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...

ABSTIIACTThe kinetics of f o r m a t i o~~ of the mo~iosulphato complex of iron (111) has bee11 examined spectrophotometrically using a co~itinuous-floxv technique over the range of temperatures 15.6 to 34.5' C in a n aqueous ~n e d i~r m of ionic strength 0.5 and a rangc of conce~~trations of hydrogen ions 0.05 to 0.30 ill. The experimental data inay be interpreted 011 thc assun~ption that the significant reactions are a bimolecular association opposed by a first-order dissociation (Fei++ + S01-= FeSO.,'). For the forxvard reaction AH* is 18.0 kcal mole-' and AS* is 19.4 cal mole-lcleg-1.

The kinetics of the reactiorls involved in the formation of the mono-fluoro comples of iron (111) in aqueous solutions have been examined spectrophotonietricaIly a t ionic strength 0.5 and over the temperature interval 0.1 to 12.1' C. The results are interpretable on the assumption that thefollo\ving t\\,oreactions contributesignilicantly to therateFe+++ + F-= FeF++ and Fe+++ + IIF = FeF++ + M+, the fornler having a heat of activation of 22.8f 2.5Iccal mole-I and an entropy of activation of 35rtB cal deg-1 moly-I, the latter having-a heat of activation of 8.7f0.7 kcal mole-' ancl an entropy of activation of -24.5&3 cal deg-I mole-'.Reactions involving association of cations and ailions may be considered displacenlent reactions in which the ligand displaced fro111 the cation is a solvent molecule, e.g.Kinetic aspects of such reactions will reflect the nature of the path by which reaction occurs. The transition state associated with the prevailing path may involve loss of solvent molecules froin the inner solvation spheres of the interacting ions (1) as well as reorgailization of more distant solvent. I t is also possible that protolytic changes LI the co-ordinated solvent may be iilvolved in some of the alternative mechanisms by which the net reactions inay occur (2, 3, 4).Although these so-called association reactions are ainong the simplest of those occurri~lg in solution, experil~~ental data relating to their kinetics are restricted. Eigen (5) is contributing valuable data about very fast reactions through his technique of relaxation spectrometry. The slow associations of chromic and thiocyanate have been studied by I'ost~nus and Icing (2), of chromic and osalate by I-Iamm and Davis (3). Below, Connick, and Coppel have recently published work on the ferric-thiocyanate associatioli (4). Smith found that ferric and iluoride associates a t a rate ineasurable with stop watch timing (6). This papel-deals with an extension of Smith's work to a wider range of acidities (and of necessity to a higher ionic strength) and to a range of temperatures. A spectrophotoinetric rather than the redox method used in the preliminary work has been used to follow the reaction, but the coilclitioils studied have beell restricted to those yielding rates mensurable ith stop watch timi~lg.The course of the reaction was followed spectropl~otometrically a t 260 1 1 1~ using Becknla~l quartz cells of 1 cnl path length as reaction vessels. At this wavelength there is a substantial increase in trans~nission acco~llpanyi~lg the association reaction, ranging from about 25 to 300% under the range of conditions studied. The segment of a Beckman DU spectrophotometer nornlally housing the cell holder was replaced by an extended segment which housed a specially constructed holder for two quartz cells. This holder was ~nachiiled fro111 a brass block so that i t had chanilels to carry therinostating water and dernisting tubes which directed thermostatecl dry gas against the windo\vs of the cells. lMa?zz~script receiucd hro-delttber 10, 1959. ...

Stopped-flow studies of the kinetics of the a nation reaction yielding iron(III) monosulfate indicate a significant dependence of rate constant on acidity and also a dependence on iron concentrations. This is consistent with association constants for outer ion pair formation between the reactants which have about three times the Fuoss values.

The quenching of the resonance radiation of potassiu~n by hydrogcn and deuterium has been studied over the temperature range 71°C. to 83°C. The quenching cross sections a t 76°C. were found to be 1.56X10-16 cm.? and 1.10 X10-l6 cm.* respectively.