Syntheses, characterization, and catalytic ability in alkane oxygenation of chloro(dimethyl sulfoxide)ruthenium(II) complexes with tris(2-pyridylmethyl) amine and its derivatives

Article abstract of DOI:10.1021/ic060722c

New ruthenium(II) complexes having a tetradentate ligand such as tris(2-pyridylmethyl)amine (TPA), tris[2-(5-methoxycarbonyl)pyridylmethyl]amine [5-(MeOCO)₃-TPA], tris(2-quinolylmethyl)amine (TQA), or bis(2-pyridylmethyl)-glycinate (BPG) have been prepared. The reaction of the ligand with [RuCl₂(Me₂SO)₄] resulted in a mixture of trans and cis isomers of the chloro(dimethyl sulfoxide-κ S)ruthenium(II) complexes containing a TPA or a BPG, whereas a trans(Cl,N _amino) isomer was selectively obtained for 5-(MeOCO)₃-TPA and TQA. The trans and cis isomers of the [RuCl(TPA)(Me₂SO)] ⁺ complex were easily separated by fractional recrystallization. The molecular structures of trans- and cis(Cl,N_amino)-[RuCl(TPA)(Me ₂SO)]⁺ complexes and the trans(Cl,N_amino)- [RuCl{5-(MeOCO)₃-TPA}(Me₂SO)]⁺ complex have been determined by X-ray structural analyses. The reaction of TPA with [RuCl₂(PhCN)₄] gave a single isomer of the chloro(benzonitrile)ruthenium(II) complex, whereas the bis(benzonitrile) ruthenium(II) complex was obtained with BPG. The cis(Cl,N_amino)- [RuCl(TPA)(Me₂SO)]⁺ complex is thermodynamically much less stable than the trans isomer and isomerizes in dimethyl sulfoxide at 65-100°C. Oxygenation of alkanes catalyzed by these ruthenium(II) complexes has been examined. The chloro(dimethyl sulfoxide-κ S)ruthenium(II) complexes with TPA and its derivatives using m-chloroperbenzoic acid as a cooxidant showed high catalytic ability. Adamantane was efficiently and selectively oxidized to give 1-adamantanol up to 88%. The chloro(dimethyl sulfoxide-κ S)-ruthenium(II) complex with 5-(MeOCO)₃-TPA was found to be the most active catalyst among the complexes examined.

Full text of DOI:10.1021/ic060722c

Inorg. Chem. 2006, 45, 8342−8354
Syntheses, Characterization, and Catalytic Ability in Alkane Oxygenation
of Chloro(dimethyl sulfoxide)ruthenium(II) Complexes with
Tris(2-pyridylmethyl)amine and Its Derivatives1,2
Motowo Yamaguchi,* Hiroyuki Kousaka, Shinichi Izawa, Yoshiki Ichii, Takashi Kumano,
Dai Masui, and Takamichi Yamagishi
Department of Applied Chemistry, Graduate School of Engineering, Tokyo Metropolitan
UniVersity, Minami-osawa, Hachioji, Tokyo 192-0397, Japan
Received April 28, 2006
New ruthenium(II) complexes having a tetradentate ligand such as tris(2-pyridylmethyl)amine (TPA), tris[2-(5-
methoxycarbonyl)pyridylmethyl]amine [5-(MeOCO)3-TPA], tris(2-quinolylmethyl)amine (TQA), or bis(2-pyridylmethyl)-
glycinate (BPG) have been prepared. The reaction of the ligand with [RuCl2(Me2SO)4] resulted in a mixture of trans
and cis isomers of the chloro(dimethyl sulfoxide-κS)ruthenium(II) complexes containing a TPA or a BPG, whereas
a trans(Cl,Namino) isomer was selectively obtained for 5-(MeOCO)3-TPA and TQA. The trans and cis isomers of the
[RuCl(TPA)(Me2SO)]+ complex were easily separated by fractional recrystallization. The molecular structures of
{5-(MeOCO)3-TPA}
trans- and cis(Cl,Namino)-[RuCl(TPA)(Me2SO)]+ complexes and the trans(Cl,Namino)-[RuCl (Me2SO)]+
complex have been determined by X-ray structural analyses. The reaction of TPA with [RuCl2(PhCN)4] gave a
single isomer of the chloro(benzonitrile)ruthenium(II) complex, whereas the bis(benzonitrile)ruthenium(II) complex
was obtained with BPG. The cis(Cl,Namino)-[RuCl(TPA)(Me2SO)]+ complex is thermodynamically much less stable
than the trans isomer and isomerizes in dimethyl sulfoxide at 65
these ruthenium(II) complexes has been examined. The chloro(dimethyl sulfoxide-
TPA and its derivatives using m-chloroperbenzoic acid as a cooxidant showed high catalytic ability. Adamantane
was efficiently and selectively oxidized to give 1-adamantanol up to 88%. The chloro(dimethyl sulfoxide- S)-
−100
°
C. Oxygenation of alkanes catalyzed by
κ
S)ruthenium(II) complexes with
κ
ruthenium(II) complex with 5-(MeOCO)3-TPA was found to be the most active catalyst among the complexes
examined.
Introduction
metalloenzymes4 containing Fe5,6 or Cu7,8 sites as dioxygen
activation centers. Ru analogues have been also studied.
The development of an efficient catalyst capable of
oxidizing saturated hydrocarbons under mild conditions is a
Tripodal tetradentate ligands, TPA and its derivatives,
containing both σ-donating tertiary amine and π-accepting
pyridyl groups are versatile ligands and have been used for
the preparation of various transition-metal complexes con-
taining the group 5-11 elements, lanthanides, and an
actinide.3 These ligands have been employed in the structural
and/or functional model complexes of mono- and dinuclear
(4) (a) Funabiki, T. Oxygenases and Model Systems; Kluwer Academic
Publishers: Dordrecht, The Netherlands, 1997; Chapter 3. (b) Ito, M.;
Fujisawa, K.; Kitajima, N.; Moro-oka, Y. Oxygenases and Model
Systems; Kluwer Academic Publishers: Dordrecht, The Netherlands,
1997; Chapter 8.
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(b) Costas, M.; Mehn, M. P.; Jensen, M. P.; Que, L., Jr. Chem. ReV.
2004, 104, 939-986.
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104, 987-1012. (b) Wasser, I. M.; Huang, H.-W.; Moe¨nne-Loccoz,
P.; Karlin, K. D. J. Am. Chem. Soc. 2005, 127, 3310-3320.
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D. Chem. ReV. 2004, 104, 1077-1133. (b) Chishiro, T.; Shimazaki,
Y.; Tani, F.; Naruta, Y. Chem. Commun. 2005, 1079-1081.
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24, 4378-4386.
* To whom correspondence should be addressed. E-mail:
yamaguchi-motowo@c.metro-u.ac.jp. Fax: +81-426-77-1223.
(1) Preliminary communication: Yamaguchi, M.; Kousaka, H.; Yamagishi,
T. Chem. Lett. 1997, 769-770.
(2) Abbreviations: TPA ) tris(2-pyridylmethyl)amine; 5-(MeOCO)3-TPA
) tris[2-(5-methoxycarbonyl)pyridylmethyl]amine; TQA ) tris(2-
quinolylmethyl)amine; BPGH ) bis(2-pyridylmethyl)glycine.
(3) The survey of the Cambridge Crystallographic Data Centre revealed
that the crystal structures of the transition-metal complexes of TPA
and derivatives of V, Cr, Mn, Re, Fe, Ru, Os, Co, Rh, Ir, Ni, Cu, Nd,
Eu, Tb, Lu, and U have been reported.
8342 Inorganic Chemistry, Vol. 45, No. 20, 2006
10.1021/ic060722c CCC: $33.50
© 2006 American Chemical Society
Published on Web 09/06/2006

Chloro(dimethyl sulfoxide)ruthenium(II) Complexes
challenging goal in synthetic chemistry, and the transition-
metal complexes are promising candidates as an alkane
oxidation catalyst.9 A number of mono- and dinuclear iron
complexes have been studied as a functional model of non-
heme iron enzymes such as methane monooxygenase
(MMO).4b,5,10 Ruthenium complexes have drawn much
attention as a functional model of MMO and have shown
high catalytic ability upon alkane oxygenation.1,11,12
A number of the iron mononuclear complexes with TPA
or BPG and their derivatives have been examined in the
catalytic oxygenation of alkanes.5,13 On the other hand,
similar studies utilizing Ru-TPA complexes are few. Kojima
et al. have reported alkane oxygenation catalyzed by mono-
and dinuclear ruthenium complexes having TPA, [RuCl2-
(TPA)]ClO4, or [RuCl(TPA)]2(ClO4)2 in the presence of
m-chloroperbenzoic acid (MCPBA),11a tert-butyl hydro-
peroxide,11c or molecular oxygen.11b We have reported the
preparation of the chloro(dimethyl sulfoxide-κS) complex
with TPA14 and its application to catalytic oxygenation of
alkane.1 It was found that trans(Cl,Namino)-[RuCl(TPA)-
(Me2SO)]PF6 showed high catalytic ability upon oxygenation
of adamantane to give 1-adamantanol selectively in high
yield in the presence of MCPBA. Recently, Jituskawa et al.
have reported alkane oxygenation in the presence of PhIO
catalyzed by monochloro- or dichlororuthenium complexes
with a TPA-type ligand having a 6-neopentylamino or
6-pivalamide group on the pyridyl group(s).11d,e The sub-
stituents at the 6 position of the TPA-type ligand may have
both a steric effect and an electronic effect on the catalytic
ability.
In this paper, we report the syntheses, characterization,
and application to catalytic alkane oxygenation of the ruthe-
nium complexes with a tripodal tetradentate ligand: TPA,
5-(MeOCO)3-TPA, TQA, and BPG. The molecular structures
of trans(Cl,Namino)-[RuCl(TPA)(Me2SO)][RuCl3(Me2SO)3],15
cis(Cl,Namino)-[RuCl(TPA)(Me2SO)]PF6‚1/2MeCN,1 and trans-
(Cl,Namino)-[RuCl{5-(MeOCO)3-TPA}(Me2SO)]PF6‚
0.2H2O16 complexes have been determined. The bulky
6-position substituents may hinder access of the substrate
and/or oxidant to the metal center, while the 5-position
substituent has little steric hindrance and is expected to show
only an electronic effect. We have prepared both trans and
cis isomers of [RuCl(TPA)(Me2SO)]X (X ) Cl, PF6);1
however, Kojima et al. reported the synthesis of cis(Cl,Namino)-
[RuCl(TPA)(Me2SO)]ClO4,14 and Bjernemose et al. recently
reported the selective synthesis of trans(Cl,Namino)-[RuCl-
(TPA)(Me2SO)]PF6.17 The inconsistency in the selectivity on
the syntheses prompted us to study the stability of these
isomers by thermal isomerization experiments, molecular
mechanics (MM), and quantum mechanics (QM) calculations
to shed light on the character of chloro(dimethyl sulfoxide-
κS)ruthenium(II) complexes with TPA and its derivatives.
The results of the oxygenation of alkanes catalyzed by these
ruthenium(II) complexes are also reported. The study of
complexes involving a TPA with electron-withdrawing
groups has thus far been rare, and the ruthenium(II) complex
[RuCl{5-(MeOCO)3-TPA}(Me2SO)]PF6 having methoxy-
carbonyl group on the pyridyl groups was found to be an
active and selective catalyst on the oxygenation of alkanes.
Experimental Section
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(10) Hu, Z.; Gorun, S. M. Biomimetic Oxidations Catalyzed by Transition
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Jitsukawa, K.; Oka, Y.; Yamaguchi, S.; Masuda, H. Inorg. Chem. 2004,
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M. H. V. Inorg. Chem. 2003, 42, 8140-8160. (c) Taqui Khan, M.
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29, 2553-2555. (b) Leising, R. A.; Kim, J.; Pe`rez, M. A.; Que, L.,
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Materials and Measurements. All chemicals were of reagent
grade and were used as received without further purification unless
otherwise noted. TPA,18 TQA,19 BPGH,18 cis-[RuCl2(Me2SO)4],20
and trans-[RuCl2(PhCN)4]21 were prepared by literature procedures.
The solvents used for catalytic oxidation reaction were purified by
refluxing over P2O5 or KMnO4 (for acetone), distilled, and stored
in a N2 atmosphere.
NMR spectra were recorded on JEOL EX-270 or JEOL LA-
400 spectrometers. Fast atom bombardment mass spectra (FAB-
MS) were obtained on a JEOL LX-1000 mass spectrometer by using
m-nitrobenzyl alcohol as a matrix. The isotopic distributions of Ru
complex ions were calculated to assign the observed peaks.
All electrochemical measurements were carried out with a BAS
CV50W voltammetry analyzer in acetonitrile using 0.1 M tetra-
ethylammonium perchlorate as the supporting electrolyte under N2
at ambient temperature. Cyclic voltammograms (CV) were obtained
(15) Masui, D.; Yamaguchi, M.; Yamagishi, T. Acta Crystallogr. E 2003,
E59, m308-309.
(16) Yamaguchi, M.; Kumano, T.; Masui, D.; Yamagishi, T. Chem.
Commun. 2004, 798-799.
(17) Bjernemose, J.; Hazell, A.; McKenzie, C. J.; Mahon, M. F.; Nielsen,
L. P.; Raithby, P. R.; Simonsen, O.; Toftlund, H.; Wolny, J. A.
Polyhedron 2003, 22, 875-885.
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M. J.; Que, L., Jr.; Wallick, D. E. J. Am. Chem. Soc. 1988, 110, 2026-
2032.
(19) Wei, N.; Murthy, N. N.; Chen, Q.; Zubieta, J.; Karlin, K. D. Inorg.
Chem. 1994, 33, 1953-1965.
(14) After our publication in ref 1, the study of cis(Cl,Namino)-[RuCl(TPA)-
(Me2SO)]ClO4 and trans(Cl,Namino)-[RuCl(5-Me3-TPA)(Me2SO)]ClO4
has been reported by Kojima and colleagues: Kojima, T.; Amano,
T.; Ishii, Y.; Ohba, M.; Okaue, Y.; Matsuda, Y. Inorg. Chem. 1998,
37, 4076-4085.
(20) Evans, I. E.; Spencer, A.; Wilkinson, G. J. Chem. Soc., Dalton Trans.
1973, 204-209.
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1977, 719-724.
Inorganic Chemistry, Vol. 45, No. 20, 2006 8343

Yamaguchi et al.
by using a platinum disk (3-mm-o.d.) working electrode, a platinum
wire counter electrode, and an Ag/Ag+ reference electrode. Redox
potentials were determined relative to a ferrocene/ferrocenium (Fc/
Fc+) ion couple as 0 V. All solutions were deoxygenated by
bubbling N2 gas through them and were maintained under N2 during
the measurements. Analyses of the oxygenated products were
performed by a Shimadzu GC-14a gas chromatograph using the
G100 column of the Chemicals Evaluation and Research Institute,
Japan (Tokyo, Japan), or a Shimadzu GCMS-QP5050 gas chro-
matograph/mass spectrometer.
MM calculations were performed using Fujitsu CAChe version
4.4 on a PC Celeron platform. Density functional theory (DFT)
calculations were performed using the Gaussian98 package22 for
UNIX, on the IBM parallel computer p690-681 located in the
Computing Center at Tokyo Metropolitan University. The basis set
LANL2DZ or 3-21G** was applied for B3LYP calculations.
Methyl 6-(Bromomethyl)nicotinate. Methyl 6-(bromomethyl)-
nicotinate was prepared by bromination of methyl 6-methylnico-
tinate using N-bromosuccinimide/benzoyl peroxide23 or methyl
6-(hydroxymethyl)nicotinate24 using CBr4/PPh3. The latter proce-
dure resulted in better yield as follows.
1H NMR (CDCl3, 270 MHz): δ 3.94 (9H, s, Me), 3.97 (6H, s,
CH2), 7.63 (3H, d, J ) 7.9 Hz, py-H3), 8.26 (3H, dd, J ) 7.9 Hz,
2.0 Hz, py-H4), 9.14 (3H, d, J ) 2.0 Hz, py-H6).
[RuCl(TPA)(Me2SO)]Cl (1). A solution of TPA (0.41 g, 1.4
mmol) and cis-[RuCl2(Me2SO)4] (0.68 g, 1.4 mmol) in 80 mL of
methanol was refluxed for 2 h. The reaction mixture was concen-
trated to dryness, and the resulting solid was dissolved in a small
amount of methanol. After the addition of ethyl acetate, the solution
was kept in a refrigerator overnight. Yellow precipitates were
collected and dried in vacuo. Yield: 0.70 g (92%). FAB-MS: (M
- Cl)+ 505.
cis(Cl,Namino)-[RuCl(TPA)(Me2SO)]Cl (2) and trans(Cl,Namino)-
[RuCl(TPA)(Me2SO)]Cl (3). The above complex 1 was a mixture
of an approximately equal amount of the trans and cis isomers,
which was isolated by careful fractional recrystallizations from
methanol and ethyl acetate (1:10, v/v). The cis isomer (2) and the
trans isomer (3) were obtained as yellow and pale-orange powders,
respectively. The complex 2 was less soluble. Yield: 0.24 g (32%)
for 2 and 0.35 g (47%) for 3. FAB-MS: (M - Cl)+ 505 for 2 and
1
3. H NMR (CD3CN, 270 MHz) for 2: δ 3.42 (6H, s, CH3), 4.69
(2H, s, CH2(ax)), 4.79 (2H, d, J ) 15 Hz, CH2(eq)), 5.76 (2H, d,
J ) 15, CH2(eq)), 6.95 (1H, d, J ) 7.9 Hz, py-H3(ax)), 7.16-7.25
(3H, m, py-H5(ax + eq)), 7.46-7.51 (3H, m, py-H4(ax) + py-
H3(eq)), 7.73 (2H, t, J ) 7.8 Hz, py-H4(eq)), 8.70 (2H, d, J ) 5.6
Hz, py-H6(eq)), 9.81 (1H, d, J ) 5.6 Hz, py-H6(ax)). 1H NMR for
3: 2.84 (6H, s, CH3), 4.53 (2H, s, CH2(ax)), 4.72 (2H, d, J ) 15
Hz, CH2(eq)), 5.39 (2H, d, J ) 15 Hz, CH2(ax)), 7.13 (1H, d, J )
7.9 Hz, py-H3(ax)), 7.26-7.36 (3H, m, py-H5(ax + eq)), 7.43 (2H,
d, J ) 7.9 Hz, py-H3(eq)), 7.64 (1H, t, J ) 7.9 Hz, py-H4(ax)),
7.76 (2H, t, J ) 7.8 Hz, py-H4(eq)), 8.75 (2H, d, J ) 5.3 Hz,
py-H6(eq)), 9.69 (1H, d, J ) 5.6 Hz, py-H6(ax)).
Methyl 6-(hydroxymethyl)nicotinate (3.21 g, 19.2 mmol) and
tetrabromomethane (8.04 g, 24.3 mmol) were dissolved in a minimal
amount of tetrahydrofuran (THF). The resultant solution was stirred
for 2 h at room temperature. To the solution was added water, and
the reaction mixture was extracted by dichloromethane three times,
dried by magnesium sulfate, filtered, and concentrated by evapora-
tion. The residue was purified by column chromatography (SiO2;
hexane:ethyl acetate ) 3:2). A reddish solid was obtained after
evaporation of the solvent. Yield: 2.85 g (64%). FAB-MS: (M +
1
H)+ 230, 232. H NMR (CDCl3, 270 MHz): δ 3.94 (3H, s, Me),
4.56 (2H, s, CH2), 7.52 (1H, d, J ) 7.8 Hz, py-H3), 8.28 (1H, dd,
J ) 7.8 Hz, 2.0 Hz, py-H4), 9.14 (1H, d, J ) 2.0 Hz, py-H6).
Tris[2-(5-methoxycarbonyl)pyridylmethyl]amine [5-(MeOCO)3-
TPA]. 5-(MeOCO)3-TPA was prepared from methyl 6-(bromo-
methyl)nicotinate by a slightly modified method for the preparation
of TQA.19 To a solution of methyl 6-(bromomethyl)nicotinate (2.756
g, 12 mmol) in 15 mL of THF was added 1.24 mL (16 mmol) of
aqueous ammonium hydroxide in four equal portions. The reaction
mixture turned instantly red with the addition of aqueous ammonium
hydroxide. The solution was stirred at room temperature, and the
following portions of aqueous ammonium hydroxide were added
after the color disappeared (it took about 24 h). The reaction mixture
was stirred for 1 week. The colorless solid was filtered, and the
filtrate was concentrated to dryness. The residue was dissolved in
methylene chloride and dried with magnesium sulfate. After
filtration, the filtrate was evaporated to dryness to yield a slightly
yellowish solid. Yield: 1.45 g (78%). FAB-MS: (M + 1)+ 465.
trans(Cl,Namino)-[RuCl(TPA)(Me2SO)][RuCl3(Me2SO)3] (4).
The trans(Cl,Namino) isomer was obtained unintentionally as the salt
with a [RuCl3(Me2SO)3] anion from the reaction mixture of the
complex 1. See text.
cis(Cl,Namino)-[RuCl(TPA)(Me2SO)]PF6‚1/2MeCN (5‚1/2MeCN).
The crude chloride salt, complex 1 (0.32 g, 0.59 mmol), and NH4PF6
(0.099 g, 0.61 mmol) were dissolved in 15 mL of methanol, and
the solution was evaporated to dryness. The solid was dissolved in
20 mL of acetonitrile and filtered. The filtrate was evaporated to
dryness. The resulting yellow powder was dried in vacuo. The
hexafluorophosphate salt, which was a mixture of the trans and cis
isomers, was dissolved in 2 mL of acetonitrile. To the resultant
solution was slowly added 3 mL of diethyl ether, and the solution
was kept in a refrigerator overnight. Orange crystals were collected
and dried in vacuo. This procedure was repeated three times and
gave 0.182 g (47%) of a single isomer, which was found to be the
cis(Cl,Namino) isomer by X-ray analysis. See below. Anal. Calcd
for C21H25.5ClF6N4.5OPRuS: C, 37.62; H, 3.83; N, 9.40. Found:
1
C, 37.57; H, 3.86; N, 9.28. FAB-MS: (M - PF6)+ 505. H NMR
(22) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb,
M. A.; Cheeseman, J. R.; Zakrzewski, V. G.; Montgomery, J. A., Jr.;
Stratmann, R. E.; Burant, J. C.; Dapprich, S.; Millam, J. M.; Daniels,
A. D.; Kudin, K. N.; Strain, M. C.; Farkas, O.; Tomasi, J.; Barone,
V.; Cossi, M.; Cammi, R.; Mennucci, B.; Pomelli, C.; Adamo, C.;
Clifford, S.; Ochterski, J.; Petersson, G. A.; Ayala, P. Y.; Cui, Q.;
Morokuma, K.; Salvador, P.; Dannenberg, J. J.; Malick, D. K.; Rabuck,
A. D.; Raghavachari, K.; Foresman, J. B.; Cioslowski, J.; Ortiz, J.
V.; Baboul, A. G.; Stefanov, B. B.; Liu, G.; Liashenko, A.; Piskorz,
P.; Komaromi, I.; Gomperts, R.; Martin, R. L.; Fox, D. J.; Keith, T.;
Al-Laham, M. A.; Peng, C. Y.; Nanayakkara, A.; Challacombe, M.;
Gill, P. M. W.; Johnson, B.; Chen, W.; Wong, M. W.; Andres, J. L.;
Gonzalez, C.; Head-Gordon, M.; Replogle, E. S.; Pople, J. A. Gaussian
98, revision A.11; Gaussian, Inc.: Pittsburgh, PA, 2001.
(CD3CN, 270 MHz): δ 3.43 (6H, s, CH3), 4.67 (2H, s, CH2(ax)),
4.77 (2H, d, J ) 15 Hz, CH2(eq)), 5.77 (2H, d, J ) 15 Hz, CH2(eq)),
6.95 (1H, d, J ) 7.9 Hz, py-H3(ax)), 7.16-7.26 (3H, m, py-H5(ax
+ eq)), 7.46-7.52 (3H, m, py-H4(ax) + py-H3(eq)), 7.74 (2H, t,
J ) 7.8 Hz, py-H4(eq)), 8.70 (2H, d, J ) 5.6 Hz, py-H6(eq)), 9.81
(1H, d, J ) 5.6 Hz, py-H6(ax)). A peak assigned to acetonitrile
was observed at 2.00 ppm in CDCl3.
trans(Cl,Namino)-[RuCl(TPA)(Me2SO)]PF6 (6). The grayish-
orange crystals, which were the trans(Cl,Namino) isomer, were
obtained from the filtrate of the above-mentioned fractional
recrystallization. Yield: 0.111 g (29%). Anal. Calcd for C20H24-
ClF6N4OPRuS: C, 37.13; H, 3.74; N, 8.65. Found: C, 37.13; H,
3.74; N, 8.65. FAB-MS: (M - PF6)+ 505. 1H NMR (CD3CN, 270
(23) Tyeklar, Z.; Jacobson, R. R.; Wei, N.; Murthy, N. N.; Zubieta, J.;
Karlin, K. D. J. Am. Chem. Soc. 1993, 115, 2677-2689.
(24) Tachi, Y.; Aita, K.; Teramae, S.; Tani, F.; Naruta, Y.; Fukuzumi, S.;
Itoh, S. Inorg. Chem. 2004, 43, 4558-4560.
8344 Inorganic Chemistry, Vol. 45, No. 20, 2006

Chloro(dimethyl sulfoxide)ruthenium(II) Complexes
MHz): δ 2.85 (6H, s, CH3), 4.49 (2H, s, CH2(ax)), 4.67 (2H, d, J
) 15 Hz, CH2(eq)), 5.41 (2H, d, J ) 15 Hz, CH2(ax)), 7.12 (1H,
d, J ) 7.9 Hz, py-H3(ax)), 7.27-7.32 (3H, m, py-H5(ax + eq)),
7.43 (2H, d, J ) 7.9 Hz, py-H3(eq)), 7.63 (1H, t, J ) 7.9 Hz,
py-H4(ax)), 7.77 (2H, t, J ) 7.8 Hz, py-H4(eq)), 8.76 (2H, d, J )
5.3 Hz, py-H6(eq)), 9.70 (1H, d, J ) 5.6 Hz, py-H6(ax)).
py-CH2(eq)), 4.58 (2H, d, J ) 14 Hz, py-CH2(eq)), 5.82 (2H, d, J
) 14 Hz, py-CH2(eq)), 5.94 (2H, d, J ) 14 Hz, py-CH2(eq)), 7.24-
7.31 (8H, m, py-H3 + py-H5), 7.62 (4H, t, J ) 7.3 Hz, py-H4),
9.00 (4H, d, J ) 5.6 Hz, py-H6).
[RuCl(PhCN)(TPA)]Cl (11). A mixture of TPA (0.204 g, 0.70
mmol) and trans-[RuCl2(PhCN)4] (0.409 g, 0.70 mmol) in 50 mL
of methanol was heated to reflux for 2 h. After evaporation to
dryness, the resulting solid was dissolved in methanol (1 mL). To
this solution was added diethyl ether (10 mL), and the resulting
solution was then kept in a refrigerator for 2 weeks. The orange
precipitates were collected and dried in vacuo. Complex 11 contains
only one isomer. Yield: 0.071 g (18%). Anal. Calcd for C25H23-
Cl2N5Ru: C, 53.10; H, 4.10; N, 12.39. Found: C, 52.92; H, 4.01;
N, 12.44. FAB-MS: (M - Cl)+ 530. 1H NMR (CD3CN, 270
MHz): δ 4.64 (2H, s, CH2(ax)), 4.78 (2H, d, J ) 15 Hz, CH2(eq)),
5.43 (2H, d, J ) 15 Hz, CH2(eq)), 7.01 (1H, d, J ) 7.8 Hz, py-
H3(ax)), 7.13 (1H, t, J ) 7.7 Hz, py-H5(ax)), 7.26 (2H, t, J ) 7.6
Hz, py-H5(eq)), 7.43 (2H, t, J ) 7.9 Hz, py-H4(eq)), 7.50 (1H, t,
J ) 7.8 Hz, py-H4(ax)), 7.63-7.80 (5H, m, PhCN), 8.08 (2H, d,
J ) 7.9 Hz, py-H3(eq)), 8.82 (2H, d, J ) 5.5 Hz, py-H6(eq)), 9.03
(1H, d, J ) 5.6 Hz, py-H6(ax)).
trans(Cl,Namino)-[RuCl{5-(MeOCO)3-TPA}(Me2SO)]Cl (7). The
complex 7 was obtained in a procedure similar to that of complex
1 using 5-(MeOCO)3-TPA and cis-[RuCl2(Me2SO)4] except that
the resulting product was recrystallized from methanol/ethyl acetate
and the orange crystals obtained were the trans(Cl,Namino) isomer.
Yield: 88%. FAB-MS: (M - Cl)+ 679, (M - Cl - Me2SO)+
1
601. H NMR (CDCl3, 270 MHz): δ 2.93 (6H, s, Me2SO), 3.95
(6H, s, CH3OCO), 3.98 (3H, s, CH3OCO), 5.38 (2H, s, CH2(ax)),
5.42 (2H, d, J ) 15.5 Hz, CH2(eq)), 5.81 (2H, d, J ) 15.5 Hz,
CH2(eq)), 7.64 (1H, d, J ) 8.2 Hz, py-H3(ax)), 7.82 (2H, J ) 8.2
Hz, py-H3(eq)), 8.17 (1H, dd, J ) 2.0 and 8.2 Hz, py-H4(ax)),
8.29 (2H, dd, J ) 2.0 and 8.2 Hz, py-H4(eq)), 9.33 (2H, d, J ) 2.0
Hz, py-H6(eq)), 10.29 (1H, d, J ) 2.0 Hz, py-H6(ax)).
trans(Cl,Namino)-[RuCl{5-(MeOCO)3-TPA}(Me2SO)]PF6‚
0.2H2O (8). Complex 7 was converted to the PF6 salt for elemental
analysis. [RuCl(Me2SO){5-(MeOCO)3-TPA}]PF6‚0.2H2O. Anal.
Calcd for C26H30.4ClF6N4O7.2PRuS: C, 37.73; H, 3.70; N, 6.77.
Found: C, 37.73; H, 3.46; N, 6.80. FAB-MS (m-NBA): (M -
[Ru(BPG)(PhCN)2]Cl (12). To 20 mL of methanol was added
trans-[RuCl2(PhCN)4] (0.351 g, 0.60 mmol), and the mixture was
heated at 80 °C. To the resultant mixture was added at one time a
solution of BPGH (0.154 g, 0.60 mmol) and KOH (0.042 g, 0.75
mmol) in 30 mL of methanol. After refluxing for 8 h, the solution
was cooled to room temperature and evaporated to dryness. The
solid was dissolved in methanol (1 mL). To this solution was slowly
added ethyl acetate (10 mL), and the resulting solution was then
kept in a refrigerator overnight. The orange needles were collected
and dried in vacuo. Yield: 0.108 g (30%). Anal. Calcd for
C28H24ClN5O2Ru: C, 56.14; H, 4.04; N, 11.69. Found: C, 56.37;
1
PF6)+ 679, (M - PF6 - Me2SO)+ 601. H NMR (CD3CN, 270
MHz): δ 2.86 (6H, s, (CH3)2SO), 3.89 (6H, s, CH3OCO), 3.93
(3H, s, CH3OCO), 4.59 (2H, s, CH2(ax)), 4.82 (2H, d, J ) 15.5
Hz, CH2(eq)), 5.44 (2H, d, J ) 15.5 Hz, CH2(eq)), 7.24 (1H, d, J
) 8.2 Hz, py-H3(ax)), 7.57 (2H, d, J ) 8.2 Hz, py-H3(eq)), 8.16
(1H, dd, J ) 2.0 and 8.2 Hz, py-H4(ax)), 8.27 (2H, dd, J ) 2.0
and 8.2 Hz, py-H4(eq)), 9.20 (2H, d, J ) 2.0 Hz, py-H6(eq)), 10.22
(1H, d, J ) 2.0 Hz, py-H6(ax)).
1
H, 4.16; N, 11.56. FAB-MS: (M - Cl)+ 564. H NMR (CD3CN,
trans(Cl,Namino)-[RuCl(TQA)(Me2SO)]Cl (9). The complex 9
was obtained in a procedure similar to that of complex 1 using
TQA and cis-[RuCl2(Me2SO)4] except that the resulting brown
powder was the trans(Cl,Namino) isomer. See the text. Yield: 62%.
Anal. Calcd for C32H30Cl2N4ORuS: C, 55.65; H, 4.38; N, 8.11.
Found: C, 55.88; H, 4.62; N, 7.90. FAB-MS: (M - Cl - Me2SO)+
577. 1H NMR ((CD3)2SO, 270 MHz): δ 2.93* (6H, s, CH3), 5.06
(2H, s, CH2(ax)), 5.23 (2H, d, J ) 16.5 Hz, CH2(eq)), 6.07 (2H, d,
J ) 16.5 Hz, CH2(eq)), 7.30 (1H, d, J ) 8.6 Hz, qn-H5(ax)), 7.50-
7.64 (5H, m, qn-H6(ax) + qn-H6(eq) + qn-H7(eq)), 7.67 (2H, d,
J ) 8.4 Hz, qn-H3(eq)), 7.80 (1H, d, J ) 7.6 Hz, qn-H3(ax)), 7.91
(2H, d, J ) 8.7 Hz, qn-H5(eq)), 8.02 (1H, t, J ) 8.0 Hz, qn-H7(ax)),
8.24 (1H, d, J ) 7.6 Hz, qn-H4(ax)), 8.48 (2H, d, J ) 8.4 Hz,
qn-H4(eq)), 9.67 (2H, d, J ) 8.6 Hz, qn-H8(eq)), 11.02 (1H, d, J
) 8.0 Hz, qn-H8(ax)). An asterisk indicates that the CH3 peak of
the Me2SO was not observed because of overlapping with the
solvent peak but was observed in CDCl3.
[Ru(BPG)Cl(Me2SO)]‚H2O (10‚H2O). To 20 mL of methanol
was added cis-[RuCl2(Me2SO)4] (0.356 g, 0.734 mmol), and the
mixture was heated at 80 °C. To the resultant mixture was added
at one time a solution of BPGH (0.380 g, 1.48 mmol) and KOH
(0.093 g, 1.7 mmol) in 20 mL of methanol. After refluxing for 2 h,
the solution was concentrated to about 5 mL and kept in a
refrigerator. The precipitates were filtered and washed with ethyl
acetate. The solid was dissolved in chloroform, filtered, evaporated
to dryness, and dried in vacuo. Complex 9 is a mixture of the trans
and cis isomers. Yield: 0.039 g (11%). Anal. Calcd for C16H20-
ClN3O3RuS‚H2O: C, 39.30; H, 4.53; N, 8.49. Found: C, 39.36;
H, 4.46; N, 8.06. FAB-MS: M+ 471. 1H NMR (CDCl3, 270
MHz): δ 3.62 (6H, s, CH3), 3.67 (6H, s, CH3), 3.77 (2H, s,
CH2CO2), 3.79 (2H, s, CH2CO2), 4.52 (2H, d, J ) 14 Hz,
270 MHz): δ 3.57 (2H, s, CH2CO2), 4.79, 4.96 (4H, AB quartet,
J ) 15 Hz, py-CH2), 7.44-7.80 (12H, m, PhCN + py-H5), 7.88
(2H, t, J ) 7.9 Hz, py-H4), 8.05 (2H, d, J ) 7.9 Hz, py-H3), 8.89
(2H, d, J ) 5.6 Hz, py-H6).
X-ray Structural Analysis of 4.15 A good single crystal of 4
was obtained as a yellow block (0.20 × 0.10 × 0.08 mm) by the
slow diffusion of ethyl acetate to a solution of complex 1 in
methanol. Pertinent crystallographic data and experimental condi-
tions are summarized in Table 1. Details of data collection and
refinement have been described previously.15 Selected bond lengths
and angles are listed in Table 2.
X-ray Structural Analysis of 5‚1/2MeCN.1 Good single crystals
of 5 containing one acetonitrile molecule per two molecules of the
complex were obtained from acetonitrile and toluene as a yellow
needle with the dimension of 0.2 × 0.1 × 0.1 mm3. The presence
of acetonitrile was confirmed by NMR and elemental analysis. Data
collection was done on a MAC Science MXC18 four-circle
diffractometer using graphite-monochromated Mo KR radiation (λ
) 0.710 73 Å). Within the range θ ) 3-55°, the data were collected
using a scan. A total of 5012 independent reflections were obtained,
and 4962 reflections with |Fo| g 2σ(Fo) were used in the further
calculations. The intensities were corrected for Lorentz and
polarization effects and for absorption as part of the refinement
model.25 Pertinent crystallographic data and experimental conditions
are summarized in Table 1. The structure was solved by direct
methods using SIR97.26 All non-H atoms were refined anisotropi-
(25) Walker, N.; Stuart, D. Acta Crystallogr. 1983, A39, 158-166.
(26) SIR97: Altomare, A.; Cascarano, G.; Giacovazzo, C.; Guagliardi, A.;
Burla, M. C.; Polidori, G.; Camalli, M. J. Appl. Crystallogr. 1994,
27, 435-436.
Inorganic Chemistry, Vol. 45, No. 20, 2006 8345

Yamaguchi et al.
Table 1. Crystallographic Data for 4, 5, and 8
4
5
8
empirical formula
fw
cryst syst
a, Å
b, Å
c, Å
R, deg
â, deg
γ, deg
V, Å3
C26H42Cl4N4O4Ru2S4
946.82
C21H25.5ClF6N4.5OPRuS
C26H30.4ClF6N4O7.2PRuS
670.51
monoclinic
19.000(4)
17.974(4)
16.262(5)
90
107.65(2)
90
5292(2)
C2/c (No. 15)
4
827.70
triclinic
11.5045(9)
14.2950(11)
11.4761(8)
104.455(3)
106.799(3)
97.201(2)
1709.4(2)
P1h (No. 2)
1
triclinic
10.1817(18)
14.221(2)
14.664(3)
114.362(3)
96.804(3)
105.610(3)
1798.1(5)
P1h (No. 2)
2
space group
Z
D
calc, g/cm3
1.749
1.683
1.608
T, K
173
14.07
4463
293
8.90
4962
293
7.25
7668
µ(Mo KR), cm-1
no. of reflns used
no. of variables
405
460
506
Ra
0.027
0.031
0.037
Rw
GOF
0.065b
0.076c
1.093
0.090d
0.98
1.138
a R ) ∑||Fo| - |Fc||/∑|Fo|. b Rw ) [∑w(Fo2 - Fc )2/∑w(Fo )2]1/2 with weight w ) 1/[σ2(Fo ) + (0.0351P)2] where P ) (Fo2 + 2Fc )/3. c Rw ) [∑w(|Fo|
2
2
2
2
- |Fc|)2/∑w|Fo| ]1/2 with weight w ) 1/[σ2(Fo ) + (0.0374P)2 + 6.4722P] where P ) (Fo + 2Fc )/3. d Rw ) [∑w(Fo - Fc )2/∑w(Fo )2]1/2 with weight w
2
2
2
2
2
2
2
2
2
2
) 1/[σ2(Fo ) + (0.0594P)2 + 0.6402P] where P ) (Fo + 2Fc )/3.
Table 2. Selected Bond Lengths (Å) and Angles (deg) for 4, 5, and 8
trans(Cl,Namino)-[RuCl(TPA)(Me2SO)]-[RuCl3(Me2SO)3] (4)
acetone. Data collection was done on a Rigaku RAXIS-RAPID
Imaging Plate diffractometer using graphite-monochromated Mo
KR radiation (λ ) 0.710 69 Å). A total of 7668 independent
reflections were obtained, and 7093 reflections with |Fo| g 2σ(Fo)
were used in the further calculations. The intensities were corrected
for Lorentz and polarization effects. Pertinent crystallographic data
and experimental conditions are summarized in Table 1. The
structure was solved by direct methods using SIR97.26 All non-H
atoms were refined anisotropically, and all H atoms were located
at the calculated positions. Refinement was carried out by a full-
matrix least-squares method on F 2 using SHELXL-97.27 Atom
scattering factors were taken from the standard source.28 The final
discrepancy factors were R ) ∑||Fo| - |Fc||/∑|Fo| ) 0.033 and
Ru1-Cl1
Ru1-S1
Ru1-N1
Ru1-N2
Ru1-N3
Ru1-N4
S1-O1
2.4321(9)
2.2385(10)
2.078(3)
2.106(3)
2.060(3)
2.070(3)
1.480(2)
Cl1-Ru1-S1
Cl1-Ru1-N4
S1-Ru1-N4
N1-Ru1-N4
N2-Ru1-N4
N3-Ru1-N4
Cl1-Ru1-S1
88.87(3)
171.41(8)
98.48(8)
80.55(10)
80.75(10)
82.90(11)
88.87(3)
cis(Cl,Namino)-[RuCl(TPA)(Me2SO)]PF6‚1/2MeCN (5)
Ru1-Cl1
Ru1-S1
Ru1-N1
Ru1-N2
Ru1-N3
Ru1-N4
S1-O1
2.4319(9)
2.2653(8)
2.095(2)
2.065(2)
2.079(2)
2.091(2)
1.479(3)
Cl1-Ru1-S1
Cl1-Ru1-N1
S1-Ru1-N1
N1-Ru1-N2
N1-Ru1-N3
N1-Ru1-N4
85.75(3)
90.99(7)
176.13(7)
81.91(10)
80.70(10)
79.93(10)
2 1/2
Rw ) [∑w(|Fo| - |Fc|)2/∑w|Fo| ] ) 0.086 with weight w )
2
2
1/[σ2(Fo ) + (0.0614P)2 + 0.5193P] where P ) (Fo + 2Fc2)/3.
Selected bond lengths and angles are listed in Table 2.
Catalytic Oxidation of Alkanes Using Ruthenium Complexes
in the Presence of MCPBA. Catalytic oxidation of adamantane,
cyclooctane, and ethylbenzene using ruthenium complexes was
carried out in the presence of MCPBA. A typical reaction procedure
of catalytic oxidation was as follows: 0.2 mmol (0.027 g) of
adamantane, 0.3 mmol (0.074 g) of MCPBA, and 1 × 10-3 mmol
of the ruthenium complex were dissolved in 5 mL of chloroform
containing 1,2-dichlorobenzene as an internal reference under a N2
atmosphere and stirred at ambient temperature. The products were
analyzed by gas chromatography (GC) or GC/mass spectrometry
(MS).
trans(Cl,Namino)-[RuCl{5-(MeOCO)3-TPA}(Me2SO)]PF6‚0.2H2O (8)
Ru1-Cl1
Ru1-S1
Ru1-N1
Ru1-N2
Ru1-N3
Ru1-N4
S1-O7
2.4253(6)
2.2585(6)
2.0778(19)
2.060(2)
2.1033(19)
2.078(2)
Cl1-Ru1-S1
Cl1-Ru1-N1
S1-Ru1-N1
N1 Ru1-N2
N1-Ru1-N3
N1-Ru1-N4
88.01(2)
172.93(5)
98.62(6)
82.61(8)
81.28(7)
80.29(8)
1.4921(19)
cally, and all H atoms except those of the solvent molecule were
located at the calculated positions. Refinements were carried out
by a full-matrix least-squares method on F 2 using SHELXL-97.27
Atom scattering factors were taken from the standard source.28 The
N atom of acetonitrile was found on the rotational axis. A
hexafluorophosphate anion was found to be disordered. The final
discrepancy factors were R ) ∑||Fo| - |Fc||/∑|Fo| ) 0.031 and
Results and Discussion
Syntheses. The ruthenium(II) complexes were synthesized
with polypyridyl tetradentate ligands, TPA, 5-(MeOCO)3-
TPA, TQA, and BPG, as shown in Figure 1. The new ligand,
5-(MeOCO)3-TPA, was prepared by a slight modification
of the method reported for TQA.19,29 The reaction of
methyl 6-(bromomethyl)nicotinate and NH4OH in THF gave
2
2 2 1/2
Rw ) [∑w(Fo - Fc2)2/∑w(Fo ) ] ) 0.076 with weight w )
1/[σ2(Fo ) + (0.0374P)2 + 6.4722P] where P ) (Fo + 2Fc2)/3.
2
2
Selected bond lengths and angles are listed in Table 2.
X-ray Structural Analysis of 8.16 Good crystals suitable for
X-ray analysis were obtained as an orange block (0.40 × 0.60 ×
0.60 mm) by the slow diffusion of ethanol to a solution of 8 in
(27) Sheldrick, G. M. SHELXL-97; University of Go¨ttingen: Go¨ttingen,
Germany, 1997.
(28) International Tables for X-ray Crystallography; Kynoch Press: Bir-
mingham, England, 1974; Vol. IV.
(29) Tris(2-fluoro-6-pyridylmethyl)amine was also prepared from 2-fluoro-
6-(bromomethyl)pyridine by an analogous procedure, although the
yield was moderate (40%). Machkour, A.; Mandon, D.; Lachkar, M.;
Welter, R. Inorg. Chem. 2004, 43, 1545-1550.
8346 Inorganic Chemistry, Vol. 45, No. 20, 2006

Chloro(dimethyl sulfoxide)ruthenium(II) Complexes
plex 4 was obtained as crystals from the reaction mixture,
which was found by X-ray analysis to be the trans(Cl,Namino
)
isomer of the trichlorotris(dimethyl sulfoxide-κS)ruthenate,
[RuCl3(Me2SO)3]-, salt as shown below. The trichlorotris-
(dimethyl sulfoxide-κS)ruthenate anion was probably pro-
duced from the starting complex during the reaction. The
hexafluorophosphate salts of the trans- and cis-[RuCl(TPA)-
(Me2SO)]+ complexes were separated by fractional recrys-
tallization from acetonitrile/diethyl ether to give complexes
5 and 6, [RuCl(TPA)(Me2SO)]PF6. Complex 5, which was
less soluble and precipitated first as yellow crystals, was
proven by X-ray analysis to be the cis(Cl,Namino) isomer as
shown below. The more soluble complex 6 was the trans-
(Cl,Namino) isomer. On the other hand, the reaction of
5-(MeOCO)3-TPA and cis-[RuCl2(Me2SO)4] gave only one
isomer of the chloro(dimethyl sulfoxide) complexes, [RuCl{5-
(MeOCO)3-TPA}(Me2SO)]Cl (7) or [RuCl{5-(MeOCO)3-
TPA}(Me2SO)]PF6 (8), even in the reaction mixture. This
is in contrast to the fact that the reaction with TPA gave
both cis and trans isomers, 2 and 3. The reaction of cis-
[RuCl2(Me2SO)4] with the TQA ligand gave complex 9,
[RuCl(TQA)(Me2SO)]Cl, which consisted of only one isomer
of each.
Figure 1. Structures of the complexes.
5-(MeOCO)3-TPA in good yield (78%), which proved to be
a convenient way for the syntheses of trisubstituted TPA
derivatives with fewer steps and a better yield compared to
a conventional method such as the reaction of 2 equiv of
methyl 6-(bromomethyl)nicotinate with methyl 6-(amino-
methyl)nicotinate. It is possible that it may be applicable to
the syntheses of other TPA derivatives.
The chloro(dimethyl sulfoxide-κS)ruthenium(II) com-
plexes, [RuCl(L)(Me2SO)]n+, were obtained from a reaction
of the ligands and cis-[RuCl2(Me2SO)4] by refluxing in
methanol.1,16,30 The Me2SO ligands in these ruthenium(II)
complexes are bound through S rather than O as shown
below. With the TPA ligand, the chloride salt of the chloro-
(dimethyl sulfoxide)ruthenium(II) complex, [RuCl(TPA)-
(Me2SO)]Cl, was obtained as a mixture of approximately
The reaction with the BPG ligand gave complex 10, which
was a mixture of both the trans and cis isomers. However,
the trans(Cl,Namino) isomer of the chloro(dimethyl sulfoxide)-
ruthenium(II) complex is the sole product with 5-(MeOCO)3-
TPA and TQA as shown below, which is in contrast to the
reactions with TPA or BPG. As for the complexes con-
taining benzonitrile, the reaction of TPA and trans-
[RuCl2(PhCN)4] gave the chloro(benzonitrile) complex,
[RuCl(PhCN)(TPA)]Cl (11). Complex 11 contained only one
isomer, though the geometry was not determined. On the
other hand, the reaction of BPG and trans-[RuCl2(PhCN)4]
gave the bis(benzonitrile) complex, [Ru(BPG)(PhCN)2]Cl
(12). Although the yields of 11 and 12 were poor, no sign
of other products was observed in the NMR and mass spectra
of the crude products.
equal amounts of two geometrical isomers: cis(Cl,Namino
)
and trans(Cl,Namino) isomers (2 and 3). This is in contrast to
the selective formation of cis(Cl,Namino)-[RuCl(TPA)(Me2SO)]-
ClO4 reported by Kojima et al., which may possibly have
been due to the insolubility of the perchlorate salt of the cis
isomer.30 Recently, Bjernemose et al. have reported the
selective preparation of trans(Cl,Namino)-[RuCl(TPA)(Me2SO)]-
PF6 in high yield,17 which is also inconsistent with our results.
It is probably due to the higher reaction temperature
employed in their studies: refluxing in ethanol. As mentioned
below, the cis isomer could be isomerized to the trans one
at higher temperatures, which accounts for the selective
formation of the trans isomer at elevated temperatures. The
trans and cis isomers of [RuCl(TPA)(Me2SO)]Cl were
separated by careful fractional recrystallization from metha-
nol and ethyl acetate. The less soluble complex was the
cis(Cl,Namino) isomer 2.
1
NMR Spectra. H NMR spectral data of the complexes
are listed in Table 3. The 1H NMR spectra of the complexes
prepared in this study are as expected for Cs symmetry, and
one axial pyridylmethyl group and two in-plane pyridyl-
methyl groups are clearly distinguished. This is in contrast
to the iron(II) complexes with TPA or its derivatives, which
showed fluxional behavior.31 The peaks of the methyl groups
of Me2SO of complexes 5 and 6 are observed at 3.43 and
2.85 ppm, respectively, and are almost identical with those
of 2 and 3. A methyl peak of Me2SO observed at 2.86-2.93
ppm for 7 and 8, which was similar to that of 3 and 6, indi-
cates that they are the trans(Cl,Namino) isomers. The structure
of 8 was confirmed by X-ray analysis as shown below.
Kojima and colleagues reported that the reaction of 5-Me3-
TPA and cis-[RuCl2(Me2SO)4] gave only trans(Cl,Namino)-
[RuCl(5-Me3-TPA)(Me2SO)]ClO4 selectively, and the peak
The 1H NMR spectra of 2 and 3 show peaks of the methyl
groups of Me2SO at 2.84 and 3.42 ppm (in CD3CN),
respectively. Attempts to obtain good crystals of these
complexes failed. However, a very small amount of com-
(30) Kojima et al. reported that the selective formation of the one isomer
of the chloro(dimethyl sulfoxide) complexes of TPA or 5-Me3-TPA,
cis(Cl,Namino)-[RuCl(TPA)(Me2SO)]ClO4, and trans(Cl,Namino)-[RuCl-
(5-Me3-TPA)(Me2SO)]ClO4 in ref 14. See the text.
(31) (a) Diebold, A.; Hagen, K. S. Inorg. Chem. 1998, 37, 215-223. (b)
Zang, Y.; Kim, J.; Dong, Y.; Wilkinson, E. C.; Appleman, E. H.; Que,
L., Jr. J. Am. Chem. Soc. 1997, 119, 4197-4205. (c) Chen, K.; Que,
L., Jr. J. Am. Chem. Soc. 2001, 123, 6327-6337.
Inorganic Chemistry, Vol. 45, No. 20, 2006 8347

Yamaguchi et al.
Table 3. 1H NMR Spectral Data of the Complexesa
CH2
chemical shift/ppm (J/Hz)
py-H3
py-H4
py-H5
py-H6
(CH3)2SO
TPAb
2, cis(Cl,Namino
3.79 (s)
4.69 (ax, s)
4.79, 5.76 (ABq, 15)
4.53 (ax, s)
4.72, 5.39 (ABq, 15)
3.97 (s)
4.59 (ax, s)
4.82, 5.44 (ABq, 16)
3.71 (d, 2)
4.43 (ax, s)
4.59, 5.33 (ABq, 15)
4.13 (s)
7.58 (d, 8)
7.69 (td, 8, 2)
7.46-7.52 (ax, m)
7.73 (t, 8)
7.64 (ax, t, 8)
7.76 (t, 8)
7.17 (t, 6)
8.46 (d, 4)
9.81 (ax, d, 6)
8.70 (d, 6)
9.69 (ax, d, 6)
8.75 (d, 5)
9.14 (d, 2)
10.22 (ax, d, 2)
9.20 (d, 2)
8.30 (d, 1)
9.53 (ax, s)
8.57 (s)
)
6.95 (ax, d, 8)
7.46-7.51 (m)
7.13 (ax, d, 8)
7.43 (d, 8)
7.63 (d, 8)
7.24 (ax, d, 8)
7.57 (d, 8)
7.43-7.53 (m)
7.00 (ax, d, 8)
7.29 (d, 8)
7.16-7.25 (ax, m)
3.42 (s)
2.84 (s)
7.16-7.25 (m)
3, trans(Cl,Namino
)
)
7.26-7.36 (ax, m)
7.26-7.36 (m)
5-MeOCO-TPAd
8, trans(Cl,Namino
8.26 (dd, 8, 2)
8.16 (ax, dd, 8, 2)
8.27 (dd, 8,2)
7.43-7.53 (m)
7.47 (ax, dd, 8, 2)
7.56 (dd, 8, 2)
8.12 (d, 8)
2.86 (s)
2.84 (s)
2.93 (s)d
5-Me3-TPAb
13, trans(Cl,Namino
7.43-7.53 (m)
b
)
TQAd
9, trans(Cl,Namino
7.74 (d, 8)
c
)
5.06 (ax, s)
7.80 (ax, d, 8)e
8.24 (ax, d, 8)e
5.23, 6.07 (ABq, 17)
3.78 (CH2COO, s)
4.46 (CH2py, s)
3.77 (A, CH2COO, s)
4.58, 5.94 (A, CH2py, ABq, 14)
3.79 (B, CH2COO, s)
4.52, 5.82 (B, CH2py, ABq, 14)
4.64 (ax, s)
7.67 (d, 8)e
8.48 (d, 8)e
BPGf
7.46-7.52 (m)
7.92 (d, 8)
7.46-7.52 (m)
7.24-7.31 (m)
8.54 (d, 5)
9.00 (d, 6)
10d,g,h
7.24-7.31 (m)
7.62 (t, 7)
3.67 (A, s)
3.62 (B, s)
11
12
7.01 (ax, d, 8)
8.08 (d, 8)
8.05 (d, 8)
7.50 (ax, t, 8)
7.43 (t, 8)
7.88 (t, 8)
7.13 (ax, t, 8)
7.26 (t, 8)
7.44-7.88 (m)
9.03 (ax, d, 6)
8.82 (d, 6)
8.89 (d, 6)
4.78, 5.43 (eq, ABq, 15)
3.57 (CH2COO, s)
4.79, 4.96 (CH2py, ABq, 15)
a Measured in CD3CN at room temperature unless noted otherwise. The protons noted ax are those of the axial pyridylmethyl group. For the data of
complexes 1 and 5-7, see the Experimental Section. b Reference 14. Measured in CD3CN. c Measured in (CD3)2SO. d Measured in CDCl3. e Quinolyl group.
f Measured in D2O. g Consisting of two isomers, A and B. See the text. h The chemical shifts of other quinolyl protons are observed at 8.06, 7.68, 7.50, and
7.77 ppm for 5H, 6H, 7H, and 8H, respectively.
of the methyl groups of Me2SO was observed at 2.84 ppm.30
The methylene protons of the axial pyridylmethyl groups
were observed as a singlet at a higher magnetic field. On
the other hand, the methylene protons of the in-plane
pyridylmethyl groups appeared as an AB quartet because
the C-H bonds point axial and equatorial. The large
differences in the chemical shifts, from 0.62 to 0.97 ppm
for the complexes with TPA-type ligands, between those
axial and equatorial protons were observed. The large
downfield shifts of the axial protons are possibly due to the
van der Waals effect between the axial methylene protons
and the Cl anion of the cis isomer or the O atom of the
Me2SO ligand as shown in the molecular structures of the
complexes.32 The chloro(dimethyl sulfoxide-κS) complex
with BPG, [Ru(BPG)Cl(Me2SO)]Cl (10), was a mixture of
trans and cis isomers. Because the methylene protons were
observed as two singlets at 3.77 and 3.79 ppm in 10 and
one singlet at 3.57 ppm in 12, the BPG ligand in these
complexes has the symmetrical configuration with two
pyridine rings trans to each other having Cs symmetry.
A peak of the methyl groups of Me2SO of the TQA
complex 9 is observed at 2.93 ppm (in CDCl3), which shows
that complex 9 is the trans(Cl,Namino) isomer. The chemical
shifts for the trans isomers are observed at 2.84-2.93 ppm,
shifting upfield about 0.6 ppm compared to those of the cis
isomers. Because the S-bound Me2SO ligands of cis-
[RuCl2(Me2SO)4] and cis,fac-[RuCl2(py)(Me2SO)3] show
methyl peaks at 3.3-3.5 ppm similar to those of the cis
isomers 2 and 5,33,34 the upfield shift observed in the trans
isomers 3, 6-9, and trans(Cl,Namino)-[RuCl(5-Me3-TPA)-
(Me2SO)]ClO4 (13) can be attributed to the ring current effect
of the pyridyl groups. The quinolyl protons, 8H, of 9 are
observed at 9.67 and 11.02 ppm and show large downfield
shifts from 7.77 ppm of the free ligand: 1.90 and 3.25 ppm
for in-plane and axial positions, respectively. Both MM and
QM calculations shown below exhibit that there are close
contacts between the Cl ligand and 8H.
Molecular Structures of Complexes 4, 5, and 8. A single
crystal of 4 was obtained as a salt with the [RuCl3(Me2SO)3]
anion unintentionally by the slow diffusion of ethyl acetate
to a solution of the crude mixture of 2 and 3 in methanol.15
Bjernemose et al. have reported the molecular structure of
6.17,35 An ORTEP drawing of the cation is shown in Figure
2, and selected bond lengths and angles are listed in Table
2. The RuII center of the cation of 4 had an octahedral
geometry with four N atoms of the TPA ligand, a Cl anion,
and a S of the S-bound Me2SO ligand. It was found that 4
is the trans(Cl,Namino) isomer: the chloride anion coordinates
to the Ru center trans to the amino N and the Me2SO ligand
cis to the amino N. There were both trans and cis isomers
in the reaction mixture; however, this isomer crystallized
because of the low solubility of the trichlorotris(dimethyl
sulfoxide-κS)ruthenate salt. The three Me2SO ligands in the
[RuCl3(Me2SO)3]- anion coordinate to a Ru center by S
atoms in the facial configuration. It is likely that the
counteranion fac-[RuCl3(Me2SO)3]- was formed by a nu-
cleophilic attack of a Cl anion during the reaction. Yamamoto
(33) Evans, I. P.; Spencer, A.; Wilkinson, G. J. Chem. Soc., Dalton Trans.
1973, 204-209.
(34) Alessio, E.; Calligaris, M.; Iwamoto, M.; Marzilli, L. G. Inorg. Chem.
1996, 35, 2538-2545.
(32) Nagata, W.; Terasawa, T.; Tori, K. J. Am. Chem. Soc. 1964, 86, 3746-
(35) The crystal of 6 contains two independent complex ions in the
asymmetric unit.
3749.
8348 Inorganic Chemistry, Vol. 45, No. 20, 2006

Chloro(dimethyl sulfoxide)ruthenium(II) Complexes
Figure 4. ORTEP drawing of the cation of 8, trans(Cl,Namino)-[RuCl{5-
(MeOCO)3-TPA}(Me2SO)]+. Thermal ellipsoids are drawn at the 50%
probability level.
Figure 2. ORTEP drawing of the cation of 4, trans(Cl,Namino)-[RuCl-
(TPA)(Me2SO)]+. Thermal ellipsoids are drawn at the 50% probability level.
selected bond lengths and angles are listed in Table 2. It
was found that 8 is a trans(Cl,Namino) isomer: the Cl anion
coordinates to the Ru center trans to the amino N and the
dimethyl sulfoxide (DMSO) ligand cis to the amino N. The
methoxycarbonyl groups were approximately in the planes
of the pyridyl groups, and the CdO groups were anti to the
N atoms of the pyridyl groups in the crystal. The dihedral
angles of OdCsC(5-pyr)sC(4-pyr) range from 1.5(5)° to
12.6(6)°.
Selected bond lengths, angles, and torsional angles of
complexes 4, 5, and 8 are listed in Table 4, including those
of 6A, 6B,17,35 and 13.14 Bond lengths of Ru-Namino in 4 and
8 are 2.070(3) and 2.0753(18) Å, respectively, which are
similar to those in 6A, 6B, and 13 of 2.082(3), 2.080(2), and
2.062(4) Å, respectively. The average of the Ru-Namino bond
lengths of the trans isomers is 2.074(4) Å. The bond length
of Ru-Namino in the cis isomer 5 is 2.095(2) Å, which is
slightly longer than those in the trans isomers. On the other
hand, the bond length between Ru and the N atom of the
axial pyridyl group in the cis isomer 5 is 2.065(2) Å, which
is shorter than those in the four trans isomers: the average
is 2.103(1) Å [2.099(2)-2.106(3) Å]. The elongation of the
Ru-N bond of the axial pyridyl group in the trans isomers
is probably due to the trans effect of the Me2SO ligand. The
S-Ru-Cl bond angle in the cis isomer 5 is 85.75(3)°, which
is smaller than those in the four trans isomers: 87.36(7)-
88.87(3)°. The proximity of the Me2SO ligand to the axial
pyridyl group in the cis isomer 5 may result in the decrease
of the S-Ru-Cl bond angle. In fact, the interatomic distance
between the O atom of the Me2SO ligand and the ortho H
atom of the axial pyridyl group O1‚‚‚H18 is 2.253 Å, which
is much shorter than the sum of the van der Waals radii. In
the structural study of cis-[RuCl(bpy)2(Me2SO)]X (X ) PF6
and I), the H bondings between the O atom of the Me2SO
ligand and the ortho proton of the pyridyl group have been
reported: the O‚‚‚H distance is 2.26 Å.37 The steric interac-
tion derived from the Me2SO ligand is partially reduced in
the trans isomers. The average interatomic distance between
Figure 3. ORTEP drawing of the cation of 5, cis(Cl,Namino)-[RuCl(TPA)-
(Me2SO)]+. Thermal ellipsoids are drawn at the 50% probability level.
and colleagues reported that the reaction of [RuCl2(Me2SO)4]
and bis(2,6-dimethoxyphenyl)phenylphosphine (BDMPP)
afforded [BDMPP(CH2Cl2)][RuCl3(Me2SO)3] as the main
product, of which the three anions were in the facial
configuration.36
A single crystal of 5‚1/2MeCN was obtained as the
hexafluorophosphate salt by recrystallization from acetonitrile
and toluene. An ORTEP drawing is shown in Figure 3, and
selected bond lengths and angles are listed in Table 2. The
presence of acetonitrile was confirmed by NMR and
elemental analysis. The RuII center of 5 had an octahedral
geometry with four N atoms of the TPA ligand, a Cl anion,
and a S of the S-bound Me2SO ligand. It was found that 5
is a cis(Cl,Namino) isomer: the Cl anion coordinates to the
Ru center cis to the amino N and the Me2SO ligand trans to
the amino N.
A good crystal of 8 suitable for X-ray analysis was
obtained by the slow diffusion of ethanol to a solution of 8
in acetone. An ORTEP drawing is shown in Figure 4, and
(36) Yamamoto, Y.; Sugawara, K.; Aiko, T.; Ma, J.-F. J. Chem. Soc.,
Dalton Trans. 1999, 4003-4008.
(37) Hasek, D.; Inoue, Y.; Everitt, S. R. L.; Ishida, H.; Kunieda, M.; Drew,
M. G. B. J. Chem. Soc., Dalton Trans. 1999, 3701-3709.
Inorganic Chemistry, Vol. 45, No. 20, 2006 8349

Yamaguchi et al.
Table 4. Selected Bond Lengths (Å), Angles (deg), Torsional Angles (deg), and Interatomic Distances (Å) for 4, 6, 8, 13, and 5a
complex
13c
5
b
b
4
6A
6B
8
Ru-Cl
Ru-S
Ru-Namino
Ru-Nax
Ru-N
2.4321(9)
2.2385(10)
2.070(3)
2.106(3)
2.078(3)
2.060(3)
1.480(2)
88.87(3)
161.71(3)
29.24(8)
2.381
2.430(1)
2.251(1)
2.082(3)
2.101(2)
2.087(3)
2.093(2)
1.492(2)d
87.75(6)d
177.70(3)d
21.15(8)d
2.382
2.420(1)
2.258(1)
2.080(2)
2.099(2)
2.079(2)
2.060(2)
1.491(2)d
88.32(6)d
178.23(3)d
4.93(8)d
2.363
2.4258(5)
2.2587(5)
2.0753(18)
2.1029(18)
2.0594(18)
2.0776(18)
1.4918(17)
88.01(2)
2.423(2)
2.236(2)
2.062(4)
2.104(5)
2.066(4)
2.090(4)
1.485(4)
87.36(7)
179.79(4)d
18.5(1)d
2.225
2.4319(9)
2.2653(8)
2.095(2)
2.065(2)
2.079(2)
2.091(2)
1.479(3)
85.75(3)
174.26(16)
1.8(5)
S-O
S-Ru-Cl
O-S-Ru-Cl
Namino-C-C-Nax
O‚‚‚Hmt
171.51(9)
28.6(3)
2.447
2.597
2.588
2.502
2.467
2.369
O‚‚‚Hpyax
Cl‚‚‚Hpyax
Cl‚‚‚Hmt
2.253
2.692
2.751
2.851
2.625
2.641
2.640
2.698
a Namino ) amine nitrogen, Nax ) axial pyridyl nitrogen, N ) pyridyl nitrogen in plane, Hmt ) methylene proton of the pyridylmethyl group in plane,
Hpyax ) ortho proton of the axial pyridyl group. b Reference 17. c Reference 14. d Calculated by VENUS developed by Dilanian and Izumi.
the O atom and the methylene protons of the TPA ligand is
2.435 Å (2.225-2.597 Å) in 4, 6, 8, and 13, although they
are still shorter than the sum of the van der Waals radii.
Complexes 5 and 6B are found to be approximately Cs
symmetrical. The axial pyridyl group is almost in the
symmetrical plane: the Namino-C-C(2-pyr)-Nax torsional
angles are 1.8(5)° in 5 and 4.93(8)° in 6B. On the other hand,
other complexes are slightly distorted from the Cs sym-
metry: the torsional angles in the axial chelate ring are
29.24(8)° in 4, 29.1(13)° and 28.6(3)° in 8, 21.15(8)° in 6A,
and 18.5(1)° in 13.
Figure 5. Rotational barriers of the S-bonded DMSO ligands of trans-
and cis(Cl,Namino)-[RuCl(TPA)(Me2SO)]+ complexes.
The bond lengths of S-O in the Me2SO ligand are
1.480(2), 1.479(3), and 1.4918(17) Å in 4, 5, and 8,
respectively. The average is 1.484(4) Å. The S-O bond
lengths of free DMSO were reported to be 1.513(5) Å for
the crystal structure of DMSO measured at 5 °C and 1.50(1)
Å for liquid DMSO determined by X-ray diffraction.38,39
Calligaris and Carugo reported that the mean S-O bond
length of the free solvate DMSO in the crystal structures
was 1.492(1) Å with exclusion of the values of the low
temperature and of the compounds involved in strong H
bonds, and the mean S-O bond length of the S-bonded
(dimethyl sulfoxide)ruthenium(II) complexes in the crystals
was 1.478(1) Å.40 Kojima and colleagues have claimed that
the S-O bond in 13, 1.485(5) Å, was elongated because of
a strong π-back-donation from dπ of the RuII ion to pπ* of
the SdO bond.41 However, the S-O bond lengths in 4, 5,
and 13 are close to the mean S-O bond value of the
S-bonded (dimethyl sulfoxide)ruthenium(II) complexes in the
crystals. The Ru-S bond lengths in 4, 5, and 8 are
2.2385(10), 2.2653(8), and 2.2587(5) Å, respectively. The
Ru-S bond lengths in 5 and 8 are close to the reported mean
Ru-S bond length of 2.265(3) Å,40 while that in 4 was
shorter than the mean value. The S-O bonds in the
complexes 4, 5, and 8 were directed approximately anti to
the Cl anion coordinated cis to the Me2SO ligand, which is
possibly due to the electrostatic repulsion between the Cl
anion and the O atom of the Me2SO ligand. The O-S-
Ru-Cl torsional angles in 4, 5, and 8 are 161.73(3)°,
174.26(16)°, and 171.51(9)°, respectively, so that the O atom
of the Me2SO ligand is anti to the Cl ligand. The rotational
barriers around the Ru-S bond were estimated to be 9-14
kcal/mol by MM calculations as shown in Figure 5. The
coordinating Cl ions are in proximity to the axial methylene
protons of the pyridylmethyl groups in 5, 2.751 and 2.851
Å, and to the ortho proton of the axial pyridyl group in 4
and 8, 2.692 and 2.640 Å, respectively. The Cl‚‚‚H inter-
atomic bond distances are much shorter than the sum of the
van der Waals radii.
Although 5-Me3-TPA and 5-(MeOCO)3-TPA have the
electron-donating and -withdrawing substituents on the 5
positions of the pyridyl groups, the molecular structures
of the trans(Cl,Namino) isomers of TPA, 5-Me3-TPA, and
5-(MeOCO)3-TPA show no notable difference. The geometry
around the Ru center does not seem to be affected signifi-
cantly by the steric and electronic effects of the substituents
on the 5 positions of the pyridyl groups.
(38) Thomas, R.; Shoemaker, C. B.; Eriks, K. Acta Crystallogr. 1966, 21,
12-20.
(39) Itoh, S.; Ohtaki, H. Z. Naturforsch. 1987, 42a, 858-862.
(40) Calligaris, M.; Carugo, O. Coord. Chem. ReV. 1996, 153, 83-154.
(41) According to Kojima et al. in ref 14, the S-O bond length of free
DMSO was 1.47 Å: Kagaku Binran, Kisohen; The Chemical Society
of Japan, Maruzen: Tokyo, Japan, 1966; Vol. II, p 1222. However,
the value was revised to be 1.485 Å in: Kagaku Binran, Kisohen, 3rd
ed.; The Chemical Society of Japan, Maruzen: Tokyo, Japan, 1984;
Vol. II, p 658.
8350 Inorganic Chemistry, Vol. 45, No. 20, 2006

Chloro(dimethyl sulfoxide)ruthenium(II) Complexes
Scheme 1
Thermal Isomerization. The cis(Cl,Namino)-[RuCl(TPA)-
(Me2SO)]+ complex 2 is found to be thermodynamically
unstable compared to the trans isomer 3. The cis isomer
isomerized to the trans one in a DMSO solution at 65-80
°C with first-order kinetics (Scheme 1), which was followed
by UV/visible spectra (Figure S1 in the Supporting Informa-
tion). The spectral change of the cis isomer 2 at 65-80 °C
was observed with isosbestic points at 387 and 265 nm, as
shown in Figure 6, although the trans isomer 3 showed no
change even at 100 °C. The rate constants were 4.7 × 10-6,
8.6 × 10-6, 2.2 × 10-5, and 4.5 × 10-5 s-1 at 65, 70, 75,
and 80 °C, respectively. From Eyring’s rate equation,42 values
of ∆Hq ) (37 ( 1) kcal/mol and ∆Sq ) +(24 ( 4) cal/mol
were determined (Figure S2 in the Supporting Information).
Figure 6. UV/visible spectral change of complex 2, cis(Cl,Namino)-[RuCl-
(TPA)(Me2SO)]+, in Me2SO at 80 °C.
Table 5. Energy Differences (kcal/mol) between the trans(Cl,NAmino
)
and cis(Cl,NAmino) Isomers of [RuCl(L)(Me2SO)]+ Complexesa
L
MM2
DFTb
TPA
5-(MeOCO)3-TPA
TQA
+6.03
+5.90
+3.03
+5.58 (+6.62)
+5.43 (+5.81)
+4.57 (+6.47)
a Energy difference (kcal/mol) ) E(cis) - E(trans). b Calculated by
B3LYP/LANL2LZ. Results using basis set 3-21G** are given in paren-
theses.
1
The H NMR measurements clearly indicate that the peaks
of the cis isomer decreased during heating at 100 °C and
those of the trans isomer evolved. After 6 h, the peaks of
the cis isomer disappeared, and the spectrum became
identical with that of the trans isomer, as shown in Figure
S3 in the Supporting Information. Because the cis isomer is
not detectable (<1%) in NMR measurements of the equili-
brated mixture, the trans isomer is estimated to be 3.4 kcal/
mol more stable than the cis isomer at 100 °C.
set). These results are in agreement with the experiments.
In the cis TPA isomer, the O-S-Ru-Cl torsional angle is
154.69° and the O‚‚‚H interatomic distance is 2.091 Å (2.253
Å is the observed value) between the O atom of the Me2SO
ligand and the H atom of the axial pyridyl group, which
suggests a strong steric repulsion between the O atom of
the Me2SO ligand and the axial pyridyl group. Similarly, the
cis(Cl,Namino) isomer of [RuCl(TQA)(Me2SO)]+ is consider-
ably less stable than the trans(Cl,Namino) isomer. The trans
isomer of [RuCl(TQA)(Me2SO)]+ is 3.03 kcal/mol more
stable than the cis isomer by MM calculations and 4.57 kcal/
mol more stable by B3LYP/LANL2DZ (or 6.47 kcal/mol
by B3LYP/3-21G**) calculations because of steric repulsion
between the Me2SO ligand and the quinolyl groups of TQA
in the cis isomer. In fact, the complex cis-[RuCl(TQA)-
(Me2SO)]+ has not been obtained.
Electrochemistry. CVs of the complexes were measured
in MeCN with 0.1 M Et4NClO4, and redox potentials were
determined relative to an Fc/Fc+ couple as 0 V. CV data are
summarized in Table 6, and CVs of complexes 2 and 3 are
shown in Figure 7.44 All ruthenium complexes measured
show a reversible redox couple due to the RuII/RuIII couple
at +0.41 to +0.94 V except for complex 10, which is a
The preparation of the chloro(dimethyl sulfoxide) complex,
[RuCl(TPA)(Me2SO)]+, by the reaction of TPA and cis-
[RuCl2(Me2SO)4] in methanol was repeated many times.
However, a mixture of the cis and trans isomers was always
obtained.43 These results may have been caused by kinetic
control, although the reaction mechanism is uncertain. The
selective synthesis of the trans isomer by a similar reaction
in ethanol reported by Bjernemose et al. was possibly due
to simultaneous isomerization in the reaction conditions.
MM and QM Calculations. We have carried out MM
and QM calculations using DFT of the chloro(dimethyl
sulfoxide) complexes with TPA or its derivative. This showed
that the trans isomers are much more stable than the cis
isomers (Tables 5 and S1 in the Supporting Information).
MM calculations using CAChe show that the energy differ-
ence is 6.03 kcal/mol for the TPA complexes and 5.90 kcal/
mol for the 5-(MeOCO)3-TPA complexes. DFT calculations
using B3LYP functionals with geometry optimization show
that the energy differences are 5.58 and 5.43 kcal/mol,
respectively, for the TPA complexes and the 5-(MeOCO)3-
TPA complexes by using the LANL2DZ basis set (or 6.62
and 5.81 kcal/mol, respectively, by using the 3-21G** basis
(44) A quasi-reversible redox couple at +0.03 V was observed in the CV
of complexes 2 and 5, which shifted negatively from the RuII/RuIII
couple (Figure 7a). Kojima et al. have reported a reversible redox
couple observed at +0.04 V in the CV of the cis(Cl,Namino)-[RuCl-
(TPA)(Me2SO)]ClO4 complex, and this redox couple is suspected to
be the linkage isomer of 2 and 5 with an O-bound DMSO ligand in
ref 30. According to Kojima et al., the linkage isomerization of the
DMSO ligand takes place in the cis(Cl,Namino) isomer of the [RuCl-
(TPA)(Me2SO)]+ complex. It is noteworthy that all of the trans isomers
3, 6-8, and 1330 show no detectable wave around 0 V. Kojima et al.
have explained the absence of the electrochemical process in the CV
of the trans(Cl,Namino)-[RuCl(5-Me3-TPA) (Me2SO)]+ complex by the
electronic effect of the 5-methyl substituents of 5-Me3-TPA, which
increase the electron density at the Ru center. However, that is not
the case because the complex having 5-(MeOCO)3-TPA, which has
the substituents with the opposite electronic effect, showed no peak
attributable to the linkage isomerization.
(42) Wilkins, R. G. Kinetics, Mechanism of Reactions of Transition Metal
Complexes, 2nd ed.; VCH: Weinheim, Germany, 1991.
(43) The thermal isomerization experiment was attempted in MeOH, either.
However, after heating at 60 °C for 5 h, only a small change in the
UV/visible absorption spectrum, which did not correspond to that of
the isomerization reaction, was observed. It is assumed that the thermal
isomerization rate in MeOH is very slow and/or the ligand substitution
by a solvent molecule proceeded simultaneously in MeOH.
Inorganic Chemistry, Vol. 45, No. 20, 2006 8351

Yamaguchi et al.
Table 6. Redox Potentials of Complexes 2-12 Measured in CH3CNa
Table 7. Catalytic Oxidation of Adamantane by Ruthenium
Complexesa
complex
Ea
Ec
E1/2
yield/%b
2-one
cis(Cl, Namino)-[RuCl(TPA)-
(Me2SO)]Cl (2)
trans(Cl,Namino)-[RuCl(TPA)-
(Me2SO)]Cl (3)
cis(Cl,Namino)-[RuCl(TPA)-
(Me2SO)]PF6 (5)
trans(Cl,Namino)-[RuCl(TPA)-
(Me2SO)]PF6 (6)
+0.63b +0.56b +0.60b
+0.60b +0.53b +0.56b
+0.66 +0.59 +0.62
+0.61 +0.54 +0.57
run
catalyst
1-ol
2-ol
1-Cl
diol
1
2c
1
5
5
6
6
6
7
7
7
7
7
7
9
63
57
21
77
58
88
46
76
5
26
10
39
63
7
trace
2
3
4
3
2
0
0
0
1
0
0
4
trace
trace
trace
trace
trace
trace
trace
2
trace
2
0
1
1
6
3
5
3
4
4
4
2
1
3
1
1
2
1
24
4
3d
4c
ndk
9
5d
6e
ndk
trace
52
1
trans(Cl,Namino)-[RuCl{5-(MeOCO)3TPA}- +0.80 +0.74 +0.77
7
(Me2SO)]PF6 (8)
trans(Cl,Namino)-[RuCl(5-Me3-TPA)-
(Me2SO)]ClO4 (13)
8f
+0.52c
9g
10h
11i
12j
13
14
88
ndk
0
50
ndk
1
trans(Cl,Namino)-[RuCl(TQA)-
(Me2SO)]Cl (9)
+0.97 +0.92 +0.94
[Ru(BPG)Cl(Me2SO)] (10)
[RuCl(PhCN)(TPA)]Cl (11)
[Ru(BPG)(PhCN)2]Cl (12)
+0.20 +0.12 +0.16
+0.45 +0.37 +0.41
+0.61 +0.51 +0.56
none
1
1
a The reaction was performed in CHCl3 at room temperature for 24 h
unless stated otherwise: [substrate] ) 4 × 10-2 mol/L, [catalyst] ) 2 ×
10-4 mol/L, [MCPBA] ) 6 × 10-2 mol/L. Abbreviation: diol )
adamantane-1,3-diol. b Determined by GC/MS analyses with an internal
standard based on the substrate. c [catalyst] ) 4 × 10-4 mol/L. d [catalyst]
) 4 × 10-4 mol/L; [MCPBA] ) 3 × 10-2 mol/L. e The catalyst was added
in three portions during 48 h. f [substrate] ) 6 × 10-2 mol/L. g [MCPBA]
) 1.8 × 10-1 mol/L. h t-BuOOH was used instead of MCPBA. i PhIO was
used instead of MCPBA. j In 1,2-dichloroethane. k nd ) not determined.
a Potentials were determined relative to a Fc/Fc+ couple as 0 V; measured
at ambient temperature in MeCN under N2; electrolyte, 0.1 M Et4NClO4;
[complex] ) 1.3 mM; working electrode ) Pt, counter electrode ) Pt;
scan rate ) 500 mV/s. b Scan rate ) 100 mV/s. c Kojima, T.; Amano, T.;
Ishii, Y.; Ohba, M.; Okaue, Y.; Matsuda, Y. Inorg. Chem. 1998, 37, 4076-
4085. Measured in 0.1 M [(n-Bu)4N]ClO4/MeCN.
derivatives.46 The redox potential of 9 is about 0.4 V more
positive than that of 6, which is probably due to both the
electronic effect and the distortion from the octahedron
caused by the quinolyl rings. Similar positive shifts of the
redox potentials were observed for the ruthenium complexes
with 2,2′-biquinoline.47
Catalytic Oxidation of Alkane. Metal-catalyzed alkane
oxidation utilizing ruthenium complexes has been studied.
Ruthenium complexes with a tetradentate ligand such as TPA
have shown considerable activity on the catalytic oxidation
of alkanes.1,11 Oxidation of adamantane catalyzed by the
ruthenium complexes having a TPA or BPG in the presence
of MCPBA was examined using 1 and 10-12 in various
solvents, as given in Table S5 in the Supporting Information.
It was found that 1-adamantanol was the main product and
the reactivity was dependent on the solvent used: CHCl3 >
CH2Cl2 > MeCN ) Me2CO. The reaction favored solvents
of halogenated C, such as dichloromethane and chloroform.1
However, 1-chloroadamantane was also obtained possibly
as a result of a free-radical process involving solvent
molecules.48 Further, the catalytic oxidation of adamantane
employing various chloro(dimethyl sulfoxide-κS)ruthenium
complexes 1, 5-7, and 9 with a TPA-type ligand, TPA,
5-(MeOCO)3-TPA, or TQA, was examined in chloroform,
with the results summarized in Table 7. An excess amount
of MCPBA was employed in these experiments because
concurrent decomposition of MCPBA was observed.49 In the
Figure 7. CVs of (a) complex 2, cis(Cl,Namino)-[RuCl(TPA)(Me2SO)]Cl,
and (b) complex 3, trans(Cl,Namino)-[RuCl(TPA)(Me2SO)]Cl, at ambient
temperature in CH3CN (500 mV/s, 0.1 M Et4NClO4, mV vs Fc/Fc+).
neutral complex, showing at +0.16 V. The redox potentials
of the cis isomers 2 and 5 are slightly more positive than
those of the trans isomers 3 and 6. As for the substituent
effects in TPA ligands, the redox potentials lie in the order
5-(MeOCO)3-TPA > TPA > 5-Me3-TPA. This is due to the
electronic property of the substituents in TPA; i.e., the
electron-withdrawing group results in the higher redox
potential because the higher oxidation state of the ruthenium
complex is destabilized by electron-withdrawing 5-position
substituents on the TPA ligand. A similar tendency has been
reported for a series of ruthenium complexes with substituted
bipyridine derivatives45 and iron complexes with TPA
(46) Chen, K. C.; Que, L., Jr. J. Am. Chem. Soc. 2001, 123, 6327-6337.
(47) Vlcek, A. A.; Dodsworth, E. S.; Pietro, W. J.; Lever, A. B. P. Inorg.
Chem. 1995, 34, 1906-1913.
(48) Bravo, A.; Fontana, F.; Minisci, F.; Serri, A. Chem. Commun. 1996,
1843-1844.
(49) Adamantane is oxidized in the absence of the catalyst by MCPBA in
a free-radical process as shown in run 14; however, the contribution
of the noncatalyzed process can be considered to be negligible. The
oxidation of adamantane by MCPBA has been reported by Bravo and
co-workers.48
(45) Elliott, C. M.; Hershenhart, E. J. J. Am. Chem. Soc. 1982, 104, 7519-
7526.
8352 Inorganic Chemistry, Vol. 45, No. 20, 2006

Chloro(dimethyl sulfoxide)ruthenium(II) Complexes
Table 8. Catalytic Oxidation of Cyclooctane and Ethylbenzene by Ruthenium Complexesa
yield/%b
yield/%b
catalyst
run
cyclooctanone
cyclooctanol
run
acetophenone
1-phenylethanol
1-chloro-1-phenylethane
1
6
7
9
10
none
1
2
3
4
5
6
27
25
50
17
8
1
5
1
4
5
1
7
8
2
8
22
0
6
1
8
ndc
4
9d
1
10
1
0
0
a The reaction was performed in CHCl3 at room temperature for 24 h: [substrate] ) 4 × 10-2 mol/L, [catalyst] ) 4 × 10-4 mol/L, [MCPBA] ) 6 × 10-2
mol/L. b Determined by GC or GC/MS analyses with an internal standard based on the substrate. c nd ) not determined. d [catalyst] ) 2 × 10-4 mol/L.
Scheme 2
of TPA was the most active catalyst. The MeOCO group at
the 5 position, which is an electron-withdrawing group,53
seems to enhance the catalytic activity on the oxidation of
alkane. The enhancement is possibly due to the trans
influence of the MeOCO group in the pyridine trans to the
reaction of adamantane, a tertiary C atom(s) was (were)
oxo. Studies of the catalyst using TPA derivatives having
selectively oxidized, and 1-adamantanol and adamantane-
electron-withdrawing group(s) have been few. The catalytic
1,3-diol were obtained in good to excellent yield (Scheme
activity of iron complexes with TPA derivatives having one
2). The selectivity for oxidation of tertiary versus secondary
or two methoxycarbonyl group(s), 5-(MeOCO)-TPA and
C-H was found to be very high: 3°/2° ratios50 were 132
5-(MeOCO)2-TPA, on alkane oxidation in the presence of
and 114 for runs 6 and 8 catalyzed by 6 and 7, respectively,
H2O2 was studied; however, no distinctive effect was
and almost no 2-adamantanol and 2-adamantanone were
reported.46 Recently, Jitsukawa et al. reported that the
obtained in runs 7 and 9 catalyzed by 7.51 The 1-adamantanol
ruthenium complexes with the TPA-type ligands having
produced by the catalytic oxidation was further oxidized to
neopentylamino group(s), an electron-donating group, at the
yield adamantane-1,3-diol, when an excess amount of
6 position of the pyridyl groups were the more active
MCPBA was present (runs 7, 9, and 12). An independent
catalysts on oxidation of adamantane compared to the
experiment showed that oxidation of 1-adamantanol cata-
complexes with TPA or the TPA derivatives with electron-
lyzed by 7 under the same conditions yielded adamantane-
withdrawing 6-pivalamide group(s).11d,e They employed
1,3-diol in 61% yield with 7 and 23% with 1. Using the cis
monochloro- or dichlororuthenium(II) complexes with
isomer (5) and the trans isomer (6) of the [RuCl(TPA)-
6-pivalamide group(s) and dichlororuthenium(III) complexes
(Me2SO)] complex individually, it was found that the trans
with 6-neopentylamino group(s) for the oxidation catalyst
isomer (6) was more active as the catalyst than the cis isomer
in the presence of PhIO as the cooxidant. The difference in
(run 2 vs 4 and run 3 vs 5). Recently, Jitsukawa et al. have
the reaction conditions and the steric effect of the substituent
proposed that the trans(Cl,Namino)-RudO species derived
at the 6 position may account for the inconsistency in the
from the chloro(dimethyl sulfoxide)ruthenium complex hav-
catalytic activity.54
ing a TPA-type ligand is more active on C-H bond
Oxidation of cis-decalin by H2O2-FeSO4 proceeds with
activation than the corresponding cis(Cl,Namino)-RudO spe-
isomerization, giving both cis- and trans-decal-9-ol (cis/trans
cies, which is probably a result of the trans influence.11e The
) 23/77), which suggests the generation of long-lived alkyl
activity of the trans isomer (6) could also be explained by
radicals.55 On the other hand, it has been reported that the
the trans influence because the DMSO ligand might be
ruthenium porphyrins catalyzed the oxidation of cis-decalin
substituted with an MCPBA to give the trans(Cl,Namino)-
to cis-decal-9-ol with complete retention.51b,56 Oxidation of
RudO species. The formation of 1-chloroadamantane de-
cis-decalin catalyzed by complex 7 has been examined. It
creased in 1,2-dichloroethane (run 12) because it is well-
was revealed that cis-decalin was hydroxylated with retention
known that the abstraction of Cl atoms from solvent
of the configuration (cis/trans ) 97/3; conversion ) 98%).
molecules occurs more easily in chloroform.48 The oxidation
This is in contrast to the fact that the oxidation of cis-decalin
of cyclooctane and ethylbenzene was also examined (Table
by MCPBA in the absence of the catalyst proceeded with
8). Ketones, cyclooctanone, and acetophenone were the main
the concurrent isomerization (cis/trans ) 71/29; conversion
products,52 and it was found that the complex 7 having three
methoxycarbonyl groups (MeOCO) at the pyridine 5 position
(53) Hansch, C.; Leo, A.; Taft, R. W. Chem. ReV. 1991, 91, 165-195.
(54) We have studied oxygenation of adamantane catalyzed by various kinds
(50) /([2-ol] + [2-one]) ratio taking account of the number of C-H bonds
in a group.
of trans(Cl,Namino)-[RuCl(5-R3-TPA)(Me2SO)]Cl complexes and found
that the complex with 5-(benzylamide)-TPA was less reactive than
that with TPA although that with 5-(benzyloxycarbonyl)-TPA was as
reactive as that with 5-(methoxycarbonyl)-TPA: Yamaguchi, M.;
Izawa, S.; Yamagishi, T., unpublished results.
(51) Selective hydroxylation of adamantane at tertiary C atom(s) catalyzed
by ruthenium porphyrin complexes was reported: (a) Ohtake, H.;
Higuchi, T.; Hirobe, M. J. Am. Chem. Soc. 1992, 114, 10660-10662.
(b) Groves, J. T.; Bonchio, M.; Carofiglio, T.; Shalyaev, K. J. Am.
Chem. Soc. 1996, 118, 8961-8962.
(55) Shul’pin, G. B.; Su¨ss-Fink, G.; Shul’pina, L. S. Chem. Commun. 2000,
1131-1132.
(52) No Baeyer-Villiger product was observed in the oxidation of
cyclooctane, although ꢀ-caprolactone was obtained in the oxidation
of cyclohexane: Yamaguchi, M.; Murakami, N.; Yamagishi, T.,
unpublished results.
(56) (a) Higuchi, T.; Hirobe, M. J. Mol. Catal. A: Chem. 1996, 113, 403-
422. (b) Shingaki, T.; Miura, K.; Higuchi, T.; Hirobe, M.; Nagano, T.
Chem. Commun. 1997, 861-862. (c) Groves, J. T.; Nemo, T. E. J.
Am. Chem. Soc. 1983, 105, 6243-6248.
Inorganic Chemistry, Vol. 45, No. 20, 2006 8353

Yamaguchi et al.
) 20%). High 3°/2° ratios in the oxidation of adamantane
and high stereoselectivity in the oxidation of cis-decalin
suggest the involvement of a metal-based oxidant that
generates short-lived alkyl radicals.46,57
stereoselectivity was observed in the oxidation of cis-decalin
to give cis-decal-9-ol with complete retention of the con-
figuration. The involvement of a metal-based oxidant that
generates short-lived alkyl radicals is suggested.
Acknowledgment. We thank Prof. Ken Sakai for helpful
advice on X-ray diffraction analysis. We thank Dr. Takahiko
Kojima for helpful discussion. We also thank Shigeru
Iokawa, Noriyasu Murakami, Masayoshi Shimo, and Kison
Han for their assistance in experiments. This work was partly
supported by a Grant-in-Aid (09640670) from the Ministry
of Education, Science, Sports, and Culture of Japan. The
Shimadzu GCMS-QP5050A gas chromatograph/mass spec-
trometer was purchased with the 1999 Fund for Special
Research Projects at Tokyo Metropolitan University.
Conclusion
A series of ruthenium(II) complexes having a tetradentate
ligand, TPA, and its derivatives, 5-(MeOCO)3-TPA and
TQA, have been prepared and characterized in both solution
and solid states. The chloro(dimethyl sulfoxide-κS) com-
plexes with a TPA derivative seem to prefer the trans-
(Cl,Namino) configuration, except that with TPA, which was
obtained as a mixture of the cis and trans isomers. A mixture
of both chloride and the hexafluorophosphate salt of the
configuration isomers of chloro(dimethyl sulfoxide-κS)(TPA)
complexes was successfully separated by fractional recrys-
tallization. The cis(Cl,Namino) isomer with TPA was found
to be much less stable than the trans one because it
isomerized in DMSO at high temperatures (65-100 °C),
which was supported by MM and DFT calculations. The
chloro(dimethyl sulfoxide-κS) complexes with TPA or its
derivatives were found to be an efficient catalyst for the
oxygenation of alkanes. The tertiary C atom was selectively
oxidized to give 1-adamantanol, and extremely high 3°/2°
ratios were observed. The most active catalyst was trans-
(Cl,Namino)-[RuCl{5-(MeOCO)3-TPA}(Me2SO)]PF6. High
Supporting Information Available: X-ray crystallographic files
in CIF format for complexes 4, 5, and 8, optimized total energies
of the chloro(dimethyl sulfoxide)ruthenium complexes with TPA
derivatives calculated by MM (CAChe) and DFT (Table S1),
Cartesian coordinates of the structures optimized by MM or DFT
calculations with B3LYP/LANL2DZ or B3LYP/3-21G**, respec-
tively (Tables S2-S4), catalytic oxidation of adamantane by
ruthenium complexes with MCPBA in various solvents (Table S5),
absorption changes monitored at 420 nm in the thermal isomer-
ization of 2 (Figure S1), Eyring’s plot for the thermal isomer-
ization of 2 (Figure S2), and 1H NMR spectra (270 MHz, Me2SO-
d6) of (a) complex 3, trans(Cl,Namino)-[RuCl(TPA)(Me2SO)]+, (b)
complex 2, cis(Cl,Namino)-[RuCl(TPA)(Me2SO)]+, before heating,
and (c) complex 2 after heating for 6 h at 100 °C (Figure S3). This
materialisavailablefreeofchargeviatheInternetathttp://pubs.acs.org.
(57) Ingold, K. U.; MacFaul, P. A. In Biomimetic Oxidations Catalyzed
by Transition Metal Complexes; Meunier, B., Ed.; Imperial College
Press: London, 2000; Chapter 2.
IC060722C
8354 Inorganic Chemistry, Vol. 45, No. 20, 2006