Tetra cobalt

Dloxygen reduction electrocatalysis by metal macrocycles adsorbed on or bound to electrodes has been an Important area of Investigation (23 ) and has achieved a substantial molecular sophistication in terms of structured design of the macrocyclic catalysts (2A). Since there have been few other electrochemical studies of polymeric porphyrin films, we elected to inspect the dloxygen electrocatalytic efficacy of films of electropolymerized cobalt tetraphenylporphyrins. All the films exhibited some activity, to differing extents, with films of the cobalt tetra(o-aminophenylporphyrin) being the most active (2-4). Curiously, this compound, both as a monomer In solution and as an electropolymerized film, also exhibited two electrochemical waves... 

Interpreting these results on a detailed molecular basis is difficult because we have at present no direct structural data proving the nature of the split Co(IIl/lI) voltammetry (which seems critical to the electrocatalytic efficacy). Experiments on the dissolved monomeric porphyrin, in CH-C solvent, reveal a strong tendency for association, especially for the tetra(o-aminophenyl)porphyrin. From this observation, we have speculated (3) that the split Co(III/II) wave may represent reactivity of non-associated (dimer ) and associated forms of the cobalt tetra(o-aminophenyl)porphyrins, and that these states play different roles in the dioxygen reduction chemistry. That dimeric cobalt porphyrins in particular can yield more efficient four electron dioxygen reduction pathways is well known (24). Our results suggest that efforts to incorporate more structurally well defined dimeric porphyrins into polymer films may be a worthwhile line of future research. 

Some 2,3-unsaturated sugars have also been prepared by the reaction of 2-iodinated carbohydrates with sodium cobalt tetra-carbonyl and carbon monoxide.188 Methyl 3,4,6-tri-0-acetyl-2-deoxy-2-iodo-/3-D-glucopyranoside (149) in ether reacts at room temperature to give, in high yield, methyl 4,6-di-0-acetyl-2,3-dideoxy-/3-D-eri/thro-hex-2-enopyranoside (150). Under the same reaction conditions,... 

Fig. 25. Potentiodynamic current/voltage curves of monomeric cobalt tetra-aza-annulene. Conditions 2 N H2SO4, 70°C, sweep rate 50 mV/min.

A. Rosenthal and J. N. C. Whyte, Reaction of anhydro sugars with sodium cobalt tetra-carbonyl and carbon monoxide, Can. J. Chem., 46 (1968) 2239-2243. 

Mashazi PN, Ozoemena K I, Maree DM, Nyokong T (2006) Self-assembled monolayers (SAMs) of cobalt tetra carboxylic acid chloride phthalocyanine covalently attached onto a preformed mercaptoethanol SAM A novel method. Electrochim Acta 51(17) 3489—3494... 

Trollund E, Ardiles P, Aguirre M J, Biaggio SR, Rocha-Filho RC (2000) Spectroelectrochemical and electrical characterization of poly(cobalt-tetra aminophthalocyanine)-modified electrodes electrocatalytic oxidation of hydrazine. Polyhedron 19(22-23) 2303-2312... 

Cobalt Tetra-carbonyl, Co(C0)4 or Co2(CO)g.—This compound may be prepared by passing carbon monoxide at a pressure of 40 atmospheres over reduced cobalt at 150° C. The higher the pressure the more rapid is the formation of the earbonyl.7 It forms as fine, orange-coloured transparent crystals, which are best preserved by hermetically sealing them in a glass tube in an atmosphere of hydrogen or of carbon monoxide. Upon exposure to air decomposition takes place resulting in the formation of a basic cobalt carbonate. With bromine it yields cobalt bromide and carbon monoxide ... 

The lack of reactivity at C-3 of the a-D anomer as compared with that of the /8-D anomer of methyl 4,6-O-benzylidene-D-glucoside has been noted by other workers. Presumably, the bulky cobalt tetra-carbonyl anion is hindered from approaching C-3 by the methoxyl group on C-1, whereas the less bulky methoxide ion, or hydroxide ion, can open the epoxide ring in the normal, frans-diaxial way. 

When the inorganic insertion product is not stable, information about the CO insertion can be obtained from the thermal decomposition products, e.g., alkyl cobalt tetra-carbonyls give ketones on decomposition ... 

Cl6C2 Hexachloroethane, 4 124 Co(CN)6K3 Potassium hexacyano-cobaltate(III), 2 225 [Co(CO)3]4 Tetracobalt dodecacar-bonyl, 2 243 5 191 n. [Co(CO)4](C6H6NH) Cobalt tetra-carbonyl hydride, pyridinium salt, 5 194... 

Co (CO) 4] (CsH jNH) Cobalt tetra carbonyl hydride, pyridinium salt, 6 194... 

A. Recoura, A. Werner and A. Gubser, A. Werner and R. Huber, P. Pfeiffer and M. Tapuach, and N. Bjerrum. The salts include (1) chloride (2) bromide (3) sulphate and (4) the cobaltic tetra-nitritodiammine. 

Raman spectra recorded under resonant or pre-resonant (i.e. the laser line is somewhat away from the optical absorption maximum) conditions were obtained for the bulk complex cobalt tetra-/7-methoxyphenylporphyrine Co(TMPP). 

Anson et found evidence for a four-electron reduction mechanism on adsorbed multilayers of cobalt tetra-4-pyridylporphyrin on a graphite electrode but considerable amounts of peroxide were produced in the reaction. In a series of articles Anson and coworkers have shown that by plac-... 

Pavez, J., M. Paez, A. Ringuede, F. Bedioui, and J.H. Zagal (2005). Effect of film thickness on the electro-reduction of molecular oxygen on electropolymerized cobalt tetra-aminophthalocyanine films. Solid State Electrochem. 9, 21-29. 

Zeng, Z.Y., S.L. Gupta, H. Huang, and E.B Yeager (1991). Oxygen reduction on poly (4-vinylpyridine)-modified ordinary pyrolytic graphite electrodes with adsorbed cobalt tetra-sulphonated phthalocyanine in acid solution. J. Appl. Electrochem. 21, 973-981. 

Tarasevich, M.R., L.A. Beketaeva, B.N. Efremov, N. M. Zagudaeva, L.N. Kuznetsova, K.V. RybaUca, and V.E. Sosenkin (2004). Electrochemical properties of carbon black AD-100 and AD-100 promoted with pyropolymer of cobalt tetra (p-methoxyphenyl)porphyrin. Russ. J. Electrochem. 40, 542-551. 

Riquelme, A., M. Isaacs, M. Lucero, E. TroUund, and M. J. Aguirre (2003). Electrocatalytic reduction of carbon dioxide at polymeric cobalt tetra (3-amino (phenyl) porphyrin glassy carbon-moditied electrodes. J. Chil. Chem. Soc. 48(2), 89-92. 

Bettelheim, A., B.A. White, and R.W. Murray (1987). Electrocatalysis of dioxygen reduction in aqueous acid and base by multimolecular layer films of electropolymerized cobalt tetra(ortho-aminophenyl)porphyrin. J. Electroanal. Chenu 217, 271-286. 

Griveau, S., J. Pavez, J.H. Zagal, and E. Bedioui (2001). Electro-oxidation of 2-mercaptoethanol on adsorbed monomeric and electropolymerized cobalt tetra-aminophthalocyanine films Effect of film thickness. J. Electroanal. Chem. 497, 75-83. 

Ozoemena KI, Nkosi D, Pillay J (2008) Influence of solution pH on the electron transport of the self-assembled nanoarrays of single-walled carbon nanotube-cobalt tetra-aminophthalocyanine on gold electrodes electrocatalytic detection of epinephrine. 

Jester CP, Rocklin RD, Murray RW (1980) Electron transfer and axial coordination reactions of cobalt tetra(aminophenyl)porphyrins covalently bonded to carbon electrodes. J Electrochem Soc 127 1979-1985... 

II) being then only to increase the rate of H2O2 production. Nan et al. [42] used activated carbon fiber (ACF) electrodes modified with cobalt tetra (2,4-dichloro-l,3,5-triazine)aminophthalocyanine (CoPc) and wrapped with titanium mesh as anode material, and stainless steel plate as cathode material, in 0.05 mol/L Na2S04- About 20 % of ARl were removed by CoPc-ACF in the absence of an applied potential, which the authors attributed to the existence of an anode potential and the electrocatalytic behavior of CoPc-ACF. 

Brown RJC, Dyson PJ, ElUs DJ, Welton T (2001) l-Butyl-3-methylimidazolium cobalt tetra-carbonyl [bmim] [Co(CO)4] a catalytically active organometallic ionic liquid. Chem Commun 18 1862-1863... 

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