2,2 -Bipyridine chromium complexes

N2C10H, 2,2 -Bipyridine, palladium complex, 22 170 mthenium complex, 21 127 NjCioH, 2,2 -Bipyridine, chromium complexes, 23 180 NiC,oH24, 1,2-Ethanediamine, Al,Al -dimethyl-N,N -bis( 1 -methylethyl), platinum complex, 21 88... 

Beattie and Basolo have investigated the reactions of the substitution-inert octahedral complexes of Pt(IV) with tris(bipyridine)chromium(II). A rapidmixing, stopped-flow apparatus was made use of in the majority of experiments. 

Caution should be observed in handling this compound, as with all perchlorate salts. The tris(bipyridine)chromium(I1) perchlorate explodes violently on slow heating to 250° and can be set off by static electricity. It does not appear to be shock-sensitive on dropping an 8.8-g. steel ball from 4 ft., although the compound was tested only once. The explosive properties of related complexes have been described.16... 

Table 6 compiles the electrode potentials of the chromium complexes with phenantroline, bipyridine and terpyridine ligands, respectively25-27. 

Figure 16 shows the octahedral geometry of two chromium complexes with N204 coordination. The first with the Schiff base [iV,./V-ethylene-bis(salicylideneimine)] + two water molecules, [Cr(salen) (H202)2]+ 29 the second with two molecules of [2,2 -bipyridine-6-phenolate], [Cr 6-(2-C6H40)bipy 2]+.3°... 

Bis-bipyridine-silver complexes were found to catalyze the B-Z (with malonic acid as substrate) reaction by Kuhnert and Pehl (1981-1). The reaction was shown to proceed in a heterogeneous medium due to the insolubility of the silver complexes. When organic compounds such as citric acid and 2,4-pentanedione, ethylacetoacetate and racemic malic acid were used as substrates, the oscillatory behavior was not observed. Kuhnert and Pehl (1981-2) also observed that the bipyridine complexes of chromium and osmium catalyze the B-Z reaction. 

The inactivity of chromium(III) in cellular short term assay systems is probably due to the fact that cell membranes appear to be quite impermeable to most chromium(III) complexes. However, it appears that heterocyclic aromatic ligands facilitate uptake of chromium(III) into cells since c -dichlorobis(2,2 -bipyridine)chromium(III), ciy-di-chlorobis(l, 10-phenanthroline)chromium(III) and cis -oxalatobis(2,2 -bipyridine)-... 

The complex formed by 2,2 -bipyridine with chromium(VI) oxide is a milder oxidant than die Collins reagent. as indicated by the need for long reaction times (up to 48 h) and a larger excess of oxidant (8 equiv.). 

Chromium(salen) catalysts are excellent reagents for the desymmetrization of OT to-epoxides. Thus, tfr-stilbene oxide is converted to the (3, 3 )-aminoalcohol in the presence of catalytic quantities of chromium-salen complex in methylene chloride solution open to the atmosphere. The addition of small quantities of triethylamine was found to dramatically increase enantioselectivities (by almost 25%). This catalytic system also promotes an efficient aminolytic kinetic resolution (AKR) of racemic epoxides with 2-type symmetry (Equation 18) <20040L2173, 1999TL7303>. W fo-Epoxides can be opened with aromatic amines in water in the presence of 1 mol% of an Sc(ni) catalyst ligated to 1.2mol% of a chiral bipyridine ligand <2005OL4593>. 

Aniline complexes of Cofll), Ni(II), Cu(II) Bis-bipyridine-silver Bipyridine complexes of osmium and chromium... 

IIIC) Kuhnert, L., Pehl, K. W. Bipyridine Complexes of Osmium and Chromium Catalyzing the 1981-2 Oscillating Reaction between Bromate and Malonic Acid. Chem. Phys. Lett. 84 (1) 159-162. 

The last method, F, which uses NiCl2-2,2 -bipyridine complex, works well only for the most reactive aryl iodides [31]. It is mechanistically more complicated because here lead(II) bromide acts as the source of lead(0) which actually reduces Ni"(bpy)X2 back to the catalytically active Ni°(bpy). Since the 2,2 -bip)ridme 75 is somewhat more electron-rich ligand than simple 2,2 -bipyridine (5), the resulting nickel(II) complex employed in the related Chen s method is sUghtly more reactive with electron-poor aryl halides, e.g. bromides, but generally the method is appUcable only with aryl iodides [30]. For instance, both iodo- and bromobenzene gave biphenyl (8) in 98 and 88% yields, respectively, but 2-bromothiophene was coupled in only 22% yield [30], Scheme 8. Chromium(II) chloride in a catalytic amount was used as an intermediate reductant as it provides an effective redox system, Cr(II) / Cr(III) between Ni(0) / Ni(II) and metallic manganese as the ultimate reductant. 

Cr(pyz)(OH2)5] " ion (pyz = pyrazine) is formed from the second-order reaction between aqueous Cr(II) and pyrazine. A transient pyrazine-radical complex of Cr(III) was also observed.Reaction of [Cr(H20)6] " with 4,4 -bi-pyridine gives a transient blue species assigned to the 4,4 -bipyridine radical. The chromium product is [Cr(H20)6] ". ... 

The acid hydrolysis of [Cr(LL)3] [LL = NH2CH2CH2OH, H0CH2CH(NH2)CH3, and NH2CH2CH(OH)CH3] was discussed previously (Reference 12). A study of the tris(ethanolamine) complex in aqueous/ acetone mixed solvents has also appeared. The acid hydrolysis of the low-spin tris(chelates) of chromium(II) with 2,2 -bipyridine and... 

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