear structure 4b has not been observed in crystal structures. The cyclic, trinuclear structure 5 has been observed in crystal structures of chromium(III) complexes with ammonia, tacn, and bispicam (40, 50, 51). 

The circular dichroism (CD) spectra of optically active di-, tri-, and tetranuclear complexes of chromium(III) and cobalt(III) have been reported and used to establish the complexes absolute configurations (55 59, 111, 115, 116, 152-157). The changes in circular dichroism resulting from ion pairing have been studied for the tetranuclear hexol Co j(OH)2Co(NH,)4J, h+ and have been shown to be attributable to the vicinal effect of the chiral oxygen centers produced stereospecifically by the ion-pair formation (56). For a series of trinuclear cobalt (III) amine complexes, cis-Co(CN)2[(OH)2Co(N4)2 J3 +, it was shown that the main CD contributions due to the two chiral Co(OH)4(CN)2 and Co(N4)(OH)2 centers are additive (155). In the case of the related tetranuclear complex Co((OH)2Co(en)2J,< + this postulate of additivity of CD spectra proved unsatisfactory (57). 

The mechanisms of the oxidation of phosphines and arsines by chromium(VI) have been examined both in solution and on a diatomite support. Kinetic parameters are presented for both supported and solution reactions. A ruthenium complex of 1,4,8,1 l-tetramethyl-l,4,8,ll-tetraazacyclotetradecane has been utilized to oxidize triphenylphosphine in acetonitrile. Although a limited temperature range was utilized, a AH value of 8.7 0.8 kcal mor and a A5 value of -20 2 cal K mor were calculated. The secondary phosphine oxides, HP(0)R (R = n-butyl, isobutyl, cyclohexyl) and 9H-9-phosphabicyclononane-9-oxide, react with cobaltocene to yield dihydrogen and cobalt(I) compounds. With the less bulky phosphorus ligands at elevated temperatures trinuclear cobalt(III, II) complexes may be obtained. Arsenious acid may be utilized to catalyze the oxygen atom... 

Fig. 12 Pyridyl-benzimidazole based ligand LI used to prepare hetero-trinuclear chromium/ erbium complexes.

In the binuclear Cr(ii) complex the bulky BU3CO ligand restricts the chromium to three-coordination, whilst in [Li(/r-OCBu3)2Mn N(SiMe3)2 ] the lithium is two-coordinated and the Mn(ii) is three-coordinated." In the trinuclear bromo complex [(thf)2Li( i-Br)2Mn(/i,-OCBu 3)2Li] one Li is two-coordinated and the other is four-coordinated like the Mn(n)." ... 

The oxidation of DL-serine by chromium(VI) proceeds via 2-amino-3-oxopropanoic acid, which is formed in the initial slow step. A mechanism has been proposed for the chromium(VI) oxidation of gallic acid (using potassium dichromate), which gives a trinuclear complex of chromium(III) containing OH and O2 bridges and a pyruvate ion ligand. The oxidation of perchloric acid-catalysed N, A—dimethylformamide (DMF) by chromium) VI) is first order in both Cr(VI) and DMF the order with respect... 

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