Russian Chemical Bulletin, International Edition, Vol. 59, No. 2, pp. 466—468, February, 2010
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Spinꢀadduct of the P4 radical anion
during the electrochemical reduction of white phosphorus
M. K. Kadirov, Yu. G. Budnikova, K. V. Kholin, M. I. Valitov, S. A. Krasnov,
T. V. Gryaznova, and O. G. Sinyashin
A. E. Arbuzov Institute of Organic and Physical Chemistry, Kazan Research Center of the Russian Academy of Sciences,
8 ul. Akad. Arbuzova, 420088 Kazan, Russian Federation.
Fax: +7 (843 2) 73 2253. Eꢀmail: kadirov2004@mail.ru
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The radical anion Р4 was detected and identified by the ESR method as a spinꢀadduct
with nitrone during the electrochemical reduction of white phosphorus in the presence of a spin
trap, viz., αꢀphenylꢀNꢀtertꢀbutylnitrone, in a special electrolysis cell with a helical platinum
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working electrode in the potentiostatic mode. The character of the behavior of Р4 and the
spin trap during electrochemical reduction was monitored by cyclic voltammetry directly in the
electrolysis cell, and the spinꢀadduct formed was detected by ESR.
Key words: white phosphorus, electrochemical reduction, ESR, radical anion, spinꢀadduct.
A solution of white phosphorus in benzene (~1.6•10–2 mol L–1
)
The problem of the selective cleavage of the Р—Р bonds
in a white phosphorus molecule is very important in the
chemistry of phosphorusꢀcontaining compounds.1,2 The
radical character of the cathodic reduction of white phosꢀ
phorus has been assumed earlier.3 However, such prodꢀ
ucts of activation of Р4 have not yet been detected. The
purpose of the present study was to observe the primary
products of cathodic reduction of a Р4 molecule. To create
a necessary concentration of paramagnetic species in the
resonator of an ESR spectrometer, we used a special cell
with the helical working electrode.4 The method of spin
traps5,6 based on the reaction of electrochemically inacꢀ
tive αꢀphenylꢀNꢀtertꢀbutylnitrone (1), resulting in the staꢀ
ble nitroxyl radical (Scheme 1), was used to detect radical
anion species. The stable nitroxyl radical can be identified
by ESR spectroscopy.
was purged with helium through a capillary immersed to the
bottom of the cell. The material of the working and auxiliary
electrodes was platinum, and Ag/AgNO3 (0.01 mol L–1) was
a reference electrode.
Measurements were carried out using the programꢀapparaꢀ
tus complex7 mounted on the basis of an analogꢀelectrochemical
setup with a PIꢀ50ꢀ1 potentiostat, a Prꢀ8 programmer, an
Xꢀrange ESR spectrometer (Radiopan), and Е14ꢀ440 analogꢀtoꢀ
digital and digitalꢀtoꢀanalog converter (LꢀCard), and a computer.
The WinSim 0.96 program (NIEHS) was used for ESR specꢀ
tra processing.
The images of the films were obtained on a HITACHI
TMꢀ1000 scanning electron microscope.
Results and Discussion
The curves obtained by cyclic voltammetry (CV) at the
Pt electrode for a solution of compound 1 in MeCN
(0.01 mol L–1) and a solution of white phosphorus in a benꢀ
zene—MeCN (1 : 1) mixture vs 0.1 M solution of Et4NBF4
are shown in Fig. 1. To exclude the formation of products
of phosphorus oxidation and hydrolysis, all procedures
were carried out in a thoroughly dehydrated solvent. It
should be mentioned that the compounds containing the
mobile hydrogen atom give no pronounced reduction peaks
on Pt down to potentials of the supporting electrolyte disꢀ
charge. The CV curves of a solution of white phosphorus
at a potential of –1.5 V contain the irreversible peak corꢀ
responding to its reduction. Thus, the reduction peak close
to the oneꢀelectron peak (estimated by the comparison
with benzophenone used as standard) relates to the elecꢀ
tron transfer to a white phosphorus molecule to form radꢀ
Scheme 1
Experimental
Benzene was dehydrated by distillation over sodium. αꢀPheꢀ
nylꢀNꢀtertꢀbutylnitrone (1) and Еt4NBF4 (Fluka) were used withꢀ
out additional purification. Acetonitrile was purified by triple
distillation over KMnO4 and P2O5, and Еt4NBF4 was dried in
vacuo for 2 days at 100 °С. Dimethylformamide was distilled,
kept for 12 h over calcined K2CO3, then distilled repeatedly over
CaH2, and stored over molecular sieves 3A calcined at 300 °С.
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ical anions Р4
.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 456—458, February, 2010.
1066ꢀ5285/10/5902ꢀ0466 © 2010 Springer Science+Business Media, Inc.