Synthesis of trinuclear Pd-Ru-Pd porphyrin complexes with axially ligated Pd centers. Prominent metal-to-ligand charge transfer band in the visible region

Article abstract of DOI:10.1016/j.jorganchem.2013.12.008

Ru-porphyrin complexes with pyridylpyrazine as metal coordination sites were synthesized. Introduction of Pd-alkyl units to the binding site led to the formation of a novel Pd-Ru-Pd trinuclear complex. The metalation causes drastic changes in the electrochemical and photophysical properties. The trinuclear complex exhibited a prominent metal-to-axial ligand charge transfer band in the visible region due to small energy gap between the Ru-based HOMO and the axial ligand-based LUMO. These changes resulted in the drastic color change from orange to green.

Full text of DOI:10.1016/j.jorganchem.2013.12.008

Journal of Organometallic Chemistry 753 (2014) 48e54
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Synthesis of trinuclear PdeRuePd porphyrin complexes with axially
ligated Pd centers. Prominent metal-to-ligand charge transfer band
in the visible region
,
a,
Yusuke Yasu a, Akiko Inagaki b , Munetaka Akita
*
*
a Chemical Resources Laboratory, Tokyo Institute of Technology, R1-27, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan
b Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University, Minami-Osawa 1-1, Hachioji, Tokyo 192-0397,
Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
Rueporphyrin complexes with pyridylpyrazine as metal coordination sites were synthesized. Intro-
duction of Pd-alkyl units to the binding site led to the formation of a novel PdeRuePd trinuclear
complex. The metalation causes drastic changes in the electrochemical and photophysical properties. The
trinuclear complex exhibited a prominent metal-to-axial ligand charge transfer band in the visible region
due to small energy gap between the Ru-based HOMO and the axial ligand-based LUMO. These changes
resulted in the drastic color change from orange to green.
Received 22 May 2013
Received in revised form
29 November 2013
Accepted 5 December 2013
Keywords:
MLCT
Ó 2013 Elsevier B.V. All rights reserved.
Rueporphyrin
Trinuclear complex
Metalloporphyrins have been used as visible-light-absorbing
units in research related to artificial photosynthesis because chlo-
rophylls, which possess a metalloporphyrin core, play central roles
in a light-harvesting antenna system [1]. One of the important
characteristics of such metalloporphyrins is the metal-to-ligand
charge-transfer (MLCT), to which the central metal makes a large
contribution. To date, a number of modified metalloporphyrins
with various fragments connected to the ring have been synthe-
sized via laborious synthetic procedures. However, in most cases,
various combination of chelating ligands and metals would further
broaden the photophysical properties of metalloporphyrin systems.
The synthetic scheme for the mononuclear and the trinuclear
Rueporphyrin complexes (1 and 1-Pd), and their reference com-
pounds with a terminal CO ligand (2 and 2-Pd) is shown in Scheme 1.
Oxidation of Ru(TTP)(CO)(EtOH) (TTP ¼ tetratolylporphyrin) by TBHP
(tert-butylhydroperoxide) produced a
m-oxo dimer m-O-[Ru(TT-
P)(OEt)]2, and subsequent reduction by NaBH4 in the presence of
pyridylpyrazine (ppyr) produced complex 1 in a good yield [5].
porphyrin
pe
p* transition dominates the MLCT to determine the
Addition of two equivalents of (cod)Pd(Me)(Cl) (cod
¼
1,5-
photophysical properties of the entire metalloporphyrin system [2].
Since it is much easier to introduce various fragments through axial
ligation compared to the modification of the porphyrin ring,
considerable attention has been given to Ru porphyrins because
they show an extremely wide variety of photophysical properties
depending on the axial ligands coordinated to the central metal
[3,4]. Herein we report syntheses and photophysical properties of
Ru porphyrins and their metalated complexes with chelating
ligands on the axial sites. Substitution of the axial carbonyl ligand
by a chelating ligand drastically changes the photophysical prop-
erties, in which distinct MLCT band appeared in the visible region
through the metalation. Simple modification of axial sites using
cyclooctadiene) led to the PdeRuePd trinuclear complex (1-Pd).
Since reported decarbonylation of Ru(TTP)(CO)(EtOH) by UV-
irradiation requires a highly diluted condition [6], these procedures
(step (a) and (b) in Scheme 1) are suitable for the gram-scale syn-
thesis. The Rueporphyrin complexes with a terminal CO ligand (2
and 2-Pd) were readily synthesized from Ru(TTP)(CO)(EtOH) (step
(d) and (e) in Scheme 1). Both di- and trinuclear complexes with the
PdMeCl fragment (2-Pd and 1-Pd) are obtained as a mixture of
stereoisomers concerning to the position of the chloride ligand trans
or cis to the pyrazine ring. These isomers could not be separated by
regular purification processes such as column chromatography and
recrystallization. Fortunately, however, each isomer possessed very
similar properties and thus we used these samples for electro-
chemical and photophysical measurements (Fig. S4). The OEP de-
rivatives 20 and 20-Pd [7] were obtained in high yields by following
similar procedures [8]. All the complexes were unambiguously
* Corresponding authors.
E-mail address: ainagaki@tmu.ac.jp (A. Inagaki).
0022-328X/$ e see front matter Ó 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.jorganchem.2013.12.008

Y. Yasu et al. / Journal of Organometallic Chemistry 753 (2014) 48e54
49
Scheme 1. Synthesis of complexes 1, 1-Pd, 2, and 2-Pd.
characterized using 1H and 13C NMR spectroscopy. To be noted,
related axial ligands such as 4-(2-pyridyl)pyrimidine can be also
introduced for the synthesis of corresponding PdeRuePd trinuclear
complex in a similar manner [9].
determined Rueporphyrins with axially ligated pyridines possess
angles in the rage 45ꢀe50ꢀ bisecting the N1eRueN2 or N3eRueN4
angle [10,11]. The characteristic small angle of 20-Pd indicates the
presence of an electronic conjugation between the Ru(d) orbital
and the pyridylpyrazine-Pd unit in the solid state.
The UVevis spectra are shown in Fig. 2 and the data are sum-
marized in Table 2. Complexes 2 and 2-Pd showed spectra similar
to that of Ru(TTP)(CO)(EtOH) (Table 2), Ru(TPP)(CO)
The structures of octaethylporphyrin derivatives of 20 and 20-Pd
were determined by X-ray crystallography (Fig. 1) and selected
bond lengths are summarized in Table 1. The averages of the four
0
0
ꢀ
ꢀ
RueN(pyrrole) distances are 2.054(7) A for 2 and 2.057(6) A for 2 -
ꢀ
Pd, which compare well with the distance of 2.052(9) A found
(TPP
¼
tetraphenylporphyrin) [12], and its pyridine adduct,
for Ru(TPP)(CO)(py) complex (TPP
¼
tetraphenylporphyrin,
Ru(TPP)(CO)(py). On the other hand, 1 and 1-Pd showed properties
considerably different from those of 2 and 2-Pd. A decrease of in-
tensity of the Soret band, and broadening and red-shift of Q band
were observed for complex 1, and this behavior is identical to that
observed for Ru(por)(py)2 [14a]. Weak MLCT band seems to be
overlapped with the Q-band to be observed as a broad shoulder
peak which ranges from 550 to 650 nm (lmax ¼ 617 nm). In com-
parison, MLCT band is much more distinct in 1-Pd, which showed a
py ¼ pyridine) [10]. The axial RueN(pyridyl) bond distances are
0
0
ꢀ
2.210(6) and 2.242(6) A for 2 and 2 -Pd, respectively. The bond
lengths increased from Ru(TPP)(CO)(py), 20, to 20-Pd. In relation
with this phenomenon, shortening of the RueCO bond distances
was observed. The clearest characteristic property was the small
pyrazine orientation angle of 20-Pd with respect to the N(1)eN(3)
vector (45ꢀ for 20, 2.0ꢀ for 20-Pd). Most of the structurally
Fig. 1. ORTEP drawings of 20 and 20-Pd drawn with thermal ellipsoids at the 30% probability level. Hydrogen atoms are omitted for clarity.

50
Y. Yasu et al. / Journal of Organometallic Chemistry 753 (2014) 48e54
Table 1
Table 2
Electronic absorption data.a
ꢀ
Comparison of bond lengths (A) for metalloporphyrin carbonyl complexes.
RueNeq
RueNax
RueCO
Complex
lmax/nm (ε ꢃ 10ꢁ4 [Mꢁ1 cmꢁ1])
Ru(CO)(py)(TPP) [8]
2.052(9)
2.054(7)
2.057(6)
2.193(4)
2.210(6)
2.242(6)
1.838(9)
1.818(10)
1.761(9)
Soret band Q band
MLCT band
20
Ru(TTP)(CO)(EtOH)b
Ru(TTP)(CO)(ppyr) (2)
Ru(TTP)(CO)(Pd(Me)Cl)
(2-Pd)
412 (26.1)
413 (25.4)
413 (24.2)
530 (2.25), 564 (0.54)
532 (2.12), 566 (0.48)
533 (2.14), 566 (0.57)
20-Pd
broad and intense absorption band in the 600e850 nm visible re-
gion. Owing to this absorption, the color of the solution of 1-Pd
appears deep-green in marked contrast to the solutions of the other
complexes which appear light orange. CV and DFT calculation data
also support the band is attributed to ab MLCT band (vide infra). The
clearly observed MLCT band of the metalloporphyrin system is rare
with the exception of a few examples [16].
Ru(TTP)(ppyr)2 (1)
Ru(TTP)(ppyr)2(Pd(Me)Cl)2 413 (19.1)
(1-Pd)
418 (13.6)
509 (1.88)
504 (1.15)
617 (0.42)
683 (1.42)
a
Measurements were carried out in deaerated CH2Cl2 at RT.
Measured by our group.
b
changes the HOMO character from porphyrin-based to Ru(d)-based
character. Additionally, paying attention to the Pd complexes, 1-Pd
and 2-Pd, Pd d-orbitals of the complexes contribute to the frontier
orbitals to a certain extent. This Pd contribution results in stabi-
lizing LUMO to a greater extent than stabilizing HOMO to reduce
HOMOeLUMO energy gap (Fig. 5). Although the qualitative values
of the energy differences do not completely match with those of the
CV data, these energy changes have good correlation with the CV
data (Figs. 4 and 5).
1. DFT calculation
In order to understand the photophysical and electrochemical
nature of the porphyrin complexes, we have examined the DFT
calculations for compound 1, 1-Pd, 2, and 2-Pd. Each isomer of 1-Pd
of 2-Pd (Me group cis and trans to the pyrazine ring) is also
calculated for comparison (Fig. S4). The following basis sets were
used in the ground-state geometry optimization using Gaussian 09
program packages [13]: Lanl2DZ for Ru and Pd, 6-31G þ for N, C, Cl
atoms coordinated to Ru or Pd, and 3-21G for the other C, H, N, and
O atoms. The RueN, PdeN, PdeCl, and RueC bond lengths between
Ru/Pd and the porphyrin, pyridylpyrazine, and carbonyl ligands of
the optimized structures reproduced the experimental results well,
although the metaleN bond lengths were longer by about 2%
(Fig. S5).
The CV charts of the obtained complexes are presented in Fig. 4
and the data are listed in Table 3. Complex 1 and 1-Pd exhibited
three one-electron oxidation waves in the anodic region. The first
oxidation waves at ꢁ0.06 (1) and þ0.28 V (1-Pd) are assigned to
RuII(TTP)/RuIII(TTP) as compared with related compounds [14]. The
second and third redox waves are attributed to the first and second
þ
oxidation processes of the porphyrin ring (RuIII(TTP)/RuIII(TTPꢂ
)
and TTPꢂþ/TTP2þ). The two oxidation steps of 2 and 2-Pd are
attributed to the oxidation processes of the porphyrin ring [14,2g].
In the negative potential region, 1-Pd, 2, and 2-Pd undergo
reversible one-electron reduction, corresponding to the ppyr/
ppyrꢂꢁ couple [15e17]. The presence of the two reduction processes
in 1-Pd indicates an electronic interaction between the two ppyr
ligands through the Ru center. This was indicated by the presence of
electronic interaction between the ppyr and Ru-porphyrin in the
frontier orbitals. In this region, no peak was observed for 1, prob-
ably due to the limitation of the potential window of the solvent
(CH2Cl2).
The frontier orbitals of the complexes, based on the theoretical
calculations, are presented in Fig. 3. For complexes 1 and 1-Pd, the
HOMOs mainly had the Ru(d) orbital character with some contri-
bution of the porphyrin ring, and the LUMOs had the pyridylpyr-
azine character. To be noted, HOMO of 1-Pd with a chloride ligand
trans to the pyrazine ring possessed notable contribution of the Pd
center to possess wide conjugation among the axial ligands (Fig. 2
and Fig. S4). These orbitals should mainly contribute to the MLCT
process observed for 1 and 1-Pd. In clear contrast, for complexes
with a CO ligand, 2 and 2-Pd, the HOMOs possessed localized
porphyrin character without any contribution of the Ru(d) orbital,
whereas both LUMOs had pyridylpyrazine character. These results
clearly indicate that the withdrawal of the CO ligand drastically
The energy levels of the molecular orbitals of the compounds
estimated on the basis of CV and calculation data are schematically
Fig. 2. UVevis spectra of 1, 1-Pd, 2, and 2-Pd in CH2Cl2 at RT.

Y. Yasu et al. / Journal of Organometallic Chemistry 753 (2014) 48e54
51
Fig. 3. Frontier orbitals of 1, 1-Pd, 2, and 2-Pd.
shown in Fig. 5. According to the data, the low-energy absorption
band observed for and 1-Pd can be assigned to Ru-to-
presence of the electronic communication based on
through the axial ligand.
p-conjugation
1
pyridylpyrazole charge transfer (MLCT; L ¼ axial ligand). Thus
appearance of the prominent MLCT band in the visible region can
be ascribed to decrease of the HOMOeLUMO band gap and
2. Conclusions
In conclusion, we have demonstrated the synthesis of Rue
porphyrin complexes with two axially ligated pyridylpyrazine as
metal coordination sites. Reaction with a Pd precursor readily
produced the trinuclear PdeRuePd complex in high yield. Metal-
ation drastically changed the electrochemical and photophysical
properties of the complexes. By introducing a Pd fragment, prom-
inent metal-to-axial ligand CT band appeared in the visible region,
which caused the drastic color change of the solution. Easy tuning
of the photophysical properties by just changing the axial ligands
and the ligating metal centers will broadens the photophysical
properties of the metalloporphyrin systems. The MLCT toward the
reactive Pd center may lead to future developments in photo-
catalysis through light-induced electron transfer.
3. Experimental
3.1. General
All manipulations were carried out under argon atmosphere
using standard Schlenk techniques. Dichloromethane was treated
with appropriate drying agents, distilled, and stored under argon.
Table 3
Electrochemical data for 1, 1-Pd, 2, and 2-Pd.a
Complex
Reduction E1/2
Oxidation E1/2 (Epa), V vs Fc/Fcþ
(Epc), V vs Fc/Fcþ
2nd
1st
1st
2nd
3rd
1
1-Pd
2
ꢁ0.06
þ0.28
þ0.35
þ0.38
þ0.86
þ0.78
þ0.90
(þ0.81)
(þ1.29)
(þ1.34)
ꢁ1.72
ꢁ1.49
ꢁ2.00
ꢁ1.47
2-Pd
þ0.84
a
In CH2Cl2 containing 0.1 M NBu4PF6 as supporting electrolyte at a scan rate of
0.1 V sꢁ1. Numbers in parenthesis are those of irreversible or quasi-reversible wave.
Fig. 4. CV charts of 1, 1-Pd, 2, and 2-Pd in CH2Cl2 at RT.

52
Y. Yasu et al. / Journal of Organometallic Chemistry 753 (2014) 48e54
3.1.2. Preparation and spectral data of Ru(TTP){(ppyr)Pd(Me)Cl}2
(1-Pd)
Fig. 5. Schematic energy diagram of 1, 1-Pd, 2, and 2-Pd.
1H and 13C NMR spectra were recorded using a Brucker AVANCE-
400. The solvents used for NMR measurements were dried over
molecular sieves, degassed, stored under Ar. The IR spectra (KBr
pellets) were obtained using a JASCO FT/IR 4200 spectrometer. ESI-
MS spectra were recorded on a ThermoQuest Finnigan LCQ Duo
mass spectrometer. UVevis spectra were recorded using a JASCO V-
670 DS spectrometer. Electrochemical measurements were made
with a Hokuto Denko HZ-5000 analyzer. Elemental analyses were
performed at the Center of Advanced Material Analysis, Technical
Department, Tokyo Institute of Technology. Other chemicals were
Under air, to a CH2Cl2 (5.00 mL)solution of Ru(TTP)(ppyr)2
(70.0 mg, 0.0646 mmol), (cod)PdMeCl (37.7 mg, 0.142 mmol) was
added. The resulting deep green solution was stirred at room
temperature for 2 h, and n-hexane (80.0 mL) was added to the
solution. The resulting solid was washed with n-pentane and Et2O
several times and dried in vacuo to afford the desired compound as
a dark green powder (73.0 mg, 0.0520 mmol, 80.0%).
purchased and used as received. m-O-[Ru(TTP)OEt]2 was synthe-
sized according to the published method [5].
3.1.1. Preparation and spectral data of Ru(TTP)(ppyr)2 (1)
1H NMR (400 MHz, CD2Cl2, RT, /ppm) (signal assigned by 1He
d
1H COSY): 8.59 (d, 1H, Hi), 8.56, 8.54, 8.51 (s, 8H, Hb), 8.15 (d,
J ¼ 5.6 Hz, 1H, Hi), 8.03e8.00 (m, 8H, Ho), 7.80e7.70 (m, 2H, Hg),
7.55 (d, J ¼ 8.0 Hz, 8H, Hm), 7.32 (m, 2H, Hh), 6.68 (dd, J ¼ 11.4 and
3.8 Hz, 1H, Hc), 6.51e6.45 (m, 2H, Hf) 6.18 (dd, J ¼ 11.4 and 3.8 Hz,
1H, Hc), 2.67 (s, 12H, PheMe), 2.35 (d, J ¼ 4.0 Hz, 2H, Hb), 2.31 (d,
J ¼ 4.0 Hz, 2H, Hb), 2.23 (d, J ¼ 1.6 Hz, 2H, Ha), 2.20 (d, J ¼ 1.6 Hz, 2H,
Ha), 0.484 (s, 3H, PdeMe), 0.476 (s, 3H, PdeMe), 0.171 (s, 3H, Pde
Me), 0.164 (s, 3H, PdeMe). 13C NMR (100 MHz, CD2Cl2, RT,
d/ppm):
154.7, 154.5, 150.9, 150.8, 150.3, 150.2, 149.7, 149.6, 149.2, 149.1,
148.3, 148.1, 146.0, 145.6, 144.3, 143.9, 140.5, 140.4, 139.7, 138.9,
138.8,138.2,138.1, 135.8, 134.1, 129.1, 128.4, 128.3, 123.5, 123.1, 121.8,
22.7 (tol-Me), 0.648 (PdeMe), 0.595 (PdeMe), ꢁ0.421 (Pde
Me), ꢁ0.481 (PdeMe).
3.1.3. Preparation and spectral data of Ru(TTP)(CO)(ppyr) (2)
To a solution of m-O-[Ru(TTP)OEt]2 (100 mg, 0.0608 mmol) in
dry-THF (16.0 mL), NaBH4 (46.0 mg, 1.21 mmol) and ppyr (38.2 mg,
0.244 mmol) were added under nitrogen atmosphere. The reaction
mixture was stirred over night, and filtered through Celite. The
filtrate was dried in vacuo, and the residue was dissolved CH2Cl2.
The resulting suspension was filtered through Celite, and the so-
lution was concentrated under reduced pressure. The solution was
precipitated with n-pentane, and dried in vacuo to afford the
desired compound as a deep purple solid (85.0 mg, 0.0784 mmol,
65.0%). 1H NMR (400 MHz, CDCl3, RT,
d/ppm) (signal assigned by
combination of 1He1H COSY, HMQC and HMBC): 8.48 (dd, J ¼ 4.8
and 1.2 Hz, 2H, Hi), 8.34 (s, 8H, Hb), 8.09 (d, J ¼ 8.0 Hz, 8H, Ho), 7.46
(d, J ¼ 8.0 Hz, 8H, Hm), 7.35 (ddd, J ¼ 7.6, 5.6 and 1.2 Hz 2H, Hg), 7.22
(d, J ¼ 8.0 Hz, 2H, Hf), 7.06 (ddd, J ¼ 5.6, 4.8 and 1.2 Hz, 2H, Hh), 6.26
(d, J ¼ 3.2 Hz, 2H, Hc), 3.37 (d, J ¼ 0.8 Hz, 2H, Ha), 2.65 (s, 12H, Phe
Under air, to a CH2Cl2 (25.0 mL) solution of Ru(CO)(TTP)(EtOH)
(300 mg, 0.350 mmol), ppyr (78.2 mg, 0.498 mmol) was added. The
red solution was stirred at room temperature for 3 h, and the so-
lution was concentrated in vacuo. The residue was purified by
chromatography on alumina eluting with CH2Cl2 to afford the
desired compound as a red solid (343 mg, 0.359 mmol, 84.0%). The
red crystals suitable for crystallography were obtained by diffusion
of n-hexane into CH2Cl2.
Me), 2.23 (d, J ¼ 3.2 Hz, 2H, Hb). 13C NMR (100 MHz, CDCl3, RT,
d/
ppm): 152.2 (Ce), 148.8 (Ci), 147.2 (Cd), 144.1 (Cb), 143.8 (Ca), 143.7
(Ca), 139.8 (C2), 139.6 (Cc), 136.3 (Cp), 136.1 (Cg), 134.1 (Co), 131.9 (Cb),
127.0 (Cm), 123.8 (Ch), 121.7 (C1), 120.4 (Cf), 21.4 (PheMe). Anal.
Calcd for C66H50N10Ru (þH2O): C, 73.11 (71.92); H, 4.65 (4.76); N,
12.92 (12.71). Found: C, 71.54; H, 4.64; N, 12.31.

Y. Yasu et al. / Journal of Organometallic Chemistry 753 (2014) 48e54
53
1H NMR (400 MHz, CD2Cl2, RT,
d
/ppm) (signal assigned by
55.0ꢀ. The structure was determined by a combination of direct
methods (SHELXS-86) [18] and Fourier synthesis (DIRDIF99) [19].
Least-squares refinements were carried out using SHELXL-97 [18]
(refined on F2). All the non-hydrogen atoms were refined aniso-
tropically, and all the hydrogen atoms were fixed at the calculated
positions.
combination of 1He1H COSY, HMQC and HMBC): 8.66 (s, 8H, Hb),
8.48 (d, J ¼ 4.4 Hz, 1H, Hi), 8.11 (dd, J ¼ 7.6 and 1.6 Hz, 4H, Ho), 8.07
(dd, J ¼ 7.6 and 1.6 Hz, 4H, Ho), 7.56 (d, J ¼ 7.6 Hz, 4H, Hm), 7.52 (d,
J ¼ 7.6 Hz, 4H, Hm), 7.35 (ddd, J ¼ 8.0, 5.6 and 1.2 Hz, 1H, Hg), 7.29
(d, J ¼ 8.0 Hz, 1H, Hf), 7.13 (ddd, J ¼ 5.6, 4.4 and 1.2 Hz, 1H, Hh),
6.50 (d, J ¼ 2.4 Hz, 1H, Hc), 2.695 (d, J ¼ 2.4 Hz, 1H, Hb), 2.68 (s, 12H,
PheMe), 1.52 (s, 1H, Ha). 13C NMR (100 MHz, CD2Cl2, RT,
d/ppm):
5. DFT calculation
181.8 (RueCO),152.0 (Ce),150.2 (Cd),149.3 (Ci),144.4 (Ca),142.0 (Cc),
140.1 (C2), 138.2 (Ca), 137.9 (Cb), 137.6 (Cp), 137.1 (Cg), 134.7 and
134.6 (Co), 132.5 (Cb), 127.8 and 127.6 (Cm), 125.0 (Ch), 122.3 (C1),
120.8 (Cf), 21.8 (PheMe). IR(KBr): nCO 1949 cmꢁ1. Anal. Calcd for
DFT calculations were performed using the Gaussian-09 quan-
tum chemistry program package at the B3LYP/LanL2DZ level. The
HOMO and LUMO energies were determined by using minimized
singlet geometries to approximate the ground state.
C
58H43N7ORu: C, 72.94; H, 4.54; N,10.27. Found: C, 73.22; H, 4.91; N,
9.98.
5.1. Electrochemical measurements
3.1.4. Preparation and spectral data of Ru(TTP)(CO)(ppyr)Pd(Me)Cl
(2-Pd)
CV measurements were performed with a Pt electrode for
CH2Cl2 solutions of the samples (ca. 2 ꢃ 10ꢁ3 M) in the presence of
an electrolyte (Bu4N$BF4: 0.1 M) at ambient temperature under an
inert atmosphere. The scan rate was 100 mV/s. After the mea-
surements, ferrocene (Fc) was added to the mixture and the po-
tentials were calibrated with respect to the Fc/Fcþ redox couple.
Acknowledgments
This research was financially supported by the Japan Science
and Technology Agency (PRESTO (Precursory Research for Embry-
onic Science and Technology; A.I.)), JSPS KAKENHI (C) Grant
Number 24550071, the Cooperative Research Program of “Network
Joint Research Center for Materials and Devices”, and the Naito
Foundation Subsidy for Female Researchers (A. I.); these supports
are gratefully acknowledged.
Under air, to a CH2Cl2 (5.00 mL) solution of Ru(CO)(TTP)(ppyr)
(200 mg, 0.210 mmol), (cod)PdMeCl (58.3 mg, 0.220 mmol) was
added. The resulting red solution was stirred at room temperature
for 2 h, and n-hexane (80.0 mL) was added to the solution. The
resulting solid was washed with n-pentane several times, and dried
in vacuo to afford the desired compound as a red powder (218 mg,
0.196 mmol, 94.0%). The product was an isomer mixture A and B at
3:2 ratio.
Appendix A. Supplementary data
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.jorganchem.2013.12.008.
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1H NMR (400 MHz, CD2Cl2, RT, /ppm) (signal assigned by 1He
d
1H COSY): isomer A: 8.75 (s, 8H, Hb), 8.13 (d, J ¼ 7.6 Hz, 4H, Ho), 8.05
(br d, 1H, Hi), 7.98 (d, J ¼ 7.6 Hz, 4H, Ho), 7.76 (dd, J ¼ 7.6 and 7.6 Hz,
1H, Hh), 7.59 (d, J ¼ 7.6 Hz, 4H, Hm), 7.53 (d, J ¼ 7.6 Hz, 4H, Hm), 7.25
(br d, 1H, Hg), 6.95 (br d, 1H, Hc), 6.30 (dd, J ¼ 8.0 and 8.0 Hz, 1H, Hf),
2.69 (s, 12H, PheMe), 1.89 (s, 1H, Ha), 1.79 (br d, 1H, Hb), 0.08 (s, 3H,
PdeMe). isomer B: 8.74 (s, 8H, Hb), 8.41 (br d, 1H, Hi), 8.13 (d,
J ¼ 7.6 Hz, 4H, Ho), 7.98 (d, J ¼ 7.6 Hz, 4H, Ho), 7.69 (dd, J ¼ 7.6 and
7.6 Hz, 1H, Hh), 7.59 (d, J ¼ 7.6 Hz, 4H, Hm), 7.53 (d, J ¼ 7.6 Hz, 4H,
Hm), 7.25 (br d, 1H, Hg), 6.52 (br d, 1H, Hc), 6.35 (dd, J ¼ 8.0 and
8.0 Hz, 1H, Hf), 2.69 (s, 12H, PheMe), 1.84 (s, 1H, Ha), 1.79 (br d, 1H,
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Hb), 0.11 (s, 3H, PdeMe). 13C NMR (100 MHz, CD2Cl2, RT,
d/ppm):
182.3,152.8,150.24, 149.25,146.5,144.4, 142.59, 142.26, 140.7, 140.2,
139.7, 139.1,138.9,137.9, 137.7, 135.0, 134.6,134.5,132.6,128.0,127.8,
122.4,122.2, 21.7 (tol-Me), ꢁ0.07 (PdeMe), ꢁ0.84 (PdeMe). IR(KBr):
nCO 1949 cmꢁ1. Anal. Calcd for C59H46N7OClRuPd: C, 63.73; H, 4.17;
N, 8.82. Found: C, 63.37; H, 4.30; N, 8.63.
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Single-crystal X-ray diffraction experiments on 20 and 20-Pd
were performed at 213 K on a Rigaku RAXIS IV imaging plate area
detector with
¼ 0.71073 A). The data were collected to a maximum 2
a
graphite monochromated Mo-K
a
radiation
q value of
ꢀ
(l

54
Y. Yasu et al. / Journal of Organometallic Chemistry 753 (2014) 48e54
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