Ruthenium terpyridine complexes with mono- And bi-dentate dithiolene ligands

Article abstract of DOI:10.1039/b007541h

The reaction of [Ru(CO)₂Cl(terpy)]PF₆ (terpy = 2,2′:6′:2″-terpyridine) with Na₂mnt (mnt = S₂C₂(CN)₂) initially produced [Ru(CO)₂(mnt-κS)(terpy-κ³NN′N ″)] 1a, which rea

Full text of DOI:10.1039/b007541h

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Ruthenium terpyridine complexes with mono- and bi-dentate
dithiolene ligands
Hideki Sugimoto, Kiyoshi Tsuge and Koji Tanaka*
Institute for Molecular Science, Myodaiji, Okazaki 444-8585, Japan
Received 18th September 2000, Accepted 30th October 2000
First published as an Advance Article on the web 6th December 2000
The reaction of [Ru(CO)2Cl(terpy)]PF6 (terpy = 2,2Ј:6Ј:2Љ-terpyridine) with Na2mnt (mnt = S2C2(CN)2) initially
produced [Ru(CO)2(mnt-κS)(terpy-κ3NNЈNЉ)] 1a, which rearranged to [Ru(CO)2(mnt-κ2SSЈ)(terpy-κ2NNЈ)] 1b in
solution. The molecular structures of 1a and 1b indicate that the rearrangement proceeds via a five-coordinated
complex with monodentate mnt and bidentate terpy. The reaction of [Ru(CO)2Cl(terpy)]PF6 with 3,4-toluenedithiol
(H2tdt) gave [Ru(CO)2(tdt-κ2SSЈ)(terpy-κ2NNЈ)] 2b but [Ru(CO)2(tdt-κS)(terpy-κ3NNЈNЉ)] 2a was not identified.
Thus, ruthenium complexes with bidentate dithiolene and bidentate terpyridine seem to be more stable than those
with monodentate dithiolene and tridentate terpyridine. Neither [Ru(CO)2(pdt-κS)(terpy-κ3NNЈNЉ)] 3a nor [Ru-
(CO)2(pdt-κ2S)(terpy-κ2NNЈ)] 3b (pdt = PhC(S)C(S)Ph) was obtained in the reaction of [Ru(CO)2Cl(terpy)]PF6
with the Csϩ salt of pdt2Ϫ in CH3OH under N2. The same reaction conducted under aerobic conditions afforded
[Ru(CO)(C(O)OCH3)(SC(Ph)C(Ph)SC(O)OMe)(terpy-κ3NNЈNЉ)] 3 resulting from double addition of CO2 and
CH3OH to the terminal sulfur of pdt and a carbonyl carbon of 3a, respectively, followed by esterification of the
resultant [Ru(CO)(C(O)OCH3)(SC(Ph)C(Ph)SC(O)OH)(terpy-κ3NNЈNЉ)] in CH3OH. The addition of CO2 to
the sulfur of 3a is ascribed to the strong basicity and weak chelating ability of pdt compared with those of mnt
and tdt. A series of [RuX(dithiolene)(terpy)]nϩ (X = dmso, Cl or OSO2CF3; n = 0 or 1) were also prepared.
Rh, Ni, Pd and Pt and trivalent V, Cr, Re, Mo, W, Ru and
Introduction
Os, respectively.6–10 Introduction of dithiolene ligands to
Transition metal complexes with redox active ligands such as
ruthenium–polypyridyl complexes would generate character-
polypyridyl and dioxolene feature multi-step redox processes
istic redox behavior because of strong interaction between
due to changes in oxidation state of both the metals and the
unoccupied 3d orbitals of the sulfur of dithiolene with RuII.
ligands themselves.1 Especially, the redox behavior of rhenium,
A few mixed chelate ruthenium complexes with polypyridyl
ruthenium, and osmium polypyridyl complexes has extensively
and dithiolene ligands have been prepared so far.11 We have
been studied in connection with their characteristic CT bands
attempted introduction of dithiolenes to ruthenium polypyridyl
depending on the electron distribution between the central
complexes with a good leaving group. The present study reports
metals and the ligands. Moreover, ruthenium() polypyridyl
complexes with a good leaving group are widely used as homo-
the preparation and properties of new ruthenium terpyridine
complexes with S2C2(CN)2 (mnt), S2C6H3Me (tdt) and S2C2Ph2
(pdt) ligands.
Ϫ 2
geneous catalysts in electrochemical reduction of NO2 and
CO2,3 and oxidation of NH3 4 and H2O,5 where ligand localized
and metal-centered redox reactions are utilized as electron
Experimental
reservoirs for these catalytic reactions. It is well known that
dithiolenes behave as redox active ligands, and adopt dianion,
anion radical and neutral oxidation states (Scheme 1). Metal–
Na2mnt,10 4,5-diphenyl-1,3-dithio-4-cyclopenten-2-one,12 and
[Ru(dmso)Cl2(terpy)]13 and [Ru(CO)2Cl(terpy)]PF6
were
14
prepared as described. All other commercially available
reagents and solvents were used as purchased.
Preparation of complexes
[Ru(CO)2(mnt-ꢀS)(terpy-ꢀ3NNЈNЉ)] 1a and [Ru(CO)2(mnt-
ꢀ2SSЈ)(terpy-ꢀ2NNЈ)] 1b. [Ru(CO)2Cl(terpy)]PF6 (114 mg,
0.2 mmol) was added to a CH3OH solution (100 ml) of Na2mnt
(37 mg, 0.2 mmol). The suspension gradually changed to a
clear red solution in 2 h, during which time small amounts of
yellow crystals of complex 1a precipitated. Then, red crystals
of 1b precipitated when the solution was allowed to stand for
another few hours. 1b was recrystallized from acetone. Yield
92 mg (87%). FAB-MS: m/z 531 ({M}ϩ), 503 ({M Ϫ CO}ϩ)
and 475 ({M Ϫ (CO)2)}ϩ). Calc. for C21H11N5O2RuS2: C, 47.54;
H, 2.09; N, 13.20. Found: C, 47.31; H, 2.25; N, 12.95%. IR
spectrum (KBr); ν(CN) 2197, 2170; ν(CO) 2093, 1962 cmϪ1.
1H NMR (CD3CN, R.T.): δ 9.06 (1H, d), 8.82 (1H, d), 8.4–8.6
(2H, m), 8.1–8.3 (2H, m), 8.01 (1H, t), 7.65–7.85 (3H, m) and
Scheme 1
dithiolene complexes, therefore, are also feasible candidates
for homogeneous catalysts for redox reactions of various
substrates.
Metal–dithiolene complexes are usually synthesized as bis-
and tris-chelate forms such as those of divalent Fe, Co,
DOI: 10.1039/b007541h
J. Chem. Soc., Dalton Trans., 2001, 57–63
This journal is © The Royal Society of Chemistry 2001
57

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7.56 (1H, t). λmax/nm (ε/dm3 molϪ1 cmϪ1) (CH3CN) 324 (12220)
diphenyl-1,3-dithio-4-cyclopenten-2-one (108 mg, 0.4 mmol)
and 390 (5350).
and CsOH (150 mg, 0.8 mmol) was refluxed for 2 h. Concen-
tration of the brown solution to ca. 2 ml under reduced pressure
precipitated dark brown [Ru(dmso)(pdt)(terpy)], which was
isolated by filtration and washed with water (5 ml) to remove
CsCl. To [Ru(dmso)(pdt)(terpy)] suspended in 10 ml of CH3OH
were added 10 drops of concentrated HCl with stirring. Treat-
ment of the resulting clear deep blue solution with aqueous
NaClO4 (100 mg, 0.82 mmol) solution (5 ml) gave a blue micro-
crystalline powder, which was filtered off and dried in vacuo.
Yield 104 mg (36%). ESI-MS: m/z 612 ({M}ϩ) and 288.5
({M Ϫ Cl}2ϩ). Calc. for C29H21N3O4RuS2: C, 48.95; H, 2.97; N,
5.91. Found: C, 48.59; H, 3.12; N, 6.06%. 1H NMR (acetone-d6,
R.T.): δ 9.02 (2H, d), 8.77 (3H, m), 8.22 (2H, t), 7.77 (2H, d),
[Ru(CO)2(tdt)(terpy)] 2b. To a solution of [Ru(CO)2Cl-
(terpy)]PF6 (114 mg, 0.2 mmol) in CH3CN (10 ml), BuOK
t
(45 mg, 0.4 mmol) and 3,4-toluenedithiol (31 mg, 0.2 mmol) in
CH3OH (10 ml) were added. The solution was stirred until red
microcrystals precipitated. The red solid was filtered off,
washed with C2H5OH and dried. Recrystallization from DMF
gave red single crystals. ESI-MS: m/z 545 ({M}ϩ), 517 ({M Ϫ
CO}ϩ) and 489 ({M Ϫ (CO)2}ϩ). Calc. for C24H17N3O2RuS2ؒ
H2O: C, 51.24; H, 3.40; N, 7.47. Found: C, 51.27; H, 3.11; N,
7.73%. IR spectrum (KBr); ν(CO) 2033 and 1979 cmϪ1 1H
.
NMR (DMF-d7, R.T.): δ 9.54 and 9.52 (2H, d), 8.92 (4H, t),
8.84 (2H, d), 8.47 (2H, t), 8.31 (2H, t), 8.17 (2H, t), 7.98 (4H, q),
7.77 (2H, q), 7.67 (2H, q), 7.04 (1H, d), 6.99 (1H, s), 6.74 (1H,
d), 6.69 (1H, s), 6.42 (1H, d), 6.37 (1H, d), 2.07 (3H, s) and 1.99
(3H, s). λmax /nm (ε/dm3 molϪ1 cmϪ1) (acetone) 323 (11170) and
395 (5420).
7.64 (2H, q) and 7.2–7.6 (10H, m). λmax /nm (ε/dm3 molϪ1 cmϪ1
)
(CH2Cl2) 315 (18130), 330 (20260) and 566 (9780).
[Ru(OSO2CF3)(pdt)(terpy)]CF3SO3 7CF3SO3. Brown [Ru-
(dmso)(pdt)(terpy)] (100 mg) gradually dissolved in 10 ml of
CH3OH after 10 drops of CF3SO3H were added to the suspen-
sion. The resultant clear blue solution was concentrated to 0.5
ml by evaporation. Addition of 5 ml of diethyl ether afforded
blue microcrystals, which were collected by filtration and dried
in vacuo. Yield 120 mg (68%). ESI-MS: m/z 726 ({M}ϩ) and
288.5 ({M Ϫ CF3SO3}2ϩ). Calc. for C31H21N3O6RuS2: C, 42.56;
H, 2.42; N, 4.80. Found: C, 42.61; H, 2.72; N, 4.61%. 1H NMR
(acetone-d6, R.T.): δ 9.02 (2H, d), 8.76 (3H, m), 8.21 (2H, t),
7.78 (2H, d), 7.58 (1H, t) and 7.2–7.55 (11H, m). λmax /nm (ε/dm3
molϪ1 cmϪ1) (CH2Cl2) 329 (18080), 568 (7540).
[Ru(CO)(C(O)OCH3)(SC(Ph)C(Ph)SC(O)OCH3)(terpy-
ꢀ3NNЈNЉ)]ؒ0.5H2O 3ؒ0.5H2O. A methanolic solution (20 ml)
of [Ru(CO)2Cl(terpy)]PF6 (228 mg, 0.4 mmol), 4,5-diphenyl-
1,3-dithio-4-cyclopenten-2-one (108 mg, 0.4 mmol) and CsOH
(150 mg, 0.8 mmol) was stirred for 2 h under aerobic conditions.
The volume of the brown solution was reduced to 2 ml and
allowed to stand for one night to give black-brown crystals of 3.
Yield 60%. ESI-MS (DMF): m/z 692 ({M Ϫ OCH3}ϩ), 664
({M Ϫ COOCH3ϩ}), 636 ({M Ϫ COOCH3 Ϫ COϩ}), 605
({M Ϫ COOCH3 Ϫ CO Ϫ OCH3ϩ}) and 577 ({M Ϫ COO-
CH3 Ϫ (CO)2 Ϫ OCH3ϩ}). Calc. for C34H28.5N3O5.5RuS2: C,
55.80; H, 3.86; N, 5.74. Found: C, 55.91; H, 3.77; N, 5.86%.
X-Ray structural determinations
IR spectrum (KBr): ν(CO) 1966, 1711 and 1684 cmϪ1
.
X-Ray data of complexes 1a, 1b and 2b were collected with
graphite-monochromated Mo-Kα radiation on a Rigaku AFC-
5S diffractometer. Crystallographic data are summarized in
Table 1. All the calculations were performed with the TEXSAN
crystallographic software package.15 The structures were solved
by direct methods for 1a and heavy-atom methods for 1b and
2b and expanded using Fourier techniques. The structure of
3 was solved by direct methods, and the ruthenium, sulfur
and nitrogen atoms, the atoms in the carbonyl and methoxy-
carbonyl ligands, and ethylene carbon atoms of Ph2C2S2-
COOCH3 were refined anisotropically.
[Ru(dmso)(mnt)(terpy)] 4. An aqueous solution (5 ml) of
[Ru(dmso)Cl2(terpy)] (48 mg, 0.1 mmol) was added to a CH3OH
solution (10 ml) of Na2mnt (19 mg, 0.1 mmol). The yellow solu-
tion changed to a brown suspension and then gradually became
a clear red solution. After 2 h, red microcrystals precipitated
and were collected, washed with ethanol, and dried. Yield 40 mg
(72%). ESI-MS: m/z 475 ({M Ϫ dmso}ϩ). Anal. Calc. for
C21H17N5ORuS3: C, 45.64; H, 3.10; N, 12.67. Found: C, 45.39;
H, 3.35; N, 12.41%. IR spectrum (KBr): ν(CN) 2191 cmϪ1
.
1H NMR (acetone-d6, R.T.): δ 8.80 (2H, d), 8.57 (2H, d), 8.52
(2H, d), 8.21 (1H, t), 8.12 (2H, t), 7.70 (2H, t) and 2.61 (6H,
s). λmax /nm (ε/dm3 molϪ1 cmϪ1) (CH3CN) 312 (20760) and 442
(6370).
CCDC reference number 186/2256.
See http://www.rsc.org/suppdata/dt/b0/b007541h/ for crystal-
lographic files in .cif format.
Measurements
[RuCl(tdt)(terpy)]BF4 5 BF4. A methanolic solution (20 ml)
containing [Ru(dmso)Cl2(terpy)] (200 mg, 0.4 mmol), H2tdt
(63 mg, 0.4 mmol) and CsOH (150 mg, 0.8 mmol) was refluxed
for 2 h. Concentration of the brown solution to ca. 2 ml under
reduced pressure resulted in a dark brown precipitate of
[Ru(dmso)(tdt)(terpy)], which was isolated by filtration and
washed with water. Addition of 10 drops of concentrated HCl
to [Ru(dmso)(tdt)(terpy)] (100 mg) suspended in 10 ml of
CH3OH gave a clear red-purple solution. Further addition
of NaBF4 (44 mg, 0.4 mmol) in 5 ml of water precipitated
[RuCl(tdt)(terpy)]BF4 5, which was collected by filtration,
washed with water and dried in vacuo. Yield 58 mg (47%).
ESI-MS: m/z 524 ({M}ϩ) and 244 ({M Ϫ Cl}2ϩ). Calc. for
C22H17BF4N3RuS2: C, 43.26; H, 2.81; N, 6.88. Found: C, 43.37;
Cyclic voltammetry was performed with a BAS CV-100W
voltammetry analyzer at a scan rate of 50 mV sϪ1. The sample
solutions (ca. 1.0 mM) containing 0.1 M NBun BF4 were
4
deoxygenated with a stream of nitrogen gas. Redox potentials
obtained were referenced to the ferrocenium–ferrocene couple.
Electronic spectra were recorded on a Shimadzu UV-vis-NIR
scanning spectrophotometer UV-3100PC. Spectroelectro-
chemistry was performed with a thin-layer electrode cell with
a platinum mini grid working electrode sandwiched between
two glass windows of an optical cell (path length 0.5 mm).
1H NMR spectra were measured on a JEOL-EX 270 (270
MHz) spectrometer, IR spectra on a Shimadzu FTIR-8100
spectrophotometer.
1
H, 3.01; N, 6.59%. H NMR (acetone-d6, R.T.): δ 9.08 (3H, t),
8.83 (2H, d), 8.73 (2H, d), 8.56 (1H, t), 8.08 (4H, dt), 7.72
(2H, d), 7.33 (1H, t), 6.83 (2H, m), 2.39, 2.35 (3H, s). The two
singlets at δ 2.39 and 2.35 indicate two geometrical isomers
of tdt. λmax /nm (ε/dm3 molϪ1 cmϪ1) (CH2Cl2) 313 (23600), 328
(620700), 393 (20700) and 527 (8060).
Results and discussion
Preparation of complexes
Reactions of [RuCl3(terpy)] with S2C2(CN)2 (mnt2Ϫ), S2C7-
2Ϫ
H62Ϫ (tdt2Ϫ) and S2C2Ph22Ϫ (pdt2Ϫ) in CH3OH gave unidentified
insoluble solids probably due to irreversible oxidation of these
“free” ligands by RuIII. To avoid such unfavorable reactions,
[RuCl(pdt)(terpy)]ClO4 6ClO)4. A methanolic solution (20
ml) containing [Ru(dmso)Cl2(terpy)] (200 mg, 0.4 mmol), 4,5-
58
J. Chem. Soc., Dalton Trans., 2001, 57–63

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Table 1 Crystallographic data for complexes 1aؒCH3OH, 1b, 2b and 3ؒH2O
1aؒCH3OH
1b
2b
3ؒH2O
Formula
M
Space group
T/ЊC
C22H15N5O3RuS2
562.6
P1 (no. 2)
C21H11N5O2RuS2
530.5
P21/n (no. 14)
23
C24H17N3O2RuS2
544.6
P21/n (no. 14)
23
C33H27N3O6RuS2
726.8
P1 (no. 2)
¯
¯
23
23
a/Å
b/Å
c/Å
α/Њ
9.389(4)
14.1223(4)
8.817(3)
90.98(3)
103.42(3)
96.32(3)
1129.2(8)
2
9.14
3174
2954
6.0
13.273(3)
9.301(3)
17.059(2)
14.202(10)
9.408(7)
18.47(1)
14.579(3)
19.743(4)
12.948(3)
108.34(2)
94.30(2)
98.16(2)
3473(1)
2
β/Њ
92.40(1)
108.52(5)
γ/Њ
V/Å3
2104.2(8)
4
9.73
5351
5136
5.4
2339(3)
4
8.74
5910
5687
5.8
Z
µ(Mo-Kα)/cmϪ1
No. of reflections
No. of observed reflections
R (%)
6.16
13678
12946
8.3
Rw (%)
5.4
5.2
6.5
7.6
[Ru(CO)2Cl(terpy)]ϩ and [Ru(dmso)Cl2(terpy)] were used as
starting complexes for preparation of dithiolene complexes.
When Na2mnt was allowed to react with [Ru(CO)2Cl(terpy)]-
PF6 suspended in CH3OH the suspension changed to a clear
yellow solution at first and then became red. Yellow [Ru(CO)2-
(mnt-κS)(terpy-κ3NNЈNЉ)] 1a and red [Ru(CO)2(mnt-κ2SSЈ)-
(terpy-κ2NNЈ)] 1b (see below) were isolated as single crystals
from the yellow and red solutions, respectively (eqn. 1). 1a was
[Ru(CO)2Cl(terpy)]PF6 ϩ pdt2Ϫ →
[Ru(CO)2(pdt-κS)(terpy-κ3NNЈNЉ)]
CH3OH, CO2
air
[Ru(CO)(C(O)OCH3)(SC(Ph)C(Ph)-
CH3OH
SC(O)OH)(terpy-κ3NNЈNЉ)]
air
[Ru(CO)(C(O)OCH3)(SC(Ph)-
C(Ph)SC(O)OCH3)(terpy-κ3NNЈNЉ)] (3)
[Ru(CO)2Cl(terpy)]PF6 ϩ mnt2Ϫ →
carbonato complexes, [Zn(L)(O2COR)],16 and [ML(OH)]n
(M = Mn, Fe, Co, Ni, Cu or Zn, L = tris(3,5-diisopropyl-1-
pyrazolyl)hydroborate, n = 1 or 2) have activity toward fixation
of atmospheric CO2, changing to [LM(µ-CO3)ML].17 The reac-
[Ru(CO)2(mnt-κS)(terpy-κ3NNЈNЉ)] →
1a (yellow)
[Ru(CO)2(mnt-κ2SSЈ)(terpy-κ2NNЈ)] (1)
1b (red)
tion of [(Ir(η5-C5Me5))2Ir(η4-C5Me5CH2CN)(µ3-S)2] with CO2
2Ϫ
produced C2O4
via [(Ir(η5-C5Me5))2Ir(η4-C5Me5CH2CN)-
(µ3-S)2]ؒ2CO2.18 The formation of 3, therefore, is explained by
attack of CO2 on the terminal sulfur of [Ru(CO)2(pdt-κS)-
(terpy-κ3-NNЈNЉ)] 3a followed by nucleophilic attack of
CH3OH on a carbonyl carbon, and then esterification of
the resultant [Ru(CO)(C(O)OCH3)(SC(Ph)C(Ph)SC(O)OH)-
(terpy-κ3NNЈNЉ)]. The selective crystallization of 3 rather
stable in the solid state, while it smoothly changed to red 1b
in CD3CN. Low solubility of 1a in CH3OH led to isolation
of the complex, but the smooth conversion from 1a into 1b in
1
solutions made it difficult to detect the H NMR spectrum of
1a. The reaction of [Ru(CO)2Cl(terpy)]PF6 with the Kϩ salt of
tdt2Ϫ in CH3OH gave red [Ru(CO)2(tdt-κ2SSЈ)(terpy-κ2NNЈ)]
2b, but [Ru(CO)2(tdt-κS)(terpy-κ3NNЈNЉ)] 2a was not con-
firmed in the reaction (eqn. 2). The reaction of [Ru(CO)2Cl-
than
[Ru(CO)(C(O)OCH3)(SC(Ph)C(Ph)SC(O)OH)(terpy-
κ3NNЈNЉ)] probably results from low solubility of the former in
CH3OH.
The reaction of [Ru(dmso)Cl2(terpy)] with mnt2Ϫ in CH3OH–
water also generated neutral [Ru(dmso)(mnt)(terpy)] 4 (eqn. 4),
[Ru(CO)2Cl(terpy)]PF6 ϩ tdt2Ϫ →
([Ru(CO)2(tdt-κS)(terpy-κ3NNЈNЉ)]) →
[Ru(CO)2(tdt-κ2SSЈ)(terpy-κ2NNЈ)] (2)
[Ru(dmso)Cl2(terpy)] ϩ mnt2Ϫ →
[Ru(dmso)(mnt)(terpy)] (4)
(terpy)]PF6 with the Csϩ salt of pdt2Ϫ in CH3OH afforded
only viscous products, and neither [Ru(CO)2(pdt-κS)(terpy-
κ3NNЈNЉ)] 3a nor [Ru(CO)2(pdt-κ2SSЈ)(terpy-κ2NNЈ)] 3b
was isolated under an N2 atmosphere. On the other hand, [Ru-
(CO)(C(O)OCH3)(SC(Ph)C(Ph)SC(O)OCH3)(terpy-κ3NNЈNЉ)]
3 (see below) selectively crystallized when the same reaction was
conducted under aerobic conditions. Based on the yield of 3
(60%), it is not a degradation product of 3a and 3b. Complex 3
has two CH3OC(O) groups; one is attached to Ru and the other
linked to the sulfur of pdt. The former apparently resulted from
nucleophilic attack of CH3OH on a carbonyl carbon of the
Ru(CO)2 moiety, while the latter is probably produced through
esterification of the Ru–SC(Ph)C(Ph)SC(O)OH framework
derived from attack of CO2 (from air) on the S2C2Ph2 group
(eqn. 3). In fact, complexes having M–OH and M–SϪ units
with high nucleophilicity have been shown to react with CO2 to
but the similar reactions with tdt2Ϫ and pdt2Ϫ gave almost
insoluble dark black and dark brown solids, respectively. In
the case of tdt2Ϫ, treatment of the dark black solid with HCl
in CH3OH resulted in a clear solution and [RuCl(tdt)(terpy)]ϩ
Ϫ
5ϩ was isolated as the BF4 salt. Similarly, in the case of
pdt2Ϫ, addition of HCl or CF3SO3H to the dark brown solid
suspended in MeOH produced cationic [RuX(pdt)(terpy)]ϩ
(X = Cl 6ϩ or OSO2CF3 7ϩ) under aerobic conditions. The mass
spectrum of the insoluble dark brown solid obtained in the
reaction of [Ru(dmso)Cl2(terpy)] with pdt2Ϫ showed the parent
peak at m/z 655 ([Ru(dmso)(pdt)(terpy)]ϩ) together with a
strong fragment peak at m/z 577 ([Ru(pdt)(terpy)]ϩ). Thus, the
formation of cationic 5ϩ, 6ϩ, and 7ϩ is expressed by eqn. (5).
[Ru(dmso)Cl2(terpy)] ϩ L2Ϫ →
Ϫ
HX
give M–OCO2H and M–SCO2 moieties, respectively. For
example, [Zn(L)][ClO4]2 (L = [14]aneN4 or [15]aneN4) take up
[Ru(dmso)(L)(terpy)]
[RuX(L)(terpy)]ϩ
(5)
CO2 in alcohol at room temperature to give the monoalkyl
L = tdt or pdt; X = Cl or CF3SO3
J. Chem. Soc., Dalton Trans., 2001, 57–63
59

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ESR specctra of the solid states of 5ϩ, 6ϩ, and 7ϩ were silent
and the 1H NMR spectra gave sharp signals in the range
from δ 0 to 10. From these results it is clear that the oxidation
state of the dithiolene is neutral and the electronic structures
of 5ϩ, 6ϩ, and 7ϩ are denoted as [RuIIX(L0)]ϩ (L = tdt or pdt).
environment. The two carbonyl ligands are situated in a cis
position to each other. One (C1–O1) is trans to the sulfur atom
(S1) of mnt and the other (C2–O2) is trans to a nitrogen atom
(N1) of terpyridine. The ruthenium–carbonyl (1.924(10) and
1.88(1) Å) and the C–O distances (1.125(10) and 1.156(10) Å)
are comparable with those found in other polypyridyl Ru(CO)2
complexes.14,19 Owing to the relatively strong interaction
between Ru and the vacant d orbital of S, the Ru–N2 bond
distance trans to S2 (2.160(5) Å) is clearly longer than the Ru–
N1 distance trans to CO (2.129(7) Å). The Ru–C1 bond dis-
tance of 1.924(10) Å trans to S1 is also slightly longer than the
other Ru–C2 bond distance of 1.88(1) Å trans to N1, suggesting
that the interaction of Ru–S is stronger than that of Ru–CO
ligand. The C19–C20 (1.372(9) Å) and C–S (1.726(7) and
1.726(8) Å) bond distances are similar to those found for
[Ni(mnt)2]2Ϫ 20 and [Me4N]2[V(mnt)3]21 that have dianionic mnt
ligands. Based on these results, the electronic structure of 1b is
expressed as [RuII(CO)2(mnt2Ϫ)(terpy)]. It is noteworthy that the
central pyridine unit of terpy of 1b should occupy the trans
position of one of the two carbonyl ligands if 1b is simply
formed through the substitution of either terminal pyridine of
terpy by the terminal sulfur of mnt in 1a. The 1H NMR spectra
in CD3CN and DMF-d7 supported retention of the configur-
ation of 1b in solution. The most reasonable rearrangement
from 1a to 1b proceeds through five-coordinate [Ru(CO)2(mnt-
κS)(terpy-κ2NNЈ)] formed by dissociation of either terminal
pyridine of terpy prior to attack of the terminal sulfur of
monodentate mnt on Ru (Scheme 2).
Molecular structures of complexes 1a, 1b, 2b and 3
The molecular structures of complexes 1a and 1b determined
by X-ray diffraction analysis are shown in Fig. 1. Selected bond
distances and angles are in Table 2. The ruthenium of 1a has an
octahedral geometry with two carbonyl carbons, three nitro-
gens of terpyridine, and one sulfur of mnt. In most metal–mnt
complexes the mnt coordinates as a bidentate ligand. The
unusual monodentate coordination of mnt of 1a is ascribed to
the stability of the Ru(terpy-κ3N,NЈ,NЉ)(CO)2 framework. The
Ru–C2 bond distance (1.85(2) Å) trans to S1 of the mnt ligand
is slightly shorter than Ru–C1 (1.94(2) Å) trans to the center of
the terpyridine. The relatively short Ru–C2 distance indicates a
strong interaction between Ru and S1. The ruthenium of 1b is
ligated by two nitrogens of terpyridine, two carbonyl carbons,
and two sulfur atoms of mnt, and has a distorted octahedral
Table 2 Selected bond lengths (Å) and angles (Њ) for complexes 1a
and 1b
1a
Ru(1)–S(1)
Ru(1)–N(2)
Ru(1)–C(1)
2.447(4)
2.04(1)
1.94(2)
Ru(1)–N(1)
Ru(1)–N(3)
Ru(1)–C(2)
2.08(1)
2.08(1)
1.85(2)
1b
Ru(1)–S(1)
Ru(1)–N(1)
Ru(1)–C(1)
C(1)–O(1)
S(1)–C(19)
C(18)–C(19)
C(20)–C(21)
C(21)–N(5)
2.408(2)
2.129(7)
1.924(10)
1.125(10)
1.726(7)
1.44(1)
Ru(1)–S(2)
Ru(1)–N(2)
Ru(1)–C(2)
C(2)–O(2)
S(2)–C(20)
C(19)–C(20)
C(18)–N(4)
2.352(2)
2.160(5)
1.88(1)
1.156(10)
1.726(8)
1.372(9)
1.125(10)
1.45(1)
1.122(8)
1b
S(1)–Ru(1)–S(2)
S(1)–Ru(1)–N(2)
S(1)–Ru(1)–C(2)
S(2)–Ru(1)–N(2)
S(2)–Ru(1)–C(2)
N(1)–Ru(1)–C(1)
N(2)–Ru(1)–C(1)
C(1)–Ru(1)–C(2)
Ru(1)–S(2)–C(20)
Ru(1)–C(2)–O(2)
S(1)–C(19)–C(18)
C(18)–C(19)–C(20)
S(2)–C(20)–C(21)
N(5)–C(21)–C(20)
88.47(7)
86.2(2)
88.5(3)
168.7(2)
87.9(2)
94.6(3)
96.2(3)
90.8(4)
102.1(2)
177.5(8)
115.5(5)
120.0(6)
114.1(6)
174(1)
S(1)–Ru(1)–N(1)
S(1)–Ru(1)–C(1)
S(2)–Ru(1)–N(1)
S(2)–Ru(1)–C(1)
N(1)–Ru(1)–N(2)
N(1)–Ru(1)–C(2)
N(2)–Ru(1)–C(2)
Ru(1)–S(1)–C(19)
Ru(1)–C(1)–O(1)
N(4)–C(18)–C(19)
S(1)–C(19)–C(20)
S(2)–C(20)–C(19)
86.2(2)
177.6(2)
92.8(2)
89.2(2)
76.9(2)
174.6(3)
102.0(3)
100.7(3)
176.6(8)
178.5(9)
124.4(6)
124.3(5)
C(19)–C(20)–C(21) 121.5(7)
Fig. 1 Molecular structures of complexes 1a and 1b.
Scheme 2
60
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Table 3 Selected bond lengths (Å) and angles (Њ) for complex 2b
Table 4 Selected bond lengths (Å) and angles (Њ) for complex 3
Ru(1)–S(1)
Ru(1)–N(1)
Ru(1)–C(1)
C(1)–O(1)
S(1)–C(22)
C(18)–C(19)
C(20)–C(21)
C(22)–C(23)
C(24)–C(19)
2.405(3)
2.148(7)
1.87(1)
1.16(1)
1.76(1)
1.50(2)
1.43(1)
1.39(1)
1.37(2)
Ru(1)–S(2)
Ru(1)–N(2)
Ru(1)–C(2)
C(2)–O(2)
S(2)–C(21)
C(19)–C(20)
C(21)–C(22)
C(23)–C(24)
2.362(3)
2.146(7)
1.847(10)
1.16(1)
1.77(1)
1.37(2)
1.39(1)
1.37(2)
Ru(1)–S(1)
Ru(1)–N(2)
Ru(1)–C(1)
C(1)–O(1)
C(2)–O(3)
2.497(5)
2.03(1)
1.86(1)
1.15(2)
1.37(2)
Ru(1)–N(1)
Ru(1)–N(3)
Ru(1)–C(2)
C(2)–O(2)
C(3)–O(3)
2.05(2)
2.08(1)
2.03(2)
1.19(2)
1.38(2)
Ru(1)–C(2)–O(2)
O(2)–C(2)–O(3)
128(1)
116(1)
Ru(1)–C(2)–O(3)
C(2)–O(3)–O(3)
115(1)
117(1)
Table 5 Electrochemical data of [RuX(dithiolene)(terpy)]nϩ (X = CO,
S(1)–Ru(1)–S(2)
S(1)–Ru(1)–N(2)
S(1)–Ru(1)–C(2)
S(2)–Ru(1)–N(2)
S(2)–Ru(1)–C(2)
N(1)–Ru(1)–C(1)
N(2)–Ru(1)–C(1)
C(1)–Ru(1)–C(2)
Ru(1)–S(2)–C(21)
Ru(1)–C(2)–O(2)
S(1)–C(22)–C(23)
S(2)–C(21)–C(22)
87.3(1)
86.5(2)
86.3(3)
169.9(2)
85.3(3)
94.8(4)
97.6(4)
91.7(5)
103.3(3)
174.9(9)
118.2(9)
122.7(7)
S(1)–Ru(1)–N(1)
S(1)–Ru(1)–C(1)
S(2)–Ru(1)–N(1)
S(2)–Ru(1)–C(1)
N(1)–Ru(1)–N(2)
N(1)–Ru(1)–C(2)
N(2)–Ru(1)–C(2)
Ru(1)–S(1)–C(22)
Ru(1)–C(1)–O(1)
S(1)–C(22)–C(21)
S(2)–C(21)–C(20)
87.2(2)
175.7(3)
95.1(2)
88.7(3)
76.6(3)
173.5(4)
102.2(3)
102.8(4)
175(1)
dmso, Cl or OSO2CF3)a
E1/2 /V vs. FeCp2ϩ/FeCp2
[complex]nϩ
(Ϫ/0)
(ϩ/0)
1b [Ru(CO)2(mnt)(terpy)]
2b [Ru(CO)2(tdt)(terpy)]
4 [Ru(dmso)(mnt)(terpy)]
0.59
0.02
Ϫ0.17
Ϫ0.13
Ϫ0.39
Ϫ0.39
122.5(7)
119.4(9)
5
6
7
ϩ [RuCl(tdt)(terpy)]BF4
Ϫ1.03
Ϫ1.30
Ϫ1.29
C(19)–C(20)–C(21) 117(1)
C(19)–C(24)–C(23) 117(1)
ϩ [RuCl(pdt)(terpy)]ClO4
C(20)–C(19)–C(24) 121(1)
C(22)–C(23)–C(24) 122(1)
ϩ [Ru(OSO2CF3)(pdt)(terpy)]CF3SO3
a E1/2 = (Epa ϩ Epc)/2, where Epa and Epc are anodic and cathodic peak
potentials, respectively.
The molecular structure of complex 2b is shown in Fig. 2 and
selected bond distances and angles are in Table 3. A significant
difference in the bond distances and angles around the
ruthenium atoms of 2b and 1b is not observed probably due
to the same electronic structures of [RuII(CO)2(L2Ϫ)(terpy)]
(L = mnt or tdt). The relatively long C–S bond distances of 2b
compared with those of 1b is explained by the difference of
the electron withdrawing ability between phenyl and two CN
groups.
The molecular structure of complex 3 is shown in Fig. 3 and
selected bond distances and angles are in Table 4. The distinct
feature of 3 is that two methoxycarbonyl groups are linked to
Ru and the terminal sulfur of monodentate pdt. Bond distances
and angles around the Ru–C(O)OCH3 unit 3 (Ru(1)–C(2)
2.03(2), C(2)–O(2) 1.19(2), C(2)–O(3) 1.37(2) Å; C(2)–O(3)–
C(3) 117(1), O(2)–C(2)–O(3) 116(1)Њ) are very similar to those
previously reported for [Ru(CO)(C(O)OCH3)(bpy)2]ϩ (Ru–C
2.042(6), C–O 1.191(8), C–O 1.344(8) Å; C–O–C 116.4(6),
O–C–O 119.2(6)Њ) which was prepared by reaction of CH3ONa
Fig. 2 Molecular structure of complex 2b.
with [Ru(CO)2(bpy)2]2ϩ 19
.
Electrochemical properties
The redox behavior of the present complexes is summarized in
Table 5. The cyclic voltammograms of 1b, 2b and 4 showed a
couple of anodic and cathodic waves at E1/2 = ϩ0.59, ϩ0.02,
and Ϫ0.17 V of the reversible 1b0/ϩ and 2b0/ϩ and 40/ϩ redox
couples, respectively, in CH3CN. There is a large difference in
the redox potentials of the two Ru–mnt complexes with CO
(1b) and with dmso (4) (∆E1/2 = 0.76 V). On the other hand, the
redox potential of the 40/ϩ couple is close to that of a metal-
centered RuII–RuIII redox reaction of the [Ru(mnt)(bpy)2]0/ϩ
couple at E1/2 = Ϫ0.27 V.11 The one-electron redox reaction of 4,
therefore, is reasonably assigned to the metal centered RuII–
RuIII couple. The difference in the oxidation potentials of 1b, 2b
and 4, therefore, is associated with the electron withdrawing
ability of the dithiolene, carbonyl and dmso ligands of these
complexes.
In contrast to neutral complexes 1b, 2b and 4, the electronic
structures of cationic 5ϩ, 6ϩ and 7ϩ are denoted as [RuII(L0)X]ϩ
(L = tdt or pdt; X = Cl or OSO2CF3). These complexes dis-
played two successive reversible cathodic processes in the range
of Ϫ0.13 to Ϫ1.30 V in CH3CN as shown for 6ϩ (in Fig. 4).
In addition, [RuCl(bpy)(terpy)]PF6 and [Ru(bpy)(terpy)-
Fig. 3 Molecular structure of complex 3.
J. Chem. Soc., Dalton Trans., 2001, 57–63
61

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Fig. 4 Cyclic voltammogram of [RuCl(pdt)(terpy)]ϩ 6ϩ in a CH2Cl2
Fig. 6 Absorption spectra of [RuCl(pdt)(terpy)]ϩ 6ϩ (solid line) and
[RuCl(pdt)(terpy)] 6 (dashed line) in CH2C2.
solution of NBun BF4 (0.1 M) at a glassy carbon electrode with a scan
4
rate of 50 mV sϪ1
.
reduced 6 obtained by controlled potential electrolysis of the
former at Ϫ0.7 V in CH2Cl2 are given in Fig. 6. Attempts to
measure the electronic spectra of 5Ϫ, 6Ϫ, and 7Ϫ under con-
trolled potential electrolysis of 5ϩ, 6ϩ and 7ϩ at Ϫ1.40 V in
CH2Cl2 were not successful due to the lability of these highly
reduced complexes. The oxidized form 6ϩ has a ruthenium to
terpy π* transition near 400 nm and a strong absorption band
at 566 nm. The latter is the most characteristic feature and
assigned to ruthenium to dithiolene, pdt, MLCT transition
because the π* level of pdt is lower than that of terpy, since
dithiolene ligands are reduced more easily than terpy. One
electron reduction of 6ϩ to generate 6 brought about strong
new bands at 500 and 720 nm with decreasing inensity of the
566 nm band. This red shift is an indication of an increase in the
electron density of the complex. Similarly, the triflate complex
7ϩ showed a strong absorption band at 568 nm, which shifted to
720 nm upon one-electron reduction at Ϫ0.7 V in CH2Cl2. The
similarity of electrochemical and spectroscopic properties
between 6nϩ and 7nϩ is an indication of the similar basicity of
Fig. 5 Absorption spectra of [Ru(dmso)(mnt)(terpy)] 4 (dashed line)
and [Ru(dmso)(mnt)(terpy)]ϩ ϩ (solid line) in CH3CN.
4
ClϪ and OSO2CF3 as monoanionic ligands. In the case of
Ϫ
(py)][PF6]2 do not undergo electrochemical reduction up to
Ϫ1.5 V.22,23 The two successive reductions of 5ϩ, 6ϩ and 7ϩ are
associated with the ligand centered [RuII(L0)X]ϩ–[RuII(LϪ)X]0
and [RuII(LϪ)X]0–[RuII(L2Ϫ)X]Ϫ redox couples.
5ϩ the ruthenium(II) to tdt π* MLCT band was observed at
527 nm. The blue shift of the band by 39 nm compared
with that of 6ϩ (λmax 566 nm) is explained by the high electron
density of pdt in 6ϩ compared with tdt in 5ϩ. In fact the tdt
moiety in 5 is reduced more easily than the pdt one in 6. When
5 was formed by controlled potential electrolysis of 5ϩ at
Ϫ0.2 V the strong band at 527 nm decreased, and a new band
appeared at 720 nm as found in the spectrum of 6.
The pdt localized redox reactions are hardly affected by the
difference between ClϪ and OSO2CF3Ϫ (6ClO4 and 7ClO4). On
the other hand, the redox potentials of the 6ϩ/0 and 60/Ϫ couples
are observed at values more negative than those of 50/ϩ and 50/Ϫ
(∆E1/2 = 260–270 mV), indicating that the electron density
(basicity) of pdt is higher than that of tdt. Strong basicity of
pdt compared with tdt and mnt is associated with the unusual
double addition of CO2 and CH3OH to the sulfur of pdt and
carbon of CO of 3a, respectively, producing 3. It is noteworthy
that a CO ligand of dicationic [Ru(bpy)2(CO)2]2ϩ undergoes
nucleophilic attack by CH3ONa but not by CH3OH.
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J. Chem. Soc., Dalton Trans., 2001, 57–63
63