Catalytic oxidation of triphenylphosphine with nitrogen(I) oxide in the presence of tetrakis(tert-butyl)phthalocyanine complexes

Full text of DOI:10.1023/A:1012316209356

Russian Journal of General Chemistry, Vol. 71, No. 4, 2001, pp. 648 649. Translated from Zhurnal Obshchei Khimii, Vol. 71, No. 4, 2001,
pp. 693 694.
Original Russian Text Copyright
2001 by Leont’ev, Tomilova, Fomicheva, Proskurina, Zefirov.
LETTERS
TO THE EDITOR
Catalytic Oxidation of Triphenylphosphine
with Nitrogen(I) Oxide in the Presence
of Tetrakis(tert-butyl)phthalocyanine Complexes
A. V. Leont’ev, L. G. Tomilova, A. O. Fomicheva, M. V. Proskurina, and N. S. Zefirov
Lomonosov Moscow State University, Moscow, Russia
Received May 31, 2000
It is known that the molecule of nitrogen(I) oxide
is thermodynamically unstable with respect to its
constituent elements ( G0f 24.9 kcal/mol,
19.6 kcal/mol). At the same time, the key reaction for
the thermal decomposition of N2O: N2O(gas)
N2(gas) + O(gas) (3P) ( H0 (39.7 kcal/mol), is highly
with oxygen in benzene solution in the presence of
excess Ph3P. The mechanism of this process for N2O
H0f is unknown. Finally, Groves and Roman [7] reported
that in a nitrogen(I) oxide atmosphere Ru(II)TMP
(THF)2 rapidly converts to trans-Ru(VI)TMP(O)2
(TMP is tetramesitylporphyrin) capable of oxidating
endothermic and has a high activation energy. As a dimethyl sulfide to sulfoxide and styrene to oxirane.
result, nitrogen(I) oxide demonstrates a significant
kinetic inertness to decomposition up to 500 C [1].
We chose as catalysts a series of 2,9,16,23-tetrakis-
(tert-butyl)phthalocyanine (I) complexes, including
those with aluminum {I[Al(III)Cl]}, cobalt {I[Co(II)]},
copper {I[Cu(II)]}, magnesium I[Mg(II)], and AlCl
applied on a basic alumina {I[(AlCl/Al2O3)]. Tri-
phenylphosphine was used as a model substrate.
Nevertheless, nitrogen(I) oxide attracts considerab-
le interest as an ecologically pure and a potentially
strong oxidative agent. Therefore, it seemed promis-
ing to make use of the ability of metal complexes to
catalyze oxygen transfer from a donor, i.e., oxidant
AO, to an acceptor, i.e., substrate S.
Metal phthalocyanines I exhibit a considerable
catalytic activity in various chemical processes, includ-
ing oxidation [8]. Molecular oxygen, alkyl and acyl
peroxides, amine N-oxides, hypochlorites, and iodo-
soarenes are most frequently used as oxo donors in
the latter reactions.
AO
A
S
M
M=O
M.
SO
From thermodynamic calculations it follows that
the oxidation of PPh3 with nitrogen(I) oxide is highly
exothermic [2].
All experiments were carried out by the following
scheme: A solution of 0.02 mmol of phthalocyanine I
and 2 mmol of a substrate in 10 ml of benzene was
placed in a 80-ml autoclave filled with nitrogen(I)
oxide. The bottom was cooled to condense about 5 ml
of N2O, after which the autoclave was hermetically
closed and heated at 85 C for 6 h. The postreaction
mixture, if necessary, was separated chromatographi-
cally (neutral Al2O3, activity grade II).
N2O(gas) + PPh3(s.)
N2(gas) + OPPh3(s.)
H0 93.6 kcal/mol.
However, only three works are available in the
literature, where this reaction was performed under
mild conditions: with low-valent nickel complexes
[3], [H3Co(PPh3)3] [4], and pentacyanooxomolybdate
[PPh4][Mo(CN)5(O)] [5] as catalysts. According to
our unpublished data, the reaction of N2O with tri-
phenylphosphine in the presence of 10 mol% of
[RhCl(PPh3)3], too, gives Ph3PO. Atlay et al. [6]
found that the peroxo complex [RhCl(PPh3)3(O2)] is
responsible for the formation of triphenylphosphine
oxide, when the starting rhodium compound reacts
With I[Al(III)Cl] and I[Cu(II)], the contents of tri-
phenylphosphine were 8 and 15%, while those of tri-
phenylphosphine oxide, 81 and 80%, respectively.
With the other catalysts and with no catalysts, the
contents of PPh3 and OPPh3 were near 40 and 50%,
respectively. At 130 C, the only oxidation product
was triphenylphosphine oxide (94% yield), even in
the absence of phthalocyanine complexes.
1070-3632/01/7104-0648$25.00 2001 MAIK Nauka/Interperiodica

CATALYTIC OXIDATION OF TRIPHENYLPHOSPHINE
Similar oxidative properties was reported by
649
REFERENCES
Saegura et al. [9], who under the similar conditions
prepared cyclohexyl isocyanate from the correspond-
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both as a reagent and as a solvent. Since with styrene
instead of PPh3 we found no oxygenated products, a
conclusion was drawn that the basicity and (or) nucleo-
philicity of PPh3 plays a noticeable role in the stage
of oxo transfer from metal complex to substrate.
Analogous dependence was, for example, was noted
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reduction of Mo(O)2(S2CNEt2) in the series of tertiary
phosphines EtnPHn 3P, where in going from n = 0 to
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ACKNOWLEDGMENTS
10. Poh, S., Hernandez, R., Inagaki, M., and Jessop, P.G.,
The work was financially supported by the Russian
Foundation for Basic Research (project no. 99-03-33-
055a).
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RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 71 No. 4 2001