Mendeleev Commun., 2002, 12(1), 1–2
Reactions of the pentaphospholide anion with half-sandwich complexes of iron:
a new route to pentaphosphaferrocenes
a
a
b
c
Vasily A. Miluykov,* Oleg G. Sinyashin, Otto Scherer and Evamarie Hey-Hawkins
a
A. E. Arbuzov Institute of Organic and Physical Chemistry, Kazan Scientific Centre of the Russian Academy of Sciences,
20088 Kazan, Russian Federation. Fax: +7 8432 76 7424; e-mail: miluykov@iopc.knc.ru, oleg@iopc.knc.ru
Universität Kaiserslautern, Fachbereich Chemie, D-67663 Kaiserslautern, Germany.
4
b
Fax: +49 631 205 2432; e-mail: oscherer@rhrk.uni-kl.de
c
Universität Leipzig, Institut für Anorganische Chemie, D-04103 Leipzig, Germany.
Fax: +49 0341 973 9319; e-mail: hey@rz.uni-leipzig.de
DOI: 10.1070/MC2002v012n01ABEH001517
Pentaphosphaferrocenes were prepared in good yields by the reaction of the pentaphospholide anion P– with half-sandwich com-
5
plexes of iron containing carbonyl groups or tertiary phosphine ligands.
–
The pentaphospholide anion P , which is an isolobal analogue
5
1
of the cyclopentadienyl anion, is of interest as a convenient
2
,3
reagent in organometallic and coordination chemistry. How-
1
10 °C
ever, only a few organometallic compounds with P fragments
+
NaP5
5
Fe
– 2CO, – NaBr
Fe
P
4
,5
were synthesised from NaP 1. In particular, pentamethyl-
5
1
OC
Br
pentaphosphaferrocene 2 was prepared in 12% yield by the
P
P
CO
reaction of 1 with iron(II) chloride and lithium pentamethyl-
P
P
cyclopentadienide.4
4
5
(~5%)
Recently, we reported a new method for preparing 1 by the
1
reaction of sodium metal with white phosphorus under the con-
singlet at 167 ppm, and the H NMR spectrum exhibits a singlet
at 1.06 ppm due to methyl groups and a broad singlet at 3.71 ppm
due to the protons of the cyclopentadienyl ring. Relative to
6
ditions of phase-transfer catalysis. This simple method makes
it possible to study the chemical behaviour of 1 towards various
organometallic compounds. It was also of interest to develop
a general high-yield route to pentaphosphaferrocenes and to
determine the factors affecting the product yields. We based our
approach on the well-known reaction of half-sandwich iron com-
1
tetra-tert-butylferrocene, the H NMR signals are shifted by an
average of 0.26 ppm.1
1,12
The mass spectrum showed a peak of
the molecular ion (m/z 388).
The main product of this reaction was 1,1',3,3'-tetra-tert-
butylferrocene 6, which was identified by H NMR spectro-
scopy and by a comparison of the physical properties with
7
1
plexes with sodium cyclopentadienide.
The reaction of 1 with pentamethylcyclopentadienyl(dicar-
†
9
bonyl)iron bromide 3 in diglyme at 110 °C for 2 h gave
published data. Clearly, at a reaction temperature of 110 °C,
pentamethylpentaphosphaferrocene 2 in ~70% yield.
pentaphosphaferrocene 5 decomposes to give compound 6.
We postulated that a decrease in the reaction temperature
increases the yield of 5. It is known that the replacement of CO
ligands in organometallic compounds with better leaving groups,
such as tertiary phosphines, facilitates the process of ligand
exchange. Therefore, we treated 1 with 1,3-di-tert-butylcyclo-
Me
Fe
Me
Me
Me
Me
Me
Me
OC
Me
110 °C
Me
Me
+
NaP5
– 2CO, – NaBr
Fe
P
‡
pentadienyl[bis(trimethylphosphine)]iron bromide 7. This reac-
tion was conducted at 70 °C to form compound 5 in high yield
1
P
P
P
Br
CO
P
(about 80%).
3
2
(~70%)
The structure of 2 was determined by 1H and 31P NMR
7
0–80 °C
spectroscopy and by a comparison with the published data.8
,9
+
NaP5
Fe
– 2PMe3, – NaBr
Fe
P
The reaction of 1 with 1,3-di-tert-butylcyclopentadienyl-
1
Br
PMe3
†
(
dicarbonyl)iron bromide 4 under similar conditions gave com-
P
P
PMe3
pound 5 in a yield of at most 5%.
P
P
The structure of 5 was determined by 1H and 31P NMR
spectroscopy and mass spectrometry. This compound also was
prepared by the interaction of Cr(CO) PCl with Cp''Fe(CO) K
7
5
Thus, we developed a new route to pentaphosphaferrocenes
based on the reaction of the pentaphospholide anion with half-
sandwich iron compounds containing carbonyl or tertiary phos-
phine ligands.
5
3
2
1
0
31
in a yield of about 10%. The P NMR spectrum exhibits a
†
A solution of pentamethylcyclopentadienyl(dicarbonyl)iron bromide
(
260 mg, 0.8 mmol) in diglyme (20 ml) was added to a solution of NaP
5
–3
in diglyme (40 ml, 0.02 mol dm ) at room temperature. The reaction
mixture was stirred for 2 h at 110 °C. After cooling, the solvent was
evaporated and the residue was purified by chromatography with light
V. Miluykov thanks the Deutsche Akademische Austausch-
dienst (A/00/06361) and the Sächsisches Ministerium für Wissen-
schaft und Kunst (SMWK, Az. 4-7531.50-04-0361-00) for finan-
cial support.
1
petroleum to give 2 (190 mg, 70%) as green crystals. H NMR, d: 1.08.
3
1
P NMR, d: 153.
A solution of 1,3-di-tert-butylcyclopentadienyl(dicarbonyl)iron bro-
mide (295 mg, 0.8 mmol) in diglyme (20 ml) was added to a solution of
–3
‡
NaP in diglyme (40 ml, 0.02 mol dm ) at room temperature. The reac-
A solution of 1,3-di-tert-butylcyclopentadienyl[bis(trimethylphosphine)]-
5
tion mixture was stirred for 2 h at 110 °C. After cooling, the solvent was
evaporated and the residue was purified by chromatography with light
petroleum to give 5 (15 mg, 5%) as green crystals and 1,1',3,3'-tetra-tert-
butylferrocene 6 (215 mg, 65%) as a yellowish orange powder (mp 193 °C;
iron bromide 7 (295 mg, 0.8 mmol) in diglyme (20 ml) was added to a
–
3
solution of NaP in diglyme (40 ml, 0.02 mol dm ) at room tempera-
5
ture. The reaction mixture was stirred for 2 h at 70 °C. After cooling, the
solvent was evaporated and the residue was purified by chromatography
with light petroleum to afford 5 (250 mg, 80%) as green crystals.
9
lit., 196 °C).
–
1 –
Kossel
