Argon Line Techniques for the Electrochemical Generation and Manipulation of Air-Sensitive Compounds An Electrochemical Zwickel Flask Peter A. Lay Department of Inorganic Chemistry, University of Sydney, NSW, 2006. Australia The combination of argon line techniques with a Zwickel flask1-' has facilitated the chemical generation and rharacterization of a large numher ofair-sensitivecomplexes. More recently, a modified (elecrrochemical) Zwirkel flask (see iigure) has heen used for studying a variety of Ru\111or OsrII) complexes.' 'It enahlesselective redurtionvoxidations 11, be performed on an argon line, without the need fur a chemical reducrantloxidant, which ran interfere with the measureinterest.' The first detailed descrintion of the elecment 01' ~~~~-~~ trochemical~wickelflask is given here. The cell desien enables either a Pt-mesh electrode (fitted into the top), o r a Hg pool (electrical contact made via the I't wire at rhe hottom) to he uhed as a workine electrode. The cell contains two ~t wires above the levelif the Hg pool, which act as workine and auxiliary electrodes for conventional elecrrochemisiry. Thir enablks the in situ monitoring of el~ctrulyzedsolution, and rhe determination of the concentration-of the electroactive species in solution (from the diffusion current). The latter feature is important, since corrections for variations in the concentration of the electroactive species (due to solvent evaporation or diffusion through the frits) can be made. If a Hg pool working electrode is used for the bulk electrolyis, then either a HMDE or a elassv .. . carbon workine electrode mav be inserted throueh the top, for in situ electrochemical monitoring. The auxilinry electrode used in the bulk electrolvsis is d~~uhlr-tritted in order to minimize the extent of mixing of the two compartments of the electrolysis cell. As an alternative, the reference and auxiliary cells i r e inserted directly into the working compartment of the cell, via unfritted sidearms. This is only recommended if they are separated from the working compartment with a double Vycor frit arrangement. The minimal amount of diffusion of electroactive soecies throueh the Vycor is particularly useful for situation; where i t ishesirable t o maintain an accurate concentration of eledroactive species. Durine the deeassine and electrolvsis stages, the four-wav tap (B);s arranged so that the ~r hubcles through thk bottom of the solution via inlets, H or I. For solution transfer, B is reversed so that the solution is forced into a spectrophotometer cell or a second reaction vessel by a positive Ar pressure. During in situ electrochemical experiments, the three-way tap on the stem (capillary tubing) of the cell is set so that Ar flows across the surface of the solution. thus ensuring that the electrochemical experiments are diffusion controlled. The three-wav tar, at the bottom of the cell enables the Ar to flow from-the-bottom of the flask when a P t working electrode is used, or over the top of a Hg pool working electrode (and prevents Hg from flowing up the stem). Two or more of these cells may he connected in tandem for mixing together two different electrolyzed solutions. ~
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A
Schematic diagram ot an elecbochernicalZwickel flask with ceil filler anschment; (a) side view: (b) front view of the ceil compmment. The labelled components are as follows: A, cell fillw attachment;B,4-way stopcock:C. 3way stopcock: D, platinum wire for connection to a Hg pool electrode; E, fine ~orosiiv . frit:. F.. R wires Workina and auxiliarv electrodes for in sltu electrP chemistry):G, reference and auxiliary electrode companments: H, gas iniet for debassing, and outlet for solution transferral (PI electrode);I, gas iniet for degassing and outlet for solution transferral (Hg electrode):J, gas inlet (in sit" electrochmical expsriments);K, gas outlet far degassing and inlet for solution transferral;L, socket joint connection to Ar line: M, gas outlet and joint for the transferraiof solutions. ~
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This increases the versatility of the electrochemical Zwickel flasks for use in Ar line techniques. Acknowledgment The majority of this work was performed in the Department of Chemistry a t Stanford University. P. A. L, gratefully acknowledges support from a CSIRO Postdoctoral Fellowship and from a National Science Foundation Grant (No. CHE79-08633) to Henry Taube, during this period. The expert technical assistance of Jan Van Gastel is also gratefully acknowledged.
' Zwickel, A. M. PhD Thesis, University of Chicago, 1959.
Kuehn. C.: Taube, H. J. Am. Chem. Soo. 1976. 98.689-702. , iorg 3Lawrence. G. A,; Lay, P. A,: Sargeson, A. M:; ~ i u b eH. Svnth. 1986. 24. 257-263. .'Lay. P. A,; Iriagnwon. R. H.; Taube, H.. horg. Chem.. In press. Wishan, J. F.; Taube, H.: Breslauer, K. J.; Isied. S. S. Inorg. Chem. 1984,23,2997-3001.
Volume 65
Number 11 November 1968
1017
