The reaction of cyclopropenylphosphonium bromides with sodium polyphosphides as an advanced method of synthesis of sodium 1,2- diphosphacyclopentadienides: Scope and limitations

Article abstract of DOI:10.1080/10426507.2010.508061

A new ring expansion reaction based on the interaction between 1,2,3- triarylcyclopropenylphosphonium bromide (1) and sodium polyphosphides gives sodium 3,4,5-triaryl-1,2-diphosphacyclopentadienides (2) containing various substituents in the para-position of the aryl groups with a high yield. However, this reaction of trialkylcyclopropenylphosphonium bromide (i.e., tri(tert-butyl)- or triisopropylcyclopropenylphosphonium bromide) does not result to the formation of sodium 1,2-diphosphacyclopentadienidesSupplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/10426507.2010.508061

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The Reaction of
Cyclopropenylphosphonium Bromides
with Sodium Polyphosphides as an
Advanced Method of Synthesis of Sodium
1,2-Diphosphacyclopentadienides: Scope
and Limitations
Il’ya Bezkishko a , Vasili Miluykov a , Oleg Sinyashin a & Evamarie
Hey-Hawkins b
a A. E. Arbuzov Institute of Organic and Physical Chemistry of the
Russian Academy of Sciences, Kazan, Russia
b Institute of Inorganic Chemistry, Universität Leipzig, Leipzig,
Germany
Version of record first published: 25 Apr 2011.
To cite this article: Il’ya Bezkishko , Vasili Miluykov , Oleg Sinyashin & Evamarie Hey-Hawkins (2011):
The Reaction of Cyclopropenylphosphonium Bromides with Sodium Polyphosphides as an Advanced
Method of Synthesis of Sodium 1,2-Diphosphacyclopentadienides: Scope and Limitations, Phosphorus,
Sulfur, and Silicon and the Related Elements, 186:4, 657-659
To link to this article: http://dx.doi.org/10.1080/10426507.2010.508061
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Phosphorus, Sulfur, and Silicon, 186:657–659, 2011
Copyright ꢀC Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426507.2010.508061
THE REACTION OF CYCLOPROPENYLPHOSPHONIUM
BROMIDES WITH SODIUM POLYPHOSPHIDES AS AN
ADVANCED METHOD OF SYNTHESIS OF SODIUM
1,2-DIPHOSPHACYCLOPENTADIENIDES: SCOPE
AND LIMITATIONS
Il’ya Bezkishko,1 Vasili Miluykov,1 Oleg Sinyashin,1
and Evamarie Hey-Hawkins2
1A. E. Arbuzov Institute of Organic and Physical Chemistry of the Russian
Academy of Sciences, Kazan, Russia
2Institute of Inorganic Chemistry, Universita¨t Leipzig, Leipzig, Germany
Abstract A new ring expansion reaction based on the interaction between 1,2,3-
triarylcyclopropenylphosphonium bromide (1) and sodium polyphosphides gives sodium
3,4,5-triaryl-1,2-diphosphacyclopentadienides (2) containing various substituents in the
para-position of the aryl groups with a high yield. However, this reaction of trialkylcyclo-
propenylphosphonium bromide (i.e., tri(tert-butyl)- or triisopropylcyclopropenylphosphonium
bromide) does not result to the formation of sodium 1,2-diphosphacyclopentadienides.
Supplemental materials are available for this article. Go to the publisher’s online edition of
Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.
Keywords
Phosphonium bromide; sodium 1,2-diphosphacyclopentadienides; sodium
polyphosphides
There is significant interest in alkali metal phosphacyclopentadienides due to their high
synthetic potential. As an isolobal anologue of Cp−, they can form η1- or η5-coordinated
complexes. However, the presence of a lone pair of electrons at the phosphorus atoms per-
mits other more complicated coordination modes with transition metals. Thus, polymetallic
complexes and clusters can be obtained that are useful as catalysts in organic reactions such
as Suzuki,1 propene polymerization,2 diethylacetylene trimerization,3 and asymmetric hy-
drogenation of amino acids.4 Moreover, alkali metal phosphacyclopentadienides can be
employed as starting materials for preparation of cage phosphanorbornadienes that ex-
hibit good activity as anticancer reagents5 or can be employed as ligands in catalysts for
asymmetric organic reactions.6–8
Among numerous alkali metal phosphacyclopentadienides the 1,2-diphosphacyclo-
pentadienide anion is especially attractive due to being isolobal to Cp−, showing pre-
dominantly η5-coordination with transition metals, and a pyrazolate anion, exhibiting
Received 21 June 2010; accepted 9 July 2010.
Address correspondence to Il’ya Bezkishko, A. E. Arbuzov Institute of Organic and Physical Chemistry of
the Russian Academy of Sciences, Arbuzov str. 8, Kazan 420088, Russia. E-mail: bezkishko@iopc.ru
657

658
I. BEZKISHKO ET AL.
predominantly bridging µ:η1,η1-coordination to form binuclear or polymeric metal com-
plexes. Recently we have demonstrated for the first time that the 3,4,5-triaryl-1,2-
diphosphacyclopentadienide anion forms bimetallic manganese complexes that exhibit
large anti-ferromagnetic exchange interaction due to metal-to-ligand charge transfer.9 Thus,
the 3,4,5-triaryl-1,2-diphosphacyclopentadienide anion may be considered as a novel type
of non-innocent ligand combining the ability of both the metal-to-ligand charge transfer
and the exchange interaction between the metals.
Two different methods are employed for preparation of alkali metal 1,2-diphos-
phacyclopentadienides. One is based on the cleavage of a P-C bond of 1-phosphetene by
lithium, followed by reaction with PCl3 and finally reduction of the formed 1,2-diphos-
phole by lithium.10 However, this method does not allow isolation of the pure lithium
1,2-diphosphacyclopentadienide. A more convenient synthesis of sodium 1,2-diphos-
phacyclopentadienide is based on reaction of triphenylcyclopropenyl nickel complexes
with sodium polyphosphides.11,12 However, this method demands the use of expensive
[Ni(cod)2] and does not allow the isolation of large amounts of sodium 3,4,5-triphenyl-
1,2-diphosphacyclopentadienide. Recently, we have found that sodium 3,4,5-triphenyl-
1,2-diphosphacyclopentadienide can be easily obtained by reaction of 1,2,3-triphenyl-
cyclopropenylphosphonium bromides with sodium polyphosphides in high yield.13
This method is scalable and allows preparation of sodium 3,4,5-triphenyl-1,2-
diphosphacyclopentadienide in significant amounts (up to 20 g) from common starting
materials. In continuation of this work we were interested in the possibility of using the same
method for the preparation of other derivatives of sodium 1,2-diphosphacyclopentadienide.
For this purpose we have synthesized a series of 1,2,3-triarylcyclopropenylphospho-
nium bromides (1), containing both acceptor or donor substituents in the para-position of
the aryl group, by reaction of the corresponding 1,2,3-triarylcyclopropenyl bromides with
PPh3. The structure of compounds 1a–f was confirmed by NMR spectroscopy. Thus, the
1
31P{ H}-NMR spectrum of 1a contains a singlet at +33 ppm typical for phosphonium
1
salts. The 13C{ H}-NMR spectrum consists of a doublet for the carbon atom C1 at +26
1
ppm, characteristic for sp3-hybridized carbon atoms, with a coupling constant JCP
=
72 Hz.
The phosphonium salts (1) were treated with a mixture of polyphosphides obtained
in situ from sodium and white phosphorus containing mainly NaP5 and Na3P7.14
Only the signals of sodium 3,4,5-triaryl-1,2-diphosphacyclopentadienides (2a–d) and
1
PPh3 were detected in the 31P{ H}-NMR spectrum of the reaction mixture after refluxing
for 3 h (Scheme 1). Compounds 2a–d can easily be isolated from the reaction mixture by
filtration. After washing with n-hexane, 2a–d were obtained in good purity and can be used
for following reactions without further purification.
However, no 1,2-diphosphacyclopentadienide anions were formed in the reaction
of sodium polyphosphides with 1,2,3-tri(tert-butyl)- or 1,2,3-tri-isopropylcyclopropenyl-
1
phosphonium bromides (1e,f); the 31P{ H}-NMR spectra of the reaction mixtures contain
only signals in the range of +50 to −100 ppm typical for sodium polyphosphides such as
Na3P21, Na3P19, and others.15
In summary, we have found that reactions of cyclopropenylphosphonium bromides
with sodium polyphosphides can be successfully used for the preparation of sodium 3,4,5-
triaryl-1,2-diphosphacyclopentadienides containing acceptor or donor substituents in the
para-position of an aryl group.

SODIUM 1,2-DIPHOSPHACYCLOPENTADIENIDES
659
R = aryl
P
P
[Na(diglyme)2]+
R
R
R
R
R
R
2a–d
PPh3
THF
NaxPy
Br–
R
Br–
diglyme
R
PPh3
R
1a–f
Na3P21, Na3P19 + other
R = But, Pri
R = p-F-C6H4 (a), p-Cl-C6H4 (b), p-Me-C6H4 (c), p-MeO-C6H4 (d), But (e), Pri (f)
Scheme 1
Supporting information for this article containing details of experiments is available
on the journal Website or from the authors.
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