2:2′-dipyridyl complexes of cobalt, Rhodium and iridium—II

Martin, B. Laville Saint; McWhinnie, William R.; Waind, Gwyneth M.

doi:10.1016/0022-1902(61)80248-0

Cited by 98 publications

(34 citation statements)

References 24 publications

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“…This slow, electrolytic decomposition of the complex is diminished by the addition of excess 2,2'-bipyridine. Acrylonitrile is without effect on the course of the controlled potential reduction of Co (bipy) 3 3 + and Co-(bipy)32+. However, if sufficient acrylonitrile is present the color developed as Co (I) is produced and is t The ratio 1s of the peak current for the oxidation of Co(bipy)s+ to that for the reduction of Co(bipy)o 2 +.…”

Section: Resultsmentioning

confidence: 91%

“…The system was therefore examined by cyclic voltammetry with a platinum electrode replacing the dropping mercury electrode. The cyclic voltammograms for Co(bipy) 3 potential separations of ca. 60 mV and no dependence of peak potentials on scan rate or the addition of 2,2'-bipyridine.…”

Section: Resultsmentioning

confidence: 99%

“…Table III Controlled potential electrolysis.-Successive electrolysis of acetonitrile solutions of Co (bipy) 33+ with mercury pool or platinum gauze electrodes at potentials on the plateau of the first and then of the second polarograph waves (i.e., -100 and -1400 m V, respectively) results in the consumption of 1F /mole for each wave as expected for successive reductions to Co-(bipy)32+ and Co(bipy) 3 +. During the reduction to Co(bipy)s+ the solution develops the deep blue color characteristic of this complex (3,4). If the electrolysis is continued at the same potential an additional faraday per mole of electricity is slowly consumed over a period of a few hours, the blue color fades, and a dark precipitate resembling metallic cobalt appears.…”

Section: Resultsmentioning

confidence: 99%

“…However, it is not the same as the product of step C because solutions resulting from the reduction of Co (bipy) 3 2 + by three electrons in the absence of acrylonitrile are noticeably bluer than those obtained when acrylonitrile is present. Moreover, the latter solutions can be converted to what appears to be the same blue color by the addition of excess 2,2'-bipyridine following the reduction.…”

Section: Discussionmentioning

confidence: 96%

“…To obtain the corresponding acrylonitrile complex 100 mg of Co(bipy) 3 (Cl04h was dissolved in 20 ml of a 1:3 mixture of water and ethanol containing 200 mg of acrylonitrile. The mixture was freed of oxygen and all subsequent steps were conducted in an atmosphere of argon.…”

Section: Preparation and Properties Of [Co(bipy)2ch2chcn]-mentioning

confidence: 99%

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Electrochemistry of 2,2′‐Bipyridine Complexes of Cobalt in the Presence of Acrylonitrile

Margel

Smith

Anson

1978

J. Electrochem. Soc.

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The previously claimed (1) catalysis of the electroreduction of acrylonitrile by means of a complex of Co(l) and 2,2'-bipyridine is shown to be erroneous. The "catalytic currents" result instead from the two-electron reduction of a mixed complex of Co (I) acrylonitrile and 2,2' -bipyridine. The equilibrium and forward rate constants for the formation of the mixed complex have been estimated and its spectrum is given. The behavior of a number of other vinyl monomers, which mimic acrylonitrile, is described.Some time ago Tanaka and Sato described experiments (1) in which they claimed to have shown that a low valent complex of cobalt with 2,2'-bipyridine, generated electrochemically in acetonitrile as solvent, was an effective catalyst for the electrochemical reduction of acrylonitrile. We were intrigued by this report for three reasons: (i) The claimed catalysis was very notable CE112 for the wave attributed to acrylonitrile reduction is shifted from -2.3 to -1.3V vs. SCE); (ii) the reduction of acrylonitrile is a reaction of considerable industrial importance; and (iii) the catalytic mechanism was speculated to involve the adsorption of a low valent complex on the surface of the mercury electrode. We have therefore examined this system in more detail at both mercury and platinum electrodes by means of controlled potential electrolysis, cyclic voltammetry, and polarography. Contrary to the previous report (1) we find that the cobalt-2,2'bipyridine complexes do not function as catalysts for the reduction of acrylonitrile. The increase in current that results when both reactants are present arises instead from the reduction of a complex containing bipyridine, acrylonitrile, and cobalt(!) to a new complex containing cobalt in the (-I) oxidation state. Several other vinyl monomers which form complexes with cobalt (I), e.g., 2,2'-bipyridine, also facilitate the reduction to cobalt( -I). This report summarizes the experimental evidence which has led us to these conclusions. ExperimentalApparatus. -Polarograms were obtained with a Princeton Applied Research (PAR) Model 174 polarographic analyzer and recorded with a Hewlett-Packard Model 7004 X-Y recorder. Cyclic voltammograms were obtained by means of a PAR Model 173 potentiostat driven by a conventional signal generator. The voltammograms were recorded with the X-Y recorder or by photographing the screen of a Tektronix 564 oscilloscope. Controlled potential coulometry was conducted with the PAR Model 173 potentiostat equipped with a Model 179 digital coulometer. Gas chromatographic analyses for acrylonitrile in acetonitrile were obtained with a Hewlett-Packard Model 5830 A gas chromatograph with an 18 ft column containihg Carbowax 20 M on Chromosorb W. Spectra were recorded with a Cary 11 spectrophotometer using cuvettes capped with rubber septums which were deoxygenated by purging with argon.Measurements were conducted in a three-compartment cell. The reference electrode was a silver wire immersed in 0.1M AgN0 3 in acetonitrile which was double isolated by frit...

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Section: Resultsmentioning

confidence: 91%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 96%

Section: Preparation and Properties Of [Co(bipy)2ch2chcn]-mentioning

confidence: 99%

See 3 more Smart Citations