Reaction of the in-situ-generated ruthenium-acetylide complex C5Me5Ru(PPh3)C≡CPh with small molecules

Article abstract of DOI:10.1021/om9705012

A coordinatively unsaturated acetylide species C₅Me₅Ru(PPh₃)C≡CPh (1) was generated in situ from the reaction of ruthenium-vinylidene complex C₅-Me₅Ru(Cl)(PPh₃)=C=CHPh (2) with Et₃N. The vinylidene complex 2 was prepared from the substitution reaction of C₅Me₅Ru(PPh₃)₂Cl with PhC≡CH. The in-situ-generated 1 was found to react readily with a variety of small molecules. For example, the reaction of 1 with CO produced the stable adduct C₅Me₅Ru(CO)-(PPh₃)C≡CPh (3) in 85% yield, the structure of which was established by X-ray crystallography. The similar reactions of 1 with H₂ and PhC≡CPh also gave the hydride complex C₅Me₅Ru(PPh₃)(H)(H₂C=CHPh) (4) (76% yield) and the alkyne complex C₅Me₅Ru(PPh₃)-(PhC≡CPh)C≡CPh (5) (85% yield), respectively. The reaction of 1 with CO₂ produced the carboxylate complex C₅Me₅Ru(PPh₃)(η²-O ₂CC≡CPh) (6) from the insertion of CO₂ to the ruthenium-acetylide carbon bond.

Full text of DOI:10.1021/om9705012

© Copyright 1997
Volume 16, Number 17, August 19, 1997
American Chemical Society
Communications
Rea ction of th e in -Situ -Gen er a ted Ru th en iu m -Acetylid e
Com p lex C5Me5Ru (P P h 3)C CP h w ith Sm a ll Molecu les
Chae S. Yi* and Nianhong Liu
Department of Chemistry, Marquette University, Milwaukee, Wisconsin 53201-1881
Arnold L. Rheingold, Louise M. Liable-Sands, and Ilia A. Guzei
Department of Chemistry, The University of Delaware, Newark, Delaware 19716-2522
Received J une 12, 1997
Summary: A coordinatively unsaturated acetylide spe-
cies C5Me5Ru(PPh3)C CPh (1) was generated in situ
from the reaction of ruthenium-vinylidene complex C5-
Me5Ru(Cl)(PPh3) C CHPh (2) with Et3N. The vi-
nylidene complex 2 was prepared from the substitution
reaction of C5Me5Ru(PPh3)2Cl with PhC CH. The
in-situ-generated 1 was found to react readily with a
variety of small molecules. For example, the reaction of
1 with CO produced the stable adduct C5Me5Ru(CO)-
(PPh3)C CPh (3) in 85% yield, the structure of which
was established by X-ray crystallography. The similar
reactions of 1 with H2 and PhC CPh also gave the
hydride complex C5Me5Ru(PPh3)(H)(H2C CHPh) (4)
(76% yield) and the alkyne complex C5Me5Ru(PPh3)-
(PhC CPh)C CPh (5) (85% yield), respectively. The
reaction of 1 with CO2 produced the carboxylate complex
C5Me5Ru(PPh3)(η2-O2CC CPh) (6) from the insertion of
CO2 to the ruthenium-acetylide carbon bond.
Interest in the metal-coordinated σ-acetylide complexes
has also grown in recent years because such complexes
have emerged as key components in generating nonlin-
ear optical, molecular conducting and liquid crystalline
materials.2 While ligand-based reactions of coordina-
tively saturated metal-acetylide complexes have been
well-established,1e,3 the reactivity of unsaturated metal-
acetylide complexes has not been thoroughly explored.
In an attempt to extend the ruthenium-mediated dimer-
ization of terminal alkynes4 and CO2 activation reac-
tions,5 we have begun searching for new ways to
generate unsaturated ruthenium-acetylide complexes.
(1) (a) Parshall, G. W.; Ittel, S. D. Homogeneous Catalysis, 2nd ed.;
J ohn Wiley & Sons: New York, 1992. (b) Henkelmann, J . In Applied
Homogeneous Catalysis with Organometallic Compounds; Cornils, B.,
Herrmann, W. A., Eds.; VCH: New York, 1996; Vol. 1. (c) Melikyan,
G. G.; Nicholas, K. M. In Modern Acetylene Chemistry; Stang, P. J .,
Diederich, F., Eds.; VCH: New York, 1995. (d) Farina, V. In Compre-
hensive Organometallic Chemistry II; Abel, E. W., Stone, F. G. A.,
Wilkinson, G., Eds.; Pergamon Press: New York, 1994; Vol. 12. (e)
Bruce, M. I. Chem. Rev. 1991, 91, 197. (f) Schore, N. E. Chem. Rev.
1988, 88, 1081. (g) Kishimoto, Y.; Eckerle, P.; Miyatake, T.; Ikariya,
T.; Noyori, R. J . Am. Chem. Soc. 1994, 116, 12131.
(2) (a) Kanis, D. R.; Ratner, M. A.; Marks, T. J . Chem. Rev. 1994,
94, 195. (b) Lang, H. Angew. Chem., Int. Ed. Engl. 1994, 33, 547. (c)
Beck, W.; Niemer, B.; Wieser, M. Angew. Chem., Int. Ed. Engl. 1993,
32, 923. (d) Materials for Nonlinear Optics: Chemical Perspectives;
Stucky, G. D., Marder, S. R., Sohn, J ., Eds.; ACS Symposium Series
455; American Chemical Society: Washington, DC, 1991. (e) Prasad,
P. N.; Williams, D. J . Nonlinear Optical Effects in Molecules and
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Comprehensive Organic Synthesis; Trost, B. M., Ed.; Pergamon Press:
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Stang, P. J ., Diederich, F., Eds.; VCH: New York, 1995.
Transition metal σ-acetylide complexes are known to
be involved in a number of catalytic and stoichiometric
reactions of alkynes.1 The copper-acetylide catalysts
have been widely employed in industrial-scale alkyne
coupling reactions, such as in the production of H2C
CHC CH from the linear dimerization of acetylene1a
and in the synthesis of butyndiol from the coupling of
acetylene with formaldehyde.1b A well-characterized
rhodium-acetylide complex has recently been shown to
promote the living polymerization of phenylacetylene.1g
Abstract published in Advance ACS Abstracts, August 1, 1997.
S0276-7333(97)00501-3 CCC: $14.00 © 1997 American Chemical Society

3730 Organometallics, Vol. 16, No. 17, 1997
Communications
Herein, we report an in situ generation of a coordina-
tively unsaturated ruthenium acetylide species C5Me5-
Ru(PPh3)C CPh (1) and its reactions with small mol-
ecules.
Recent reports on the ruthenium-vinylidene com-
plexes1e,3 suggested that the coordinatively unsaturated
ruthenium acetylide species 1 could be generated from
the reaction of ruthenium-vinylidene complexes
with a base. Following a literature procedure,6 a chiral
ruthenium-vinylidene precursor C5Me5Ru(PPh3)(Cl)
C
CHPh (2) was readily prepared from the ligand
F igu r e 1. Molecular structure of 2 drawn with 30%
thermal ellipsoids. Selected bond lengths (Å) and bond
angles (deg): Ru-C(11), 1.817(3); C(11)-C(12), 1.315(4);
Ru-Cl, 2.4018(7); Ru-P, 2.3099(7); Ru-Cp* (cent), 1.936-
(3); Cl-Ru-P, 89.17(3); C(11)-Ru-P, 88.03(9); Ru-C(11)-
C(12), 175.3(3); C(11)-C(12)-C(13), 123.6(3).
substitution reaction of C5Me5Ru(PPh3)2Cl7 with
PhC CH and a subsequent acetylene-to-vinylidene
tautomerization reaction. Thus, treatment of C5Me5-
Ru(PPh3)2Cl (1.0 g, 1.26 mmol) with excess PhC CH
(1.38 mL, 10 equiv) in THF at 60 °C for 12 h produced
the vinylidene complex 2 (698 mg, 88% yield). The
structure of 2 was completely established by both
solution spectroscopic methods8 and by single-crystal
X-ray crystallography (Figure 1).9 The X-ray crystal
structure of 2 showed an antiperiplanar geometry
between the â-vinylidene hydrogen and the chloride
ligand, as indicated by the dihedral angle between the
plane of the â-vinylidene carbon and the Ph group
(C(12)-C(13)) and the plane containing the Ru and Cl
atoms (Ru-Cl) (Θ ) 20.0°). The bond distance between
Ru and the R-vinylidene carbon (Ru-C(11) ) 1.817(3)
Å) was typical for a ruthenium(II) complex.1e Recently,
(3) For a recent review on Ru-acetylide complexes, see: (a) Hill,
A. F. In Comprehensive Organometallic Chemistry II; Abel, E. W.,
Stone, F. G. A., Wilkinson, G., Eds.; Pergamon Press: New York, 1994;
Vol. 7. (b) Davies, S. G.; McNally, J . P.; Smallridge, A. J . Adv.
Organomet. Chem. 1990, 30, 1. Other recent selected examples: (c)
Lemke, F. R.; Szalda, D. J .; Bullock, R. M. J . Am. Chem. Soc. 1991,
113, 8466. (d) Sun, Y.; Taylor, N. J .; Carty, A. J . Organometallics 1992,
11, 4293. (e) Kelley, C.; Lugan, N.; Terry, M. R.; Geoffroy, G. L.;
Haggerty, B. S.; Rheingold, A. L. J . Am. Chem. Soc. 1992, 114, 6735.
(f) Lomprey, J . R.; Selegue, J . P. J . Am. Chem. Soc. 1992, 114, 5518.
(g) Lichtenberger, D. L.; Renshaw, S. K.; Bullock, R. M. J . Am. Chem.
Soc. 1993, 115, 3276. (h) Matsuzaka, H.; Hirayama, Y.; Nishio, M.;
Mizobe, Y.; Hidai, M. Organometallics 1993, 12, 36. (i) Shih, K.-Y.;
Schrock, R. R.; Kempe, R. J . Am. Chem. Soc. 1994, 116, 8804. (j) Weng,
W.; Bartik, T.; Brady, M.; Bartik, B.; Ramsden, J . A.; Arif, A. M.;
Gladysz, J . A. J . Am. Chem. Soc. 1995, 117, 11922. (k) Weng, W.;
Bartik, T.; J ohnson, M. T.; Arif, A. M.; Gladysz, J . A. Organometallics
1995, 14, 889. (l) Brady, M.; Weng, W.; Zhou, Y.; Seyler, J . W.; Amoroso,
A. J .; Arif, A. M.; Bo¨hme, M.; Frenking, G.; Gladysz, J . A. J . Am. Chem.
Soc. 1997, 119, 775. (m) Kawata, Y.; Sato, M. Organometallics 1997,
16, 1093. (n) Field, L. D.; George, A. V.; Malouf, E. Y.; Hambley, T.
W.; Turner, P. J . Chem. Soc., Chem. Commun. 1997, 133. (o) Whiteford,
J . A.; Lu, C. V.; Stang, P. J . J . Am. Chem. Soc. 1997, 119, 2524.
(4) Yi, C. S.; Liu, N. Organometallics 1996, 15, 3968.
F igu r e 2. Molecular structure of 3 drawn with 30%
thermal ellipsoids. Selected bond lengths (Å) and bond
angles (deg): Ru-C(11), 2.030(4); C(11)-C(12), 1.203(5);
Ru-C(19), 1.850(4); Ru-P, 2.3144(10); Ru-Cp* (cent),
1.902(4); C(11)-Ru-P, 82.52(10); C(11)-Ru-C(19), 93.5-
(2); C(11)-C(12)-C(18), 173.7(4).
a crystal structure of a similar ruthenium-vinylidene
complex, TpRu(Cl)(PPh3) C CHPh, has been reported.10
The antiperiplanar geometry between the â-vinylidene
proton and the chloride ligand of complex 2 is nicely
set up for the elimination of HCl. The treatment of
complex 2 (200 mg, 0.31 mmol) with Et3N (0.22 mL, 5
equiv) in the presence of CO (1 atm) at room tempera-
ture cleanly gave the stable acetylide complex C5Me5-
Ru(CO)(PPh3)C CPh (3) in an 85% isolated yield
(Scheme 1). The structure of 3 was established by both
spectroscopic methods8 and by X-ray crystallography
(Figure 2).11 Bond lengths of the acetylide ligand (Ru-
C(11) ) 2.030(4) Å, C(11)-C(12) ) 1.203(5) Å, and
(5) Yi, C. S.; Liu, N. Organometallics 1995, 14, 2616.
(6) (a) Bianchini, C.; Casares, J . A.; Peruzzini, M.; Romerosa, A.;
Zanobini, F. J . Am. Chem. Soc. 1996, 118, 4585. (b) Bianchini, C.;
Innocenti, P.; Peruzzini, M.; Romerosa, A.; Zanobini, F. Organometal-
lics 1996, 15, 272.
(7) (a) Serron, S. A.; Luo, L.; Li, C.; Cucullu, M. E.; Stevens, E. D.;
Nolan, S. P. Organometallics 1995, 14, 5290. (b) Luo, L.; Nolan, S. P.;
Fagan, P. J . Organometallics 1993, 12, 4305. (c) Conroy-Lewis, F. M.;
Simpson, S. J . J . Organomet. Chem. 1987, 322, 221.
(8) See the Supporting Information for the spectroscopic data of the
complexes 2-6.
(9) Crystal data for 2: C36H36ClPRu, orthorhombic, P212121, a )
9.2332(2) Å, b ) 16.27470(10) Å, c ) 20.35730(10) Å, V ) 3059.04(7)
Å3, Z ) 4, T ) 222 K, Dcalcd ) 1.381 g cm-1, R(F) ) 2.81% for 6240
observed independent reflections (3.20° 2θ 56.80°).
(10) Slugovc, C.; Mereiter, K.; Zobetz, E.; Schmid, R.; Kirchner, K.
Organometallics 1996, 15, 5275.

Communications
Organometallics, Vol. 16, No. 17, 1997 3731
Sch em e 1
single ruthenium-hydride resonance at δ -10.20 (d, J PH
) 36.8 Hz), along with the coordinated alkene reso-
nances.8 The similar reaction of 1 with PhC CPh
produced the alkyne adduct 5 in 85% yield.8 The
addition of Et3N was found to be essential in initiating
these reactions since the vinylidene complex 2 alone did
not produce 4 or 5 in its absence.
The addition of CO2 (2-3 atm) to a C6D6 solution of
in-situ-generated 1 at 60 °C resulted in the formation
of the carboxylate complex 6. Complex 6 was cleanly
formed in a sealed NMR tube (>90%) but decomposed
to uncharacterizable products upon evaporation of the
solvent. The η2-carboxylate geometry of 6 was estab-
lished from the observations of a carbonyl carbon at δ
168.2 (d, J PC ) 8.6 Hz) in the 13C NMR and two carbonyl
stretching modes (νCO (sym) ) 1452, νCO (asym) ) 1618
C(12)-C(18) ) 1.446(5) Å) indicate a minimal π-delo-
calization between the acetylide ligand and the metal
center.
2
2
cm-1) in the IR spectrum, which are similar to the
previously characterized formate complex C5Me5Ru-
(PCy3)(η2-O2CH).5 The formation of 6 can be explained
by migratory insertion of the nucleophilic acetylide
ligand to a weakly coordinated carbonyl carbon of CO2.
The insertion of CO2 to metal-carbon and -hydrogen
bonds has been commonly observed in other organome-
tallic CO2 reactions.13 The addition of CO2 to a satu-
rated metal-acetylide complex is usually known to
occur at the â-acetylide carbon to produce a carboxylate-
substituted vinylidene complex.14 Related CS2 insertion
to a ruthenium-acetylide complex has also been
documented.3a,b
The formation of 3 was consistent with the generation
of an unsaturated acetylide species 1. In an attempt
to directly detect the acetylide 1 in the reaction mixture,
the reaction of 2 with Et3N in THF-d8 was monitored
by 1H NMR spectroscopy. No detectable intermediates
were detected with or without CO in the temperature
range of 25-60 °C, and the reaction did not proceed in
the absence of CO at room temperature. The relatively
long reaction time (∼24 h) for the formation of complex
3 suggested that the concentration of 1 was too low to
be detected by NMR with the weak base NEt3. The
reaction of complex 2 (10 mg, 0.016 mmol) with the
strong base LiOMe (6 mg, 10 equiv) in THF-d8 (0.5 mL)
In summary, the unsaturated ruthenium-acetylide
complex 1 was cleanly generated in situ from the
reaction of ruthenium-vinylidene complex 2 with a
base. Complex 1 was shown to react with a variety of
small molecules, such as CO, H2, PhC CPh, and CO2.
Recent preliminary results indicate that complex 1 is
an effective catalyst for the dimerization of terminal
alkynes.15 Studies directed toward the reactions of 1
with alkenes and alkynes are currently underway.
1
was monitored by H NMR at room temperature. The
initially red-colored solution turned to brownish-yellow
after 5 h, and a set of new peaks gradually appeared at
the expense of those due to 2. The spectral data of the
new species was consistent with the solvent-coordinated
form of the acetylide complex 1‚THF,12 but several
attempts to isolate the complex were not successful as
it decomposed during evaporation of the solvent. Treat-
ment of this solution with CO (1 atm) led to the
formation of the same adduct 3.
The in-situ-generated acetylide species 1 was found
to react with small molecules, such as H2, PhC CPh,
and CO2, under mild reaction conditions. For example,
the reaction of in-situ-generated 1 with H2 at room
temperature cleanly produced the hydride-alkene com-
plex 4. In a typical reaction, H2 (1 atm) was transferred
via a vacuum line to a THF solution containing complex
2 (200 mg, 0.31 mmol) and Et3N (0.44 mL, 10 equiv)
and the reaction mixture was stirred at room temper-
ature for 24 h. Analytically pure ruthenium product 4
was obtained after a recrystallization in Et2O/hexanes
(144 mg, 76% yield). The 1H NMR of 4 exhibited a
Ack n ow led gm en t . Financial support from Mar-
quette University, Committee-on-Research, is gratefully
acknowledged.
Su p p or tin g In for m a tion Ava ila ble: Tables of crystal
data and structure refinement, atomic coordinates, bond
lengths and angles, and H-atom coordinates for 2 and 3 and
spectroscopic data for the ruthenium complexes 2-6 (14
pages). Ordering information is given on any current mast-
head page.
OM9705012
(13) For recent reviews, see: (a) Behr, A. Carbon Dioxide Activation
by Metal Complexes; VCH: New York, 1988. (b) Braunstein, P.; Matt,
D.; Nobel, D. Chem. Rev. 1988, 88, 747. (c) Catalytic Activation of
Carbon Dioxide; Ayers, W. M., Ed.; ACS Symposium Series 363;
American Chemical Society: Washington, DC, 1988. (d) Leitner, W.
Angew. Chem. Int. Ed., Engl. 1995, 34, 2207.
(14) Birdwhistell, K. R.; Templeton, J . L. Organometallics 1985, 4,
2062.
(15) Yi, C. S.; Liu, N.; Rheingold, A. L.; Liable-Sands, L. M.
Organometallics in press.
(11) Crystal data for 3: C37H35OPRu: monoclinic, P21/n, a ) 8.7254-
(2) Å, b ) 17.8548(5) Å, c ) 19.5265(5) Å, â ) 98.9732(3)°, V ) 3004.81-
(13) Å3, Z ) 4, T ) 223(2) K, Dcalcd ) 1.388 g cm-1, R(F) ) 4.90% for
4588 observed independent reflections (3.10° 2θ 56.54°).
(12) Selected spectroscopic data for 1‚THF: 1H NMR (THF-d8, 300
MHz) δ 1.21 (s, C5Me5); 13C{1H} NMR (THF-d8, 75 MHz) δ 124.5 (d,
J PC ) 24.5 Hz, Ru-C ), 114.5 (Ru-C C), 94.4 (C5Me5), 10.1 (C5Me5);
31P{1H} NMR (THF-d8, 121.6 MHz) δ 53.0 (s, PPh3); IR (C6H6) νC
C
2067 cm-1
.