Bipyridine complex catalysts

The vanadium(IV) complex of salen in zeolite was found to be an effective catalyst for the room temperature epoxidation of cyclohexene using t-butyl hydroperoxide as oxidant.88 Well-characterized vanadyl bis-bipyridine complexes encapsulated in Y zeolite were used as oxidation catalysts.101 Ligation of manganese ions in zeolites with 1,4,7-triazacyclononanes gives rise to a binu-clear complex stabilized by the zeolites but allows oxidation with excellent selectivity (Scheme 7.4). 

Several dyes or transition-metal complexes can be used as redox mediators in indirect electrolyses. Pentamethylcyclopentadienyl-rhodium(bipyridine) complexes [Cp Rhnl(bpy)(H20)]2+ 9 [33], which were pioneered and intensively studied by Steckhan et al. [34—36], are very versatile catalysts for the reduction of cofactors. 

Recently, chloro-, bromo-, and iodoben-zenes have been subjected to electroreduction using Ni(0) complex mediators to yield biphenyl. NiCl2L2 and NiBr2L2 [L= P(Ph)3, (Ph)2PCH2CH2P(Ph)2] have been used as catalysts [259-265]. Pro-tic media such as alcohols, that is, methanol, ethanol or alcohol-water mixtures are found to be suitable solvents for achieving the electrosynthesis of biaryls from aryl halides according to a procedure that involves a catalytic process by nickel-2,2 -bipyridine complexes [266]. Electrochemical cross-coupling between... 

The possibility of the practical application of the catalytic photode-composition of water based on the reactivity of the excited states of tris(2,2 -bipyridine) complexes of ruthenium(III) and ruthenium(II) has attracted considerable interest, but it is now clear that the efficiency of this process is limited not only by the lack of efficient catalysts, particularly for the dioxygen-evolving path, but also by both thermal and photochemical ligand oxidation 1,2) and ligand substitution reactions (3) of the 2,2 -bipyridine complexes. The stoichiometrically analogous tris(2,2 -bipyridine) and tris(l,10-phenanthroline) complexes of both... 

Angelescu, E., Che, M., Andruh, M., Zavoianu, R., Costentin, G., Mirica, C. and Dumitru Pavel, O. Ethylene selective dimerization on polymer complex catalyst of Ni(4,4 -bipyridine)Cl2 coactivated with A1C1(C2H5)2. J. Mol. Catal., A, 219, 2004, 13-19. 

In solution, bis-bipyridine complexes of Mn (4a) easily form dinuclear complexes, in which the two Mn nuclei are hnked through //-oxo or It -hydroxy ligands. These complexes are highly active catalysts for the decomposition of H2O2. 

Propargylic aryl ethers (also esters) are cleaved by benzyltriethylammonium tetrathiomolyb-date in acetonitrile at room temperature. Allyl esters are not cleaved under these conditions. Electroreduction in the presence of Ni-bipyridine complex as catalyst is another method to affect the deprotection of propargyl ethers (Scheme 1.22). 

Long-range electron transfer is postulated to occur from ferrocene to tris(bipyridine)iron(lll) constructed within the pores of a NaY zeoUte. The iron bipyridine complex is too large to move throughout the faujasite pores to the surface, thus requiring the long-range transfer. The asyimnetric catalyst, titanium tartrate, has been prepared inside NaY and used as an immobilized catalyst for the epoxidation of cinnamyl alcohol. ... 

Electrogenerated nickel(O) bipyridine complexes serve as catalysts for a number of syntheses (a) formation of ketones from acyl halides and either alkyl or aryl halides [319], (b) production of, )/-unsaturated esters via coupling of a -haloesters with aryl or vinyl halides [320], (c) coupling of a-chloroesters or a-chloronitriles with carbonyl... 

Figure 9. (a) yields as a function of pH in water oxidation with [M(bipy)3] (10 moldm" ) complexes in the presence of RuOi catalyst (10 mol dm ), (b) -pH diagram for water oxidation, RUO4 reduction and redox potentials of tris(bipyridine) complexes (O, [Ru(bipy)3] , [Fefbipy) ] , [Os(bipy)3] ) reproduced from ref. 292)... 

P-29 - Pt-2,2 bipyridine complex encapsulated in Y zeolite - catalysts for ethylene selective dimerization... 

Using nickel-2,2 -bipyridine complex as the catalyst, electroreductive coupling of 5-bromoindole gave rise to the bis-indole shown using NaBr as the electrolyte and iron and the sacrificial electrode [219]. 

Trinuclear and dinuclear Ru complexes are capable of 4-electron oxidation of water but, for mononuclear complexes, only the cw-tetraammine Ru complexes are capable of 4-electron oxidation, and other mononuclear ones are 2-electron catalysts by one molecule. For the 2-electron catalysts, the cooperative distance (fco) for bimolecular water oxidation was also estimated by a similar procedure to ra- the ammine complex shows much higher activity than the bipyridine complex. 

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