Triphenylphosphine Phenylimide 의 전기화학적인 환원 Electrochemical

DAEHAN HWAHAK HWOEJEE (Journal of the Korean Chemical Society) Vol. 18, No. 5, 1974 Printed in Republic of Korea Triphenylphosphine Phenylimide 의 전기화학적인 환원 朴鍾民* , Wilson M. Gulick, Jr. 미국 후로리다주립대학교 화학과 (1974. 7. 13 접수 ) Electrochemical Reduction of Triphenylphosphine Phenylimide Chong Min *Pak and Wilson M. Gulick, Jr. Department of Chemistry^ Floridia State University^ Tallahassee, Florida 32306, U, S. A. 요 약 . Triphenylphosphine phenylimid合의 비수용액에서의 전기화학적인 환원반응을 polarography, cyclic voltammetry, controlled-potential coulometry 및 electron spin resonance 법 을 써 서 고 찰하였다 . 이 유기 인화합물은 cme-electon transfer 에 따라서 anion radical 형성되 나 순간일 뿐이 고 protonation 과 재차 one-electon reduction 결과 인과 질소사이의 이중결합이 끊어진다 . 그 결과 아 닐린이 주요 반응생성물로서 발견되었다 . 또 한편 동반하는 화학반응결과 생긴 주산물의 하나인 triphenylposphine oxide 의 환원결과 인과 페닐사이의 단일결합이 끊어지는 것도 관찰할 수 있었다 . Abstract. The electrochemical reduction of triphenylphosphine penylimide in nonaqueous media has been examined by polarography, cyclic voltammetry, controlled-potential coulometry and electron spin resonance spectroscopy. The reduction of tiiphe교 ylphosphine phenylimide proceeds by a one- electron transfer to form anion radical which undergoes both protonation and a second one-electron reduction followed by cleavage of the phosphorus-nitrogen double bond. Aniline is a major product. The cleavage of a phosphours-phenyl bond was also observed after reduction of triphenylphosphine oxide which is one of the major products of the chemical reaction which follow the primary process. synthesis and ligands in coordination chemistry. 1. Introduction The range of application of phosphorus com Phosphorus compounds have become increas pounds in modern technology is extremely broad ingly important as intermediates in organic and varied. Since phosphorus is sometimes *Present Address: Department of Chemistry, Soong found in minute quantities often in the form of Jun University, Taejon 300, Korea. Author to whom labile or nonvolatile compounds, the detection, correspondence should be addressed. Presented at the assay, and identification of its compounds re 33rd National Korean Chemical Society Meeting, Seoul, Korea (Apr, 26~27, 1964). quire considerable skill, forcing the chemist to —341 — 342 朴鍾民 , Wilson M. Gulik, Jr. push his analytical tools to their limits of per 2. Experimental formance. Free radical intermediates have frequently 2.1. Chemicals been postulated for reactions involving or음 ano- Acetonitrile and tetraethylammonium perchlo phosphorus compounds. However, compara rate (TEAP) supporting electrolytes were pre tively few phosphorus-containing radicals have pared by standard literature methods.12 PPPI been prepared in solution under conditions which was prepared by reaction of phenyl azide permitted their study in detail by esr. As early (in hydrocarbon solution obtained from Pfaltz as 1953 Heine and coworkers1 reported that the and Bauer, Inc., Flushing, N. Y.) and tri reaction of phosphine oxides with alkali metals phenylphosphine in ether solution. This re led to colored, paramagnetic solution; however, action is known as Staudinger reaction.13 a review2 of the literature of phosphorus esr in After three recrystallizations from ?z-hexane, 1966 counted only 16 publications. Since that the resulting crystals melted at 131 〜131.5° time, a number of additional studies have ap which is in agreement with the melting point peared. Cowley3 has reported several radicals reported by Wiegraebe and Bock.14 Other che containing phosphorus, Lucken4 has observed micals were available from standard commercial phosphorus redicals in irradiated solids, and sources. several radicals have been detected as an adjunct 2.2. Electrochemistry to the electrochemical studies by Bard and co- Polarographic measurements were made with workers5"'7, Recently Matcalfe and Waters8 have the solid state polarograph, employing oper reported the formation of radicals from phospho ational amplifier circuiting with a three electrode rus and phosphoric acid esters in a fast flow configuration, described previously.15 For rapid system and Dimroth9 has prepared a novel het sweep cyclic voltammetry, a Tektronix type erocyclic phorphorus radical. The first indication 201—W oscilloscope equipped with type D of hindered intramolecular motion in a phospho plug-in aplifiers was employed. Pictures were rus radical has been detected recently by recorded with an oscilloscope camera and a Rieker10 via line-width variations. type 2620 Polaroid attachment. At slow-sweep From the industrial point of view, triphe- rates. Moseley model 2D—2M X—Y recorder nylphosphine phenylimide (PPPI) was chosen as was used. A Hewelett—Packard model 3300 A phosphorus—nitrogen compound; considerable function generator with a model 3302 A trigger interest has arisen recently in polymers which served as the signal generator. Controlled- have the general formula (N™ P (OR) 2) 11 Some potential electrolysis were carried out using a of the desirable properties of these materials Princeton Applied Research (PAR) model 173 have been attributed specifically to the presence potentiostat equipped with PAR model 177 of the phosphorus—double bond(一 current readout module. Coulometry was carried N=P—) which is, it is pointed out,11 isoelec- out using a nitrogen— coulometer as tronic with the —Si—O— skeletal unit of the described by Lingane.16 Additional cyclic vol silicon series, and the two units behave simi tammetry experiments were carried out usin흠 the larly in many instances. We have now examined signal generator and oscilloscope described above the mechanism of the reduction of PPPI, which in conjunction with the PAR 173. In these is subject of this report. experiments, a PAR model 176 current to Journal of the Korean Chemical Society Triphenylphosphine Penylimide 의 전기화학적인 환원 343 voltage converter was used and positive feedback voltammetric experiment, fr毕hly prepared so IR compensation was employed. lutions were used, identical with those employed The electrolysis cell was a three compartment in polarography. The same cell as used for vessel for polarography and cyclic voltammetry. polarography was employed except for the use Anaqueous saturated calomel electrode (see) was of a mercury-coated platinum wire or platinum used as the reference electrode which was iso disk working electrode. After each solution was lated from the working electrode compartment purged with nitrogen the potential range was by means of a fritted disk, the auxiliary elec swept back and forth by means of the triangle trode was a platinum wire and a dropping mer wave generator connected to the summing point cury electrode was the working electrode. For of the control amplifier in the polarograph. cyclic voltammetry, a mercury-coated platinum17 The frequency range of 0. 01 〜10 cps was usually or a platinum-disk electrode replaced the drop investigated, with the voltammograms being ping mercury electrode. The mercury-coated recorded either on X—Y recorder (>1 cps) or platinum wire electrode was made by sealing by photography from the oscilloscope for the platinum wire into a soft-glass tube, as described higher sweep rates. The precision of potentials previously.18 The auxiliary electrode was a measured from chart recording is estimated at platinum wire and the reference electrode was the ±5 mV level. Larger uncertainties, esti an aqueous see. The working electrode in the mated at 5 % were encountered in oscilloscopic controlled-potential electrolysis was a mercury measurements. pool of approximately 7 cm2 area which was Controlled-potential Electrolysis. When stirred continously during the controlled-potential coulometric measurments were made, cathodi- electrolysis. The reference (see) and auxiliary cally reactive impurities were destroyed by (mercury pool) electrodes were separated from pre-electrolysis; a measured volume (usually 25 the working electrode compartment by means m/) of background solution (0.1 M TEAP一 of, respectively, a glass fritted disk and a MeCN) was introduced into the working bridge containing solvent and supporting elec electrode compartment of a three compartment trolyte between two fritted disks. cell. This solution was electrolyzed at the po- Polarography and Cyclic Voltammetry. In tental which was employed for the controlled- a typical polarographic experiment, a freshly potential electrolysis of the compound until a prepared solution of TEAP (0. 1 M) and start steady-state current was reached. After pre ing material (ca. 1 〜4 mA】) in acetonitrile electrolysis, a weighed amount of the sample (25 mZ) was transferred to the electrolysis sufficient to make the solution ca. 1 〜4 mAf was cell and the three electrodes were intro introduced into the working electrod compart duced. The solution was then purged for ment. After dissolution, electrolysis was recom 30 minutes with prepurified nitrogen which menced at the same potential, stirring rate was passed first over hot copper wool and and flow rate of nitrogen. The temperature was then through purified acetonitrile. The pre not controlled. However, cell heating was not saturation step minimized loss of solvent from observed to any great extent. Completion of the cell. An atmosphere of nitrogen was then electrolysis was confirmed by obtaining a steady maintained over the solution as the vol- state current. tammograms were recorded. In a typical cyclic 2.3. Product Analysis Vol. 18, No. 5, 1974 344 朴鍾比 , Wilron M. Gulik, Jr. Analysis of electrolysis products were carried solvent was evaporated from each

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