Ruthenium(II) σ-acetylide and carbene complexes supported by the terpyridine-bipyridine ligand set: Structural, spectroscopic, and photochemical studies

Article abstract of DOI:10.1021/om034379k

A series of acetylide- and carbene-ruthenium complexes containing polypyridine ligands, [(tpy(bpy)RuC=CR]⁺ (tpy = 2,2′:6′, 2″-terpyridine, bpy = 2,2′-bipyridine; R = C₆H ₄F-4 (1), C₆H₄Cl-4 (2), C₆H ₅ (3), C₆H₄Me-4 (4), C₆H ₄OMe-4 (5), t-Bu (6), (C₆H₄C≡C) _nC₆H₅ [n = 1 (7) and 2 (8)]) and [(tpy)(bpy)Ru=C(OMe)(CH₂R)]²⁺ (R = C₆H ₄OMe-4 (9), t-Bu (10)) have been prepared. The molecular structures of 4(PF₆), 5(PF₆), and 9(ClO₄₎₂ reveal Ru-C distances of 2.025(9), 2.025(7), and 1.933(6) A, respectively. The Ru(III/II) oxidation waves are irreversible for 1-8 (E_pa = 0.15-0.26 V vs FeCp₂^+/0) but reversible for 9 and 10 (E _1/2 = 0.99 and 1.00 V, respectively). The absorption bands in the visible region for 1-8 (λ_max = 502-526 nm) and 9 and 10 (λ_max ca. 410 nm) are assigned as d_π(Ru ^II) → π*(polypyridine) MLCT transitions. Complexes 1-8 weakly emit at λ_max = 748-786 nm in CH₃CN solution at 298 K (λ_ex = 550 nm). Complexes 9 and 10 are nonemissive in CH₂Cl₂ solution at 298 K, but in glassy n-butyronitrile at 77 K, excitation at λ = 415 nm produces emission at λ_max = 597 and 615 nm, respectively. These emissions are tentatively ascribed as d_π(Ru^II) → π*(polypyridyl) ₃MLCT in nature. The carbene derivatives 9 and 10 undergo photochemical reactions upon irradiation in solution, and [(tpy)(bpy)RuN≡CCH₃]²⁺ and 4-methoxybenzaldehyde were isolated from the photolysis of 9 in CH₃CN.

Full text of DOI:10.1021/om034379k

Organometallics 2004, 23, 2263-2272
2263
Ru th en iu m (II) σ-Acetylid e a n d Ca r ben e Com p lexes
Su p p or ted by th e Ter p yr id in e-Bip yr id in e Liga n d Set:
Str u ctu r a l, Sp ectr oscop ic, a n d P h otoch em ica l Stu d ies†
Chun-Yuen Wong, Michael C. W. Chan, Nianyong Zhu, and Chi-Ming Che*
Department of Chemistry and HKU-CAS J oint Laboratory on New Materials,
The University of Hong Kong, Pokfulam Road, Hong Kong SAR, China
Received December 17, 2003
A series of acetylide- and carbene-ruthenium complexes containing polypyridine ligands,
[(tpy)(bpy)RuCtCR]+ (tpy ) 2,2′:6′,2′′-terpyridine, bpy ) 2,2′-bipyridine; R ) C6H4F-4 (1),
C6H4Cl-4 (2), C6H5 (3), C6H4Me-4 (4), C6H4OMe-4 (5), t-Bu (6), (C6H4CtC)nC6H5 [n ) 1 (7)
and 2 (8)]) and [(tpy)(bpy)RudC(OMe)(CH2R)]2+ (R ) C6H4OMe-4 (9), t-Bu (10)) have been
prepared. The molecular structures of 4(PF6), 5(PF6), and 9(ClO4)2 reveal Ru-C distances
of 2.025(9), 2.025(7), and 1.933(6) Å, respectively. The Ru(III/II) oxidation waves are
irreversible for 1-8 (Epa ) 0.15-0.26 V vs FeCp2+/0) but reversible for 9 and 10 (E1/2 ) 0.99
and 1.00 V, respectively). The absorption bands in the visible region for 1-8 (λmax ) 502-
526 nm) and 9 and 10 (λmax ca. 410 nm) are assigned as dπ(RuII) f π*(polypyridine) MLCT
transitions. Complexes 1-8 weakly emit at λmax ) 748-786 nm in CH3CN solution at 298
K (λex ) 550 nm). Complexes 9 and 10 are nonemissive in CH2Cl2 solution at 298 K, but in
glassy n-butyronitrile at 77 K, excitation at λ ) 415 nm produces emission at λmax ) 597
and 615 nm, respectively. These emissions are tentatively ascribed as dπ(RuII) f π*(poly-
pyridyl) 3MLCT in nature. The carbene derivatives 9 and 10 undergo photochemical reactions
upon irradiation in solution, and [(tpy)(bpy)RuNtCCH3]2+ and 4-methoxybenzaldehyde were
isolated from the photolysis of 9 in CH3CN.
In tr od u ction
by aromatic diimine ligands has arisen because they
exhibit rich photophysical and photochemical properties,
which originate from the triplet [dπ(RuII) f π*(aromatic
diimine)] metal-to-ligand charge transfer (MLCT) ex-
cited state, the prototypical example being [Ru(bpy)3]2+
(bpy ) 2,2′-bipyridine). Hence, the long-lived emissive
3MLCT excited state of [Ru(bpy)3]2+ and its derivatives
have found important applications in many disciplines.6
Ruthenium(II) complexes bearing tridentate polypyri-
dine ligands such as [Ru(tpy)2]2+ (tpy ) 2,2′:6′,2′′-
Ruthenium complexes containing aromatic diimine or
polypyridyl ligands have been a focal point for investi-
gations in many research topics including photochem-
istry,1 electron transfer reactions,2 luminescent sens-
ing,3 light-emitting devices,4 and photosensitizers.5 The
attention devoted to ruthenium(II) complexes supported
† The “RudC” formalism is used for the ruthenium-carbene moiety
to denote a single σ-bond with π-back-bonding character.
(1) (a) Kalyanasundaram, K. Coord. Chem. Rev. 1982, 46, 159. (b)
J uris, A.; Balzani, V.; Barigelletti, F.; Campagna, S.; Belser, P.; von
Zelewsky, A. Coord. Chem. Rev. 1988, 84, 85. (c) Balzani, V.; Bari-
gelletti, F.; De Cola, L. Top. Curr. Chem. 1990, 158, 31. (d) Sauvage,
J .-P.; Collin, J .-P.; Chambron, J .-C.; Guillerez, S.; Coudret, C.; Balzani,
V.; Barigelletti, F.; De Cola, L.; Flamigni, L. Chem. Rev. 1994, 94, 993.
(2) (a) Meyer, T. J . Acc. Chem. Res. 1989, 22, 163. (b) Balzani, V.;
J uris, A.; Venturi, M.; Campagna, S.; Serroni, S. Chem. Rev. 1996,
96, 759. (c) De Cola, L.; Belser, P. Coord. Chem. Rev. 1998, 177, 301.
(3) (a) Balzani, V.; Sabbatini, N.; Scandola, F. Chem. Rev. 1986, 86,
319. (b) de Silva, A. P.; Gunaratne, H. Q. N.; Gunnlaugsson, T.; Huxley,
A. J . M.; McCoy, C. P.; Rademacher, J . T.; Rice, T. E. Chem. Rev. 1997,
97, 1515.
(4) (a) Lee, J .-K.; Yoo, D. S.; Handy, E. S.; Rubner, M. F. Appl. Phys.
Lett. 1996, 69, 1686. (b) Elliott, C. M.; Pichot, F.; Bloom, C. J .; Rider,
L. S. J . Am. Chem. Soc. 1998, 120, 6781. (c) Handy, E. S.; Pal, A. J .;
Rubner, M. F. J . Am. Chem. Soc. 1999, 121, 3525. (d) Buda, M.;
Kalyuzhny, G.; Bard, A. J . J . Am. Chem. Soc. 2002, 124, 6090. (e)
Bernhard, S.; Barron, J . A.; Houston, P. L.; Abrun˜a, H. D.; Ruglovksy,
J . L.; Gao, X.; Malliaras, G. G. J . Am. Chem. Soc. 2002, 124, 13624.
(5) (a) O’Regan, B.; Gra¨tzel, M. Nature 1991, 353, 737. (b) Nazeer-
uddin, M. K.; Kay, A.; Rodicio, I.; Humphry-Baker, R.; Mu¨ller, E.;
Liska, P.; Vlachopoulos, N.; Gra¨tzel, M. J . Am. Chem. Soc. 1993, 115,
6382. (c) Bignozzi, C. A.; Schoonover, J . R.; Scandola, F. Prog. Inorg.
Chem. 1997, 44, 1. (d) Gerfin, T.; Gra¨tzel, M.; Walder, L. Prog. Inorg.
Chem. 1997, 44, 345. (e) Kalyanasundaram, K.; Gra¨tzel, M. Coord.
Chem. Rev. 1998, 177, 347. (f) Bach, U.; Lupo, D.; Comte, P.; Moser,
J . E.; Weisso¨rtel, F.; Salbeck, J .; Spreitzer, H.; Gra¨tzel, M. Nature 1998,
395, 583. (g) Hagfeldt, A.; Gra¨tzel, M. Acc. Chem. Res. 2000, 33, 269.
(6) For recent works, see: (a) Sykora, M.; Kincaid, J . R. Nature 1997,
387, 162. (b) Sun, L.; Berglund, H.; Davydov, R.; Norrby, T.; Ham-
marstro¨m, L.; Korall, P.; Bo¨rje, A.; Philouze, C.; Berg, K.; Tran, A.;
Andersson, M.; Stenhagen, G.; Mårtensson, J .; Almgren, M.; Styring,
S.; Åkermark, B. J . Am. Chem. Soc. 1997, 119, 6996. (c) Beer, P. D.;
Szemes, F.; Balzani, V.; Sala`, C. M.; Drew, M. G. B.; Dent, S. W.;
Maestri, M. J . Am. Chem. Soc. 1997, 119, 11864. (d) Lee, J .-K.; Yoo,
D.; Rubner, M. F. Chem. Mater. 1997, 9, 1710. (e) Watanabe, S.;
Onogawa, O.; Komatsu, Y.; Yoshida, K. J . Am. Chem. Soc. 1998, 120,
229. (f) Wu, A.; Yoo, D.; Lee, J .-K.; Rubner, M. F. J . Am. Chem. Soc.
1999, 121, 4883. (g) Farzad, F.; Thompson, D. W.; Kelly, C. A.; Meyer,
G. J . J . Am. Chem. Soc. 1999, 121, 5577. (h) Liebsch, G.; Klimant, I.;
Wolfbeis, O. S. Adv. Mater. 1999, 11, 1296. (i) Gao, F. G.; Bard, A. J .
J . Am. Chem. Soc. 2000, 122, 7426. (j) Nazeeruddin, M. K.; Pe´chy, P.;
Renouard, T.; Zakeeruddin, S. M.; Humphry-Baker, R.; Comte, P.;
Liska, P.; Cevey, L.; Costa, E.; Shklover, V.; Spiccia, L.; Deacon, G.
B.; Bignozzi, C. A.; Gra¨tzel, M. J . Am. Chem. Soc. 2001, 123, 1613. (k)
Watanabe, S.; Ikishima, S.; Matsuo, T.; Yoshida, K. J . Am. Chem. Soc.
2001, 123, 8402. (l) Rudmann, H.; Shimada, S.; Rubner, M. F. J . Am.
Chem. Soc. 2002, 124, 4918. (m) Anzenbacher, P., J r.; Tyson, D. S.;
J urs´ıkova´, K.; Castellano, F. N. J . Am. Chem. Soc. 2002, 124, 6232.
(n) Galoppini, E.; Guo, W.; Zhang, W.; Hoertz, P. G.; Qu, P.; Meyer, G.
J . J . Am. Chem. Soc. 2002, 124, 7801. (o) Zhan, W.; Alvarez, J .; Crooks,
R. M. J . Am. Chem. Soc. 2002, 124, 13265. (p) Potvin, P. G.; Luyen, P.
U.; Bra¨ckow, J . J . Am. Chem. Soc. 2003, 125, 4894. (q) Kalyuzhny, G.;
Buda, M.; McNeill, J .; Barbara, P.; Bard, A. J . J . Am. Chem. Soc. 2003,
125, 6272. (r) Welter, S.; Brunner, K.; Hofstraat, J . W.; De Cola, L.
Nature 2003, 421, 54.
10.1021/om034379k CCC: $27.50 © 2004 American Chemical Society
Publication on Web 04/03/2004

2264 Organometallics, Vol. 23, No. 10, 2004
Wong et al.
terpyridine) have recently attracted interest as building
blocks for the fabrication of linear molecular rods/wires
for vectorial energy and electron transfer processes.7
Meanwhile, the pursuit of [Ru(bpy)3]2+-related com-
plexes exhibiting desirable and unprecedented photo-
physical characteristics continues unabated.8
lary ligands. Significantly, reports on the preparation
and characterization of tpy-bpy ruthenium derivatives
bearing organometallic-type ligands are conspicuous by
their rarity.12 We now describe the synthesis of a series
of acetylide- and carbene-ruthenium complexes contain-
ing the bpy and tpy auxiliaries. The structural, electro-
chemical, photophysical, and photochemical properties
of these complexes, plus comparisons with [Ru(tpy)-
(bpy)L]n+ analogues (L ) anionic or neutral donor), are
presented.
Polypyridyl auxiliaries act as π-acidic and oxidatively
robust ligands upon coordination to the ruthenium ion.
In the literature, reports on highly oxidizing and isolable
RudO complexes bearing polypyridyl ligands, such as
[(tpy)(bpy)RudO]2+ 9
have appeared. The oxidation
,
chemistry of these RudO complexes has significantly
impacted organic oxidation reactions over many years,10
and their DNA cleavage capabilities have been recently
highlighted.11 We regard ruthenium-carbon multiply
bonded species supported by the tpy-bpy ligand set as
an interesting class of compounds. First, they may
exhibit group transfer reactivities analogous to the
oxygen atom transfer chemistry of the RudO congeners.
Second, the electrochemistry and photophysics of [(tpy)-
(bpy)RuL]n+ species (L ) anionic or neutral donor) are
well established, thus the nature of the ruthenium-
carbon bonding interaction for organoruthenium deriva-
tives can be probed spectroscopically and electrochemi-
cally by comparisons with known relatives. Third, it
may be feasible to generate highly reactive ruthenium-
carbon bonded species upon photoexcitation of the Ru
f π*(polypyridyl) charge transfer state. Incorporation
of carbon-rich π-extended conjugated ligands into ru-
thenium-polypyridine moieties can yield new classes of
emissive organoruthenium compounds with potential
applications in material science. We therefore initiated
a program directed toward the synthetic chemistry of
organoruthenium complexes based on polypyridyl ancil-
Exp er im en ta l Section
Gen er a l P r oced u r es. All reactions were performed under
a nitrogen atmosphere using standard Schlenk techniques
unless otherwise stated. All reagents were used as received,
and solvents were purified by standard methods. [Ru(tpy)(bpy)-
(OH2)](Y)2 (Y ) ClO4-, PF6-) were prepared according to
published procedures.13 (Ca u tion ! Perchlorate salts are po-
tentially explosive and should be handled with care and in
small amounts.)
P h ysica l Mea su r em en ts a n d In str u m en ta tion . 1H, 13C-
{1H}, 1H-1H COSY, 1H-1H NOESY, and 13C-1H COSY NMR
spectra were recorded on Bruker 500 DRX and 600 DRX FT-
NMR spectrometers. Peak positions were calibrated with Me4-
Si as internal standard. Fast atom bombardment (FAB) mass
spectra were obtained on a Finnigan MAT 95 mass spectrom-
eter with 3-nitrobenzyl alcohol matrix. Infrared spectra were
recorded as KBr plates on a Bio-Rad FT-IR spectrometer. UV-
visible spectra were recorded on a Hewlett-Packard HP8452A
diode array spectrophotometer interfaced with an IBM-
compatible PC. Elemental analyses were performed by the
Institute of Chemistry of the Chinese Academy of Sciences in
Beijing.
P h otolu m in escen ce Mea su r em en ts. Steady-state emis-
sion spectra were obtained on a SPEX Fluorolog-2 Model F111
fluorescence spectrophotometer. Low-temperature (77 K) emis-
sion spectra for glasses and solid-state samples were recorded
in 5 mm diameter quartz tubes, which were placed in a liquid
nitrogen Dewar equipped with quartz windows. Sample and
standard solutions were degassed with at least three freeze-
pump-thaw cycles. The emission quantum yield was mea-
sured by the method of Demas and Crosby14 with [Ru(bpy)3]-
(PF6)2 in degassed CH3CN as standard (Φr ) 0.062) and
calculated by Φs ) Φr(Br/Bs)(ns/nr)2(Ds/Dr), where the subscripts
s and r refer to sample and reference standard solution,
respectively, n is the refractive index of the solvents, D is the
integrated intensity, and Φ is the luminescence quantum yield.
The quantity B is calculated by B ) 1 - 10-AL, where A is the
absorbance at the excitation wavelength and L is the optical
path length. Emission lifetime measurements were performed
with a Quanta Ray DCR-3 pulsed Nd:YAG laser system (pulse
output 355 nm, 8 ns). Errors for λ values ((1 nm), τ ((10%),
and Φ ((10%) are estimated.
(7) (a) Schwab, P. F. H.; Levin, M. D.; Michl, J . Chem. Rev. 1999,
99, 1863. (b) Harriman, A.; Khatyr, A.; Ziessel, R.; Benniston, A. C.
Angew. Chem., Int. Ed. 2000, 39, 4287. (c) El-ghayoury, A.; Harriman,
A.; Khatyr, A.; Ziessel, R. Angew. Chem., Int. Ed. 2000, 39, 185. (d)
Passalacqua, R.; Loiseau, F.; Campagna, S.; Fang, Y.-Q.; Hanan, G.
S. Angew. Chem., Int. Ed. 2003, 42, 1608.
(8) (a) Collin, J .-P.; Kayhanian, R.; Sauvage, J .-P.; Calogero, G.;
Barigelletti, F.; Cian, A. D.; Fischer, J . Chem. Commun. 1997, 775.
(b) Barigelletti, F.; Flamigni, L.; Calogero, G.; Hammarstro¨m, L.;
Sauvage, J .-P.; Collin, J .-P. Chem. Commun. 1998, 2333. (c) Harriman,
A.; Hissler, M.; Trompette, O.; Ziessel, R. J . Am. Chem. Soc. 1999,
121, 2516. (d) Harriman, A.; Hissler, M.; Khatyr, A.; Ziessel, R. Chem.
Commun. 1999, 735. (e) Fang, Y.-Q.; Taylor, N. J .; Hanan, G. S.;
Loiseau, F.; Passalacqua, R.; Campagna, S.; Nierengarten, H.; Dors-
selaer, A. V. J . Am. Chem. Soc. 2002, 124, 7912. (f) Polson, M. I.; Taylor,
N. J .; Hanan, G. S. Chem. Commun. 2002, 1356. (g) McClenaghan, N.
D.; Passalacqua, R.; Loiseau, F.; Campagna, S.; Verheyde, B.;
Hameurlaine, A.; Dehaen, W. J . Am. Chem. Soc. 2003, 125, 5356. (h)
Schofield, E. R.; Collin, J .-P.; Gruber, N.; Sauvage, J .-P. Chem.
Commun. 2003, 188.
(9) (a) Moyer, B. A.; Thompson, M. S.; Meyer, T. J . J . Am. Chem.
Soc. 1980, 102, 2310. (b) Thompson, M. S.; Meyer, T. J . J . Am. Chem.
Soc. 1982, 104, 4106. (c) Thompson, M. S.; Meyer, T. J . J . Am. Chem.
Soc. 1982, 104, 5070. (d) Thompson, M. S.; Giovani, W. F. D.; Moyer,
B. A.; Meyer, T. J . J . Org. Chem. 1984, 49, 4972.
(10) (a) Che, C.-M.; Yam, V. W.-W. Adv. Inorg. Chem. 1992, 39, 233.
(b) Griffith, W. P. Chem. Soc. Rev. 1992, 179. (c) Goldstein, A. S.; Beer,
R. H.; Drago, R. S. J . Am. Chem. Soc. 1994, 116, 2424. (d) Bailey, A.
J .; Griffith, W. P.; Savage, P. D. J . Chem. Soc., Dalton Trans. 1995,
3537. (e) Che, C.-M.; Cheng, K.-W.; Chan, M. C. W.; Lau, T.-C.; Mak,
C.-K. J . Org. Chem. 2000, 65, 7996. (f) Che, C.-M.; Yu, W.-Y.; Chan,
P.-M.; Cheng, W.-C.; Peng, S.-M.; Lau, K.-C.; Li, W.-K. J . Am. Chem.
Soc. 2000, 122, 11380. (g) Huynh, M. H. V.; Witham, L. M.; Lasker, J .
M.; Wetzler, M.; Mort, B.; J ameson, D. L.; White, P. S.; Takeuchi, K.
J . J . Am. Chem. Soc. 2003, 125, 308.
Electr och em ica l Mea su r em en ts. Cyclic voltammetry was
performed with a Princeton Applied Research Model 273A
potentiostat. A conventional two-compartment electrochemical
cell was used. The glassy-carbon electrode was polished with
(12) For L ) CtO, see: (a) Thomas, N. C.; Fischer, J . J . Coord.
Chem. 1990, 21, 119. (b) Nagao, H.; Mizukawa, T.; Tanaka, K. Inorg.
Chem. 1994, 33, 3415. (c) Fletcher, N. C.; Keene, F. R. J . Chem. Soc.,
Dalton Trans. 1998, 2293. For L ) -CtN, see: (d) Belser, P.; von
Zelewsky, A.; J uris, A.; Barigelletti, F.; Balzani, V. Gazz. Chim. Ital.
1985, 115, 723. (e) Yang, J .; Seneviratne, D.; Arbatin, G.; Andersson,
A. M.; Curtis, J . C. J . Am. Chem. Soc. 1997, 119, 5329. For L ) NCCH3,
see: (f) Hecker, C. R.; Fanwick, P. E.; McMillin, D. R. Inorg. Chem.
1991, 30, 659. (g) Fagalde, F.; Lis de Katz, N. D.; Katz, N. E.
Polyhedron 1997, 16, 1921.
(11) (a) Grover, N.; Thorp, H. H. J . Am. Chem. Soc. 1991, 113, 7030.
(b) Neyhart, G. A.; Grover, N.; Smith, S. R.; Kalsbeck, W. A.; Fairley,
T. A.; Cory, M.; Thorp, H. H. J . Am. Chem. Soc. 1993, 115, 4423. (c)
Cheng, C.-C.; Goll, J . G.; Neyhart, G. A.; Welch, T. W.; Singh, P.; Thorp,
H. H. J . Am. Chem. Soc. 1995, 117, 2970. (d) Carter, P. J .; Cheng,
C.-C.; Thorp, H. H. J . Am. Chem. Soc. 1998, 120, 632.
(13) Takeuchi, K. J .; Thompson, M. S.; Pipes, D. W.; Meyer, T. J .
Inorg. Chem. 1984, 23, 1845.
(14) Demas, J . N.; Crosby, G. A. J . Phys. Chem. 1971, 75, 991.

Ruthenium(II) σ-Acetylide and Carbene Complexes
Organometallics, Vol. 23, No. 10, 2004 2265
Ta ble 1. Cr ysta llogr a p h y Da ta
4(PF6)‚21/2CH3CN
5(PF6)
9(ClO4)2‚2CH2Cl2
chemical formula
fw
cryst size, mm
cryst syst
space group
a, Å
b, Å
c, Å
R, deg
â, deg
γ, deg
V, Å3
C39H33.5F6N7.5PRu
853.27
0.4 × 0.15 × 0.1
monoclinic
C2/c
31.662(6)
8.807(2)
27.268(6)
90
95.52(3)
90
7568(3)
8
1.498
0.526
3464
C34H26F6N5OPRu
766.64
C37H35Cl6N5O10Ru
1023.47
0.4 × 0.2 × 0.15
monoclinic
P21/c
10.453(2)
11.733(2)
35.257(7)
90
97.44(3)
90
4287.7(15)
4
0.35 × 0.25 × 0.15
triclinic
P1h (no. 2)
8.596(2)
12.617(3)
14.961(3)
77.98(3)
80.13(3)
86.92(3)
1563.3(6)
2
Z
D
c, g cm-3
1.629
0.626
772
1.585
0.800
2072
µ, mm-1
F(000)
2θmax, deg
50.6
4311 (0.063)
4311
494
0.051, 0.11
50.9
4131 (0.051)
4131
434
0.061, 0.15
50.4
4321 (0.042)
4321
534
0.034, 0.062
no. indep reflns (Rint
)
no. of obsd data [I g 2σ(I)]
no. of variables
R,a Rw
b
a
2
R ) ∑||Fo| - |Fc||/∑|Fo|. bRw ) [∑w(|Fo| - |Fc|)2/∑w|Fo| ]1/2
.
0.05 µm alumina on a microcloth, sonicated for 5 min in
deionized water, and rinsed with acetonitrile before use. An
Ag/AgNO3 (0.1 M in CH3CN) electrode was used as reference
electrode. All solutions were degassed with argon before
experiments. E1/2 values are the average of the cathodic and
anodic peak potentials for the oxidative and reductive waves.
redissolved in MeOH (10 mL), and a saturated aqueous
solution of LiClO4 (3 mL) was added. After evaporation of the
solvent under vacuum, the orange-red precipitate was washed
with water (2 × 5 mL) and recrystallized by slow diffusion of
1
Et2O into CH2Cl2 solution to give bright red crystals. The H
NMR spectral data are summarized in the Supporting Infor-
mation.
The E1/2 value of the ferrocenium/ferrocene couple (Cp2Fe+/0
)
measured in the same solution was used as an internal
reference. All the E1/2 values reported in this work and quoted
from literature are converted to values versus the Cp2Fe+/0
couple.15
Com p lex 9(ClO4)2 (R ) C6H4OMe-4): yield 0.10 g, 80%.
Anal. Calcd for C35H30N5RuCl3O10‚0.7CH2Cl2: C, 45.25; H,
3.34; N, 7.39. Found: C, 45.20; H, 3.52; N, 7.09. 13C{1H} NMR
(126 MHz, CD2Cl2): δ 51.3 (CH2); 55.5 (OMe of Ar); 64.5 (d
C-OMe); 114.7, 119.8, 123.2, 123.6, 124.1, 124.2, 127.4, 128.1,
128.4, 128.5, 138.5, 138.9, 139.1, 142.1, 147.6, 152.9, 153.5,
154.9, 155.5, 156.5, 157.1, 158.8; 317.7 (RudC). FAB-MS: m/z
654 [M+].
Syn th eses. [(tp y)(bp y)Ru CtCR](ClO4), 1-8(ClO4). Ex-
cess HCtCR (0.3 mmol) was added to a mixture containing
[Ru(tpy)(bpy)(OH2)](ClO4)2 (0.10 g, 0.14 mmol) and Et3N (1 mL)
in acetone (20 mL). After refluxing for 10 h, the solvent was
removed under reduced pressure and the crude product was
eluted by column chromatography (neutral alumina, 1:3 (v/v)
CH3CN/toluene as eluent) as a purple band. After removal of
solvent, the purple solid was washed with diethyl ether and
air-dried. This solid was recrystallized by slow diffusion of Et2O
into a CH3CN solution to give bright violet crystals.
Com p lex 3(ClO4) (R ) P h ): yield 0.068 g, 70%. Anal. Calcd
for C33H24N5RuClO4: C, 57.35; H, 3.50; N, 10.13. Found: C,
56.95; H, 3.56; N, 10.07. 1H NMR (500 MHz, (CD3)2CO): δ
6.85-6.98 (m, 5H, Ph), 7.21 (t, J HH ) 6.5 Hz, 1H, Hm), 7.36 (t,
J HH ) 6.5 Hz, 1H, He), 7.49 (d, J HH ) 4.9 Hz, 1H, Hn), 7.86 (d,
J HH ) 5.0 Hz, 1H, Hf), 7.91 (t, J HH ) 7.9 Hz, 1H, Hl), 7.96 (t,
J HH ) 7.7 Hz, 1H, Hd), 8.01 (t, J HH ) 6.6 Hz, 1H, Hh), 8.13 (d,
J HH ) 8.1 Hz, 1H, Ha), 8.31 (t, J HH ) 7.9 Hz, 1H, Hi), 8.57 (d,
J HH ) 8.0 Hz, 1H, Hc), 8.64 (d, J HH ) 8.2 Hz, 1H, Hk), 8.67 (d,
J HH ) 8.1 Hz, 1H, Hb), 8.83 (d, J HH ) 8.1 Hz, 1H, Hj), 10.57 (d,
J HH ) 5.6 Hz, 1H, Hg). 13C{1H} NMR (126 MHz, (CD3)2CO): δ
104.3 (CR), 122.3 (Cb), 123.3 (Ck), 123.5 (Cc), 123.9 (Cj), 124.0
(para of Ph), 126.6 (Ch), 127.0 (Cm), 127.3 (Ce), 127.8 (ortho of
Ph), 129.4 (Cipso), 131.3 (meta of Ph), 132.4 (Ca), 136.4 (Cd),
136.4 (Ci), 136.9 (Cl), 149.6 (Cn), 151.8 (Cf), 154.5, 154.7 (Cg),
156.3, 156.5, 157.0, 158.4 (quarternary carbons of tpy and bpy),
Câ not resolved. IR (cm-1): νCtC 2059, 2068. FAB-MS: m/z 592
[M+]. For 1, 2, and 4-8, see Supporting Information.
Com p lex 10(ClO4)2 (R ) t-Bu ): yield 0.09 g, 71%. Anal.
Calcd for C32H33N5RuCl2O9‚0.3CH2Cl2: C, 46.79; H, 4.08; N,
8.45. Found: C, 46.94; H, 4.05; N, 8.46. 13C{1H} NMR (126
MHz, CD2Cl2): δ 30.5 (CMe3); 33.8 (CMe3); 62.7 (CH2); 66.1
(OMe); 123.6, 123.8, 124.4, 125.0, 125.2, 127.9, 128.5, 128.7,
137.4, 139.1, 139.2, 139.6, 147.7, 153.5, 153.9, 154.0, 156.3,
157.0, 157.4; 328.9 (RudC). FAB-MS: m/z 624 [M+].
P h otoch em ica l Rea ction . Complex 9(ClO4)2 (0.05 g) was
dissolved in CH3CN (2 mL), transferred into a sealed quartz
cell, and three freeze-pump-thaw cycles were performed. The
sample was placed into a RPR-100 Rayonet photochemical
chamber reactor equipped with 16 8-W RPR 3500 Å Hg lamps
and irradiated for 12 h. Et2O (10 mL) was then added to
precipitate any inorganic salt. The remaining solution was
filtered through an alumina column and concentrated. The
1
inorganic salt precipitated was characterized using H NMR
and FAB-MS, and the organic product was identified by 1H
NMR and GC-MS. Photolysis of 10(ClO4)2 in CH2Cl2 was
similarly performed.
X-r a y Cr ysta llogr a p h y. The crystal data and details of
data collection and refinement for 4(PF6)‚21/2CH3CN, 5(PF6),
and 9(ClO4)2‚2CH2Cl2 are summarized in Table 1. A MAR
diffractometer with a 300 mm image plate detector using
graphite-monochromatized Mo KR radiation (λ ) 0.71073 Å)
was employed for data collection at 253(2) K. The images were
interpreted and intensities integrated using the program
DENZO,16 and structures were solved by direct methods
[(tpy)(bpy)Ru dC(OMe)(CH2R)](ClO4)2, 9-10(ClO4)2. CF3-
COOH (1 mL) was added to a deep violet suspension of [(tpy)-
(bpy)RuCtCR](ClO4) (0.15 mmol) in methanol (5 mL), and this
resulted in a change in appearance to a clear orange solution.
After stirring for 1 h at room temperature, the solvent was
removed under vacuum to leave an oily residue. This was
(16) DENZO: In The HKL Manual, A description of programs
DENZO, XDISPLAYF and SCALEPACK; written by Gewirth, D. with
the cooperation of the program authors Otwinowski, Z.; and Minor,
W. Yale University: New Haven, CT, 1995.
(15) Connelly, N. G.; Geiger, W. E. Chem. Rev. 1996, 96, 877.

2266 Organometallics, Vol. 23, No. 10, 2004
Wong et al.
employing the SIR-97 program17 on a PC. The Ru, P, Cl, and
many non-H atoms were located according to the direct
methods. The positions of the other non-hydrogen atoms were
found after successful refinement by full-matrix least-squares
using the program SHELXL-97 on a PC.18 Except for disor-
dered atoms, non-hydrogen atoms were refined anisotropically
in the final stage of least-squares refinement. Unless otherwise
stated, the positions of the H atoms were calculated on the
basis of the riding mode with thermal parameters equal to 1.2
times that of the associated C atom. For 4(PF6)‚21/2CH3CN,
one formula unit was located in the asymmetric unit. Disorder
Sch em e 1
-
is observed in the PF6 anion, and some restraints had been
applied. For both 5(PF6) and 9(ClO4)2‚2CH2Cl2, one crystal-
lographic asymmetric unit consists of one formula unit.
Resu lts
Syn th eses a n d Ch a r a cter iza tion . In the literature,
accounts of the preparation of acetylide- and alkoxy-
carbene-ruthenium complexes supported by phosphine
and cyclopentadienyl/arene ligands are extensive,19
while congeners bearing N-donor auxiliaries have also
been described.20 We recently reported on arylacetylide-
ruthenium(II) complexes supported by macrocyclic N-
donor ligands, namely, [Ru(Me3tacn)(PMe3)2(CtCAr)]-
PF6 (Me3tacn ) 1,4,7-trimethyl-1,4,7-triazacyclononane)21
and trans-[Ru(16-TMC)(CtCAr)2] (16-TMC ) 1,5,9,13-
tetramethyl-1,5,9,13-tetraazacyclohexadecane).22 In this
work, we have synthesized acetylide-, and methoxycar-
bene-ruthenium complexes containing only polypyridyl
ligands. Reaction of the aqua complex [(tpy)(bpy)Ru-
(OH2)]2+ with HCtCR in the presence of Et3N in
refluxing acetone afforded the acetylide complexes
[(tpy)(bpy)RuCtCR]+ (Scheme 1) with overall yields of
around 70%. Purification by column chromatography
(neutral alumina, 1:3 (v/v) CH3CN/toluene as eluent)
prior to recrystallization (slow diffusion of Et2O into a
CH3CN solution) was needed to obtain analytically pure
[(tpy)(bpy)RuCtCR]+ salts. The desired product [(tpy)-
(bpy)RuCtCR]+ was eluted as a purple band, followed
by an orange band, which was characterized as [(tpy)-
(bpy)Ru(NtCCH3)]2+ 12f
We have attempted to improve
.
the product yield by varying the amount of HCtCR and
Et3N, but no significant improvement was found. The
acetylide complexes 1-8 are sufficiently stable to be
handled in air under ambient conditions in solution and
solid forms. For example, the UV-visible spectrum of
3 remains unchanged in CH3CN or CH2Cl2 after 5 days.
The acetylide complexes have been characterized by
various spectroscopic means. Their IR spectra show
stretching frequencies at 2050-2070 cm-1, which are
attributed to the ν(CtC) stretching of the coordinated
acetylide ligand. It is interesting to note that the νCtC
(17) SIR-97: Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano,
G.; Giacovazzo, C.; Guagliardi, A.; Moliterni, A. G. G.; Polidori, G.;
Spagna, R. J . Appl. Crystallogr. 1998, 32, 115.
frequencies of [(tpy)(bpy)RuCtCR]+ are higher than
22a
(18) Sheldrick, G. M. SHELXL-97, Programs for Crystal Structure
Analysis (release 97-2); University of Goetingen: Germany, 1997.
(19) For example, see: (a) Bozec, H. L.; Ouzzine, K.; Dixneuf, P. H.
Organometallics 1991, 10, 2768. (b) Pilette, D.; Ouzzine, K.; Bozec, H.
L.; Dixneuf, P. H.; Rickard, C. E. F.; Roper, W. R. Organometallics
1992, 11, 809. (c) Uno, M.; Dixneuf, P. H. Angew. Chem., Int. Ed. 1998,
37, 1714. (d) Colbert, M. C. B.; Lewis, J .; Long, N. J .; Raithby, P. R.;
Younus, M.; White, A. J . P.; Williams, D. J .; Payne, N. N.; Yellowlees,
L.; Beljonne, D.; Chawdhury, N.; Friend, R. H. Organometallics 1998,
17, 3034. (e) McDonagh, A. M.; Humphrey, M. G.; Samoc, M.; Luther-
Davies, B.; Houbrechts, S.; Wada, T.; Sasabe, H.; Persoons, A. J . Am.
Chem. Soc. 1999, 121, 1405. (f) Bruce, M. I.; Low, P. J .; Costuas, K.;
Halet, J .-F.; Best, S. P.; Heath, G. A. J . Am. Chem. Soc. 2000, 122,
1949. (g) Rigaut, S.; Monnier, F.; Mousset, F.; Touchard, D.; Dixneuf,
P. H. Organometallics 2002, 21, 2654. (h) Powell, C. E.; Cifuentes, M.
P.; Morrall, J . P.; Stranger, R.; Humphrey, M. G.; Samoc, M.; Luther-
Davies, B.; Heath, G. A. J . Am. Chem. Soc. 2003, 125, 602. (i) Long,
N. J .; Williams, C. K. Angew. Chem., Int. Ed. 2003, 42, 2586.
(20) (a) Yam, V. W.-W.; Chu, B. W.-K.; Cheung, K.-K. Chem.
Commun. 1998, 2261. (b) Slugovc, C.; Mereiter, K.; Schmid, R.;
Kirchner, K. Organometallics 1998, 17, 827. (c) Ru¨ba, E.; Gemel, C.;
Slugovc, C.; Mereiter, K.; Schmid, R.; Kirchner, K. Organometallics
1999, 18, 2275. (d) Cadierno, V.; Gamasa, M. P.; Gimeno, J .; Iglesias,
L.; Garc´ıa-Granda, S. Inorg. Chem. 1999, 38, 2874. (e) Tenorio, M. A.
J .; Tenorio, M. J .; Puerta, M. C.; Valerga, P. Organometallics 2000,
19, 1333. (f) Bianchini, C.; Lee, H. M. Organometallics 2000, 19, 1833.
(g) Mene´ndez, C.; Morales, D.; Pe´rez, J .; Riera, V.; Miguel, D.
Organometallics 2001, 20, 2775. (h) Ru¨ba, E.; Hummel, A.; Mereiter,
K.; Schmid, R.; Kirchner, K. Organometallics 2002, 21, 4955.
(21) Yang, S.-M.; Chan, M. C.-W.; Cheung, K.-K.; Che, C.-M.; Peng,
S.-M. Organometallics 1997, 16, 2819.
those of trans-[Ru(16-TMC)(CtCAr)2]
(νCtC 2002-
2012 cm-1), which are supported by a purely σ-donating
macrocyclic amine ligand. The H NMR signals for the
1
polypyridyl ligands (see Figure 1 for the labeling
scheme) have been unambiguously assigned using 1H-
1H COSY and 1H-1H NOESY NMR techniques (see
1
Supporting Information). The H-1H COSY technique
gives information on through-bond coupling, and thus
associated protons on each pyridyl ring can be distin-
guished. The through-space relationships of Hb-Hc and
1
Hj-Hk are revealed by the H-1H NOESY technique,
while the NOE response between Hf and Hg signifies
that the pyridyl group containing Hg-j is trans to the
central tpy ring, while the pyridyl group with Hk-n is
1
trans to the acetylide ligand. The aromatic H signals
(22) (a) Choi, M.-Y.; Chan, M. C.-W.; Zhang, S.; Cheung, K.-K.; Che,
C.-M.; Wong, K.-Y. Organometallics 1999, 18, 2074. (b) Choi, M.-Y.;
Chan, M. C. W.; Peng, S.-M.; Cheung, K.-K.; Che, C.-M. Chem.
Commun. 2000, 1259.
F igu r e 1. Labeling scheme for hydrogen and carbon atoms
in complexes 1-10.

Ruthenium(II) σ-Acetylide and Carbene Complexes
Organometallics, Vol. 23, No. 10, 2004 2267
of the arylacetylide group appear at 6.54-7.60 ppm, and
the t-Bu group for complex 6 is observed at 0.82 ppm.
The carbene-ruthenium complexes [(tpy)(bpy)Rud
C(OMe)(CH2R)]2+ (R ) C6H4OMe (9), t-Bu (10)) were
synthesized by treatment of the corresponding acetylide
complexes [(tpy)(bpy)RuCtCR]+ with MeOH under
acidic conditions. Hence addition of CF3COOH or HCl
gas into the reaction mixture yielded the carbene
complexes. However, prolonged bubbling of HCl gas
(over 1 h) gave [(tpy)(bpy)RuCl](ClO4) as the major
product. Similarly, the same procedure can be adopted
using EtOH to synthesize the ethoxycarbene derivatives
[(tpy)(bpy)RudC(OEt)(CH2R)]2+ 23
The carbene com-
.
plexes are stable as solids under air, but they are
unstable in solution. For example, the use of a CH3CN/
Et2O mixture for recrystallization of 9 afforded [(tpy)-
(bpy)Ru(NtCCH3)](ClO4)2 as the major product. Deaer-
ated acetone-d6 was used for NMR studies on the
carbene complexes, but changes in the spectra were
detected after 5 h. After careful consideration of the
stability and solubility of the ruthenium carbene com-
plexes in this work, CH2Cl2 was selected as the solvent
of choice; complexes 9 and 10 remain unchanged in CH2-
Cl2 solutions at room temperature in the dark for at
least 5 days (by UV-vis and 1H NMR spectroscopy),
although they are transformed into [(tpy)(bpy)RuCl]+
in refluxing CH2Cl2. Indeed, we have found that com-
plexes 9 and 10 are unstable in CH2Cl2 and CH3CN
solutions at room temperature under ambient light
(changes in their UV-vis and 1H NMR spectra are
detectable after 1 day) and when irradiated with UV-
visible light (see Photochemistry section).
F igu r e 2. UV-visible spectral trace for 10 in CH3CN
during photolysis. The inset shows the time trace at 2 min
intervals.
complexes 9 and 10 with styrene. For example, excess
styrene (10 equiv) was added to a CH2Cl2 solution (10
mL) of 10 (0.1 mmol), and this was stirred at room
temperature in the dark and monitored by UV-visible
spectroscopy. However, no observable change in the
spectrum and no reaction was found after 48 h.
P h otoch em istr y. The carbene complexes 9 and 10
are unstable in solution upon strong irradiation. Pre-
liminary photolyses of 9 in CH2Cl2 and 10 in CH3CN
were performed by irradiating samples with UV-visible
light using Hg air lamps for 5 h in a photochemical
reaction chamber. Figure 2 shows the time trace of the
UV-visible spectra for 10 in CH3CN during the pho-
tolysis reaction; no further spectral changes were ob-
served after 1 h, and the reactions were clearly com-
plete. The metal-organic products were precipitated by
adding Et2O to the CH2Cl2 and CH3CN solutions, and
the isolated salts were characterized as [(tpy)(bpy)-
RuCl]+ and [(tpy)(bpy)Ru(NCCH3)]2+, respectively, us-
Complexes 9 and 10 show low-field 13C NMR signals
at 317.7 and 328.9 ppm, respectively, which are char-
1
acteristic for the carbene carbon atom,19a,b,24 and the H
signals at 4.43 and 4.39 ppm (s, 3H) respectively confirm
the presence of the -OMe group on the carbene carbon.
Upon comparing the corresponding 1H signals of the
polypyridyl ligands for the acetylide and carbene com-
plexes (5 vs 9; 6 vs 10), it was found that all of them
gave very similar chemical shifts in CD2Cl2 (differences
less than 0.2 ppm) except for Hg, which appears for 5
and 6 at 10.51 and 10.55 ppm, respectively, and for 9
and 10 at 9.34 and 8.86 ppm, respectively. In addition,
the 1H shift of Hg for [(tpy)(bpy)Ru(NtCCH3)]2+ appears
at 9.75 ppm in CD2Cl2. The highly sensitive nature of
the chemical shift for Hg as the ligand changes from
acetonitrile to acetylide and carbene is consistent with
their proximity to each other; Hg is the only proton
among the polypyridine rings that protrudes above the
tpy plane and toward these ligands.
1
ing H NMR and FAB-MS techniques.
A detailed investigation on the photochemical reactiv-
ity of 9 in CH3CN was performed. Complex 9(ClO4)2 in
degassed CH3CN was irradiated by UV-visible light in
the photochemical reaction chamber for 12 h, after
which Et2O was added to the resultant mixture to
precipitate [(tpy)(bpy)RuNtCCH3](ClO4)2 (characterized
1
by H NMR and FAB-MS). To characterize the organic
product(s), the remaining solution was passed through
a short alumina column, concentrated, and analyzed by
1H and GC-MS; the major product and indeed the only
identifiable compound was 4-methoxybenzaldehyde.
Cr ysta l Str u ctu r es. The structures of 4(PF6), 5(PF6),
and 9(ClO4)2 have been determined by X-ray crystal-
Since the insertion of carbene groups into CdC bonds
mediated by carbene-ruthenium complexes is of great
current interest,25,26 we have examined the reactions of
(25) (a) Doyle, M. P.; Forbes, D. C. Chem. Rev. 1998, 98, 911. (b)
Naota, T.; Takaya, H.; Murahashi, S.-I. Chem. Rev. 1998, 98, 2599.
(c) Trost, B. M.; Toste, F. D.; Pinkerton, A. B. Chem. Rev. 2001, 101,
2067.
(23) Characterization data for [(tpy)(bpy)RudC(OEt)(CH2C6H4OMe)]-
(26) (a) Nishiyama, H.; Itoh, Y.; Matsumoto, H.; Park, S.-B.; Itoh,
K. J . Am. Chem. Soc. 1994, 116, 2223. (b) Park, S.-B.; Sakata, N.;
Nishiyama, H. Chem. Eur. J . 1996, 2, 303. (c) Lee, H. M.; Bianchini,
C.; J ia, G.; Barbaro, P. Organometallics 1999, 18, 1961. (d) Galardon,
E.; Maux, P. L.; Simonneaux, G. Tetrahedron 2000, 56, 615. (e)
Munslow, I. J .; Gillespie, K. M.; Deeth, R. J .; Scott, P. Chem. Commun.
2001, 1638. (f) Che, C.-M.; Huang, J .-S.; Lee, F.-W.; Li, Y.; Lai, T.-S.;
Kwong, H.-L.; Teng, P.-F.; Lee, W.-S.; Lo, W.-C.; Peng, S.-M.; Zhou,
Z.-Y. J . Am. Chem. Soc. 2001, 123, 4119. (g) Li, Y.; Huang, J .-S.; Zhou,
Z.-Y.; Che, C.-M. J . Am. Chem. Soc. 2001, 123, 4843. (h) Miller, J . A.;
J in, W.; Nguyen, S. T. Angew. Chem., Int. Ed. 2002, 41, 2953. (i) Li,
Y.; Huang, J .-S.; Zhou, Z.-Y.; Che, C.-M.; You, X.-Z. J . Am. Chem. Soc.
2002, 124, 13185.
3
(ClO4)2: 1H NMR (400 MHz, (CD2Cl2): δ 1.29 (t, J HH ) 7.5 Hz, 3H,
OCH2CH3), 3.69 (s, 3H, OMe), 4.23 (s, 2H, CH2C6H4OMe), 4.62 (q, 3J HH
3
) 7.0 Hz, 2H, OCH2CH3), 5.98 (d, J HH ) 8.7 Hz, 2H, Ar), 6.44 (d,
3J HH ) 8.7 Hz, 2H, Ar), 7.08 (d, J HH ) 5.3 Hz, 1H, Hn), 7.25 (t, J HH
)
6.5 Hz, 1H, Hm), 7.34 (t, J HH ) 6.6 Hz, 1H, He), 7.71 (d, J HH ) 5.5 Hz,
1H, Hf), 7.86-7.92 (m, 2H, Hd and Hl), 7.99 (t, J HH ) 6.7 Hz, 1H, Hh),
8.14 (d, J HH ) 7.8 Hz, 1H, Hc), 8.17 (t, J HH ) 8.2 Hz, 1H, Ha), 8.22-
8.26 (m, 2H, Hb and Hi), 8.50 (d, J HH ) 7.6 Hz, 1H, Hj), 9.26 (d, J HH
)
5.6 Hz, 1H, Hg). FAB-MS: m/z 669 [M+].
(24) (a) Ruiz, N.; Pe´ron, D.; Dixneuf, P. H. Organometallics 1995,
14, 1095. (b) Sˇteˇpnicˇka, P.; Gyepes, R.; Lavastre, O.; Dixneuf, P. H.
Organometallics 1997, 16, 5089.

2268 Organometallics, Vol. 23, No. 10, 2004
Wong et al.
Ta ble 2. Selected Bon d Len gth (Å) a n d An gles
(d eg)
4
5
9
Ru-C(1)
2.025(9)
1.192(10)
2.047(5)
1.948(5)
2.065(6)
2.127(6)
2.100(7)
2.025(7)
1.191(9)
2.081(6)
1.961(5)
2.054(6)
2.102(6)
2.128(5)
1.933(6)
1.529(7)
2.054(4)
1.965(4)
2.073(5)
2.104(4)
2.177(4)
1.305(6)
126.3(5)
93.8(2)
94.8(2)
87.6(2)
96.3(2)
171.9(2)
116.1(4)
C(1)-C(2)
Ru-N(1)
Ru-N(2)
Ru-N(3)
Ru-N(4)
Ru-N(5)
C(1)-O(1)
Ru-C(1)-C(2)
C(1)-Ru-N(1)
C(1)-Ru-N(2)
C(1)-Ru-N(3)
C(1)-Ru-N(4)
C(1)-Ru-N(5)
Ru-C(1)-O(1)
170.7(7)
92.0(3)
95.4(3)
91.2(3)
91.8(3)
168.8(3)
170.8(6)
91.3(2)
90.5(3)
92.3(2)
92.0(2)
167.6(2)
Å).27 The short Ru-C(1) distance in 9 [1.933(6) Å],
together with the angles around the C(1) atom (which
are consistent with sp2 hybridization), indicate the
presence of ruthenium-carbon multiple bonding, pre-
sumably via Ru(II) f π*(carbene) π-back-bonding in-
teractions. The C(1)-C(2) and C(1)-O(1) distances
[1.529(7) and 1.305(6) Å, respectively] in 9 demonstrate
their single-bonded nature.
Electr och em istr y. Cyclic voltammetry was used to
examine the electrochemistry of complexes 1-10 (Table
3; all values vs Cp2Fe+/0). Complexes 1-8 show two
reversible/quasi-reversible couples at E1/2 ) -2.22 to
-2.14 and -1.95 to -1.87 V, and an irreversible wave
at Epa ) 0.15 to 0.26 V (scan rate ) 50 mV s-1, 0.1 M
[Bu4N]PF6 in CH3CN as supporting electrolyte; the
latter wave is irreversible even at scan rates of up to
1000 mV s-1). The span in the Epa values for the
irreversible wave from R ) C6H4F-4 (1) to C6H4OMe-4
(5) is 110 mV. The electrochemistry of 7 was also
examined in CH2Cl2 solution (0.1 M [Bu4N]PF6 as
supporting electrolyte), and very similar results were
F igu r e 3. Perspective view of the cation in 4 (30%
probability ellipsoids).
lography. Perspective views of the complex cations of 4
and 9 are shown in Figures 3 and 4, respectively.
Relevant bond lengths and angles are listed in Table 2.
In each case, the Ru atom adopts a distorted octahedral
geometry. The Ru-C(1) [4, 2.025(9); 5, 2.025(7) Å] and
C(1)-C(2) distances [4, 1.192(10); 5, 1.191(9) Å] are
comparable to previously reported Ru(II) acetylide
complexes (Ru-CR ) 1.91-2.12 Å, CR-Câ ) 1.13-1.22
observed, namely, a quasi-reversible couple at E1/2
)
-1.94 V and an irreversible wave at Epa ) 0.26 V.
F igu r e 4. Perspective view of the cation in 9 (30% probability ellipsoids).

Ruthenium(II) σ-Acetylide and Carbene Complexes
Organometallics, Vol. 23, No. 10, 2004 2269
Ta ble 3. Electr och em ica l Da ta for
[(tp y)(bp y)Ru CtCR]ClO4 (1-8)a a n d
[(tp y)(bp y)Ru dC(OMe)(CH2R)](ClO4)2 (9 a n d 10)b
complex
E1/2c/V vs Cp2Fe+/0
1 (R ) C6H4F-4)
2 (R ) C6H4Cl-4)
3 (R ) Ph)
4 (R ) C6H4Me-4)
5 (R ) C6H4OMe-4)
6 (R ) t-Bu)
7 (R ) C6H4CtCPh)
8 (R ) (C6H4CtC)2Ph)
9 (R ) C6H4OMe-4)
10 (R ) t-Bu)
-2.15
-2.16
-2.16
-2.17
-2.17
-2.22
-2.16
-2.14
-2.03
-2.04
-1.90
-1.89
-1.89
-1.90
-1.90
-1.95
-1.88
-1.87
-1.57
-1.50
0.26d
0.26d
0.24d
0.20d
0.15d
0.18d
0.25d
0.26d
0.99
1.00
a
Supporting electrolyte: 0.1 M [Bu4N]PF6 in CH3CN. bSup-
c
porting electrolyte: 0.1 M [Bu4N]PF6 in CH2Cl2. E1/2 ) (Epc
+
E
pa)/2 at 25 °C for reversible couples. dIrreversible; the recorded
potential is the anodic peak potential at a scan rate of 50 mV s-1
.
F igu r e 5. Cyclic voltammogram for 9 in CH2Cl2 with
[nBu4N]PF6 (0.1 M) as supporting electrolyte. Conditions:
F igu r e 6. Absorption (s, CH3CN, 298 K) and emission
(- - -, CH3CN, 298 K, λex ) 550 nm, complex concentration
) 1 × 10-4 M) spectra of [(tpy)(bpy)Ru(CtCC6H4)nCt
CPh]+ [n ) 0 (3, top), 1 (7, middle), and 2 (8, bottom)].
working electrode, glassy-carbon; scan rate, 50 mV s-1
.
Complexes 9 and 10 show three reversible/quasi-revers-
ible couples at E1/2 ) -2.03 and -2.04, -1.57 and -1.50,
and 0.99 and 1.00 V, respectively, and the cyclic volta-
mmogram for 9 is depicted in Figure 5.
and 524 nm in CH2Cl2, respectively. The impact of the
para substituent on the arylacetylide ligand upon the
profile of the absorption band in the visible region is
not dramatic. The peak maximum slightly red-shifts in
energy as the electron-donating ability of the para
substituent in R ) C6H4X-4 increases, except for X ) F
[λmax ) 513 nm for 2 (X ) Cl), 516 nm for 1 (F), ∼516
nm for 3 (H), 518 nm for 4 (Me), 520 nm for 5 (OMe)],
and they are all blue-shifted with respect to 6 (R ) t-Bu,
λmax ) 526 nm). The range of λmax values for 1-6 is
small, and the energy difference between 2 (513 nm)
and 6 (526 nm) is 482 cm-1. Complexes 7 and 8 display
intense absorption bands with peak maxima at 367 and
381 nm, respectively (ꢀmax ) (3-5) × 104 dm3 mol-1
cm-1), plus bands in the visible region at λmax ) 454
Electr on ic Sp ectr oscop y. The UV-visible spectral
data of [(tpy)(bpy)RuCtCR]ClO4 (1-8) and [(tpy)(bpy)-
RudC(OMe)(CH2R)](ClO4)2 (9 and 10) are summarized
in Table 4. The absorption spectra of 3, 7, and 8 (in CH3-
CN) are depicted in Figure 6. Complexes 1-6 exhibit
intense high-energy bands at λmax e 400 nm (ꢀmax g 104
dm3 mol-1 cm-1) and a moderately intense band at λmax
) 513-526 nm (ꢀmax ) (9-10) × 103 dm3 mol-1 cm-1
)
with a shoulder around 456-463 nm (ꢀmax ) (6-7) ×
103 dm3 mol-1 cm-1). The absorption maxima, especially
for the low-energy bands, are affected by the nature of
the solvent: for 3, the absorption peak maxima at 295,
316, 367, and 516 nm in CH3CN shift to 296, 317, 360,
and 513 nm for 7 and 446 and 502 nm for 8 (all ꢀmax
≈
Ta ble 4. UV-Visible Absor p tion Da ta for [(tp y)(bp y)Ru CtCR]ClO4 (1-8) in CH3CN a n d
[(tp y)(bp y)Ru dC(OMe)(CH2R)](ClO4)2 (9 a n d 10) in CH2Cl2
complex
absorption λabs/nm (ꢀ/dm3 mol-1 cm-1
)
1 (R ) C6H4F-4)
2 (R ) C6H4Cl-4)
3 (R ) Ph)
4 (R ) C6H4Me-4)
5 (R ) C6H4OMe-4)
6 (R ) t-Bu)
7 (R ) C6H4CtCPh)
8 (R ) (C6H4CtC)2Ph)
9 (R ) C6H4OMe-4)
10 (R ) t-Bu)
283 (sh) (39 550), 294 (44 460), 316 (31 100), 370 (sh) (8790), 457 (sh) (6310), 516 (8570), 681 (sh) (870)
284 (sh) (38 410), 295 (46 230), 316 (36 500), 361 (sh) (12 860), 456 (sh) (6860), 513 (8750), 681 (sh) (810)
284 (sh) (44 180), 295 (50 940), 316 (35 950), 367 (sh) (12 430), 456 (sh) (6750), 516 (8990), 682 (sh) (840)
283 (sh) (42 300), 295 (47 700), 316 (34 330), 363 (sh) (10 700), 456 (sh) (6460), 518 (8600), 680 (sh) (970)
282 (sh) (44 330), 295 (47 090), 317 (33 660), 364 (sh) (10 860), 459 (sh) (6480), 520 (8500), 680 (sh) (1060)
276 (sh) (42 850), 295 (47 770), 315 (29 020), 362 (sh) (9700), 463 (sh) (6350), 526 (10 250), 684 (sh) (1300)
278 (sh) (48 650), 295 (56 490), 318 (37 480), 367 (37 890), 454 (9690), 513 (9580), 686 (sh) (590)
278 (sh) (49 150), 296 (70 150), 318 (75 930), 381 (45 740), 446 (14 580), 502 (11 060), 683 (sh) (930)
230 (29 650), 285 (42 220), 310 (34 030), 335 (sh) (16 380), 415 (8620), 515 (sh) (1670)
242 (36 040), 285 (62 940), 312 (sh) (47 800), 334 (sh) (28 670), 408 (13 350), 503 (sh) (3570)

2270 Organometallics, Vol. 23, No. 10, 2004
Wong et al.
nm with short lifetimes (e0.1 µs) and very low quantum
yields (ca. 10-4). The emission of 3 was also examined
in CH2Cl2 solution, and the luminescent properties are
similar to those found in CH3CN (see Supporting
Information). For 1-5, the emission maximum slightly
red-shifts in energy as the electron-donating ability of
the substituent on C6H4X-4 increases, except for X ) F
[λmax ) 750 nm for 2 (X ) Cl), 752 nm for 1 (F), 758 nm
for 3 (H), 765 nm for 4 (Me), 775 nm for 5 (OMe)]. The
emission maximum of the alkylacetylide complex 6 (R
) t-Bu, λmax ) 786 nm) is red-shifted from those of 1-5
(R ) C6H4X-4). From the emission spectra of 3, 7, and
8 (Figure 6), it is noteworthy that the emission maxi-
mum slightly blue-shifts in energy with the increased
conjugation and length of the acetylide ligand (Ct
CC6H4)nCtCPh [λmax ) 758 nm for 3 (n ) 0), 749 nm
for 7 (n ) 1), 748 nm for 8 (n ) 2)], and the difference
F igu r e 7. Absorption (s, CH3CN, 298 K) and glass
emission (- - -, n-butyronitrile, 77 K, λex ) 415 nm, complex
concentration ) 1 × 10-4 M) spectra of 9.
in energy from 3 to 8 is 176 cm-1
.
Ta ble 5. Em ission Da ta for
[(tp y)(bp y)Ru CtCR]ClO4 (1-8) a n d
Complexes 9 and 10 are nonemissive in CH2Cl2
solution at room temperature, but they are emissive in
glassy n-butyronitrile solution at 77 K and the solid
state (298 and 77 K). Excitation of 9 and 10 at λ ) 415
nm in n-butyronitrile glass at 77 K produces red
emission with λmax ) 597 and 615 nm, respectively. In
the solid state, 9 and 10 emit at 616 and 630 nm at 77
K and 649 and 711 nm at 298 K, respectively. The glassy
emission for 9 and 10 was studied in n-butyronitrile
rather than MeOH/EtOH because the solubility of 9 and
10 in alcoholic solutions is poor. The glassy emission of
9 at 77 K was also investigated in CH2Cl2/toluene (1/1,
v/v) solution, and the emission maximum is detected at
592 nm, which is similar to that measured in n-
butyronitrile.
[(tp y)(bp y)Ru dC(OMe)(CH2R)](ClO4)2 (9 a n d 10)a
fluid solution
298 K:b,c λmax
nm; Φ
/
77 K:d λmax
nm; τ/µs
/
(2.5 × 10-5 M)
1 (R ) C6H4F-4)
2 (R ) C6H4Cl-4)
3 (R ) Ph)
4 (R ) C6H4Me-4)
5 (R ) C6H4OMe-4)
6 (R ) t-Bu)
7 (R ) C6H4CtCPh)
8 (R ) (C6H4CtC)2Ph)
9 (R ) C6H4OMe-4)
10 (R ) t-Bu)
752; 2.1 × 10-4
750; 3.2 × 10-4
758; 2.3 × 10-4
765; 1.2 × 10-4
775; 0.4 × 10-4
786; 0.9 × 10-4
749; 4.4 × 10-4
748; 3.6 × 10-4
nonemissive
721; 1.1
723; 1.1
720; 1.3
718; 1.0
733; 0.7
722; 1.2
728; 1.5
725; 1.3
597; 8.3
615; 3.9
nonemissive
298 K:c λmax
/
77 K:c λmax
/
solid state
nm
nm
1 (R ) C6H4F-4)
2 (R ) C6H4Cl-4)
3 (R ) Ph)
4 (R ) C6H4Me-4)
5 (R ) C6H4OMe-4)
6 (R ) t-Bu)
7 (R ) C6H4CtCPh)
8 (R ) (C6H4CtC)2Ph)
9 (R ) C6H4OMe-4)
10 (R ) t-Bu)
770
752
745
765
776
780
742
746
649
711
738
747
741
755
767
780
749
745
616
630
Discu ssion
Gen er a l Rem a r k s. Acetylide- and carbene-ruthe-
nium(II) complexes containing the tpy-bpy ligand set
have been prepared in this work. [(tpy)(bpy)Ru(H2O)]2+
was used as the precursor rather than [(tpy)(bpy)RuCl]+
because the latter does not react with acetylene sub-
strates in the presence of Et3N. For the syntheses of
the acetylide complexes, the choice of solvent is critical.
It was found that the yield of the acetylide complexes
was low (ca 10%) when the reaction was performed in
MeOH or EtOH. When CH3CN or CH2Cl2 was used,
[(tpy)(bpy)Ru(NCCH3)]2+ or [(tpy)(bpy)RuCl]+ was iso-
lated as the major product, respectively. We found that
acetone was the best solvent for this procedure, and
yields of around 60-80% were generally obtained. This
is presumably because acetone is a noncoordinating (or
very poor) ligand for the [(tpy)(bpy)Ru]2+ moiety com-
pared to CH3CN and Cl-.
There are several accounts of vinylidene-ruthenium
complexes that are unstable toward interaction with
alcohol to give alkoxycarbene-ruthenium complexes.28
For example, Bruce and co-workers reported that [Cp-
(PPh3)(PMe3)RudCdCHPh]PF6 reacts with methanol to
give [Cp(PPh3)(PMe3)RudC(OMe)CH2Ph]PF6.29 In this
work, we pursued the vinylidene derivatives [(tpy)(bpy)-
RudCdCHR]2+ as precursors for alkoxycarbene species.
a
λex ) 550 nm for 1-8 and 415 nm for 9 and 10. bMeasured in
acetonitrile for 1-8 and in CH2Cl2 for 9 and 10 at 298 K.
cLifetimes of e0.1 µs were detected for all complexes in the solid
state and at 298 K in solution. dMeasured in MeOH/EtOH (1/4
v/v) for 1-8 and in n-butyronitrile for 9 and 10.
1 × 104 dm3 mol-1 cm-1) that are similar to 1-6. It
should be noted that the absorption profile and extinc-
tion coefficients of the absorption bands for 8 at λ )
280-350 nm are different from those for 1-7. The
absorption spectrum of 9 in CH2Cl2 is depicted in Figure
7. The spectra of 9 and 10 show intense high-energy
bands at λmax e 350 nm (ꢀmax g 104 dm3 mol-1 cm-1
)
and a moderately intense band at λmax ) 415 and 408
nm (ꢀmax ) (8-10) × 103 dm3 mol-1 cm-1) with a
shoulder near 515 and 503 nm (ꢀmax ) (2-4) × 103 dm3
mol-1 cm-1), respectively.
Em ission Sp ectr oscop y. The emission properties of
the complexes are summarized in Table 5. Complexes
1-8 are emissive in CH3CN (298 K) and glassy MeOH/
EtOH (1/4, v/v; 77 K) solutions and in the solid state
(298 and 77 K). Excitation of 1-8 at λ ) 550 nm in CH3-
CN at 298 K gave a red emission at λmax ) 748-786
(27) Manna, J .; J ohn, K. D.; Hopkins, M. D. Adv. Organomet. Chem.
1995, 38, 79.
(28) Bruce, M. I. Chem. Rev. 1991, 91, 197.
(29) Bruce, M. I.; Swincer, A. G. Aust. J . Chem. 1980, 33, 1471.

Ruthenium(II) σ-Acetylide and Carbene Complexes
Organometallics, Vol. 23, No. 10, 2004 2271
Preparation of vinylidene derivatives was attempted in
CH2Cl2 by (1) reacting HCtCR with [(tpy)(bpy)Ru(OH2)]-
(ClO4)2 in the absence of Et3N and (2) treating [(tpy)-
(bpy)RuCtCR]ClO4 with HCl or CF3COOH. However,
no vinylidene product was isolated from these routes.
We reasoned that the vinylidene derivatives may be too
reactive to be isolated, and we therefore attempted to
prepare the alkoxycarbene species by reacting CF3-
COOH with [(tpy)(bpy)RuCtCR]ClO4 in the presence
of MeOH; we envisioned that this may generate the
vinylidene intermediate in situ, which would react with
MeOH to give the methoxycarbene complex. Hence the
isolated product was the targeted carbene complexes
[(tpy)(bpy)RudC(OMe)(CH2R)]2+ (9 and 10).
Electr och em ica l In for m a tion a n d Com p a r ison s
w ith [(tp y)(bp y)Ru L]n +. The acetylide complexes 1-8
show two reversible/quasi-reversible reduction waves at
E1/2 ) -2.22 to -2.14 and -1.95 to -1.87 V, plus an
irreversible oxidation wave at Epa ) 0.15 to 0.26 V (scan
rate ) 50 mV s-1), whereas the carbene complexes 9
and 10 show three reversible/quasi-reversible couples
at E1/2 ) -2.03 and -2.04, -1.57 and -1.50, and 0.99
and 1.00 V, respectively. The reduction waves for
complexes 1-10 are assigned as reduction of the poly-
pyridyl ligands, while the oxidation waves are assigned
as metal-centered Ru(III/II) oxidations. The more posi-
tive E1/2 values of the redox couples for 9 and 10
compared to 1-8 can be rationalized by the increase in
electronic charge in the complexes. In the literature, the
electrochemical behavior of ruthenium-polypyridyl com-
plexes with the general formula [Ru(tpy)(bpy)L]n+ have
been extensively studied.12,30 Complexes of this type
show reduction waves corresponding to successive re-
duction at the polypyridyl ligands. The tpy ligand is
preferentially reduced because its π* level is lower than
that of bpy. With reference to previous works, we assign
the more negative reduction couples at E1/2 ) -2.22 to
-2.14, -2.03, and -2.04 V (for 1-8, 9, and 10, respec-
tively) to the reduction of the bpy ligand, and the other
reduction couple at E1/2 ) -1.95 to -1.87, -1.57, and
-1.50 V (for 1-8, 9, and 10, respectively) to tpy
reduction.
The irreversible oxidation waves for 1-8 are assigned
as metal-centered, because the coordinated tpy or bpy
ligands in [Ru(tpy)(bpy)L]n+ are not oxidized at around
this potential. Comparing the reported Ru(III/II) redox
potentials of [Ru(tpy)(bpy)L]+ (L ) -Cl,12c -NCNAr,30b
and -CtN:12e E1/2 ) 0.41, 0.34-0.43, and 0.67 V,
respectively) and Epa of [Ru(tpy)(bpy)CtCR]+ (0.15 to
0.26 V), [Ru(tpy)(bpy)CtCR]+ is clearly more easily
oxidized. It is interesting to compare the Ru(III/II)
waves for [Ru(tpy)(bpy)CtCR]+ and [Ru(tpy)(bpy)Ct
N]+, because -CtCR and -CtN are isoelectronic and
both ligands can coordinate with metal centers through
σ-bonding and π-back-bonding interactions. We have
observed that the oxidation of [Ru(tpy)(bpy)CtCR]+
occurs at more cathodic potentials than that of [Ru(tpy)-
(bpy)CtN]+, which reflects the nature of -CtCR as a
stronger σ-donating and weaker π-accepting ligand than
-CtN. This correlates with the spectroscopic data (see
below), which shows that the Ru(II) f π*(polypyridyl)
1MLCT absorption band for [Ru(tpy)(bpy)CtCR]+ (λmax
) 513-526 nm) is red-shifted from that for [Ru(tpy)-
(bpy)CtN]+ (λmax ) 470 nm).12e
The E1/2 values of the Ru(III/II) oxidation couple for
[(tpy)(bpy)RudC(OMe)(CH2R)]2+ (9 and 10) are 0.99 and
1.00 V, respectively, which are slightly higher than
those for [(tpy)(bpy)Ru(py)]2+ and [(tpy)(bpy)Ru-
(NCCH3)]2+ (0.86 and 0.89 V, respectively).30a The
crystallographic data indicate that the methoxyalkyl-
carbene group in this work is a Fischer-type carbene,
which can coordinate to metal centers through σ and
π-back-bonding interactions like pyridine and CH3CN.
These data suggest that methoxyalkylcarbene ligands
can stabilize the Ru(II) center more effectively than
pyridine and CH3CN. This is also consistent with the
spectroscopic data (see below), which depicts the Ru(II)
f π*(polypyridyl) 1MLCT absorption for [Ru(tpy)(bpy)d
C(OMe)(CH2R)]2+ (λmax ) 415 (9) and 408 (10) nm) at a
higher energy than that for [Ru(tpy)(bpy)(py)]2+ and
[(tpy)(bpy)Ru(NCCH3)]2+ (λmax ) 466 and 455 nm,
respectively).30a The reversibility of the Ru(III)/(II)
couple for 9 and 10 shows that the coordinated Fischer
carbene ligand is stable, at least during the cyclic
voltammetric scans, in the oxidizing Ru(III) complexes
with an oxidation potential of 0.99 and 1.00 V, respec-
tively.
Electr on ic a n d Em ission Sp ectr oscop y. In the
literature, polypyridyl complexes of ruthenium(II) fea-
ture two types of absorption bands: highly intense
absorptions in the UV region and moderately intense
absorptions in the visible region. The former are at-
tributed to intraligand (polypyridyl) π f π* transitions,
while the latter are ascribed to dπ(RuII) f π*(polypy-
ridyl) charge transfer (MLCT) transitions.1d In this
work, the absorption bands in the visible region for
1-10 are assigned to dπ(RuII) f π*(polypyridyl) 1MLCT
transitions. However, we note that for the [(tpy)(bpy)-
RuCtCR]+ complexes, this MLCT transition slightly
blue-shifts in energy (by 909 cm-1) as the π-conjugation
length of the arylacetylide ligand increases: λmax for R
) C6H4X-4 > C6H4CtCPh > (C6H4CtC)2Ph. This
suggests that the HOMO may contain a contribution
from the acetylide ligand. Indeed, the decrease in π*
energy for more conjugated arylacetylide ligands would
result in enhanced metal-to-ligand (Ru-to-acetylide)
π-back-bonding and a decrease in electron density
around Ru, leading to a larger energy gap between the
Ru(II) dπ orbitals and polypyridyl π* orbitals. The
alternative assignment for the visible absorptions to dπ-
(RuII) f π*(CtCAr) transitions for 1-8 is unreasonable
because the analogous transition for trans-[Ru(16-
TMC)(CtCC6H4X-p)2] (X ) F, Cl, H, Me, and OMe)
occurs at λmax ) 379-408 nm.22a In any case, the Ru f
π*(CtCAr) MLCT transition for polypyridine complexes
should appear at a higher energy than for derivatives
supported by 16-TMC because 16-TMC is a stronger
σ-donor and weaker π-acceptor than polypyridines.
1
The Ru(II) f π*(polypyridyl) MLCT transitions for
1-8 are noticeably different from those of 9 and 10 (415
and 408 nm, respectively). Indeed the MLCT transition
for [(tpy)(bpy)RuL]n+ is sensitive to the nature of the
ligand L. For example, the Ru(II) f π*(polypyridyl)
(30) (a) Rasmussen, S. C.; Ronco, S. E.; Mlsna, D. A.; Billadeau, M.
A.; Pennington, W. T.; Kolis, J . W.; Petersen, J . D. Inorg. Chem. 1995,
34, 821. (b) Mosher, P. J .; Yap, G. P. A.; Crutchley, R. J . Inorg. Chem.
2001, 40, 550.
transitions for [Ru(tpy)(bpy)(NtCCH3)]2+ 30a
,
[Ru(tpy)-
(bpy)(py)]2+ 30a
,
[Ru(tpy)(bpy)(CtN)]+,12e [Ru(tpy)(bpy)-

2272 Organometallics, Vol. 23, No. 10, 2004
Wong et al.
(NCNAr)]+,30b and [Ru(tpy)(bpy)Cl]+ 12c occur at λmax
)
1MLCT transition from 9 and 10 to 1-8, these emissions
are tentatively ascribed as dπ(RuII) f π*(polypyridyl)
3MLCT in nature.
455, 466, 470, 489-496, and 502 nm, respectively. The
λmax of the 1MLCT transitions for 1-8 (502-526 nm)
are clearly red-shifted in energy in comparison; this is
consistent with the greater σ-donating ability of the
-CtCR ligand, which destabilizes the dπ(Ru) energy
levels. The blue-shifted absorption maximum of the
1MLCT transitions for 9 and 10 reflects the greater
π-accepting ability of the [:C(OMe)(CH2R)] Fischer
carbene moieties. The Ru f π*(carbene) π-back-bonding
interaction would stabilize the dπ(Ru) orbitals, leading
to an increase in energy for the dπ f π*(polypyridine)
charge transfer transition. However, the extent of the
π-back-bonding interaction is not as substantial as that
in [Ru(tpy)(bpy)(CO)]2+ (λmax ) 368 nm).12c
Su m m a r y
A series of acetylide- and methoxyalkylcarbene-
ruthenium(II) complexes supported by the tpy-bpy
ligand set have been synthesized. The molecular struc-
tures of 4(PF6), 5(PF6), and 9(ClO4)2 have been charac-
terized by X-ray crystallography. The absorption bands
in the visible region for 1-8 (λmax ) 502-526 nm) and
9 and 10 (λmax ca. 410 nm) are assigned as dπ(RuII) f
π*(polypyridyl) 1MLCT transitions, while the emissions
of complexes 1-8 at λmax ) 748-786 nm in CH3CN
solution at 298 K (λex ) 550 nm) are tentatively assigned
In the literature, ruthenium(II) complexes of terpy-
ridine ligand(s) are typically nonemissive or weakly
emissive with short excited-state lifetimes at room
temperature. This has been attributed to effective
radiationless decay from low lying 3MC (metal-centered)
excited states.1d In this work, excitation of 1-8 at λ )
3
as dπ(RuII) f π*(polypyridyl) MLCT in nature. Com-
parisons of their electrochemical and spectroscopic data
with those of related [(tpy)(bpy)RuL]n+ derivatives sug-
gest that acetylide ligands are strong σ-donors while
methoxyalkylcarbene ligands are better π-acceptors
than pyridine and CH3CN. The Fischer-type carbene
complexes 9 and 10 undergo photochemical reaction
upon irradiation in CH3CN and CH2Cl2, and [(tpy)(bpy)-
RuNtCCH3]2+ and 4-methoxybenzaldehyde were char-
acterized as reaction products from the photolysis of 9
in CH3CN.
550 nm in CH3CN at 298 K gave emission at λmax
)
748-786 nm, and the energy of the emission maximum
increases in the order R ) t-Bu (12 720 cm-1) < C6H4X-4
(12 900-13 330 cm-1) e C6H4CtCPh (13 350 cm-1) ≈
(C6H4CtC)2Ph (13 370 cm-1). Moreover, the emission
maximum for R ) C6H4X-4 partially blue-shifts in
energy (by 430 cm-1) as the electron-donating ability of
X decreases in the order: λmax for X ) OMe < Me < H
< F ≈ Cl. The anomalous effect of the fluoro substituent
can be rationalized by its negative inductive and positive
mesomeric effects. Excitation of 9 and 10 at λ ) 415
nm in n-butyronitrile at 77 K produces emission at λmax
) 597 and 615 nm, respectively. As the trend in
emission maxima for 1-8 parallels the corresponding
Ack n ow led gm en t. This work was supported by the
Research Grants Council of the Hong Kong SAR, China
(HKU 7077/01P), the Croucher Foundation (Hong Kong),
and The University of Hong Kong.
Su p p or tin g In for m a tion Ava ila ble: Characterization
data;crystaldata for 4(PF6)‚21/2CH3CN,5(PF6),and 9(ClO4)2‚2CH2-
Cl2; perspective view of cation in 5; absorption and emission
spectra of 3 in CH2Cl2; UV-visible spectral trace for photolysis
of 9 in CH2Cl2. This material is available free of charge via
the Internet at http://pubs.acs.org.
1
Ru(II) f π*(polypyridyl) MLCT absorption maxima,
and the red-shift in emission maxima from the carbene
complexes 9 and 10 to the acetylide complexes 1-8 is
also reflected in the red-shift in Ru(II) f π*(polypyridyl)
OM034379K