Syntheses and reactivity of ruthenium σ-pyridylacetylides

Article abstract of DOI:10.1021/om9610657

Ruthenium σ-acetylides containing a dangling pyridine were synthesized from the reactions of CpRu(L)₂Cl (L = PPh₃, 1/2 (C₅H₄PPh₂)₂Fe) with 4-ethynylpyridine, (E)-1-(4-ethynylphenyl)2-(4-pyridyl)ethylene, or 4-(ethynylphenyl)(4-pyridyl)acetylene in the presence of NH₄⁺PF₆^- followed by deprotonation with a base. The dangling pyridine can be protonated, methylated, or ligated to tungsten carbonyl fragments. The ruthenium donor to the pyridinium acceptor charge-transfer absorption appears at longer wavelength as the conjugation chain becomes longer. The quadratic hyperpolarizabilities of the methylated derivatives were determined using the hyper Rayleigh scattering method. X-ray analysis was employed to examine the structure of the dinuclear complex Ru(C≡CC₅H₄N{W(CO)₄(PPh ₃)})(η²-dppf)(η⁵-C₅H ₅) (dppf = 1,1′-bis(diphenylphosphino)ferrocene).

Full text of DOI:10.1021/om9610657

2038
Organometallics 1997, 16, 2038-2048
Syn th eses a n d Rea ctivity of Ru th en iu m
σ-P yr id yla cetylid es
Iuan-Yuan Wu,† J iann T. Lin,*,† J immy Luo,‡ Shih-Sheng Sun,† Chyi-Shiun Li,†
Kuan J . Lin,† Chiitang Tsai,‡ Chia-Chen Hsu,§ and J iunn-Lih Lin§
Institute of Chemistry, Academia Sinica, Nankang, Taipei, Taiwan, Republic of China,
Department of Chemistry, Chinese Culture University, Taipei, Taiwan, Republic of China,
and Department of Physics, National Chung Cheng University, Ming-Hsiung, Chia-Yi,
Taiwan, Republic of China
Received December 17, 1996X
Ruthenium σ-acetylides containing a dangling pyridine were synthesized from the reactions
of CpRu(L)2Cl (L ) PPh3, 1/2 (C5H4PPh2)2Fe) with 4-ethynylpyridine, (E)-1-(4-ethynylphenyl)-
-
2-(4-pyridyl)ethylene, or 4-(ethynylphenyl)(4-pyridyl)acetylene in the presence of NH4+PF6
followed by deprotonation with a base. The dangling pyridine can be protonated, methylated,
or ligated to tungsten carbonyl fragments. The ruthenium donor to the pyridinium acceptor
charge-transfer absorption appears at longer wavelength as the conjugation chain becomes
longer. The quadratic hyperpolarizabilities of the methylated derivatives were determined
using the hyper Rayleigh scattering method. X-ray analysis was employed to examine the
structure of the dinuclear complex Ru(CtCC5H4N{W(CO)4(PPh3)})(η2-dppf)(η5-C5H5) (dppf
) 1,1′-bis(diphenylphosphino)ferrocene).
In tr od u ction
We have been interested in transition-metal com-
plexes ligated with conjugated pyridines9 for applica-
tions in materials chemistry. In view of the fact that
the pyridine ring can function as an electron acceptor
upon coordination to an organometallic electron acceptor
moiety,10 we set out to assemble a cyclopentadienylru-
thenium σ-acetylide donor and a pyridylmetal group in
the same molecule. Here we report the syntheses and
characterization of such dinuclear complexes. Some
mononuclear ruthenium σ-acetylides with a pyridinium
acceptor are also included.
Metal acetylides are invloved in several important
organometallic processes such as surface organometal-
lics and palladium catalyzed carbon-carbon coupling
reactions.1 Metal acetylides have also attracted con-
siderable study due to their possible applications in
materials chemistry.2 The pioneering work by Green
and co-workers on organometallic nonlinear optics3 has
stimulated considerable effort in this area.4 Metal
σ-acetylide complexes are potentially useful nonlinear
optical materials, since the metal atom resides in the
same plane as the π-system, a criterion suggested by
Marder.5 Cyclopentadienylruthenium σ-acetylides are
of interest because of their easy preparation.6 In
addition, the electron-donating capability of the ruthe-
nium moiety has been found to be beneficial to molec-
ular quadratic hyperpolarizability.7 Systematic studies
of these ruthenium complexes on optical nonlinearity
have also appeared recently.8
Exp er im en ta l Section
The general procedures and physical measurements are
those described in an earlier report.9 4-Ethynylpyridine,11
RuCl(PPh3)2(η5-C5H5),12 RuCl(η2-dppf)(η5-C5H5) (dppf ) 1,1′-
bis(diphenylphosphino)ferrocene),13 W(CO)5L (L ) PPh3, PMe3),14
W(CO)3(dppe)(acetone),15 and [(MeCN)Re(2,2′-bpy)(CO)3][PF6]16
were prepared by following the published methods.
[Ru (CtCC5H4NH)(P P h 3)2(η5-C5H5)][P F 6] (1). A solution
of 4-ethynylpyridine (340 mg, 2.75 mmol) in MeOH (50 mL)
was added to a solution of RuCl(PPh3)2(η5-C5H5) (2.0 g, 2.75
mmol) and NH4+PF6- (540 mg, 3.31 mmol) in 100 mL of CH2-
* To whom correspondence should be addressed. Telefax: 886-2-
7831237. E-mail: jtlin@chem.sinica.edu.tw.
† Academia Sinica.
‡ Chinese Culture University.
§ National Chung Cheng University.
(8) (a) Whittall, I. R.; Humphrey, M. G.; Hockless, D. C. R.; Skelton,
B. W.; White, A. H. Organometallics 1995, 14, 3970. (b) Whittall, I.
R.; Humphrey, M. G.; Persoons, A.; Houbrechts, S. Organometallics
1996, 15, 1935.
(9) (a) Lin, J . T.; Sun, S. S.; Wu, J . J .; Lee, L. S.; Lin, K. J .; Huang,
Y. F. Inorg. Chem. 1995, 34, 2323. (b) Lin, J . T.; Sun, S. S.; Wu, J . J .;
Liaw, Y. C.; Lin, K. J . J . Organomet. Chem. 1996, 517, 217.
(10) (a) Kanis, D. R.; Lacroix, P. G.; Ratner, M. A.; Marks, T. J . J .
Am. Chem. Soc. 1994, 116, 10089. (b) Bourgault, M.; Mountassir, C.;
Le Bozec, H.; Ledoux, I.; Pucetti, G.; Zyss, J . J . Chem. Soc., Chem.
Commun. 1993, 1623.
(11) King, R. B., Ed. Organometallic Synthesis, Transition-Metal
Compounds; Academic: New York, 1965; Vol. 1.
(12) Bruce, M. I.; Hameister, C.; Swincer, A. G.; Wallis, R. C. Inorg.
Synth. 1990, 28, 270.
(13) Sato, M.; Sekino, M. J . Organomet. Chem. 1993, 444, 185.
(14) (a) Kolodziej, R. M.; Lees, A. J . Organometallics 1986, 5, 450.
(b) Bancroft, R. T.; Arndt, L. W.; Delord, T.; Darensbourg, M. Y. J .
Am. Chem. Soc. 1986, 108, 2617.
X Abstract published in Advance ACS Abstracts, April 15, 1997.
(1) (a) Beck, W.; Niemer, B.; Wieser, M. Angew. Chem., Int. Ed. Engl.
1993, 32, 923. (b) Hegedus, L. S. In Organometallics in Synthesis;
Schlosser, M., Ed.; Wiley: New York, 1994; p 383.
(2) (a) Myers, L. K.; Langhoff, C.; Thompson, M. E. J . Am. Chem.
Soc. 1992, 114, 7560. (b) Kaharu, T.; Matsubara, H.; Takahashi, S. J .
Mater. Chem. 1992, 2, 43. (c) Hagihara, M.; Sonogashira, K.; Taka-
hashi, S. Adv. Polym. Sci. 1981, 41, 149.
(3) Green, M. L. H.; Marder, S. R.; Thompson, M. E.; Bandy, J . A.;
Bloor, D.; Kolinsky, P. V.; J ones, K. J . Nature (London) 1987, 330, 360.
(4) (a) Long, N. J . Angew. Chem.. Int. Ed. Engl. 1995, 34, 21. (b)
Kanis, D. R.; Ratner, M. A.; Marks, T. J . J . Am. Chem. Soc. 1992, 114,
10338.
(5) Calabrese, J . C.; Cheng, L. T.; Green, J . C.; Marder, S. R.; Tam,
W. J . Am. Chem. Soc. 1992, 113, 7227.
(6) Davies, S. G.; McNally, J . P.; Smallridge, A. J . In Advances in
Organometallic Chemistry; West, R., Stone, F. G. A., Eds.; Academic:
New York, 1990; Vol. 30, p 30.
(7) Laidlaw, W. M.; Denning, R. G.; Verbiest, T.; Chauchard, E.;
Persoons, A. Nature (London) 1993, 363, 58.
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S0276-7333(96)01065-5 CCC: $14.00 © 1997 American Chemical Society

Ruthenium σ-Pyridylacetylides
Organometallics, Vol. 16, No. 10, 1997 2039
Cl2. The mixture was stirred at room temperature for 20 h.
The solution was then pumped dry and the residue recrystal-
lized from CH2Cl2/hexane to provide brownish 1 in 63% yield
(1.64 g). Anal. Calcd for C48H40F6NP3Ru: C, 61.02; H, 4.27;
N, 1.49. Found: C, 61.14; H, 4.08; N, 1.32.
[Ru (CtCC5H4NH)(η2-d p p f)(η5-C5H5)][P F 6] (2). Complex
2 was synthesized by the same procedure employed for 1,
except that RuCl(η2-dppf)(η5-C5H5) was used instead of RuCl-
(PPh3)2(η5-C5H5). The brownish complex 2 was isolated in 87%
yield. Anal. Calcd for C46H38F6NP3FeRu: C, 57.04; H, 3.93;
N, 1.45. Found: C, 57.20; H, 4.27; N, 1.40.
The solution was stirred for 1 h at room temperature and the
solvent removed under vacuum. The residue was chromato-
graphed under nitrogen. Elution by CH2Cl2/hexane (1:10)
provided a yellow band from which a powdery 7 was isolated
in 52% yield (437 mg). Anal. Calcd for C48H39NP2Ru: C,
72.72; H, 4.96; N, 1.77. Found: C, 72.55; H, 5.20; N, 1.69.
Ru (CtCC5H4N)(η2-d p p f)(η5-C5H5) (8). Complex 8 was
synthesized by the same procedure as for the synthesis of 7,
except that 2 was used instead of 1. The orange-red 8 was
isolated in 65% yield. Anal. Calcd for C46H37NP2FeRu: C,
67.16; H, 4.53; N, 1.70. Found: C, 66.88; H, 4.71; N, 1.55.
Ru (CtCC6H4CHdCHC5H4N)(P P h 3)2(η5-C5H5) (9). An
orange-yellow precipitate rapidly formed upon addition of a
MeOH solution of NaOMe (0.10 M, 15 mL) to a solution of 6
(1.04 g, 1.00 mmol) in MeOH (60 mL) over a period of 10 min.
The solution was stirred for a further 15 min, and 300 mL of
H2O was added to cause a complete precipitation of the
product. The precipitate was collected on a fritted-glass filter,
and then washed five times with 30 mL of H2O. The crude
product was recrystallized from CH2Cl2/hexane to afford
orange-yellow crystalline 9 in 89% yield (800 mg). Anal. Calcd
for C56H45NP2Ru: C, 75.15; H, 5.07; N, 1.57. Found: C, 74.66;
H, 5.31; N, 1.61.
(E)-1-(4-Br om oph en yl)-2-(4-pyr idyl)eth ylen e (3). A pres-
sure tube was charged with 1-bromo-4-iodobenzene (5.66 g,
20.0 mmol), Pd(OAc)2 (45 mg, 0.20 mmol), NEt3 (6 mL), CH3-
CN (4 mL), and 4-vinylpyridine (2.39 mL, 22.0 mmol) under a
nitrogen atmosphere. The mixture was heated to 100-110
°C for 36 h; when it was cooled to room temperature, aggrega-
tion occurred to form a solid. It was then extracted with a
mixture of CH2Cl2/H2O. The organic layer was collected, dried
over MgSO4, passed through a neutral alumina column (2 cm
in length), and dried. The crude product was recrystallized
from CH2Cl2/hexane to afford 3 as a white powder (4.67 g,
90%); mp 157.0-157.5 °C. 1H NMR (CDCl3): δ 8.56 (d, 2 H,
J H-H ) 6.1 Hz, NCH), 7.49 (d, 2 H, J H-H ) 8.4 Hz, C6H4), 7.38
(4-Br om op h en yl)(4-p yr id yl)a cetylen e (10). A flask was
charged with 4-ethynylpyridine (1.03 g, 10.0 mmol), 1-bromo-
4-iodobenzene (2.83 g, 10.0 mmol), PdCl2(PPh3)2 (70 mg, 0.12
mmol), CuI (23 mg, 0.12 mmol), and 40 mL of Et2NH was
added to it. The mixture was then stirred at room temperature
for 16 h. The solvent was removed under vacuum, and the
yellow residue was extracted with CH2Cl2/H2O. The organic
layer was collected, dried over MgSO4, passed through a
neutral alumina column (2 cm in length), and dried. The crude
product was further washed with hexane (2 × 10 mL) to give
10 as a pale yellow powder (2.28 g, 88%); mp 142.5-143.0 °C.
1H NMR (CDCl3): δ 8.58 (d, 2 H, J H-H ) 6.1 Hz, NCH), 7.49
(d, 2 H, J H-H ) 8.6 Hz, C6H4), 7.39 (d, 2 H, C6H4), 7.35 (d, 2 H,
NCHCH). Anal. Calcd for C13H8BrN: C, 60.49; H, 3.12; N,
5.43. Found: C, 60.58; H, 3.27; N, 5.36.
(d, 2 H, C6H4), 7.33 (d, 2 H, NCHCH), 7.20 (d, 2 H, J H-H
)
16.4 Hz, dCH), 6.98 (d, 2 H, dCH). Anal. Calcd for C13H10
-
BrN: C, 60.02; H, 3.88; N, 5.38. Found: C, 60.02; H, 4.09; N,
5.38.
4-[4-(2-(4-P yr idyl-(E)-eth en yl)ph en yl]-2-m eth yl-3-bu tyn -
2-ol (4). To a flask containing a mixture of 3 (5.20 g, 20.0
mmol), PdCl2(PPh3)2 (140 mg, 0.24 mmol), CuI (46 mg, 0.24
mmol), and Et2NH (70 mL) was added 2-methyl-3-butyn-2-ol
(2.30 mL, 24.0 mmol). The resulting mixture was refluxed for
20 h to afford an orange-yellow slurry. The slurry was pumped
dry, and the residue was extracted with CH2Cl2/H2O. The
organic layer was collected, dried over MgSO4, passed through
a neutral alumina column (2 cm in length), and dried. The
crude product was washed with hexane (2 × 10 mL) to afford
4 as a white powder (4.00 g, 76%). 1H NMR (CDCl3): δ 8.58
(br, 2 H, NCH), 7.46 (d, 2 H, J H-H ) 8.3 Hz, C6H4), 7.42 (d, 2
H, C6H4), 7.35 (d, 2 H, J H-H ) 6.1 Hz, NCHCH), 7.25 (d, 2 H,
J H-H ) 16.3 Hz, dCH), 7.01 (d, 2 H, dCH), 1.61 (s, 6 H, CH3).
The compound was not purified and was adequate for further
reaction.
(E)-1-(4-Eth yn ylp h en yl)-2-(4-p yr id yl)eth ylen e (5). Ap-
proximately 50 mL of benzene was added to a flask containing
4 (2.50 g, 9.5 mmol) and powdery KOH (0.50 g, 8.9 mmol).
The mixture was stirred for 16 h, cooled, filtered through
Celite, and dried. Recrystallization of the crude product from
CH2Cl2/hexane provides white powdery 5 in 79% yield (1.55
g). mp 205.0-205.5 °C. MS (EI): m/ e 205 (M+). Anal. Calcd
for C15H11N: C, 87.77; H, 5.40; N, 6.82. Found: C, 87.57; H,
5.50; N, 6.73.
[4-(Tr im eth ylsilyl)eth yn yl](4-p yr id yl)a cetylen e (11).
(Trimethylsilyl)acetylene (1.42 mL, 10.0 mmol) was added to
a flask containing 10 (2.06 g, 8.0 mmol), PdCl2(PPh3)2 (120
mg, 0.20 mmol), CuI (19 mg, 0.10 mmol), and Et2NH (40 mL).
The resulting mixture was heated to 40 °C for 16 h. The
solvent was removed under vacuum, and the residue was
extracted with CH2Cl2/H2O. The organic layer was collected,
dried over MgSO4, passed through a neutral alumina column
(2 cm in length), and dried. The crude product was further
washed with hexane (2 × 10 mL) to give 11 as a white powder
(1.72 g, 78%). 1H NMR (CDCl3): δ 8.56 (d, 2 H, J H-H ) 6.0
Hz, NCH), 7.43 (s, 4 H, C6H4), 7.33 (d, 2 H, NCHCH), 0.23 (s,
9 H, CH3). The compound was not purified and was adequate
for further reaction.
[R u (CtCC6H 4CH dCH C5H 4NH )(P P h 3)2(η5-C5H 5)][P F 6]
(6a ) a n d [R u (dCdC(H )C6H 4CH dCH C5H 4N)(P P h 3)2(η5-
C5H5)][P F 6] (6b). To a mixture of RuCl(PPh3)2(η5-C5H5) (1.45
g, 2.00 mmol), NH4+PF6- (360 mg, 2.20 mmol), and 5 (490 mg,
2.40 mmol) was added 50 mL of CH2Cl2 and 10 mL of MeOH.
The resulting mixture was stirred at room temperature for
16 h. The solvent was removed under vacuum, and the residue
was extracted with CH2Cl2 (30 mL). The CH2Cl2 solution was
filtered through Celite and the filtrate added dropwise to a
rapidly stirred mixture of Et2O (200 mL) and hexane (200 mL).
The solution was filtered, and the filtrate was pumped dry.
The yellow residue was dissolved in 25 mL of CH2Cl2/hexane
(1:10) and refrigerated for 2 days to provide an orange-yellow
crystalline material which contains 6a and 6b (1.67 g, 80%).
Anal. Calcd for C56H46F6NP3Ru: C, 64.61; H, 4.45; N, 1.35.
Found: C, 64.08; H, 4.65; N, 1.30. Complex 9 (vide infra) was
also isolated from the Et2O washings in 17% yield (310 mg).
Ru (CtCC5H4N)(P P h 3)2(η5-C5H5) (7). To a THF solution
(50 mL) of 1 (1.00 g, 1.06 mmol) was added dropwise 1,8-
diazabicyclo[5.4.0]undec-7-ene (DBU; 1.91 mL, 1.28 mmol).
(4-Eth yn ylp h en yl)(4-p yr id yl)a cetylen e (12). Powdery
KOH (168 mg, 3.0 mmol) was added to a solution of 11 (826
mg, 3.0 mmol) in 40 mL of MeOH, and the resulting solution
was stirred at room temperature for 2 h. The solvent was
removed under vacuum, and the residue was extracted with
CH2Cl2/H2O. The organic layer was collected, dried over
MgSO4, filtered, and dried. The yellow-brown powder was
chromatographed using CH2Cl2/hexane (1:1) as eluent to afford
12 as a white powder in 92% yield (560 mg); mp 179.5-180.0
°C. MS (EI): m/ e 203 (M+). Anal. Calcd for C15H9N: C,
88.64; H, 4.46; N, 6.89. Found: C, 88.66; H, 4.54; N, 6.71.
[Ru (CtCC6H4CtCC5H4NH)(P P h 3)2(η5-C5H5)][P F6] (13a )
a n d [Ru (dCdC(H)C6H4CtCC5H4N)(P P h 3)2(η5-C5H5)][P F 6]
(13b). A mixture of complexes 13a and 13b was synthesized
in a manner similar to that employed for 9, except that 12
was used instead of 6. The dark brown complex 13 was
isolated in 70% yield. Complex 14 (vide infra) was also isolated
in 23% yield from the Et2O washings. MS (FAB): m/ e 896
(M+ - PF6). Anal. Calcd for C56H44F6NP3Ru: C, 64.37; H,
4.24; N, 1.34. Found: C, 64.18; H, 4.71; N, 1.25.

2040 Organometallics, Vol. 16, No. 10, 1997
Wu et al.
Ru (CtCC6H4CtCC5H4N)(P P h 3)2(η5-C5H5) (14). Com-
plex 14 was synthesized by the same procedure employed for
9, except that 13 was used instead of 6. The yellow complex
14 was isolated in 92% yield (820 mg). MS (FAB): m/ e 895
(M+). Anal. Calcd for C56H43NP2Ru: C, 75.32; H, 4.85; N, 1.57.
Found: C, 74.76; H, 5.20; N, 1.58.
Ru (CtCC5H4N{W(CO)4L})(P P h 3)2(η5-C5H5) (15, L ) CO;
16, L ) P P h 3; 17, L ) P Me3). Essentially the same
procedures were applied to synthesize 15-17; consequently,
only the preparation of 17 is described in detail. A THF
solution of W(CO)4(PMe3)(THF)14 prepared in situ from W(CO)5-
(PMe3) (600 mg, 1.51 mmol) was reduced in volume and
transferred to a flask containing 7 (1.00 g, 1.26 mmol). The
solution was stirred at room temperature for 20 h and
the solvent removed under vacuum. The residue was chro-
matographed in nitrogen. Elution by CH2Cl2/hexane (1:5)
caused a yellow band to appear from which yellow powdery
17 was isolated in 41% yield (602 mg). Anal. Calcd for
in CH2Cl2 (15 mL), and 5 mL of NEt3 was added. The mixture
was stirred for 3 h, and the solvent was removed under
vacuum. The residue was then recrystallized from CH2Cl2/
hexane. The crude product was further washed with Et2O and
hexane to afford yellow powdery 25 in 59% yield (40 mg).
Anal. Calcd for C61H47F6N3O3P3ReRu: C, 53.47; H, 3.46; N,
3.07. Found: C, 53.22; H, 3.30; N, 2.95.
[R u (CtCC5H 4NMe)(P P h 3)2(η5-C5H 5)][P F 6] (26), [R u -
(CtCC6H4CHdCHC5H4NMe)(P P h 3)2(η5-C5H5)][P F 6] (27),
a n d [Ru (CtCC6H4CtCC5H4NMe)(P P h 3)2(η5-C5H5)][P F 6]
(28). Complexes 26-28 were prepared similarly, except that
7, 9, and 14, were used, respectively. Only the preparation of
27 will be described in detail. Methyl iodide (94 µL, 1.50
mmol) was added to a solution of 9 (447 mg, 0.50 mmol) in
THF (50 mL). After being stirred at room temperature in
the dark for 5 h, the solution was filtered through Celite (2
cm in length) and the filtrate was pumped dry. To the
resulting residue was added Tl+PF6- (192 mg, 0.55 mmol) and
50 mL of THF. The solution was then stirred for 1.5 h, and
the solvent was removed under vacuum. The crude product
was extracted with CH2Cl2 (2 × 20 mL), and the extract was
filtered through Celite (2 cm in length). The volume of the
solution was reduced to 8 mL, and 20 mL of hexane was added.
Purple microcrystals formed after 30 min. These were col-
lected by filtration and washed with hexane to provide
analytically pure 27 in 72% yield (380 mg). Anal. Calcd for
C
55H48NO4P3RuW: C, 56.71; H, 4.15; N, 1.20. Found: C,
56.41; H, 4.38; N, 1.04.
The yellow complex 15 was isolated with a yield of 36%.
Anal. Calcd for C53H39NO5P2RuW: C, 57.00; H, 3.52; N, 1.25.
Found: C, 56.65; H, 3.38; N, 1.12.
The yellow complex 16 was isolated with a yield of 32%.
Anal. Calcd for C70H54NO4P3RuW: C, 62.23; H, 4.03; N, 1.04.
Found: C, 62.06; H, 4.09; N, 0.86.
Ru (CtCC5H4N{W(CO)4L})(η2-d p p f)(η5-C5H5) (18, L )
CO; 19, L ) P P h 3; 20, L ) P Me3). Complexes 18-20 were
synthesized in a manner similar to that employed for 15-17,
except that RuCl(η2-dppf)(η5-C5H5) was used instead of RuCl-
(PPh3)2(η5-C5H5). The yellow complex 18 was isolated in 39%
yield. Anal. Calcd for C51H37NO5P2FeRuW: C, 53.42; H, 3.25;
N, 1.22. Found: C, 53.09; H, 3.21; N, 1.27.
The yellow complex 19 was isolated with a yield of 41%.
Anal. Calcd for C68H52NO4P3FeRuW: C, 59.15; H, 3.80; N,
1.01. Found: C, 58.83; H, 4.00; N, 0.93.
C
57H48F6NP3Ru: C, 64.53; H, 4.56; N, 1.32. Found: C, 64.18;
H, 4.32; N, 1.22.
The orange complex 26 was isolated with a yield of 76%.
Anal. Calcd for C49H42F6NP3Ru: C, 61.38; H, 4.42; N, 1.46.
Found: C, 61.01; H, 4.25; N, 1.38.
Violet complex 28 was isolated with a yield of 75%. MS
(FAB): m/ e 910 (M+ - PF6). Anal. Calcd for C57H46F6NP3-
Ru: C, 64.65; H, 4.38; N, 1.32. Found: C, 64.30; H, 4.25; N,
1.24.
Ru (CtCsth )(P P h 3)2(η5-C5H5) (29; th ) 5-Nitr o-2-th ie-
n yl). A solution of 5-nitro-2-thienylacetylene17 in 20 mL of
MeOH was added to a solution of RuCl(PPh3)2(η5-C5H5) (725
mg, 1.00 mmol) and NH4+PF6- (228 mg, 1.10 mmol) in 30 mL
of CH2Cl2. The mixture was stirred at room temperature for
20 h. The solution was then pumped dry and the residue
recrystallized from CH2Cl2/hexane to provide a brownish
powder. The brownish powder was dissolved in 15 mL of
MeOH, and a MeOH solution of NaOMe (0.10 M, 15 mL) was
added. The solution was stirred for 15 min, and 100 mL of
H2O was added. The precipitate formed was collected, washed
with H2O, and dried. The crude product was chromatographed
using CH2Cl2/hexane (1:1) as eluent to afford 29 as a purple
powder in 37% yield (300 mg). Anal. Calcd for C47H37NO2P2-
Ru: C, 69.62; H, 4.60; N, 1.73. Found: C, 69.39; H, 4.48; N,
1.64.
Cr ysta llogr a p h ic Stu d ies. Crystals of 19 were grown by
slow diffusion of hexane into a concentrated solution of complex
19 in CH2Cl2. Crystals were mounted on a glass fiber covered
with epoxy. Diffraction measurements were made on an
Enraf-Nonius CAD4 diffractometer by using graphite-mono-
chromated Mo KR radiation (λ ) 0.7107 Å) with the θ-2θ scan
mode. Unit cells were determined by centering 25 reflections
in the suitable 2θ range. Other relevant experimental details
are listed in Table 1. The structure was solved by direct
methods using NRCVAX18 and refined by full-matrix least
squares (based on F2) using SHELXL-93.19 All non-hydrogen
atoms were refined with anisotropic displacement parameters,
and all hydrogen atoms were placed in idealized positions. The
selected interatomic distances and bond angles are given in
Table 2. All other crystal data for 19 are given in the
Supporting Information.
The yellow complex 20 was isolated with a yield of 35%.
Anal. Calcd for C53H46NO4P3FeRuW: C, 53.29; H, 3.88; N,
1.17. Found: C, 52.92; H, 3.68; N, 1.06.
Ru (CtCC5H4N{W(CO)3(d p p e)})(P P h 3)2(η5-C5H5) (21). A
THF solution (50 mL) of W(CO)3(dppe)(acetone) (360 mg, 0.50
mmol) was added slowly to a solution of 7 (400 mg, 0.50 mmol)
in THF (50 mL). The solution was stirred at room temperature
for 2 h and filtered through Celite. After removal of the
solvent, the residue was dissolved in CH2Cl2/hexane (1:5); this
solution was stored at 0 °C for 2 days. The yellow precipitate
formed was collected on a fritted-glass filter, washed two times
with 10 mL of hexane, and pumped dry to provide 21 in 81%
yield (590 mg). Anal. Calcd for C77H63NO3P4RuW: C, 63.38;
H, 4.35; N, 0.96. Found: C, 62.07; H, 4.41; N, 0.84.
Ru (CtCC6H4CHdCHC5H4N{W(CO)3(d p p e)})(P P h 3)2(η5-
C5H5) (22). Complex 22 was synthesized by the same proce-
dures as for the synthesis of 21, except that 9 was used instead
of 7. Yellow powdery 22 was isolated in 80% yield. Anal.
Calcd for
C85H69NO3P4RuW: C, 65.39; H, 4.45; N, 0.90.
Found: C, 65.19; H, 4.61; N, 0.86.
[Re(NC5H4CtCH)(2,2′-bp y)(CO)3][P F6] (23). Freshly dis-
tilled THF (150 mL) was transferred to a flask containing a
mixture of [(MeCN)Re(2,2′-bpy)(CO)3][PF6] (835 mg, 1.38
mmol) and 4-ethynylpyridine (150 mg, 1.46 mmol). The
mixture was refluxed in the dark for 5 h. The solvent was
then removed under vacuum and the residue obtained was
washed several times with Et2O to give yellow powdery 23 in
73% yield (680 mg). Anal. Calcd for C20H13F6N3O3PRe: C,
35.30; H, 1.93; N, 6.18. Found: C, 35.05; H, 1.92; N, 6.09.
[R u (dCdC(H )C5H 4N{R e (CO)3(2,2′-b p y)})(P P h 3)2(η5-
C5H5)][P F 6]2 (24). The synthesis of 24 is analogous to the
synthesis of 1, except that 23 was used instead of 4-ethynylpy-
ridine. Orange powdery 24 was isolated in 60% yield. Anal.
Calcd for C61H48F12N3O3P4ReRu: C, 48.13; H, 3.18; N, 2.76.
Found: C, 47.90; H, 2.92; N, 2.75.
(17) Vech, D.; Kovac, J .; Dandarova, M. Tetrahedron Lett. 1980, 21,
969.
(18) Gabe, E. J .; LePage, Y.; Charland, J . P.; Lee, F. L.; White, P.
S. J . Appl. Crystallogr. 1989, 22, 384.
(19) Sheldrick, G. M. SHELXL-93, Program for Crystal Structure
Refinement; University of Gottingen, Gottingen, Germany, 1993.
[R u (CtCC5H 4N{R e(CO)3(2,2′-b p y)})(P P h 3)2(η5-C5H 5)]-
[P F 6] (25). Complex 24 (75 mg, 0.050 mmol) was dissolved

Ruthenium σ-Pyridylacetylides
Organometallics, Vol. 16, No. 10, 1997 2041
Ta ble 1. Cr ysta l Da ta for Com p ou n d 19
Ta ble 2. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for Com p lex 19
chem formula
fw
cryst size, mm
cryst system
space group
a, Å
C68H52NO4P3FeRuW
1380.79
Distances
0.24 × 0.16 × 0.14
Ru-C1
Ru-C2
Ru-C3
Ru-C4
Ru-C5
Ru-C6
Ru-P2
Ru-P3
W-C13
W-C14
W-C15
W-C16
W-N
2.24(1)
2.26(1)
2.25(1)
2.26(1)
2.24(1)
1.99(1)
2.297(3)
2.284(3)
1.96(1)
1.98(1)
2.03(1)
2.02(1)
2.263(8)
2.548(3)
2.02(1)
2.02(1)
2.03(1)
2.05(1)
Fe-C21
Fe-C22
Fe-C23
Fe-C24
Fe-C25
Fe-C26
C6-C7
2.03(1)
2.04(1)
2.01(1)
2.02(1)
2.05(1)
2.05(1)
1.21(1)
1.42(2)
1.43(2)
1.37(2)
1.34(1)
1.35(1)
1.39(2)
1.40(2)
1.17(1)
1.14(1)
1.14(2)
1.13(2)
triclinic
P1h
14.270(2)
b, Å
16.106(2)
c, Å
16.147(2)
R, deg
103.19(3)
â, deg
106.65(3)
C7-C8
γ, deg
108.32(3)
C8-C9
V, Å3
3162(1)
2
C9-C10
C10-N
Z
T, °C
+20
N-C11
F(000)
λ(Mo KR), Å
1376
C11-C12
C8-C12
C13-O13
C14-O14
C15-O15
C16-O16
0.7107
1.450
24.0
W-P1
F
calcd, g cm-3
Fe-C17
Fe-C18
Fe-C19
Fe-C20
µ, cm-1
transmissn coeff
2θmax, deg
1.00-0.87
45
-15 to +14, 0-17, -17 to +16
hkl range
Angles
total no. of rflns
no. of unique rflns
no. of obsd rflns (I > 2.0σ(I))
no. of refined params
Ra
8934
8258
5764
712
0.046
0.14
1.04
N-W-C13
N-W-C14
N-W-C15
N-W-C16
N-W-P1
C13-W-C14
C13-W-C15
C13-W-C16
C13-W-P1
C14-W-C15
C14-W-C16
C14-W-P1
175.7(4)
90.6(4)
89.4(4)
95.1(4)
88.1(2)
89.0(4)
86.2(5)
89.2(5)
92.8(3)
88.9(6)
86.8(6)
172.9(5)
C15-W-C16
C15-W-P1
C16-W-P1
P2-Ru-P3
C6-Ru-P2
C6-Ru-P3
Ru-C6-C7
C6-C7-C8
C7-C8-C9
C7-C8-C12
W-N-C10
W-N-C11
173.8(5)
98.0(4)
86.3(4)
97.7(1)
85.8(3)
89.8(3)
175.9(9)
180(1)
Rw(F2)b
GOF(F2)c
a
b
2
R ) ∑||Fo| - |Fc||/∑|Fo|. w ) 1/[σ2(Fo + (0.1025P)2, where P
) (Max(Fo2, 0) + 2Fc2)/3. c GOF ) [∑w(Fo2 - Fc2)2/(n - p)]1/2, where
n ) number of observed reflections and p ) number of variables.
122(1)
123.0(9)
123.0(6)
121.9(7)
Resu lts a n d Discu ssion
Syn th esis a n d Ch a r a cter iza tion of Ru th en iu m
Com p lexes w ith a P en d a n t P yr id in e. Two new
conjugated terminal alkynes with a pendant pyridine,
5 and 12, can be synthesized in good yield via Sono-
gashira coupling20 or Heck type coupling21 catalyzed by
PdCl2(PPh3)2 or Pd(OAc)2, as depicted in Scheme 1.
Metal vinylidene complexes are ubiquitous in the reac-
tions of terminal alkynes with coordinatively unsatur-
ated metal complexes.22 Due to the intrinsic basicity
of the pyridine, reactions of 4-ethynylpyridine, 5, and
12 with Ru(η5-C5H5)(PPh3)2Cl appear to be somewhat
different from those of regular terminal alkynes (Scheme
2). From the reaction of 4-ethynylpyridine, ruthenium
σ-acetylide species with a pendant pyridinium, [Ru-
vinylidene (isomer b) and the pyridinium (isomer a )
species are also in equilibrium, and the ratio of 13a +
and 13b+ is 1/6. The relative proportion of the vi-
nylidene isomer vs the pyridinium isomer has to be
related to the acidity of the â-H, and the basicity of the
pendant pyridine, in the corresponding vinylidene in-
termediates. The phosphine ligands at ruthenium likely
act only as spectators in these reactions, at least in case
of the reactions of 4-ethynylpyridine.
Formation of a vinylidene complex can be induced if
the nitrogen atom of 4-ethynylpyridine and 5 is proto-
nated, methylated, or ligated to a metal fragment
(Scheme 3). Although it proved difficult to isolate
analytically pure dicationic vinylidene species 30-33,
these species were fully characterized by spectroscopic
data.23 All of these and the aforementioned vinylidenes
exhibit characteristic chemical shifts and a small cou-
1
(CtCC5H4NH)L2(η5-C5H5)]+ (1+, L ) PPh3; 2+, L ) /2
dppf), were obtained instead of [Ru(dCdC(H)C5H4N)-
L2(η5-C5H5)]+. If 5 is used instead of 4-ethynylpyridine,
the product is isolated as a mixture of [Ru(CtCC6H4-
CHdC(H)C5H4NH)(PPh3)2(η5-C5H5)]+ (6a +) and [Ru-
(dCdC(H)C6H4CHdC(H)C5H4N)(PPh3)2(η5-C5H5)]+ (6b+).
A similar reaction of 12 provides a mixture of Ru-
(dCdC(H)C6H4CtCC5H4N)(PPh3)2(η5-C5H5)+ (13b+) and
Ru(CtCC6H4CtCC5H4NH)(PPh3)2(η5-C5H5)+ (13a +). In
these reactions, it is likely that a vinylidene complex
formed as the primary product, which is then converted
(23) Selected spectral data for the dicationic derivatives are listed
below. 30: 1H NMR (acetone-d6) δ 8.50 (d, 2 H, J ) 6.6 Hz, NCH),
7.60 (d, 2 H, NCHCH), 7.55-7.18 (m, 30 H, Ph), 6.30 (t, J H-P ) 1.8,
RudCdCH), 5.80 (s, 5 H, C5H5); 13C{1H} NMR (acetone-d6) δ 348.01
(t, J C-P ) 14.2 Hz, RudC), 157.78 (s, NCHCHC), 141.25 (s, NCH),
134.35 (t, J C-P ) 5.1, PCCH), 134.06 (m, PC), 132.32 (s, PCCHCHC),
129.87 (t, J C-P ) 4.2, PCCHCH), 123.03 (s, NCHCH), 117.92 (s,
RudCdC), 97.55 (s, C5H5); 31P{1H} NMR (acetone-d6) δ 37.3 (s, RuP);
λmax 372 nm-1 (CH2Cl2). 31: 1H NMR (acetone-d6) δ 8.89 (d, 2 H, J )
6.7 Hz, NCH), 8.30 (d, 2 H, NCHCH), 8.01 (d, 1 H, J ) 16.4, CHd),
7.70 (d, 2 H, J ) 5.3, C6H4), 7.51-7.17 (m, 33 H, PPh3 and C6H4 and
CHd), 5.80 (t, J H-P ) 2.4, RudCdCH), 5.62 (s, 5 H, C5H5); 31P{1H}
NMR (acetone-d6) δ 40.9 (s, RuP); λmax 420 nm-1 (CH2Cl2). 32: 1H NMR
(acetone-d6) δ 8.47 (d, 2 H, J ) 6.5 Hz, NCH), 7.54-7.17 (m, 30 H, Ph
and NCHCH), 6.24 (t, J H-P ) 2.0, RudCdCH), 5.79 (s, 5 H, C5H5),
4.32 (s, 3 H, NCH3); 31P{1H} NMR (acetone-d6) δ 37.7 (s, RuP); λmax
375 nm-1 (CH2Cl2). 33: 1H NMR (acetone-d6) δ 8.85 (d, 2 H, J ) 6.8
Hz, NCH), 8.23 (d, 2 H, NCHCH), 7.96 (d, 1 H, J ) 16.3, CHdCH),
7.66 (2 H, J ) 8.3, C6H4), 7.51-7.16 (m, 30 H, Ph), 7.45 (d, 1 H, J )
16.3, CHdCH), 7.29 (2 H, J ) 8.3, C6H4), 5.79 (t, J H-P ) 2.4,
RudCdCH), 5.63 (s, 5 H, C5H5), 4.48 (s, 3 H, NCH3); 13C{1H} NMR
(acetone-d6) δ 355.69 (t, J C-P ) 14.7, RudC), 154.44 (s, NCHCHC),
145.91 (s, NCH), 141.59 (s, C6H4CHdCH), 134.47 (m, PC), 134.40,
129.74, 128.46, 120.19 (s, C6H4CHdCH), 134.28 (t, J C-P ) 4.5, PCCH),
131.97 (s, PCCHCHC), 129.62 (t, J C-P ) 4.5, PCCHCH), 128.41 (s,
C6H4CHdCH), 124.66 (s, NCHCH), 123.13 (s, RudCdC), 96.49 (s,
C5H5), 47.97 (s, NCH3); 31P{1H} NMR (acetone-d6) δ 40.9 (s, RuP); λmax
434 nm-1 (CH2Cl2).
1
to a pyridinium species. The variable-temperature H
and 31P{1H} NMR spectra (Figures 1 and 2) confirm the
presence of a rapid exchange between the two isomers
of 6+, the pyridinium (6a ) and the vinylidene (6b)
species. The limiting spectra were reached when the
temperature was lowered to 243 K, at which point 6a +
and 6b+ exist in a ratio of 8.5/10. For 13+, the
(20) Sonogashira, K. In Comprehensive Organic Synthesis; Trost,
B. M., Fleming, I., Eds.; Pergamon: Oxford, U.K., 1991; Vol. 3, pp 521-
548.
(21) (a) Cabri, W.; Candiani, I. Acc. Chem. Res. 1995, 28, 2. (b) Heck,
R. F. Palladium Reagents in Organic Syntheses; Academic Press: New
York, 1985.
(22) (a) Bruce, M. I. Chem. Rev. 1991, 91, 270. (b) Bruce, M. I.;
Swincer, A. G. Adv. Organomet. Chem. 1983, 22, 59.

2042 Organometallics, Vol. 16, No. 10, 1997
Wu et al.
Sch em e 1
Sch em e 2
1
pling to two equivalent phosphorus atoms (6b, δ 5.75,
J ) 2.4 Hz; 13b, δ 5.82, J ) 2.5 Hz; 30, δ 6.30, J ) 1.8
Hz; 31, δ 5.80, J ) 2.4 Hz; 32, δ 6.24, J ) 2.0 Hz; 33, δ
5.79, J ) 2.4 Hz; 24, δ 5.90, J ) 2.1 Hz) for â-H. The
chemical shifts of R- and â-carbons of these complexes
L′ ) PPh3; 20, n ) 0, L ) /2 dppf, L′ ) PMe3) and
Ru(CtC(C6H4CHdCH)nC5H4N{W(CO)3(dppe)})(PPh3)2-
(η5-C5H5) (21, n ) 0; 22, n ) 1). An X-ray structural
analysis for complex 19 was carried out (vide infra).
Conversion of the pendant pyridine to pyridinium may
also be achieved by treating the complexes with methyl
iodide (Scheme 4).
in the 13C{1H} NMR spectra (30, CR δ 348.01, J C-P
)
14.2 Hz, Câ δ 117.92; 33, CR δ 355.69, J C-P ) 14.7 Hz,
Câ δ 123.13; 24, CR δ 350.08, J C-P 14.1 Hz, Câ δ 117.49)
are also consistent with literature values.22
The spectroscopic properties (Table 3) of the new
complexes in this study are consistent with their
formulations. The three moderate/strong carbonyl
stretching bands for 15 and 18 in the infrared spectra
are characteristic of a C4v arrangement of the carbonyl
ligands at the tungsten center, and the three moderate/
strong carbonyl stretching bands for 16, 17, 19, and 20
require that the phosphorus donor ligand and pyridine
be mutually cis at the tungsten center. The three
carbonyl stretching bands and the magnetic equivalency
of the phosphorus nuclei in dppe suggest that the three
carbonyl ligands in 21 and 22 are in a facial disposition.
A symmetrical bpy ligand and two intense carbonyl
stretching bands in 23-25 also imply a facial disposition
of the three carbonyl ligands at the rhenium center. In
Removal of the â-H atoms of the vinylidene com-
plexes, or the protons bonded to the pyridine, by
methoxide or DBU causes the formation of ruthenium
σ-acetylide complexes which contain a pendant pyridine.
As expected,24 the pyridine is capable of ligation to a
metal fragment and useful for construction of several
dinuclear metal complexes, Ru(CtCC5H4N{W(CO)4L′})-
(L)2(η5-C5H5) (15, n ) 0, L ) PPh3, L′ ) CO; 16, n ) 0,
L ) PPh3, L′ ) PPh3; 17, n ) 0, L ) PPh3, L′ ) PMe3;
18, n ) 0, L ) 1/2 dppf, L′ ) CO; 19, n ) 0, L ) 1/2 dppf,
(24) (a) Balzani, V.; J uris, A.; Venturi, M.; Campagna, S.; Serroni,
S. Chem. Rev. 1996, 96, 759. (b) Geoffroy, G. L., Wrighton, M. S., Eds.
Organometallic Photochemistry; Academia: New York, 1979.

Ruthenium σ-Pyridylacetylides
Organometallics, Vol. 16, No. 10, 1997 2043
1
F igu r e 1. Variable-temperature H NMR spectra of complex 6 in acetone-d6 at (a) 243, (b) 263, (c) 283, (d) 303, and (e)
333 K. Peaks marked with an asterisk are from Cp of 6a , and those marked with two asterisks are from H2O.
general, the carbonyl stretching frequencies decrease as
the π-accepting ability of phosphine ligands decreases
or the number of phosphine ligands increases. In 31P
NMR spectra, the signal for the phosphine ligand
coordinated to the tungsten atom is accompanied by a
(338 nm, in CH2Cl2) vs 15 (397 nm), 16 (400 nm), 17
(380 nm), 21 (357 nm), and 25 (402 nm), 8 (339 nm) vs
18 (396 nm), 19 (403 nm), and 20 (380 nm) and 9 (419
nm) vs 22 (462 nm). This observation is consistent with
the presence of a charge-transfer band from the electron-
donor ruthenium fragment to the electron-acceptor
metal carbonyl fragment.10 There is considerable su-
perposition of this band with the metal-to-pyridine π*
charge-transfer band of the tungsten carbonyl fragment,
however. In contrast, this charge-transfer band in 25
is free from the rhenium-to-pyridine π* charge-transfer
band, judging from comparison of the spectra between
23 and 25. The pyridinium moiety, being a good
electron acceptor,26 has been reported to induce a strong
low-lying charge-transfer band upon connecting to an
organometallic electron donor.27 The bathochromic shift
of λmax is even greater if the pendant pyridine is
converted to pyridinium: for example, 7 (338 nm, in
CH2Cl2) vs 1 (446 nm) and 26 (460 nm), 8 (339 nm) vs
1
pair of satellites with J P-W ) 228-240 Hz, in agree-
ment with literature values.25 The 13C{1H} NMR
spectra for vinylidene complexes have been discussed
earlier. The 13C{1H} NMR spectra for two of the
σ-acetylide complexes, 7 and 9, were also checked and
found to be normal (7, CR t, δ 132.82, J C-P ) 24.3 Hz,
Câ δ 113.65; 9, CR t, δ 123.37, J C-P ) 24.7 Hz, Câ
δ
115.56).22 Another unique feature of the σ-acetylide
complexes is the existence of a ν(CtC) stretching
(2025-2070 cm-1) in the infrared spectra.
Op tica l Absor p tion Sp ectr a . Table 4 illustrates
the optical absorption spectra of new organometallic
complexes in CH2Cl2 and/or CH3CN. Ligation of the
pendant pyridine in 7-9 to metal carbonyl fragments
results in a bathochromic shift of λmax: for instance, 7
(26) (a) Marder, S. R.; Perry, J . W.; Yakymyshyn, C. P. Chem. Mater.
1994, 6, 1137. (b) Marder, S. R.; Perry, J . W.; Tiemann, B. G.; Schaefer,
W. P. Organometallics 1991, 10, 1896.
(25) Pregosin, P. S.; Kunz, R. W. 31P and 13C NMR of Transition
Metal Phosphine Complexes; Springer-Verlag: New York, 1979.

2044 Organometallics, Vol. 16, No. 10, 1997
Wu et al.
upon changing from CH2Cl2 to CH3CN. The negative
solvatochromic behavior is larger for complexes with
extension of the conjugation length (26 vs 27 and 28).
Organometallic sesquifulvalene complexes with a cat-
ionic electron acceptor were also reported to have a
similar hypsochromic shift of λmax upon changing from
CH2Cl2 to a polar solvent (CH3CN or acetone).30 The
neutral complex Ru(CtCC6H4NO2-4)(PPh3)2(η5-C5H5)
was reported to have a bathochromic shift of λmax as the
solvent polarity increases (437 nm in cyclohexane; 476
nm in dimethylformamide). We observe a similar trend
for the neutral complex 29 (λmax 506 nm in benzene and
535 nm in dimethylformamide). It is interesting to note
that the charge-transfer band of complex 29 is signifi-
cantly longer than that of Ru(CtCC6H4NO2-4)(PPh3)2-
(η5-C5H5), which is in accordance with the fact that a
nitrothienyl moiety is a better electron acceptor than a
nitrophenyl moiety.31
Previously we mentioned that the dicationic vi-
nylidene complexes 30 and 31 could be synthesized by
the method described in Scheme 3. They may also be
prepared by double protonation of 7 and 9 with a strong
acid, HBF4 or CF3CO2H. The λmax values of 30 (372 nm
in CH2Cl2) and 31 (410 nm in CH2Cl2) are smaller than
those of 1 and 6a , suggesting a lesser degree of electron
delocalization in 30 and 31 than in 1 and 6a . Use of
optical absorption spectra in monitoring protonation/
deprotonation in some of the complexes proved to be
informative. For instance, gradual addition of NEt3 to
a CH2Cl2 solution of 30 first results in removal of a â-H
and formation of 1, which is then transformed to 4
(Figure 3). This result illustrates that the pyridyl
nitrogen is more basic than the â-carbon in 7 and pro-
vides a rationale for the absence of a vinylidene inter-
mediate in the formation of 1 (vide supra). Monitoring
the protonation of 9 indicated first the formation of 6a
and 6b; however, both 6a and 6b were then converted
to 31. Conversely, the deprotonation of 31 resulted in
sequential formation of 6a /6b and 9. Protonation of 14
and the deprotonation of the dication of 14 were followed
similarly, both via the intermediates 13a /13b, consis-
tent with the observation from the NMR spectra.
Electr och em istr y. The oxidation potentials (Table
5) for the metals Ru, Fe, W, and Re can be readily
assigned. In general, the ruthenium and iron complexes
have reversible oxidation waves (Ru(II)/Ru(III) and Fe-
(II)/Fe(III)). Similar to what has been reported for Cp2-
Fes[CtCsC6H4]nsSO2Me,32 and bimetallic sesquifu-
valene complexes,30b increase of the conjugation length
lowers the oxidation potential of the metal (7 vs 9 and
14 and 26 vs 27 and 28). Humphrey reported that Ru-
(CtCC6H4NO2-4)(PPh3)2(η5-C5H5) was oxidized at po-
tential 0.2 V higher than Ru(CtCC6H5)(PPh3)2(η5-
C5H5).8a We also found that ruthenium is oxidized at
higher potential upon increasing the acceptor strength
of the acetylide (7 vs 1 and 26; 9 vs 27; 14 vs 28). The
effect is decreased considerably in 27 and 28, and this
can be attributed to the longer distance between ruthe-
F igu r e 2. Variable-temperature 31P{1H} NMR spectra of
complex 6 in acetone-d6 at (a) 243, (b) 263, (c) 283, (d) 303,
and (e) 333 K. Peaks marked with an asterisk are from
6a .
2 (441 nm), 9 (419 nm) vs 27 (582 nm), and 14 (397 nm)
vs 28 (558 nm). This effect seems to be much larger
than that of analogous ruthenium σ-acetylide complexes
in which the nitrophenyl moiety is an electron acceptor.8b
It is well-known that elongation of the conjugation
length in a second-order nonlinear optical organic
chromophore results in a decrease in the energy of the
charge-transfer band.28 In our case, elongation of the
conjugation also causes a dramatic red shift of the
charge-transfer band, i.e., 26 (460 nm) vs 27 (582 nm)
and 28 (558 nm). The diminished red shift in 28
compared to that in 27 may be attributed to the
mismatch of a phenyl p orbital and an alkynyl p orbital
in energy.28b,29 Complexes with an end-capping pyri-
dinium (1, 2, 26-28) exhibit a hypsochromic shift of λmax
(29) Stiegman, A. E.; Graham, E.; Perry, K. J .; Khundkar, L. R.;
Cheng, L. T.; Perry, J . W. J . Am. Chem. Soc. 1991, 113, 7658.
(30) (a) Tamm, M.; Grzegorzewski, A.; Steiner, T.; J entzsch, T.;
Werncke, W. Organometallics 1996, 15, 4984. (b) Behrens, U.; Brus-
saard, H.; Hagenau, U.; Heck, J .; Hendrickx, E.; Kornich, J .; van der
Linden, J . G. M.; Persoons, A.; Spek, A. L.; Veldman, N.; Voss, B.;
Wong, H. Chem. Eur. J . 1996, 2, 98.
(27) (a) Alain, V.; Fort, A.; Marguerite, B.; Chen, C. T. Inorg. Chim.
Acta 1996, 242, 43. (b) Alain, V.; Blanchard-Desce, B.; Chen, C. T.;
Marder, S. R.; Fort, A.; Barzoukas, M. Synth. Met., in press. (c) Lin, J .
T.; Wu, J . J .; Li, C. S.; Wen, Y. S.; Lin, K. J . Organometallics 1996,
15, 5028.
(28) (a) Tiemann, B. G.; Cheng, L. T.; Marder, S. R. J . Chem. Soc.,
Chem. Commun. 1993, 735. (b) Cheng, L. T.; Tam, W.; Marder, S. R.;
Stiegman, A. E.; Rikken, G.; Spangler, C. W. J . Phys. Chem. 1991, 95,
10643.
(31) Rao, V. P.; Cai, Y. M.; J en, A. K. Y. J . Chem. Soc., Chem.
Commun. 1994, 1689.
(32) Hsung, R. P.; Chidsey, C. E. D.; Sita, L. R. Organometallics
1995, 14, 4808.

Ruthenium σ-Pyridylacetylides
Organometallics, Vol. 16, No. 10, 1997 2045
Sch em e 3
Sch em e 4
nium and pyridinium in 27 (or 28) than in 9 (or 14).
The oxidation of the tungsten atom is an irreversible
process, and the oxidation potentials of the homologous
complexes are in the order W(CO)5 > W(CO)4(PPh3) >
W(CO)4(PMe3) > W(CO)3(η2-dppe), which is in ac-
cordance with the π-accepting ability of the ligands.
Similar to our previous observation,9 the reduction
potential of the pendant pyridine in 7, 8, 9, and 14
appears to be very negative (<-2.50 V). A reliable
reduction potential for the pyridine in 15-22 was not
observed, possibly because ligation of pyridine to metal
carbonyls dowa not significantly lower the π* orbital of
pyridine, or the complexes were not stable upon reduc-
tion. A reversible reduction in complex 25 is most likely
to be due to reduction of the bipyridine ligand, which
generally has a lower lying π* orbital than pyridine.

2046 Organometallics, Vol. 16, No. 10, 1997
Wu et al.

Ruthenium σ-Pyridylacetylides
Organometallics, Vol. 16, No. 10, 1997 2047
Ta ble 4. Op tica l Absor p tion Sp ectr a of
Ta ble 5. Red ox P oten tia ls for Com p lexes in
CH2Cl2 a t 298 Ka
Com p ou n d s (λm a x, n m )
compd
CH2Cl2
CH3CN
Eox (∆Ep)
1
2
6a
6b
7
446
441
432
433
516a
348a
336
337
410
490a
320a
complex
Ru(+2/+3)
Fe(+2/+3)
W(0/+1)
Ered (∆Ep)c
1
2
7
8
9
+0.37 (73)
+0.25 (61)
+0.15 (95)
>-2.50
>-2.50
>-2.50
>-2.50
338
339
419
+0.10 (106) +0.48 (104)
+0.00 (84)
8
9
14
15
16
17
18
19
20
21
22
25
26
27
28
29
+0.04 (87)
13a
13b
14
15
16
17
18
19
20
21
22
23
25
26
27
28
29
30
33
+0.24 (110)
+0.22
+0.62
+0.14
+0.08
+0.55
+0.14
+0.06
-0.16
-0.09
+0.70d
397
397
400
407
396
402
+0.16
394
397
401
394
400
401
+0.20 (99)
+0.26 (90)
+0.25 (83)
+0.17
+0.55
+0.52 (99)
+0.51 (80)
+0.05
+0.26 (100)
+0.36 (95)
+0.06 (84)
+0.09 (100)
+0.22 (96)
-1.61 (78)
-2.00 (i)
-1.33 (i)
-1.41 (i)
-1.62(98)
404
462
441
350
398
437
520
498
526
402
460
582
558
543
372
434
a
Analyses performed in 10-3 M deoxygenated CH2Cl2 solutions
containing 0.1 M TBAP; scan rate 60 mV. All potentials in volts
vs ferrocene (0.00 V with peak separation of 105 mV in CH2Cl2);
b
scan range +0.8 to -1.8 V; i ) irreversible process. The mea-
surements were taken in CH2Cl2/CH3CN since the oxidation peak
for tungsten is almost merged in the reversible peak of Fe(2+/
3+) when the measurements were taken in CH2Cl2. c ∆Ep ) Epa
a
The measurements were taken in acetone.
d
- Epc (mV). Eox (∆Ep) for Re(+/2+).
metal-centered for σ-acetylide complexes of that type.
The potential difference (Ep) between the oxidation
potential of Ru and the reduction potential of the
acceptor for complexes 26-29 seems to be in agreement
with this. The Ep values are in the order 26 (2.36 V) >
29 (1.88 V) > 28 (1.50 V) > 27 (1.39 V), in accordance
with the the energy of the charge-transfer band in
electronic spectra (vide supra). As expected, the Ep
value for complex 7 is calculated to be higher than 2.65
V because of the high-lying π* orbital of the pyridine.
NLO Mea su r em en ts. Hyper Rayleigh scattering
(HRS) experiments were performed on complexes 26-
28 at a wavelength of 1064 nm with a Q-switch Nd:YAG
laser (Continuum Surelite I). Solutions of p-nitroaniline
in CH2Cl2 were used as external references (â ) 16.9 ×
10-30 esu at 1064 nm).34 The experimental setup was
described elsewhere.35 From the HRS experiment, the
first hyperpolarizabilities (â, 10-30 esu) of complexes
26-28 are determined to be 152, 1682, and 1505,
respectively. Recently, it has been reported that the
HRS signal is found mixed with the two-photon absorp-
tion (TPA) fluorescence at the second harmonic wave-
length (532 nm).34,36 To obtain the intrinsic â value,
the TPA-induced fluorescence must be discriminated
against. The TPA-induced fluorescence spectra of com-
plexes 26-28 were measured (see Figure S1 in the
Supporting Information) in an manner identical with
that for the HRS experiment, except the interference
filter was replaced by a monochromator. As shown in
Figure S1, the overall spectra can be divided into two
contributions: a sharp URS peak at 532 nm and a much
F igu r e 3. UV-vis spectra (in CH2Cl2) for the deprotona-
tion of 29 with NEt3: λmax 372 nm (29), 446 nm (1), 338
nm (9). V indicates the intensity is decreasing with time, v
indicates the intensity is increasing with time, and Vv indi-
cates the intensity is first increasing and then decreasing
with time. The isosbestic points appear at 390 and 373 nm.
Complex 29 also has a reversible reduction wave, and
this can be assigned to the reduction of the nitro
substituent on the thienyl ring, similar to the case of
Ru(CtCC6H4NO2-4)(PPh3)2(η5-C5H5).8a The irreducible
reduction waves appearing at -2.00, -1.49, and -1.46
V, respectively, for complexes with a pendant 1-methyl-
4-pyridiniumyl moiety (26-28) were assigned as the
reduction of the pyridinium.
(33) Kostic, N. M.; Fenske, R. F. Organometallics 1982, 1, 974.
(34) Stahelin, M.; Burland, D. M.; Rice, J . E. Chem. Phys. Lett. 1992,
191, 245.
(35) Hsu, C. C.; Huang, T. H.; Zang, Y. L.; Lin, J . L.; Chen, Y. Y.;
Lin, J . T.; Wu, H. H.; Wang, C. H.; Kuo, C. T.; Chen, C. H. J . Appl.
Phys. 1996, 80, 5996.
(36) Flipse, M. C.; de J onge, R.; Woudenberg, R. H.; Marsman, A.
W.; van Walree, C. A.; J enneskens, L. W. Chem. Phys. Lett. 1995, 245,
297.
Theoretical studies by Kostic and Fenske33 on Fe-
(CtCH)(PH3)2(η5-C5H5) suggested that the LUMO is

2048 Organometallics, Vol. 16, No. 10, 1997
Wu et al.
F igu r e 4. ORTEP drawing of complex 19. Thermal ellipsoids are drawn with 30% probability boundaries.
(1.99(1) Å), C6-C7 (1.21(1) Å), and C7-C8 (1.42(2) Å)
appear to be normal compared to those of known
ruthenium σ-acetylides.8a
broader TPA-induced fluorescence. Assuming the TPA-
induced fluorescence has no substructure at 532 nm, the
ratio of the TPA-induced fluorescence to the HRS signal
at 532 nm can thus be obtained. From the ratio, the
TPA-induced fluorescence contribution to the HRS â
value is removed. After removal of the contribution
from the TPA-induced fluorescence,35 the first hyper-
polarizabilities (â, 10-30 esu) obtained for 26-28 are 80,
1600, and 1400, respectively. The calculated static
hyperpolarizabilities (â0, 10-30 esu)37 are 16 (26), 154
(27), and 102 (28) and appear to be within the values
reported for analogous ruthenium acetylides reported
by Humphrey.8b The larger optical nonlinearity of 27
and 28 compared to that of 26 is consistent with the
greater conjugation length in the former. More com-
prehensive nonlinear optical studies on complexes in
this paper and congeners are currently ongoing and will
be the subject of future publications.
Molecu la r Str u ctu r e of Ru (CtCC5H4N{W(CO)4-
(P P h 3)})(η2-d p p f)(η5-C5H5) (19). An ORTEP drawing
of 19 is shown in Figure 4. The tungsten atom resides
in an approximately octahedral environment, and the
pyridyl ligand is cis to the phosphine ligand, which is
similar to pyridyltungsten carbonyl structures reported
by us.9a,27c The bite angle of dppf, P1-Ru-P2 (97.7-
(1)°), appears to be smaller than those (99.01(6)-101.17-
(7)°) of σ-acetylides of CpRu(PPh3)2 reported by Hum-
phrey.8 Humphrey suggested that the presence of a
strong acceptor acetylide ligand might lengthen the
Ru-P distance.8b However, we found that Ru-P dis-
tances for 19 (2.284(3), 2.297(3) Å), though comparable
to those of Ru(CtC(C6H4CHdCH)nC6H4NO2)(PPh3)2(η5-
C5H5) (n ) 0, 1),° are barely longer than those in 8
(2.273(2), 2.274(2) Å).38 The bond distances of Ru-C6
Con clu sion s. We have synthesized new types of
ruthenium σ-acetylides with conjugated pendant pyri-
dine ligands. These complexes are useful precursors for
construction of heterodinuclear complexes. Their pyri-
dinium derivatives exhibit efficient charge transfer from
the ruthenium donor to the organic acceptor and appear
to be promising nonlinear optical materials. Further
variation of conjugation bridges, such as interposition
of thienyl moieties in the conjugation chain, as well as
the investigation of the optical nonlinearity of new
chromophores will be the subject of future study.
Ap p en d ix
After submission of our paper, a paper describing
(indenyl)bis(triphenylphosphine)ruthenium acetylides
with dangling terminal pyridines that were free or were
attached to chromium or tungsten pentacarbonyl also
appeared.39
Ack n ow led gm en t. We thank the Academia Sinica
and the National Science Council for financial support
(Grant NSC-86-2113-M-001-009).
Su p p or tin g In for m a tion Ava ila ble: Tables of atomic
coordinates (including hydrogen atoms), thermal parameters,
and bond distances and angles for complex 19 and Figure S1,
giving TPA-induced fluorescence spectra of complexes 26-28
(16 pages). Ordering information is given on any current
masthead page.
OM9610657
(37) The â0 value was obtained using the two-level model, with â0
) â[1 - (2λmax/1064)2][1 - (λmax/1064)2]. However, it should be noted
that separation of resonance enhancement contributions would require
the determination of â at a different basic laser wavelength.
(38) Lo, C. M.; Lin, J . T., unpublished results.
(39) Houbrechts, S.; Clays, K.; Persoon, A.; Cadierno, V.; Gamasa,
M. P.; Gimeno, J . Organometallics 1996, 15, 5266.