Unexpected formation of the vinyl-phosphonio complex [CpRu(PPh 3)(C6H4PPh2CH=CH2)] [PF6] from a vinylidene complex via nucleophilic addition and ortho metalation of triphenylphosphine

Article abstract of DOI:10.1021/om049440f

The reaction of Ru-vinylidene complexes with triphenylphosphine led to the formation of vinyl-phosphonio complexes in good yields. The results obtained by using a deuterium-labeled complex and a methyldiphenylphosphine analogue indicated that the present reaction proceeded via nucleophilic addition to the α-carbon of the vinylidene group, followed by ortho metalation of the phenyl ring on the cationic phosphorus atom.

Full text of DOI:10.1021/om049440f

5630
Organometallics 2004, 23, 5630-5632
Unexpected Formation of the Vinyl-Phosphonio
Complex [CpRu(PPh3)(C6H4PPh2CHdCH2)][PF6] from a
Vinylidene Complex via Nucleophilic Addition and Ortho
Metalation of Triphenylphosphine
Kiyotaka Onitsuka,* Masayoshi Nishii, Yuji Matsushima, and
Shigetoshi Takahashi
The Institute of Scientific and Industrial Research, Osaka University,
8-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan
Received July 23, 2004
Summary: The reaction of Ru-vinylidene complexes
with triphenylphosphine led to the formation of vinyl-
phosphonio complexes in good yields. The results ob-
tained by using a deuterium-labeled complex and a
methyldiphenylphosphine analogue indicated that the
present reaction proceeded via nucleophilic addition to
the R-carbon of the vinylidene group, followed by ortho
metalation of the phenyl ring on the cationic phosphorus
atom.
a nucleophile usually attacks the R-carbon of vinylidene
ligands to produce a Fischer-type carbene complex,6
whereas an electrophile attacks the â-carbon to generate
a carbyne complex.7 In the course of our studies on Ru-
vinylidene complexes,8 we discovered the formation of
vinyl-phosphonio complexes, in which one of the phenyl
groups on the cationic phosphorus atom is bound to the
Ru atom at the ortho position and the vinyl group is in
the π-coordination mode. In contrast to the report that
the reactions of vinylidene complexes of metals other
than Ru with phosphine led to addition at the R-carbon
to give σ-alkenyl complexes,9 there have been reports
that the Ru-vinylidene complexes show unusual reac-
tivity toward phosphine. For example, the reactions of
the Ru-vinylidene complexes with phosphine and phos-
phite resulted in formal addition at the â-carbon10 and
the displacement of the vinylidene ligand,11 respectively.
We report herein our experimental results of the reac-
tion of Ru-vinylidene complexes, yielding vinyl-phos-
phonio complexes.
Introduction
During the past decade, the chemistry of Ru-vi-
nylidene complexes has become increasingly attractive,
because it has been disclosed that the catalytic organic
transformation of terminal alkynes often proceeds via
a vinylidene intermediate.1 Representative examples of
such a catalytic reaction include dimerization,2 coupling
with alkene and pyridine,3 cyclization of alkynes,4 and
addition of heteroatom nucleophiles to alkynes.5 The
reactivity of Ru-vinylidene complexes has been studied
extensively in order to not only understand the reaction
mechanism but also obtain fundamental information for
the development of new catalytic reactions. For example,
Results and Discussion
Heating of an acetonitrile solution of the vinylidene
complex 1a at 80 °C led to the slow formation of the
new complex 2a (eq 1). After 24 h, the conversion was
approximately 50%, and 5 days was needed for the
(1) For recent reviews, see: (a) Bruce, M. I. Chem. Rev. 1991, 91,
197. (b) Puerta, M. C.; Valerga, P. Coord. Chem. Rev. 1999, 193-195,
977. (c) Bruneau, C.; Dixneuf, P. H. Acc. Chem. Res. 1999, 32, 311.
(2) (a) Wakatsuki, Y.; Yamazaki, H.; Kumegawa, N.; Satoh, T.;
Satoh, J. Y. J. Am. Chem. Soc. 1991, 113, 9604. (b) Wakatsuki, Y.;
Yamazaki, H.; Kumegawa, N.; Johar, P. S. Bull. Chem. Soc. Jpn. 1993,
66, 987. (c) Bianchini, C.; Frediani, P.; Masi, D.; Peruzzini, M.;
Zanobini, F. Organometallics 1994, 13, 4616. (d) Matsuzaka, H.;
Takagi, Y.; Ishii, Y.; Nishio, M.; Hidai, M. Organometallics 1995, 14,
2153. (e) Yi, C. S.; Liu, N. Organometallics 1996, 15, 3968. (f) Slugovc,
C.; Mereiter, K.; Zobetz, E.; Schmid, R.; Kirchner, K. Organometallics
1996, 15, 5275.
(3) (a) Murakami, M.; Ubukata, M.; Ito, Y. Tetrahedron Lett. 1998,
39, 7361. (b) Murakami, M.; Hori, S. J. Am. Chem. Soc. 2003, 125,
4720.
(4) (a) Onitsuka, K.; Katayama, H.; Sonogashira, K.; Ozawa, F. J.
Chem. Soc., Chem. Commun. 1995, 2267. (b) Merlic, C. A.; Pauly, M.
E. J. Am. Chem. Soc. 1996, 118, 11319. (c) Murakami, M.; Ubukata,
M.; Ito, Y. Chem. Lett. 2002, 294.
complete consumption of 1a to give 2a in quantitative
(5) (a) Mahe´, R.; Sasaki, Y.; Bruneau, C.; Dixneuf, P. H. J. Org.
Chem. 1989, 54, 1518. (b) Trost, B. M.; Dyker, G.; Kulawiec, R. J. J.
Am. Chem. Soc. 1990, 112, 7809. (c) Trost, B. M.; Kulawiec, R. J. J.
Am. Chem. Soc. 1992, 114, 5579. (d) Doucet, H.; Martin-Vaca, B.;
Bruneau, C.; Dixneuf, P. H. J. Org. Chem. 1995, 60, 7247. (e) Trost,
B. M.; Rhee, Y. H. J. Am. Chem. Soc. 1999, 121, 11680. (f) Tokunaga,
M.; Suzuki, T.; Koga, N.; Fukushima, T.; Horiuchi, A.; Wakatsuki, Y.
J. Am. Chem. Soc. 2001, 123, 11917. (g) Trost, B. M.; Rhee, Y. H. J.
Am. Chem. Soc. 2002, 124, 2528. (h) Fukumoto, Y.; Dohi, T.; Masaoka,
H.; Chatani, N.; Murai, S. Organometallics 2002, 21, 3845. (i) Je´roˆme,
F.; Monnier, F.; Lawicka, H.; De´rien, S.; Dixneuf, P. H. Chem.
Commun. 2003, 696.
(6) (a) Bruce, M. I.; Swincer, A. G.; Wallis, R. C. J. Organomet. Chem.
1979, 171, C5. (b) Bruce, M. I.; Swincer, A. G. Aust. J. Chem. 1980,
33, 1471. (c) Ouzzine, K.; Le Bozec, H.; Dixneuf, P. H. J. Organomet.
Chem. 1986, 317, C25. (d) Davies, S. G.; Smallridge, A. J. J. Organomet.
Chem. 1990, 395, C39.
(7) (a) Stu¨er, W.; Wolf, J.; Werner, H.; Schwab, P.; Schulz, M. Angew.
Chem., Int. Ed. 1998, 37, 3421. (b) Gonzalez-Herrero, P.; Weberndo-
erfer, B.; Ilg, K.; Wolf, J.; Werner, H. Organometallics 2001, 20, 3672.
(c) Beach, N. J.; Jenkins, H. A.; Spivak, G. J. Organometallics 2003,
22, 5179.
(8) Ajioka, Y.; Matsushima, Y.; Onitsuka, K.; Yamazaki, H.; Taka-
hashi, S. J. Organomet. Chem. 2001, 617-618, 601.
10.1021/om049440f CCC: $27.50 © 2004 American Chemical Society
Publication on Web 09/25/2004

Notes
Organometallics, Vol. 23, No. 23, 2004 5631
signals due to the vinyl protons at δ 3.6 and 1.7. The
small coupling constant (J ) 2.4 Hz) between those two
signals suggested that those protons were bound to the
same carbon atom; this was unequivocally supported by
2D-NMR (HMQC) experiments. Therefore, the proton
derived from the phenyl group of triphenylphosphine
must be located on the R-carbon of the vinyl group.
When the reaction was performed in the presence of
1.5 equiv of triphenylphosphine, 1a was completely
consumed within 2 h to produce another complex (3),
which was converted into 2a after reaction for 18 h. The
1H NMR spectrum of 3 revealed three signals at δ 3.8,
3.2, and 2.2, which were similar to those of 2a, suggest-
ing that 3 might have a vinyl group. Although 3 was
surmised to be an intermediate of the present reaction,
we could not determine its structure. The marked
acceleration of the reaction by the addition of triph-
enylphosphine to a solution of 1a indicated that the
intermolecular attack of triphenylphosphine took place.
On the other hand, the reaction of 1c, which is a
methyldiphenylphosphine analogue of 1a, with 1.5 equiv
of methyldiphenylphosphine at room temperature pro-
duced a new complex (4), whereas no reaction took place
by heating an acetonitrile solution of 1c in the absence
of additional methyldiphenylphosphine (eq 3). Although
Figure 1. Molecular structure of the cation of complex 2b.
Hydrogen atoms are omitted for clarity.
yield. The 31P NMR spectrum of 2a showed two doublets
at δ 56.7 (J ) 4 Hz) and 39.7 (J ) 4 Hz). The fairly
small coupling constant suggested that 2a had no CpRu-
(PPh3)2 skeleton. In the 1H NMR spectrum, three
characteristic signals were observed at δ 4.1, 3.7, and
1.7. As each signal was attributed to one proton, two of
those signals would be due to the protons originating
from the vinylidene ligands. The reaction of 1b, which
has a Cp* ligand instead of a Cp ligand, proceeded more
quickly than that of 1a under similar conditions. Heat-
ing of an acetonitrile solution of 1b for 24 h resulted in
complete consumption to give 2b in 83% yield. The
spectral data of 2b were similar to those of 2a. Fortu-
nately, single crystals of 2b were obtained by recrys-
tallization from ethyl acetate-diethyl ether, and the
structure was determined by X-ray analysis. As shown
in Figure 1, complex 2b has a three-legged piano-stool
structure in which one phenyl group on the cationic
phosphorus atom is bound to the Ru atom by a σ-bond
at the ortho position and the vinyl group derived from
the vinylidene ligand coordinates to the Ru atom in an
η2 fashion. Thus, one proton on the vinyl group would
be derived from the phenyl group linking to the Ru
atom.
we could not isolate 4 in pure form, spectral data
suggested that 4 was an alkenyl complex. For example,
the FAB mass spectrum showed a peak (m/z 794) that
corresponded to the product of the cationic part of 4 with
one molecule of methyldiphenylphosphine. In the 1H
NMR spectrum, two doublet signals assignable to the
protons of the noncoordinated olefin were observed at
δ 6.1 and 6.0 with large coupling constants of J ) 39
and 73 Hz, respectively, similar to those of an analogous
alkenyl Fe complex.9a Although we examined further
the reaction of 4 at high temperatures, no reaction was
detected.
One plausible pathway for the formation of 2 is given
in Scheme 1. At the first stage, phosphine, which is
added to the system or generated by dissociation from
another molecule of 1, attacks the R-carbon of the
vinylidene group to give an alkenyl complex.9 After one
of the two phosphine ligands is dissociated, ortho
metalation takes place to give a Ru(IV) hydride complex.
Reductive elimination followed by the coordination of
To confirm the origin of the hydrogen atom on the
vinyl group, we performed the reaction using the triph-
enylphosphine-d15 complex 1a-d30 (eq 2). The 1H NMR
spectrum of the resulting complex (2a-d30) showed two
Scheme 1. Plausible Pathwaya
(9) (a) Boland-Lussier, B. E.; Churchill, M. R.; Hughes, R. P.;
Rheingold, A. L. Organometallics 1982, 1, 628. (b) Senn, D. R.; Wong,
A.; Patton, A. T.; Marsi, M.; Strouse, C. E.; Gladysz, J. A. J. Am. Chem.
Soc. 1988, 110, 6096. (c) Bianchini, C.; Meli, A.; Peruzzini, M.; Zanobini,
F.; Zanello, P. Organometallics 1990, 9, 241. (d) Ipaktschi, J.; Klotz-
bach, T.; Du¨lmer, A. Organometallics 2000, 19, 5281.
a Counter-anions are omitted for clarity.
(10) Cadierno, V.; Gamasa, M. P.; Gimeno, J.; Borge, J.; Garcia-
Granda, S. Organometallics 1997, 16, 3178.
(11) Bruce, M. I.; Hall, B. C.; Tiekink, E. R. T. Aust. J. Chem. 1997,
50, 1097.

5632 Organometallics, Vol. 23, No. 23, 2004
Notes
Table 1. Crystallographic Data for Complex 2b
the olefin produces 2. This pathway agrees with the
result of deuterium-labeled experiments.
empirical formula
fw
cryst dimens
cryst system
lattice params
C
48H47F6P3Ru
931.88
In summary, we have described here the formation
of vinyl-phosphonio complexes from the reaction of Ru-
vinylidene complexes with phosphine. Our results may
provide useful information for understanding the mech-
anism underlying the hydrophosphonation of alkyne.
Further studies on the extension of these findings to
the development of new catalytic reactions are in
progress.
0.33 × 0.13 × 0.05 mm
monoclinic
a ) 12.366(6) Å
b ) 30.378(5) Å
c ) 11.245(5) Å
â ) 93.51(3)°
V ) 4216(2) Å3
P21/c (No. 14)
4
space proup
Z
Dcalcd
1.468 g cm-3
1912
F(000)
Experimental Section
µ(Mo KR)
5.47 cm-1
no. of rflns measd
total
All reactions were carried out under an argon atmosphere,
whereas the workup was performed in air. 1H, 13C, and 31P
NMR spectra were measured on JEOL JNM-LA400 and JEOL
JNM-LA600 spectrometers. Chemical shifts are given in ppm
based on SiMe4 as the internal standard for 1H and 13C NMR
and 85% H3PO4 as the external standard for 31P NMR. IR
spectra were recorded on a Perkin-Elmer System 2000 FT-IR
instrument. FAB mass spectra were obtained on a JEOL JMS-
600H spectrometer. Elemental analyses were performed by the
Material Analysis Center, ISIR, Osaka University. Complexes
1a-c were prepared according to the literature method.12
Synthesis of [CpRu(PPh3)(C6H4PPh2CHdCH2)][PF6]
(2a). To a solution of complex 1a (150 mg, 0.17 mmol) in
acetonitrile (10 mL) was added triphenylphosphine (68 mg,
0.26 mg), and the reaction mixture was refluxed for 18 h. After
removal of the solvent, the residue was purified by alumina
column chromatography using dichloromethane as eluent to
give a pale yellow solid in quantitative yield. 1H NMR (CDCl3,
400 MHz): δ 7.68-6.80 (m, 29H, Ar), 4.98 (s, 5H, Cp), 4.10
(ddt, 1H, J ) 14.2, 10.7, 1.7 Hz, olefin), 3.73 (ddd, 1H, J )
23.4, 10.7, 2.2 Hz, olefin), 1.71 (ddt, 1H, J ) 16.4, 10.5, 2.2
Hz, olefin). 13C NMR (CDCl3, 150 MHz): δ 145.2 (d, J ) 6 Hz),
145.0 (d, J ) 6 Hz), 133.6, 133.3 (d, J ) 11 Hz), 133.1, 132.9
(d, J ) 5 Hz), 132.5 (d, J ) 10 Hz), 131.9 (d, J ) 11 Hz), 129.9
(d, J ) 10 Hz), 129.4 (d, J ) 11 Hz), 129.2, 128.7, 128.5 (d, J
) 7 Hz), 128.3 (d, J ) 5 Hz), 123.7 (d, J ) 11 Hz), 41.5, 32.9
(d, J ) 78 Hz). 31P NMR (CDCl3, 160 MHz): δ 56.7 (d, J ) 4
Hz), 39.7 (d, J ) 4 Hz). IR (cm-1, KBr): 840 (νP-F). Anal. Calcd
for C43H37F6P3Ru: C, 59.93; H, 4.33. Found: C, 59.82; H, 4.58.
Synthesis of [Cp*Ru(PPh3)(C6H4PPh2CHdCH2)][PF6]
(2b). The title complex was prepared by a method similar to
that for complex 2a in 83% yield. 1H NMR (CDCl3, 400 MHz):
δ 7.76-6.66 (m, 29H, Ar), 2.73 (dd, 1H, J ) 23.0, 8.1 Hz,
olefin), 2.59-2.50 (m, 2H, olefin), 1.32 (s, 15H, CH3). 13C NMR
(CDCl3, 150 MHz): δ 133.6 (d, J ) 11 Hz), 132.9 (d, J ) 11
Hz), 132.7, 132.4 (d, J ) 15 Hz), 132.0 (d, J ) 15 Hz), 130.0-
129.3 (m), 128.3 (d, J ) 15 Hz), 127.6 (d, J ) 14 Hz), 127.4 (d,
J ) 14 Hz), 127.4-127.2 (m), 45.7, 40.9 (d, J ) 106 Hz). 31P
10 373
unique
10 174 (Rint ) 0.153)
4168 (I > 2.0σ(I))
570
no. of observns
no. of params
residuals: R; Rw
goodness of fit indicator
0.069; 0.080
1.18
NMR (CDCl3, 160 MHz): δ 56.5 (d, J ) 4 Hz), 41.1 (d, J ) 4
Hz). IR (cm-1, KBr): 842 (νP-F). Anal. Calcd for C48H47F6P3-
Ru: C, 61.87; H, 5.08. Found: C, 62.03; H, 5.36.
X-ray Diffraction Analysis. A crystal of complex 2b
suitable for X-ray diffraction was mounted on a glass fiber with
epoxy resin. All measurements were performed on a Rigaku
AFC7R automated four-circle diffractometer using graphite-
monochromated Mo KR radiation (λ ) 0.710 69 Å) at -50 °C
in the range of 6° < 2θ < 55° with a scan rate of 8° min-1
.
Intensities were measured by the ω-scan method. Three
standard reflections were monitored every 150 measurements
as a check of the stability of the crystals, and no damage was
observed in all of the measurements. Intensities were corrected
for Lorentz and polarization effects. The structure was solved
by direct methods (SIR92) and expanded using Fourier tech-
niques. All non-hydrogen atoms were refined by full-matrix
least squares using anisotropic thermal parameters, and all
hydrogen atoms were refined using the riding model. A
summary of the crystallographic data is given in Table 1.
Acknowledgment. This work was supported in part
by a Grant-in-Aid for Scientific Research from the
Ministry of Education, Culture, Sports, Science and
Technology and by the Tokuyama Science Foundation
(K.O.). We thank the members of the Material Analysis
Center, ISIR, Osaka University, for spectral measure-
ments, X-ray diffraction data, and microanalyses.
Supporting Information Available: Crystallographic
data of complex 2b as a CIF file. This material is available
free of charge via the Internet at http://pubs.acs.org.
(12) (a) Bruce, M. I.; Koutsantonis, G. A. Aust. J. Chem. 1991, 44,
207. (b) Kawata, Y.; Sato, M. Organometallics 1997, 16, 1093.
OM049440F