Synthesis of the first stable Fischer-type carbene metal complex with a C-O-P structural motive of the carbene ligand

Article abstract of DOI:10.1016/S0022-328X(00)00454-X

Fischer-type (phenyl)carbene pentacarbonyltungsten complexes, which have an organo phosphorus moiety bonded to oxygen (5, 8) or to nitrogen (10a,b), are synthesized by reaction of the O-Li and N-Li precursor carbene complexes with either bis(diisopropylamino)chlorophosphane (5) and/or [bis(trimethylsilyl)methylene]chlorophosphane (8, 10a,b) via lithiumchloride elimination; whereas the bulky substituted complex 5 decomposed in solution under formation of bis(diisopropylamino)-chlorophosphaneoxide via an unknown reaction pathway, complex 8 was stable at ambient temperature; complexes 10a,b slowly rearranged in solution to the 2H-azaphosphirene complex 11; the complexes 8 and 10a,b were unambiguously confirmed by NMR spectroscopy.

Full text of DOI:10.1016/S0022-328X(00)00454-X

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 613 (2000) 56–59
Synthesis of the first stable Fischer-type carbene metal complex
with a CꢀOꢀP structural motive of the carbene ligand
Rainer Streubel *, Markus Hobbold, Siegfried Priemer
Institut fu¨r Anorganische und Analytische Chemie der Technischen Uni6ersita¨t Braunschweig, PO Box 3329, D-38023 Braunschweig, Germany
Received 27 April 2000
Dedicated to Professor Othmar Stelzer on the occasion of his 60th birthday.
Abstract
Fischer-type (phenyl)carbene pentacarbonyltungsten complexes, which have an organo phosphorus moiety bonded to oxygen
(5, 8) or to nitrogen (10a,b), are synthesized by reaction of the OꢀLi and NꢀLi precursor carbene complexes with either
bis(diisopropylamino)chlorophosphane (5) and/or [bis(trimethylsilyl)methylene]chlorophosphane (8, 10a,b) via lithiumchloride
elimination; whereas the bulky substituted complex 5 decomposed in solution under formation of bis(diisopropylamino)-
chlorophosphaneoxide via an unknown reaction pathway, complex 8 was stable at ambient temperature; complexes 10a,b slowly
rearranged in solution to the 2H-azaphosphirene complex 11; the complexes 8 and 10a,b were unambiguously confirmed by NMR
spectroscopy. © 2000 Elsevier Science B.V. All rights reserved.
Keywords: Aminocarbene complexes; 2H-Azaphosphirene complexes; Tungsten; Rearrangements
tures of stable Fischer-type amino(methyl)- and
amino(phenyl)carbene metal complexes having the bis(-
diisopropylamino)phosphanyl group bonded to nitro-
gen [9]. The observation that these complexes are
perfectly stable at ambient temperature was a stimulus
to attempt the synthesis of carbene complexes of the
type III by using the bulkyness of the bis(diisopropy-
lamino)phosphanyl group for kinetic stabilisation; our
hope was to exclude subsequent reactions such as
dimerization and/or coordination. Furthermore, we
carried out a preliminary study on the influence of the
coordination number of the phosphorus atom on the
stability of such heteroatom-substituted carbene metal
complexes (Scheme 1).
1. Introduction
Since the discovery of stable carbene complexes by
Fischer [1] alkoxycarbene metal complexes I have re-
ceived widespread interest as powerful synthons in or-
ganic and organometallic synthesis [2]. Although the
chemistry of carbene complexes that have a metal or a
metalloid (Ti [3], B [4], Si [5]) bonded to the carbene
oxygen atom II has been much less investigated, some
useful applications have been described [6]. In contrast,
no stable carbene metal complexes III that have an
organo phosphorus moiety bonded to oxygen have
been described, so far (Scheme 1). Reports showed that
intermediately formed derivatives such as 1 [7] and 2 [8]
undergo subsequent reactions like decomposition of 1
yielding
a
trans-bromocarbyne complex, carbon
2. Results and discussion
monoxide and triphenylphosphaneoxide [7] or, in the
case of 2, a dinuclear Z-1,2-diphosphite-alkene complex
via a dimerization-like process and carbon monoxide
[8]. Recently, we reported the first syntheses and struc-
Treatment of the acyl tungstate 3, obtained by the
reaction of tungsten hexacarbonyl with phenyllithium,
[10] with the bis(diisopropylamino)chlorophosphane
[11] 4 in diethyl ether at −30°C gave the O-phos-
phanyl-substituted derivative 5 only as a reactive inter-
mediate, which was detected by 31P-NMR spectroscopy
* Corresponding author. Tel.: +49-531-3917350; fax: +49-531-
3915387.
E-mail address: r.streubel@tu-bs.de (R. Streubel).
0022-328X/00/$ - see front matter © 2000 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(00)00454-X

R. Streubel et al. / Journal of Organometallic Chemistry 613 (2000) 56–59
57
Scheme 1. Fischer-type carbene complexes with various C, O, E linkages ([M]=metal complex fragment, R denotes ubiquitous organic
substituents, E=TiLn, BRn, SiRn).
(5a: l 152.9). This intermediate was unexpectedly un-
stable in solution at 0°C and decomposed to bis-
(diisopropylamino)phosphaneoxide [12] (6) (l 9.6,
1J(P, H)=569.4 Hz) via an unknown reaction pathway
(Scheme 2); the identity of phosphaneoxide 6 was estab-
lished by using an authentic sample. So far, the fate of
the complex fragment could not be determined (Scheme
2).
temperature (Scheme 3). A comparative study using the
tungstate 9 [9a] and the methylene(chloro)phosphane 7
showed that the stability of the first products formed,
complexes 10a,b, and the general reaction course de-
pended significantly on the sequence of reactants. If the
tungstate 9 was added to the methylene(chloro)-
phosphane 7 complexes 10a,b were formed as main
products (1:1 mixture) and small quantities of the 2H-
azaphosphirene complex 11 [14]; the latter was iden-
tified by adding an authentic sample (Scheme 4).
Noteworthy is that a solution of the complexes 10a,b
Treatment of the tungstate 3 with the [bis(trimethylsi-
lyl)methylene]chlorophosphane [13] (7) in diethyl ether
at −30°C gave complex 8, which was stable at ambient
Scheme 2. Attempted synthesis of complex 5.
Scheme 3. Synthesis of complex 8.
Scheme 4. Synthesis and rearrangement of complexes 10a,b.

58
R. Streubel et al. / Journal of Organometallic Chemistry 613 (2000) 56–59
showed a slow and clean conversion to the 2H-aza-
phosphirene complex 11, thus confirming our earlier
assumption [15] on the intermediacy of such complexes
in 2H-azaphosphirene complex formation. The compo-
sition of complex 8 was confirmed by elemental analy-
ses and mass spectrometry and the structural
formulation of the complexes 8 and 10a,b is based on
their characteristic NMR spectral data in solution. The
phosphorus nuclei of 8 and 10a,b display resonances at
l=348.1 (8), 309.1 and 332.9 (10a,b), which are in the
expected range of compounds with a low-coordinated
phosphorus moiety, [16] thus excluding in both cases
the h2-coordination mode of the PꢁC unit to tungsten
[17]. The conclusion that there is also no h1 P,W-coor-
dination in these cases derives from the absence of 183W
satellites in the 31P-NMR spectra of complexes 8 and
10a,b [17]. Proof for the structures of the complexes 8
and 10a,b is given through the carbene atom resonances
(8: l=320.6, 2J(P, C)=18.8 Hz; 10a,b: l=276.7,
2J(P, C)=1.6 Hz and l=277.2, 2J(P, C)=1.4 Hz)
[18], which are in the typical range of related Fischer-
type alkoxycarbene metal complexes. Also interesting is
that the carbonyl carbon atoms of complexes 10a,b
showed no phosphorus–carbon couplings, whereas
those of complex 8 did. Noteworthy is also that the
complexes 10a,b display an E,Z-isomerism at the CꢀN
bond, thus representing the first examples of E,Z-iso-
mers of N-phosphanyl aminocarbene complexes [9]; for
related N-alkyl aminocarbene complexes such a phe-
nomena has been reported earlier [18].
3.2. Attempted synthesis of
{{O-[bis(diisopropylamino)phosphanyl]oxy(phenyl)-
carbene}pentacarbonyltungsten(0)} (5)
A suspension of 0.40 g (1.5 mmol) of [bis(diisopropyl-
amino)]chlorophosphane (4) in diethyl ether was added
slowly to a stirred solution of freshly prepared 3 (reac-
tion of 0.53 g (1 mmol) of W(CO)6 with 0.75 ml (1.50
mmol) of a 1.6 m solution of phenyllithium in n-hex-
ane) in 8 ml of diethyl ether at −15°C; afterwards the
temperature was raised and the solution stirred for 3 h
at 0°C. The 31P-NMR spectrum (after 15 h) showed
decomposition of the intermediately formed complex 5
to yield phosphaneoxide 6 as the main product.
3.3. Synthesis of {{O-[bis(trimethylsilyl)-
methylenephosphanyl]oxy(phenyl)carbene}-
pentacarbonyltungsten(0)} (8)
A solution of 0.36 g (1.5 mmol) of [bis(trimethylsi-
lyl)methylene)chlorophosphane (7) in 1 ml of diethyl
ether was added slowly to a stirred solution of freshly
prepared 3 (reaction of 0.53 g (1.5 mmol) of W(CO)6
with 0.60 ml of a 1.6 M solution of phenyllithium in
n-hexane) at −30°C; afterwards the temperature was
raised to ambient temperature and the solution stirred
for 20 h. Evaporation of the solvent, filtration of lithi-
umchloride and concentration of the brown solution
yielded complex 8 as a brownish solid (yield: 0.65 g
(70%), m.p.: 83°C (dec.)). Elemental analysis: Anal.
Found: C, 36.82; H, 3.63. Calc. For C19H23O6PSi2W
(618.42): C, 36.90; H 3.75%. IR (KBr): w˜ =1915 (vs),
1949 (s), 1980 (m), 2061 (m). MS [EI, 184 W, m/z (%)]:
618 [2, M+], 590 [6, M+−CO], 562 [2, M+−2CO],
534 [5, M+−3CO], 506 [5, M+−4CO], 478 [14, M+
−5CO], 401 [24, M+−5CO−Ph], 373 [32, M+−
5CO−PhCO], 266 [30, (C13H23PSi2)+], 105 [23,
3. Experimental
3.1. General
PhCO+], 77 [16, C6H5+], 73 [100, C3H9Si+]. H-NMR
1
All operations were carried out under an inert atmo-
sphere of deoxygenated dry nitrogen. Solvents were
dried according to standard procedures. NMR spectra
were recorded on a Bruker AC-200 spectrometer (200
(CDCl3, 20°C): l=0.19 (s, 9H, Si(CH3)3), 0.37 (d,
4J(H, P)=2.5 Hz, 9H, Si(CH3)3), 7.49 (mc, 3H, m-,
p-Ph), 7.83 (mc, 2H, o-Ph). 13C{1H}-NMR (CDCl3,
3
20°C): l=1.5 (d, J(C, P)=14.4 Hz, Si(CH3)3), 2.3 (d,
MHz for H; 50.3 MHz for 13C; 81 MHz for 31P) using
3J(C, P)=2.5 Hz, Si(CH3)3), 128.4 (s, Ph), 128.6 (s,
1
3
chloroform-d6 and benzene-d6 as solvents, the latter as
internal standard; shifts are given relative to te-
tramethylsilane (1H, 13C) and 85% H3PO4 (31P); only
coupling constant magnitudes are given. MS: Finnigan
Mat 8430 (70 eV).Elemental analysis: Carlo Erba ana-
lytical gas chromatograph. IR: Biorad FTIR-165; se-
lected data (w(CO) bands) are given.
Ph), 133.3 (s, Ph), 154.8 (d, J(C, P)=3.9 Hz, i-Ph),
1
4
173.9 (d, J(C, P)=78.4 Hz, CꢁP), 198.0 (d, J(C, P)=
8.3 Hz, 1J(C, W)=127.6 Hz, cis-CO), 203.7 (d,
2J(C, P)=2.4 Hz, trans-CO), 320.6 (d, J(C, P)=18.8
4
Hz, WꢁCR2). 31P{1H}-NMR (CDCl3, 20°C): l=348.1
(s).
The following compounds were synthesized accord-
ing to the literature: bis(diisopropylamino)chlorophos-
phane [11] (4), bis(diisopropylamino)phosphaneoxide
[12] (6), [bis(trimethylsilyl)methylene]chlorophosphane
[13] (7) and {[2-bis(trimethylsilyl)methyl-3-phenyl-2H-
azaphosphirene-sP]pentacarbonyl}tungsten(0)}(11)[14].
3.4. Synthesis and rearrangement of a 1:1-mixture of
E,Z-{{N-[bis(trimethylsilyl)methylenephosphanyl]-
amino(phenyl)carbene}pentacarbonyltungsten(0)} (10a,b)
A solution of 0.36 g (1.5 mmol) of chlorophosphane
7 in 4 ml of diethyl ether was added slowly to a stirred

R. Streubel et al. / Journal of Organometallic Chemistry 613 (2000) 56–59
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solution of freshly prepared 9 (reaction of 0.65 g (1.5
mmol) of {(CO)5W[C(NH2)Ph]} with 0.75 ml of a 1.6
M solution of methyllithium in n-hexane at 0°C, 10 ml
of diethyl ether, 5 min) in 8 ml of diethyl ether at
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up to 0°C and stirred for 0.5 h (yields of the crude
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10a,b rearranged slowly at ambient temperature to the
2H-azaphosphirene complex 11.
Characterization of a 1:1 mixture of 10a,b: 13C{1H}-
NMR (C6D6, 20°C): l=2.0 (s, Si(CH3)3), 2.1 (s,
Si(CH3)3), 2.3 (s br, Si(CH3)3), 122.1 (s br, Ph), 127.3 (s,
Ph), 128.3 (s, Ph), 129.7 (s, Ph), 129.8 (s, Ph), 154.27 (d,
3
3J(C, P)=8.7 Hz, i-Ph), 154.31 (d, J(C, P)=9.1 Hz,
i-Ph), 176.1 (d, 1J(C, P)=87.8 Hz, PꢁC), 185.6 (d,
1J(C, P)=89.4 Hz, PꢁC), 199.1 (s, 1J(C, W)=127.3
Hz, cis-CO), 199.2 (s, 1J(C, W)=128.2 Hz, cis-CO),
202.6 (s, trans-CO), 202.7 (s, trans-CO), 276.7 (d,
2J(C, P)=1.6 Hz, WꢁCR2), 277.2 (d, 2J(C, P)=1.4 Hz,
WꢁCR2). 31P{1H}-NMR (C6D6, 20°C): l=309.1 (s,
br), 332.9 (s, br).
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Acknowledgements
Financial support by the Deutsche Forschungsge-
meinschaft and the Fonds der Chemischen Industrie
and MS measurements by Dr Hans-Martin Schiebel
(Universita¨t Braunschweig) are gratefully acknowl-
edged.
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Jones, Eur. J. Inorg. Chem. (1998) 257.
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