Synthesis, characterization and reactivity of polypyridyl ruthenium(II) carbonyl complexes with phosphine derivatives: Ruthenium-carbon bond labilization based on steric and electronic effects

Article abstract of DOI:10.1016/j.ica.2005.04.040

Ruthenium phosphine complexes with a CO ligand [Ru(tpy)(PR ₃)(CO)Cl]⁺ (tpy = 2,2′:6′,2″- terpyridine, R = Ph or p-tolyl), were prepared by introduction of CO gas to the corresponding dichloro complexes at room temperature. New carbonyl complexes were characterized by various methods including structural analyses. They were shown to release CO following the addition of several N-donors to form the corresponding substituted complexes. The kinetic data and structural results observed in this study indicated that the CO release reactions proceeded in an interchange mechanism. The molecular structures of [Ru(tpy)(PPh ₃)(CO)Cl]PF₆, [Ru(tpy)(P(p-tolyl)₃)(CO)Cl] PF₆ and [Ru(tpy)(PPh₃)(CH₃CN)Cl]PF₆ were determined by X-ray crystallography.

Full text of DOI:10.1016/j.ica.2005.04.040

Inorganica Chimica Acta 359 (2006) 800–806
www.elsevier.com/locate/ica
Synthesis, characterization and reactivity of
polypyridyl ruthenium(II) carbonyl complexes with
phosphine derivatives: Ruthenium–carbon bond labilization based
on steric and electronic effects
a,
b
Dai Ooyama *, Madoka Saito
a
Department of Industrial Systems Engineering, Cluster of Science and Technology, Fukushima University, Kanayagawa, Fukushima 960-1296, Japan
b
Department of Environmental Science, Faculty of Education, Fukushima University, Kanayagawa, Fukushima 960-1296, Japan
Received 8 March 2005; accepted 26 April 2005
Available online 13 June 2005
Ruthenium and Osmium Chemistry Topical Issue
Abstract
Ruthenium phosphine complexes with a CO ligand [Ru(tpy)(PR3)(CO)Cl]+ (tpy = 2,20:60,200-terpyridine, R = Ph or p-tolyl), were
prepared by introduction of CO gas to the corresponding dichloro complexes at room temperature. New carbonyl complexes were
characterized by various methods including structural analyses. They were shown to release CO following the addition of several
N-donors to form the corresponding substituted complexes. The kinetic data and structural results observed in this study indicated
that the CO release reactions proceeded in an interchange mechanism. The molecular structures of [Ru(tpy)(PPh3)(CO)Cl]PF6,
[Ru(tpy)(P(p-tolyl)3)(CO)Cl]PF6 and [Ru(tpy)(PPh3)(CH3CN)Cl]PF6 were determined by X-ray crystallography.
ꢀ 2005 Elsevier B.V. All rights reserved.
Keywords: Ruthenium; Carbonyl; Polypyridyl complexes; Crystal structures; CO-release reaction; Reaction mechanism
1. Introduction
In general, polypyridyl ruthenium (II) carbonyl com-
plexes are kinetically inert for CO release since they are
usually saturated 18-electron complexes. Therefore,
reactions to remove CO ligands are carried out using re-
agents such as NaBH4 [3], redox reactions [4], or phot-
oirradiation [5]. On the other hand, some studies
reported that coligands on other ruthenium(II) carbonyl
systems facilitate a Ru–CO bond breaking through ste-
ric and electronic effects [6]. Such studies gave us some
ideas to achieve the lability of inert Ru–CO bond with-
out reagents or redox/photo reactions. That is, the de-
sign of complexes considering their steric and electron
donor/acceptor effects of coligands may allow the sys-
tematic control of Ru–CO bond strength in polypyridyl
ruthenium(II) carbonyl complexes system.
For several reasons, we have recently developed an
increasing interest in the analysis of the bond characteris-
tics of polypyridyl ruthenium(II) complexes involving
carbonyl ligands. The bond scission of ruthenium–
carbon in Ru–CO moiety is a key reaction in utilizing
polypyridyl ruthenium(II) complexes as catalysts for the
reduction of carbon dioxide [1]. Synthesis of complexes
capable of CO release is needed to investigate the biolog-
ical activities of CO because it is known that CO gas is gen-
erated in the human body and plays an important role [2].
*
Corresponding author. Tel./fax: +81 24 548 8199.
E-mail address: ooyama@sss.fukushima-u.ac.jp (D. Ooyama).
0020-1693/$ - see front matter ꢀ 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2005.04.040

D. Ooyama, M. Saito / Inorganica Chimica Acta 359 (2006) 800–806
801
In the present study, we introduced two kinds of
phosphorous compounds (PPh3 and P(p-tolyl)3) as
candidates for achieving the lability of Ru–CO bond
to the trans position of a CO ligand and constructed a
the crude product, and then the precipitate was collected
to give [Ru(tpy)(PPh3)(CO)Cl]PF6 with a 66% yield.
IR (KBr): 2008 cmꢀ1 m(C„O). ESI-MS: m/z = 632
([M ꢀ CO]+). Anal. Calc. for C34H26N3OF6ClP2Ru: C,
50.73;H, 3.26; N, 5.22. Found: C, 50.77;H, 3.26; N, 5.22%.
suitable
complex
system
(trans(CO,PR3)-[Ru
(tpy)(PR3)(CO)Cl]+: tpy = 2,20:60,200-terpyridine; R =
phenyl, p-tolyl). We further reported kinetic investiga-
tions to determine the CO dissociation rate and mecha-
nistic assignments using several N-donor compounds
which can coordinate with the ruthenium(II) center.
2.2.2. trans(CO,P(p-tolyl)3)-[Ru(tpy)(P(p-tolyl)3)
(CO)Cl]PF6
A similar reaction between cis(Cl)-[Ru(tpy)(P(p-to-
lyl)3)Cl2] and CO gas under the same conditions
described above gave rise to [Ru(tpy)(P(p-tolyl)3)
(CO)Cl]PF6 with 77% yield. IR (KBr): 2004 cmꢀ1
m(C„O). ESI-MS: m/z = 674 ([M ꢀ CO]+). Anal. Calc.
for C37H32N3OF6ClP2Ru: C, 52.46; H, 3.81; N, 4.96.
Found: C, 52.56; H, 3.81; N, 4.99%.
2. Experimental
2.1. Physical and kinetic measurements
Elemental analyses were carried out at the Research
Center for Molecular-Scale Nanoscience, Institute for
Molecular Science. IR spectra were obtained on KBr
pellets or in CH3CN solution (window: KRS-5) with a
Shimadzu FT-IR 8100 spectrometer. ESI-MS were ob-
tained with a Shimadzu LC-MS 2100 mass spectrome-
ter. UV–Vis spectra were obtained with an Ocean
Optics S2000 fiber optics spectrometer equipped with
an Analytical Instrument Systems light source. Kinetic
measurements were carried out at 25(1) ꢁC in a constant
temperature room. Stock solutions of [Ru(tpy)(PPh3)
(CO)Cl]+ and [Ru(tpy)(P(p-tolyl)3)(CO)Cl]+ were pre-
pared in 1,2-dichloroethane (DCE) under N2. Each
complex concentration was 1.0 · 10ꢀ4 mol dmꢀ3. Liquid
entering ligands (acetonitrile, benzonitrile and propio-
nitrile) were added using a syringe to the solution of
the carbonyl complexes. A portion of the mixed solution
was transferred by syringe to the UV–Vis spectral cell
and the spectrum of the sample was recorded at appro-
priate intervals. For the determination of kobs the in-
crease in absorption (At) at 460–470 nm corresponding
to the substituted species was recorded as a function
2.3. CO-release of [Ru(tpy)(PR3)(CO)Cl]PF6
(R = Ph or p-tolyl) in acetonitrile solution: isolation of
trans(Cl,PR3)-[Ru(tpy)(PR3)(CH3CN)Cl]PF6
(R = Ph or p-tolyl)
Either of the complexes [Ru(tpy)(PPh3)(CO)Cl]PF6
or [Ru(tpy)(P(p-tolyl)3)(CO)Cl]PF6 (30 mg) were
dissolved in CH3CN (2 cm3) at room temperature in
the dark. The solution was stirred for 4 days and
then ether (3 cm3) was added into the solution at
4 ꢁC. Orange crystals of [Ru(tpy)(PPh3)(CH3CN)Cl]PF6
or [Ru(tpy)(P(p-tolyl)3)(CH3CN)Cl]PF6 gradually ap-
peared out of the solution. The yield of [Ru
(tpy)(PPh3)(CH3CN)Cl]PF6 was 85%. ESI-MS: m/z =
673 ([M]+), 632 ([M ꢀ CH3CN]+). Anal. Calc. for
C35H29N4F6ClP2Ru: C, 51.38; H, 3.57; N, 6.85. Found:
C, 51.16; H, 3.65; N, 6.85%. The yield of [Ru(tpy)(P-
(p-tolyl)3)(CH3CN)Cl]PF6 was 87%. ESI-MS: m/z =
715 ([M]+), 674 ([M ꢀ CH3CN]+). Anal. Calc. for
C38H35N4F6ClP2Ru: C, 53.06; H, 4.10; N, 6.51. Found:
C, 52.92; H, 4.17; N, 6.45%.
of time (t). A was measured when the intensity changes
2.4. X-ray crystallography
1
leveled off. Values of pseudo-first order rate constants
were obtained from the slopes of linear least-squares
plots of ꢀln(A1 ꢀ At) against t [7].
Crystallographic data for [Ru(tpy)(PPh3)(CO)Cl]PF6,
[Ru(tpy)(P(p-tolyl)3)(CO)Cl]PF6 and [Ru(tpy)(PPh3)
(CH3CN)Cl]PF6 are summarized in Table 1. Data for
these complexes were collected on a Rigaku/MSC Mer-
cury CCD diffractometer with graphite monochromated
2.2. Preparation of complexes
˚
[Ru(PPh3)3Cl2],
(PPh3)Cl2], and [Ru(tpy)(P(p-tolyl)3)Cl2] were prepared
according to procedures outlined elsewhere [8,9].
[Ru(P(p-tolyl)3)3Cl2],
[Ru(tpy)-
Mo Ka radiation (k = 0.71070 A) at ꢀ100 ꢁC. Data
were collected to a maximum of 2h value of 55.0ꢁ. A to-
tal of 720 oscillation images were collected. All calcula-
tions were carried out on a workstation of Silicon
Graphics Corporation, using the TEXSAN crystallo-
graphic software package of the Molecular Structure
Corporation. The structures were solved either by the
Patterson method ([Ru(tpy)(PPh3)(CO)Cl]PF6 and
[Ru(tpy)(P(p-tolyl)3)(CO)Cl]PF6) [10] or by a direct
method ([Ru(tpy)(PPh3)(CH3CN)Cl]PF6) [11] and were
expanded using Fourier techniques. Empirical absorp-
2.2.1. trans(CO,PPh3)-[Ru(tpy)(PPh3)(CO)Cl]PF6
A CH2Cl2 solution (40 cm3) of cis(Cl)-[Ru(tpy)-
(PPh3)Cl2] (40 mg) was stirred at room temperature
under 10 atm of CO for 6 h. Once the reaction mixture
was concentrated under reduced pressure, crystals were
precipitated by the addition of ether. An aqueous
KPF6 solution was added to a methanolic solution of

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D. Ooyama, M. Saito / Inorganica Chimica Acta 359 (2006) 800–806
Table 1
Crystallographic data for [Ru(tpy)(PPh3)(CO)Cl]PF6, [Ru(tpy)(P(p-tolyl)3)(CO)Cl]PF6 and [Ru(tpy)(PPh3)(CH3CN)Cl]PF6
Chemical formula
Formula weight
Temperature (K)
Crystal system
C34H26N3OF6ClP2Ru
805.06
173
C37H32N3OF6ClP2Ru
847.14
173
C35H29N4F6ClP2Ru
818.10
173
monoclinic
P21/c
monoclinic
P21/c
monoclinic
P21/n
Space group
Unit cell parameters
˚
a (A)
10.5843(5)
14.5950(8)
21.086(3)
91.523(2)
3256.1(3)
4
14.796(8)
13.937(7)
18.55(1)
109.027(7)
3616(3)
4
13.323(4)
26.363(7)
19.652(6)
92.529(4)
6896(3)
8
˚
b (A)
˚
c (A)
b (ꢁ)
3
˚
V (A )
Z
l(Mo Ka) (cmꢀ1
Number of reflections measured
Number of observations
Parameters
)
7.30
7701
6.62
8508
6.90
16103
7402 (all)
433
0.046
8175 (all)
460
0.083
15751 (all)
883
0.083
R1a
b
Rw
0.107 (all data)
1.40
0.148 (all data)
1.23
0.159 (all data)
1.62
S
P
P
a
R = ||Fo|ꢀ|Fc||/ |Fo|.
P
P
2
2 1=2
b
Rw ¼ f wðF 2o ꢀ F c2Þ = wðF o2Þ g
.
tion corrections were applied using Lorentz polarization
(Lp) and absorption. Structures were refined with the
full-matrix least-square techniques. The non-hydrogen
atoms were refined anisotropically, and hydrogen atoms
were placed in idealized positions. The final cycle of
full-matrix least-squares refinements was based on
7402 observations (all data), 433 variable parameters
for [Ru(tpy)(PPh3)(CO)Cl]PF6, 8175 and 460 for [Ru
(tpy)(P(p-tolyl)3)(CO)Cl]PF6, and 15751 and 883 for
[Ru(tpy)(PPh3)(CH3CN)Cl]PF6, respectively.
CO
tpy
Ru
Cl
Cl
(a) CO, ∆
PR3
Cl
tpy
Cl
Ru
(b) CO, r.t.
PR3
Cl
tpy
Ru
3. Results and discussion
OC
R = Ph or p-tolyl
Scheme 1.
3.1. Syntheses and characterization of carbonyl
complexes
We synthesized the desirable complexes to labilize the
Ru–CO bond: ruthenium complexes contained both a
CO and a p-acidic phosphine compound at the trans po-
sition mutually. In Scheme 1, the implied difference in
synthesis is shown. In pass (a), the precursors cis(Cl)-
[Ru(tpy)(PR3)Cl2] react with CO in DCE at reflux to
give cis(Cl)-[Ru(tpy)(CO)Cl2] [9], whereas they undergo
a chloride substitution reaction with CO gas under high-
pressure at room temperature to form trans(CO,PR3)-
[Ru(tpy)(PR3)(CO)Cl]+ in pass (b).
These carbonyl complexes were characterized by var-
ious measurements. ESI-mass spectra in CH3CN solu-
tion showed the main peaks (m/z : 632 for R = Ph, 674
for R = p-tolyl, respectively) together with the isotope
distribution pattern of ruthenium nuclei. These peak
values corresponded to CO-loss forms. IR spectra of
the complexes displayed a strong band m(C„O) at
2008 (for R = Ph) and 2004 cmꢀ1 (for R = p-tolyl),
respectively. The 2008 cmꢀ1 value in R = Ph, is
51 cmꢀ1 higher than that of the corresponding chloro
complex (1957 cmꢀ1) [9] due to the existence of more
electron-accepting phosphine ligand trans to CO. A sin-
gle m(C„O) band also displayed no other isomers in
these complexes.
Figs. 1 and 2 display the molecular structures of
R = Ph and p-tolyl, respectively. Selected bond lengths
and angles are listed in Table 2. The coordinating envi-
ronments around the ruthenium atom of both R = Ph
and p-tolyl were essentially the same: each complex
had a distorted octahedral geometry with three nitrogen
atoms of the tpy ligand, one phosphorous atom, one
chloride ion and one carbon at the terminal carbonyl
group. The carbonyl ligand was at the trans position

D. Ooyama, M. Saito / Inorganica Chimica Acta 359 (2006) 800–806
803
Fig. 2. An ORTEP view of [Ru(tpy)(P(p-tolyl)3)(CO)Cl]+ with atom
labeling. Hydrogen atoms are omitted for clarity. The thermal
ellipsoids are shown at the 50% probability level.
Fig. 1. An ORTEP view of [Ru(tpy)(PPh3)(CO)Cl]+ with atom
labeling. Hydrogen atoms are omitted for clarity. The thermal
ellipsoids are shown at the 50% probability level.
(175.6(2)ꢁ for R = Ph, 174.7(5)ꢁ for R = p-tolyl, respec-
tively) and the Ru–C and the C–O bond lengths
˚
(1.891(3) and 1.138(3) A, respectively for R = Ph,
˚
1.897(5) and 1.134(6) A, respectively, for R = p-tolyl)
with respect to the phosphine. The Ru–P bond lengths
˚
of R = Ph and p-tolyl (2.4811(7) and 2.467(2) A, respec-
were similar to typical values in other Ru(II) carbonyl
complexes [1].
tively) were in the range of those of Ru(II)–phosphine
complexes [12]. The bond lengths of the three Ru–N in
˚
R = Ph (2.102(2), 1.978(2) and 2.082(2) A) were compa-
rable to those of R = p-tolyl (2.097(4), 1.974(4) and
˚
2.089(4) A). These lengths are typical in the structure
of other Ru(II) complexes with terpyridine [13]. The
˚
bond lengths of Ru–Cl (2.4228(7) and 2.425(1) A,
3.2. Ru–CO bond lability in the complexes: CO-release
behavior in solutions
The UV–Vis spectrum of [Ru(tpy)(PR3)(CO)Cl]+
showed
a
weak MLCT band at 405 nm
respectively) were also in the range of those of Ru(II)–
terpyridine–chloro complexes [13]. Both Ru–CO units
were essentially linear with the ruthenium atom
(e = 3.2 · 103 dm3 molꢀ1 cmꢀ1) for R = Ph and 407 nm
(e = 3.0 · 103 dm3 molꢀ1 cmꢀ1) for R = p-tolyl in DCE.
Table 2
Selected bond lengths (A) and angles (ꢁ) for [Ru(tpy)(PPh3)(CO)Cl]PF6, [Ru(tpy)(P(p-tolyl)3)(CO)Cl]PF6 and [Ru(tpy)(PPh3)(CH3CN)Cl]PF6
˚
[Ru(tpy)(PPh3)(CO)Cl]+
[Ru(tpy)(P(p-tolyl)3)(CO)Cl]+
[Ru(tpy)(PPh3)(CH3CN)Cl]+
Bond lengths
Ru1–P1
Ru1–Cl1
Ru1–C1
Ru1–N1
Ru1–N2
Ru1–N3
C1–O1
2.4811(7)
2.4228(7)
1.891(3)
2.102(2)
1.978(2)
2.082(2)
1.138(3)
Ru1–P1
Ru1–Cl1
Ru1–C1
Ru1–N1
Ru1–N2
Ru1–N3
C1–O1
2.467(2)
2.425(1)
1.897(5)
2.097(4)
1.974(4)
2.089(4)
1.134(6)
Ru1–P1
Ru1–Cl1
Ru1–N1
Ru1–N2
Ru1–N3
Ru1–N4
N4–C16
C16–C17
2.312(1)
2.446(1)
2.095(4)
1.954(3)
2.079(4)
2.063(4)
1.380(5)
1.448(6)
Bond angles
N1–Ru1–N2
N2–Ru1–N3
P1–Ru1–Cl1
P1–Ru1–C1
Cl1–Ru1–C1
Ru1–C1–O1
79.27(9)
79.48(10)
89.11(2)
177.02(8)
87.91(8)
175.6(2)
N1–Ru1–N2
N2–Ru1–N3
P1–Ru1–Cl1
P1–Ru1–C1
Cl1–Ru1–C1
Ru1–C1–O1
79.3(2)
79.4(2)
N1–Ru1–N2
N2–Ru1–N3
P1–Ru1–Cl1
P1–Ru1–N4
Cl1–Ru1–N4
Ru1–N4–C16
N4–C16–C17
79.6(1)
79.9(1)
91.59(5)
175.2(2)
83.6(2)
176.23(4)
97.1(1)
84.6(1)
174.7(5)
164.6(4)
176.9(5)

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D. Ooyama, M. Saito / Inorganica Chimica Acta 359 (2006) 800–806
Fig. 3. Time dependence of the electronic spectra of [Ru(tpy)(PPh3)(CO)Cl]+ in CH3CN at 25 ꢁC (1.0 · 10ꢀ4 mol dmꢀ3).
No spectral change was observed in both complexes
after 1 day. On the other hand, the light orange PPh3
complex solution gradually changed to a deep orange
color when the complex was dissolved in CH3CN in
the dark (Fig. 3). The original band at 405 nm gradually
decreased with time, and new bands increased at 320
and 466 nm with the isosbestic points. The solution IR
spectrum after this reaction showed the disappearance
of the characteristic peak of the terminal CO triple
bond. Therefore, it is suggested that this was a substitu-
tion reaction between the coordinated carbonyl and an
acetonitrile (solvent)
Examples of ln(Dabsorbance) versus time plots are
shown in Fig. 4 for the reaction with acetonitrile
(0.02 mol dmꢀ3 in DCE). Fig. 4 indicates that this reac-
tion allows for a first-order rate constant kobs. In addi-
tion, the reaction was studied using different
concentrations or kinds of entering ligands (R0CN). In
principle, the rate constants kobs are pseudo-first order
because
the
entering
ligand
concentrations
(>0.01 mol dmꢀ3) were always larger than that of [Ru-
(tpy)(PR3)(CO)Cl]+ (<1 · 10ꢀ4 mol dmꢀ3). We found
that the rates for all of the reactions were independent
of the concentration of acetonitrile (Table 3). This ten-
dency was established for concentrations of acetonitrile
between 0.01 and 0.05 mol dmꢀ3 in DCE. Therefore, the
rate law for the Eq. (1) is given by
½RuðtpyÞðPR3ÞðCOÞClꢁþ þ R0CN
kobs
!½RuðtpyÞðPR3ÞðR0CNÞClꢁþ þ CO
ð1Þ
rate ¼ kobs½RuðtpyÞðPR3ÞðCOÞClꢁ.
ð2Þ
The kinetics of the reactions shown in Eq. (1) have been
monitored by UV–Vis spectroscopy to determine the
rate constants and to obtain mechanistic evidences.
Additionally, the value of kobs was found to be indepen-
dent of the nature of the entering ligands (R0CN) includ-
ing their basicity and steric requirements (Table 3). As a
result, this system is consistent with a dissociative
mechanism rather than an associative one. Similarly,
[Ru(tpy)(P(p-tolyl)3)(CO)Cl]+ also indicated CO dissoci-
ation. Taking into account the stability of the Ru–CO
bond in the analogous complexes trans- and cis(Cl)-
Table 3
Summary of PR3 properties and CO-release rate constants for
[Ru(tpy)(PR3)(CO)Cl]+ (R = Ph or p-tolyl)
106k (sꢀ1
R0 = Me R0 = Et R0 = Ph
)
a
R
pKa
Cone
angleb (mol dmꢀ3
[R0CN]
)
Ph
2.73 145ꢁ
0.01
0.02
0.05
4.00
3.76
4.80
4.56
5.01
p-Tolyl 3.84 145ꢁ
0.01
5.85
Fig. 4. Plots of ln(Dabsorbance) vs. time for the reaction of
a
[Ru(tpy)(PPh3)(CO)Cl]+ (1.0 · 10ꢀ4 mol dmꢀ3
mol dmꢀ3) in DCE at 25 ꢁC.
)
with CH3CN (0.02
Ref. [15].
Ref. [16].
b

D. Ooyama, M. Saito / Inorganica Chimica Acta 359 (2006) 800–806
805
[Ru(tpy)(CO)Cl2] [9], it is suggested that the selection of
3.3. Isolation of the substituted complexes: CO-release
reaction with steric change
this configuration and the phosphine ligands make the
Ru–CO lability possible. In general, ligands with elec-
tron-donating substituents are strong donors. Thus,
P(p-tolyl)3 donates more strongly than PPh3 to the
ruthenium. As a result, [Ru(tpy)(P(p-tolyl)3)(CO)Cl]+
is more electron-rich than [Ru(tpy)(PPh3)(CO)Cl]+ and
therefore the former is considered to have stronger basi-
city [14]. However, both complexes showed a similar
rate constant (Table 3). These results indicated that
the Ru–C bond strength was minimally affected by the
small difference of pKa values. Therefore, systematic
preparation of complexes containing suitable ligands
(with much higher or lower pKaÕs for phosphines
compared with the present ones) may be required for a
better discussion on the relationship between Ru–C
bond strengths and ligand basicities.
We quantitatively isolated the substituted complexes
from each solution and attempted to characterize them.
The CO stretching band disappeared from the IR mea-
surements. From ESI-MS measurements, the com-
pounds were characterized as the corresponding
solvent complexes, [Ru(tpy)(PR3)(R0CN)Cl]PF6 (R =
Ph or p-tolyl; R0 = Me, Et or Ph). In addition, the ace-
tonitrile complexes [Ru(tpy)(PPh3)(CH3CN)Cl]+ and
[Ru(tpy)(P(p-tolyl)3)(CH3CN)Cl]+, were characterized
by elemental analyses (see Experimental section). The
crystal structure was determined using a suitable crystal
in [Ru(tpy)(PPh3)(CH3CN)Cl]PF6. Interestingly, it was
confirmed that an acetonitirile molecule attached to
the cis position with respect to the phosphine ligand,
which was different from the dissociated CO position
(Fig. 5). We suggested that an interchange mechanism
(I-mechanism) rather than a simple dissociative one
(D-mechanism) was employed due to steric change
accompanying the CO-release reaction [17]. Scheme 2
shows the possible mechanism of the CO-release reac-
tion. It is possible that the entering ligands (R0CN) at-
tack to the ruthenium center from the phosphine side
rather than the CO side. Results from the structural
studies apparently supported the assumption that the
reaction proceeded via I-mechanism.
On the other hand, when CO was introduced into the
formed complexes, [Ru(tpy)(PR3)(CH3CN)Cl]+, the ori-
ginal carbonyl complexes with the same configuration
were reproduced (by IR and 1H NMR spectra). As
shown in Scheme 3, the results obtained led to the
+
+
R'CN
CO
PR3
Cl
PR3
R'CN
tpy
tpy
Cl
Ru
Ru
OC
Fig. 5. An ORTEP view of [Ru(tpy)(PPh3)(CH3CN)Cl]+ with atom
labeling. Hydrogen atoms are omitted for clarity. The thermal
ellipsoids are shown at the 50% probability level.
cis-(PR3,Cl) form
trans-(PR3,Cl) form
Scheme 3.
+
+
PR3
PR3
R'CN
PR3
tpy
tpy
tpy
Cl
Ru
Ru
Ru
OC
Cl
R'CN
OC
Cl
Scheme 2.

806
D. Ooyama, M. Saito / Inorganica Chimica Acta 359 (2006) 800–806
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4. Conclusion
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From this study, we can conclude that the selection
and introduction of phosphine ligands allows labiliza-
tion of the Ru–CO bond, which results in the regulation
of reactivity of the compounds in biological or catalytic
processes. The present topic will be addressed in a future
publication on the reactivity of [Ru(tpy)(PR3)(CO)Cl]+
having various phosphines.
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5. Supplementary material
Crystallographic data for structural analysis have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC Nos. 254144 for [Ru(tpy)(PPh3)
(CO)Cl]PF6, 258940 for [Ru(tpy)(P(p-tolyl)3)(CO)Cl]
PF6 and 254145 for [Ru(tpy)(PPh3)(CH3CN)Cl]PF6,
respectively. Copies of this information may be obtained
free of charge from The Director, CCDC, 12 Union
Road, Cambridge CB2 1EZ, UK.
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Acknowledgments
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We are indebted to Professor Koji Tanaka of the
Institute for Molecular Science for his helpful advice
and discussion. We thank Dr. Kazushi Shiren for per-
forming the X-ray measurements. This work was sup-
ported by the Joint Studies Program (2003–2004) of
the Institute for Molecular Science.
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