Ruthenium complexes of thiaporphyrin and dithiaporphyrin

Article abstract of DOI:10.1021/ic200977n

Successful synthesis and characterization of the six-coordinated complex [Ru(STTP)(CO)Cl] (1; STTP = 5,10,15,20-tetratolyl-21-thiaporphyrinato) allowed the development of the coordination chemistry of ruthenium-thiaporphyrin through dechlorination and metathesis reactions. Accordingly, [Ru^II(STTP) (CO)X] (X = NO₃^- (2), NO₂^- (3), and N₃^- (4)) was synthesized and analyzed by single-crystal X-ray structural determination and NMR, UV-vis, and FT-IR spectroscopic methods. An independent reaction of STPPH and [Ru(COD)Cl₂] led to [Ru ^III(STTP)Cl₂] (5), which possessed a higher-valent Ru(III) center and exhibited good stability in the solution state. This stability allowed reversible redox processes in a cyclic voltammetric study. Reactions of [Ru(S₂TTP)Cl₂] (S₂TTP = 5,10,15,20-tetratolyl- 21,23-dithiaporphyrinato) with AgNO₃ and NaSePh, also via the metathesis strategy, resulted in novel dithiaporphyrin complexes [Ru ^II(S₂TTP)(NO₃)₂] (6) and [Ru ⁰(S₂TTP)(PhSeCH₂SePh)₂] (7), respectively. The structures of 6 and 7 were corroborated by X-ray crystallographic analyses. Complex 7 is an unprecedented ruthenium(0)- dithiaporphyrin with two bis(phenylseleno)methanes as axial ligands. A comparison of the analyses of the crude products from reactions of NaSePh and CH₂Cl₂ with or without [Ru(S₂TTP)Cl ₂], further supported by UV-vis spectral changes under stoichiometric reactions between [Ru(S₂TTP)Cl₂] and NaSePh, suggested a reaction sequence in the order of (1) formation of a putative [Ru ^II(S₂TTP)(SePh)₂] intermediate, followed by (2) the concerted formation of PhSe-CH₂Cl and simultaneously a reduction of Ru(II) to Ru(0) and finally (3) nucleophilic substitution of PhSeCH ₂Cl by excess PhSe^-, resulting in PhSeCH₂SePh, which readily coordinated to the Ru(0) and completed the formation of bis(phenylseleno)methane complex 7.

Full text of DOI:10.1021/ic200977n

Article
pubs.acs.org/IC
Ruthenium Complexes of Thiaporphyrin and Dithiaporphyrin
Chuan-Hung Chuang,†,§ Chen-Kuo Ou,‡ Shan-Tung Liu,† Anil Kumar,†,⊥ Wei-Min Ching,†,∥
Pei-Chun Chiang,† Mira Anne C. dela Rosa,† and Chen-Hsiung Hung*,†
†Institute of Chemistry, Academia Sinica, Nankang, Taipei 115, Taiwan
‡Department of Chemistry, National Changhua University of Education, Changhua 500, Taiwan
§Department of Chemistry, National Tsing Hua University, Hsinchu 300, Taiwan
∥Department of Chemistry, National Taiwan Normal University, Taipei 106, Taiwan
S
* Supporting Information
ABSTRACT: Successful synthesis and characterization of the
six-coordinated complex [Ru(STTP)(CO)Cl] (1; STTP =
5,10,15,20-tetratolyl-21-thiaporphyrinato) allowed the devel-
opment of the coordination chemistry of ruthenium−
thiaporphyrin through dechlorination and metathesis reac-
tions. Accordingly, [RuII(STTP)(CO)X] (X = NO3 (2),
−
−
−
NO2 (3), and N3 (4)) was synthesized and analyzed by
single-crystal X-ray structural determination and NMR, UV−
vis, and FT-IR spectroscopic methods. An independent
reaction of STPPH and [Ru(COD)Cl2] led to [RuIII(STTP)-
Cl2] (5), which possessed a higher-valent Ru(III) center and exhibited good stability in the solution state. This stability allowed
reversible redox processes in a cyclic voltammetric study. Reactions of [Ru(S2TTP)Cl2] (S2TTP = 5,10,15,20-tetratolyl-21,23-
dithiaporphyrinato) with AgNO3 and NaSePh, also via the metathesis strategy, resulted in novel dithiaporphyrin complexes
[RuII(S2TTP)(NO3)2] (6) and [Ru0(S2TTP)(PhSeCH2SePh)2] (7), respectively. The structures of 6 and 7 were corroborated
by X-ray crystallographic analyses. Complex 7 is an unprecedented ruthenium(0)−dithiaporphyrin with two bis(phenylseleno)-
methanes as axial ligands. A comparison of the analyses of the crude products from reactions of NaSePh and CH2Cl2 with or
without [Ru(S2TTP)Cl2], further supported by UV−vis spectral changes under stoichiometric reactions between
[Ru(S2TTP)Cl2] and NaSePh, suggested a reaction sequence in the order of (1) formation of a putative [RuII(S2TTP)(SePh)2]
intermediate, followed by (2) the concerted formation of PhSe−CH2Cl and simultaneously a reduction of Ru(II) to Ru(0) and
finally (3) nucleophilic substitution of PhSeCH2Cl by excess PhSe−, resulting in PhSeCH2SePh, which readily coordinated to the
Ru(0) and completed the formation of bis(phenylseleno)methane complex 7.
barriers toward a concerted hydroxylation mechanism.16
INTRODUCTION
■
Additionally, conversion of cyclohexene to 2-cyclohexen-1-ol
through an aerobic oxidation at room temperature has been
successfully achieved using perhalogenated ruthenium complex
[(TFPPCl8)Ru(CO)] (TFPPCl8 = octachloro[tetrakis-
(pentafluorophenyl)]porphyrin) as the catalyst.15 Recently,
hydroxylation of hydrocarbons utilizing ruthenium(II)−carbon-
yl tetrakis(pentafluorophenyl)porphyrin complex
[RuII(TPFPP)(CO)], in the presence of 2,6-dichloropyridine
N-oxide as an oxidant, displayed good yields and high turnover
numbers.17 On the contrary, the development of ruthenium
core-modified porphyrin chemistry is lagging far behind. Even
though structurally characterized metal complexes of Ni-
(II),18−20 Hg(II),21 Pd(II),22 Fe(II),18 Cu(II),9,18 Rh(III),23
and Li(I) with a core-modified porphyrin as the ligand have
been documented, there is no report on the preparation of the
ruthenium−thiaporphyrin complex.24 It was not until recently
that metal−dithiaporphyrin complex [RuII(S2TTP)Cl2] was
Metalloporphyrins have been extensively used as catalysts to
study biomimetic oxidation reactions.1−4 Although not as
broadly examined as metal complexes of regular porphyrin,
core-modified porphyrins, e.g., carbon-,5,6 silicon-,7 phospho-
rus-,8 and chalcogen-containing porphyrins,9,10 which exhibit
distinctively different chemical properties from regular
porphyrins, have the potential to catalytically functionalize
hydrocarbon substrates.
Bioinspired catalytic reactions using metalloporphyrins as
catalysts can be performed not only by iron porphyrins but also
by chromium,11,12 manganese,13,14 and ruthenium analogues.
Ruthenium porphyrins containing a wide variety of peripheral
substituents under different metal oxidation states have been
reported to exhibit high activity toward catalytic reactions. As
an example, dioxo(tetramesitylporphyrinato)ruthenium(VI),
first reported by Groves and co-workers, showed good activity
for the aerobic epoxidation of olefins.15 Density function theory
(DFT) calculations revealed that the low-spin ruthenium−oxo
species, which are more electrophilic and robust catalysts than
iron−oxo counterparts, gave lower hydrogen abstraction
Received: May 10, 2011
Published: November 7, 2011
© 2011 American Chemical Society
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synthesized and structurally characterized.25 Because the
presence of long carbon−sulfur and metal−sulfur bonds in
the thiaporphyrin complexes resulted in a distorted porphyrin
core, the stability of thiaporphyrin complexes was significantly
decreased. Consequently, spontaneous demetalation of Fe(II)−
tetraphenyl-21-thiaporphyrin in the solution state has been
observed.18 Interestingly, [RuII(S2TTP)Cl2] exhibited rever-
sible redox processes under cyclic voltammetric measurements,
which demonstrates good stability of this complex in the
solution state.25 To gain more insight into the ruthenium
chemistry of sulfur-containing core-modified porphyrins, herein
we reported the syntheses, characterizations, and crystal
structures of new ruthenium−thiaporphyrin and dithiaporphyr-
in complexes.
tolyl-H), 7.50 (m, 10H, tolyl-H), 2.67 (s, 12H, p-tolyl-CH3). UV−vis
in CH2Cl2 [λmax, nm, (log ε)]: 433 (4.64), 575 (3.64), 690 (3.50).
Infrared (KBr, cm−1): ν(CO) = 1956. Elemental Anal. Calcd. (found)
for Ru1C49H36N3S1O1Cl1·0.5CH2Cl2: C, 66.51 (66.31); H, 4.17
(4.47); N, 4.70 (5.47).
Preparation of [Ru(STTP)(CO)(NO3)] (2). In a Schlenk flask,
[Ru(STTP)(CO)Cl] (1; 0.45 g, 0.529 mmol) and AgNO3 (0.9 g, 5.29
mmol) dissolved in anhydrous dichloromethane (25 mL) under N2
were allowed to stir at room temperature for 5 h. The resulting
solution was filtered through a sinter-glass filter to remove unreacted
AgNO3 and AgCl. The filtrate was concentrated under reduced
pressure on a rotovap, and n-hexane was added to precipitate the
product. The resulting black solid of 2 was filtered and dried in vacuo.
1
Yield: 0.3032 g (63%). H NMR (200 MHz, 25 °C, chlororform-d,
ppm): 9.32 (s, 2H, β-thiophene-H), 8.83 (d, J = 6.9 Hz, 2H, tolyl-H),
8.72 (m, 4H, β-pyrrole-H), 8.64 (s, 2H, β-pyrrole-H), 8.14 (dd, 2H,
tolyl-H), 8.02 (d, J = 9.5 Hz, 2H, tolyl-H), 7.78 (d, J = 7.8 Hz, 2H,
tolyl-H), 7.48 (m, 8H, tolyl-H), 2.69 (s, 12H, CH3). UV−vis in
CH2Cl2 [λmax, nm, (log ε)]: 432 (4.93), 562 (3.86), 681 (3.69).
Infrared (KBr, cm−1): ν(CO) = 1965, ν(NO) = 1279, νs(NO2) =
1385, ν a(NO2) = 1468. Elemental Anal. Calcd. (found) for
Ru1C49H36N4S1O4·0.2CH2Cl2: C, 66.03 (66.20); H, 4.10 (4.20); N,
6.26 (6.72).
EXPERIMENTAL SECTION
■
Instruments. Schlenk techniques and a nitrogen atmospheric
drybox (Innovative Technology, Inc.) were used for handling air-
sensitive compounds. UV−vis spectra were recorded on an Agilent
HP8453 spectrophotometer. Elemental analyses (C, H, N) were
1
obtained on a CHN analyzer (Heraeus). H and 13C NMR spectra
Preparation of [Ru(STTP)(CO)(NO2)] (3). In a Schlenk flask,
[Ru(STTP)(CO)Cl] (1; 0.21 g, 0.246 mmol) and AgNO2 (0.38 g,
2.47 mmol) dissolved in dichloromethane (25 mL) under N2 were
allowed to stir under ambient temperature for 9 h. Following the
workup procedures as described for 2, black solid 3 was obtained.
were measured on a Varian Unity Inova Bruker AMX 400 or a Bruker
AC 200 spectrometer. Chemical shifts are expressed in parts per
million relative to residual CHCl3 (7.258 ppm). Infrared spectra were
recorded on a Biorad FTS-185 spectrophotometer. All cyclic
voltammetric experiments were performed with a CHI 600D
Potentiostat/Galvanostat (CH Instruments, Inc.). The cell consisted
of a glassy carbon working electrode, a platinum wire auxiliary
electrode, and a silver wire reference electrode, with 0.1 M tetra-n-
butylammonium hexafluorophosphate as the supporting electrolyte in
THF.
Materials. Dichloromethane and chloroform were dried with
calcium hydride and distilled under nitrogen. Toluene and hexane
were distilled under nitrogen in the presence of sodium chips using
benzophenone ketyl as an indicator. Dried solvents, which were
transferred into round-bottom flasks, bubbled with nitrogen for at least
10 min to remove residual dioxygen, and then sealed with a J-Young
cap, were stored in the nitrogen atmosphere drybox prior to use.
Pyrrole was freshly distilled under nitrogen from calcium hydride prior
to use. Other starting materials were obtained commercially and used
directly without further purification. Silica gel (100−120 mesh, Merck)
or neutral alumina (Merck) was used for column chromatography.
The starting 5,10,15,20-tetra-p-tolyl-21-thiaporphyrin, STTPH, was
prepared using a mixed condensation of 2,5-bis-(tolylhydroxylmethyl)-
thiophene, pyrrole, and p-tolylaldehyde or a condensation of 2,5-bis-
(tolylhydroxylmethyl)thiophene and 5-p-tolyl-dipyrromethane accord-
ing to the literature method.24 5,10,15,20-Tetra-p-tolyl-21,23-dithia-
porphyrin, S2TTP, was prepared through a condensation of 2,5-bis-
(tolylhydroxylmethyl)thiophene and pyrrole.25 Sodium phenylselenide
was prepared from the reaction of diphenyl diselenide with sodium
chips in anhydrous THF.
1
Yield: 0.117 g (55%). H NMR (200 MHz, 25 °C, chlororform-d,
ppm): 9.33 (s, 2H, β-thiophene-H), 8.84 (d, J = 7.7 Hz, 2H, tolyl-H),
8.73 (dd, 4H, β-pyrrole-H), 8.66 (s, 2H, β-pyrrole-H), 8.16 (d, J = 6.8
Hz, 2H, tolyl-H), 8.06 (d, J = 7.2 Hz, 2H, tolyl-H), 7.79 (d, J = 7.3 Hz,
2H, tolyl-H), 7.51 (m, 8H, tolyl-H), 2.69 (s, 12H, CH3). UV−vis in
CH2Cl2 [λmax, nm, (log ε)]: 432 (4.43), 581 (3.46), 682 (3.29).
Infrared (KBr, cm−1): ν(CO) = 1977, νa(NO2) = 1366, νs(NO2) =
1323. Elemental Anal. Calcd. (found) for Ru1C49H36N4S1O3·2CH2Cl2:
C, 59.36 (58.73); H, 3.91 (3.91); N, 5.43 (6.80).
Preparation of [Ru(STTP)(CO)(N3)] (4). [Ru(STTP)(CO)Cl]
(1; 0.2 g, 0.235 mmol) and NaN3 (0.153 g, 2.35 mmol) dissolved in
dry dichloromethane (25 mL) were allowed to stir at room
temperature for 4 h. The resulting solution was filtered. The filtrate
was concentrated under reduced pressure, and n-hexane (5 mL) was
added. The solution was then stored in a freezer. A black precipitate
formed overnight and was filtered and dried in vacuo to give black
solid 4. Yield: 0.144 g (72%). 1H NMR (200 MHz, 25 °C, chloroform-
d, ppm): 9.26 (s, 2H, β-thiophene-H), 8.64 (m, 4H, β-pyrrole-H), 8.58
(s, 2H, β-pyrrole-H), 8.07 (m, 6H, tolyl-H), 7.73 (d, J = 8.0 Hz, 2H,
tolyl-H), 7.50 (m, 8H, tolyl-H), 2.67 (s, 12H, CH3). UV−vis
(CH2Cl2) [λmax, nm, (log ε)]: 440 (4.81), 571 (3.82), 687 (3.63).
Infrared (KBr, cm−1): ν(CO) = 1958, νa(azido) = 2035, νs(azido) =
1 2 6 2 . E l e m e n t a l A n a l . C a l c d . ( f o u n d ) f o r
Ru1C49H36N6S1O1·0.5CH2Cl2·0.5C6H14: C, 66.83 (66.42); H, 4.70
(4.37); N, 8.91 (8.53).
Preparation of [Ru(STTP)Cl2] (5). STTPH (0.33 g, 0.479 mmol)
and [Ru(COD)Cl2] (0.6 g, 2.87 mmol) dissolved in o-dichloroben-
zene (200 mL) were allowed to stir under reflux for 5 h. The
completion of the reaction was monitored by UV−vis spectroscopy.
The resulting solution was filtered through Celite to remove excess
[Ru(COD)Cl2], and the solvent was removed under reduced pressure.
The crude product was recrystallized from CH2Cl2/n-hexane to afford
black solid 5. Yield: 0.33 g (80%). UV−vis in CH2Cl2 [λmax, nm, (log
ε)]: 448 (4.74). Elemental Anal. Calcd. (found) for
Ru1C49H36N3S1Cl2·1.2CH2Cl2·0.5C6H14: C, 62.90 (62.16); H, 4.50
(4.88); N, 4.14 (4.20).
Preparation of [Ru(S2TTP)(NO3)2] (6). In a Schlenk-flask,
[Ru(S2TTP)Cl2]25 (0.126 g, 0.144 mmol) and AgNO3 (0.3 g, 1.77
mmol) were dissolved in 25 mL of anhydrous CH2Cl2 under nitrogen.
After stirring for 4 h at ambient temperature, the residual AgNO3 was
filtered through a patch of Celite under a nitrogen atmosphere. The
resulting solution was concentrated to about 5 mL, and n-hexane was
Preparation of [Ru(STTP)(CO)Cl] (1). In a Schlenk flask, the
solution of STTPH (0.2 g, 0.291 mmol) and Ru3(CO)12 (0.4 g, 0.625
mmol) in o-dichlorobenzene (100 mL) was degassed with N2. The
solution was heated to reflux for 2.5 h under N2. The completion of
the reaction was confirmed from the absence of STTPH32+ absorption
in UV−vis spectra after the addition of TFA into the aliquots solution
diluted in CH2Cl2. The reaction mixture was then cooled to room
temperature and passed through a sinter-glass filter filled with Celite.
The brown filtrate was combined and dried using a rotovap to give a
black solid. The crude solid was then dissolved in 100 mL of CH2Cl2
and washed with 0.1 M HCl(aq). The CH2Cl2 solution was dried over
MgSO4, and the solvent was evaporated in vacuo to give a black solid.
The crude product was recrystallized from dichloromethane/n-hexane
1
to afford black solid 1. Yield: 0.10 g (40%). H NMR (200 MHz, 25
°C, chloroform-d, ppm): 9.26 (s, 2H, β-thiophene-H), 8.66 (d, J = 5.2
Hz, 2H, β-pyrrole-H), 8.61 (d, J = 5.1 Hz, 2H, β-pyrrole-H), 8.57 (s,
2H, β-pyrrole -H), 8.06 (m, 4H, tolyl-H), 7.73 (d, J = 8.0 Hz, 2H,
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Scheme 1
added dropwise. The crystalline precipitate was collected and dried in
vacuo to afford black solid 6. Yield: 0.105 g (78%). H NMR (300
for all optimized structures to confirm that the obtained geometries
represent true minima without an imaginary frequency. In all
calculations, convergence was reached when the relative change in
the density matrix between subsequent iterations was less than 1 ×
10−8. A time-dependent density functional theory (TDDFT) approach
was used for the prediction of UV−vis spectra of ruthenium
thiaporphyrin complexes. Molecular geometries were optimized
using the above-mentioned exchange-correlation functional and basis
sets, coupled with a self-consistent reaction field method (SCRF),
specifically, Tomasi’s PCM,35 in dichloromethane (ε = 8.93).
Molecular orbitals were visualized using Gauss View, revision 3.0.9.
1
MHz, 25 °C, chloroform-d, ppm): 8.90 (s, 1H, β-thiophene-H), 8.85
(s, 1H, β-thiophene-H), 8.79 (s, 2H, β-pyrrole-H), 8.20−8.40 (br, 4H,
tolyl-H), 7.96 (ABq, 2H, ΔδAB = 0.04, JAB = 6 Hz), 7.87 (s, 2H, β-
pyrrole-H), 7.10−7.70 (br, 12H, tolyl-H), 2.56 (s, 12H, CH3). UV−vis
in CH2Cl2 [λmax, nm, (log ε)]: 467 (4.67), 556 (4.05), 593 (3.95), 822
(3.67). Infrared (KBr, cm−1): νa(NO2) = 1467, νs(NO2) = 1384,
ν(NO)
= 1262. Elemental anal. calcd. (found) for
RuC48H36N4S2O6·2.4 CH2Cl2: C, 53.39 (53.34); H, 3.63 (3.64); N,
4.94 (5.26).
Preparation of [Ru(S2TTP)(PhSeCH2SePh)2] (7). In a N2(g)
-
filled Schlenk flask, [Ru(S2TTP)Cl2] (0.1 g, 0.114 mmol) and NaSePh
(0.3 g, 1.68 mmol) were dissolved in 25 mL of anhydrous CH2Cl2.
The solution was allowed to stir for 8 h at ambient temperature, and
the color of the solution changed from deep yellow-green to dark-red.
The resulting solution was filtered through Celite under N2, and the
solvent was removed under reduced pressure. An analytically pure
compound was obtained from recrystallization of the crude compound
from CH2Cl2/hexane/DMF. Yield: 0.129 g (78%). UV−vis in CH2Cl2
[λmax, nm, (log ε)]: 343 (sh, 4.24), 401 (4.44). Elemental Anal. Calcd.
(found) for RuC74H60N2S2Se4·1.5 CH2Cl2·C3H7NO: C, 58.37
(58.60); H, 4.05 (4.03); N, 1.82 (1.88).
X-Ray Crystallography. Diffraction measurements for complexes
1−7 were carried out on a Bruker SMART 1000 or an Apex CCD
diffractometer equipped with graphite-monochromated Mo Kα
radiation (λ = 0.71073 Å). Crystallographic data and data collection
parameters are summarized in Table 1. Structural refinements were
performed by means of SHELXTL software.26 Phase determination for
the structures was done through the Patterson method and expanded
using Fourier techniques. Least-squares refinement of the positional
and anisotropic thermal parameters for the contribution of all non-
hydrogen atoms and fixed hydrogen atoms was based on F2. A
SADABS27 absorption correction was made. The weighted R factor
(wR2) and goodness of fit (GOF) were against F2. The threshold
expression of F2 > 2σ(F2) was used only for calculating R factors and
is not relevant to the choice of reflections for refinement.
Theoretical Calculation. Theoretical calculations were per-
formed with the Gaussian 03 revision D.02 program.28 Starting
geometries were obtained from the crystal structures 1−4. Geometry
optimizations were performed at the restricted Hartree−Fock level
under an unconstrained C1 symmetry. Preliminarily optimized
structures for complexes 1−4, after the Hartree−Fock calculation,
were fully optimized using the DFT method at the B3LYP29−32 level
with 6-31+G** as a basis set for light atoms (C, H, N, and O), MIDIX
for chloride, and LanL2DZ33,34 for ruthenium atom. Harmonic
vibrational frequencies were calculated using analytical second
derivatives for all systems. Vibrational frequencies were calculated
RESULTS AND DISCUSSION
■
Ruthenium Carbonyl Thiaporphyrin Complexes.
Either [Ru3(CO)12] or [Ru(COD)Cl2] was used as a starting
metal source for the metalation of thiaporphyrin through
oxidative insertion. The use of [Ru3(CO)12] as the ruthenium
source introduced a carbonyl to the axial position, while a high-
valent Ru(III)−thiaporphyrin was obtained when [Ru(COD)-
Cl2] was used as the starting compound. As shown in Scheme
1, the refluxing of STTPH and [Ru3(CO)12] in o-
dichlorobenzene followed by an extraction using aqueous
HCl solution affords [Ru(STTP)(CO)Cl] (1). A temperature
above 150 °C appeared to be a prerequisite for ruthenium
metalation. No product was observed when solvents with a
lower boiling point, such as toluene, benzene, or CHCl3, were
used. Alternatively, ruthenium metalation can be achieved with
comparable yields using mesitylene as the solvent, albeit a
longer reaction time is required. Compound 1, which is stable
under the solution state in the ambient atmosphere, had a good
solubility in dichloromethane and chloroform but moderate
solubility in tetrahydrofuran or methanol. Dechlorination of 1
with AgBF4 followed by treatment with an oxidant, e.g., H2O2
or m-chloroperbenzoic acid (m-CPBA), under room temper-
ature for 24 h resulted in a product lacking a carbonyl group
stretching frequency. However, no reaction between 1 and the
oxidant can be observed without prior dechlorination by the
silver ion, implying that axial chloride increases the stability of
1.
In comparison with the Soret band at 429 nm and Q-bands at
414, 550, 618, and 678 nm for the free base STPPH, the
absorption spectrum for 1 with a λmax at 433 nm for the Soret
band and 575 and 690 nm for Q bands is significantly red-
shifted. The red-shift might be attributed to the nonplanarity of
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Figure 1. Molecular structure of [Ru(STTP)(CO)Cl] (1) in 30% ellipsoids (left) and the side view of 1 with phenyl rings omitted for clarity (right).
the thiaporphyrin core after ruthenium metalation, suggesting
the presence of the hybrid orbital deformation (HOD) effect.36
The NMR pattern of complex 1 is consistent with a Cs
symmetrical molecule with axial ligands, the ruthenium center,
the sulfur atom, and a pyrrolic nitrogen embedded in a plane of
symmetry. AB quartet resonances at 8.66 and 8.61 ppm arising
from H7, H8, H17, and H18 (see Scheme 1) on β-pyrrolic
carbons neighboring the thiophene rings were observed. The
protons on symmetry embedding thiophene and pyrrole rings
were located at 9.26 and 8.57 ppm, respectively.
Substitution of Axial Chloride on [Ru(STTP)(CO)Cl]
with NO3 , NO2 , or N3− through Metathesis Reactions.
The axial chloride in 1 allows the preparation of a series of
ruthenium thiaporphyrin complexes through a metathesis
reaction, as shown in Scheme 1. Ruthenium(II) thiaporphyrin
complexes [Ru(STTP)(CO)X] (X = NO3− (2), NO2− (3), and
N3− (4)) were obtained in moderate yield from the reaction of
1 with corresponding silver(I) salts (for 2 and 3) or sodium salt
(for 4) in CH2Cl2. The azido product 4 was stable in both solid
and solution states under aerobic conditions. Black crystals of 4
were readily obtained through crystallization from a near-
saturated CH2Cl2 solution of 4. The nitrato (2) and nitro (3)
complexes, however, are less stable; demetalation proceeded
slowly in the solution of 2 and 3 under atmospheric conditions.
Complexes 2, 3, and 4 were characterized by means of UV−
vis, NMR, and IR spectroscopies and single-crystal X-ray
structural determination. As shown in Figure 2, the
−
−
Single-crystal X-ray structure determination provides explicit
information for the conformation of 1. As shown in Figure 1,
complex 1 displays a nonplanar thiaporphyrin macrocycle with
the thiophene moiety tilted away from the mean porphyrinic
plane. Values of deviations for thiophenic atoms from the mean
plane defined by the tripyrrin moiety are as follows: S(1),
−0.50 Å; C(3), 0.38 Å; C(2):, 1.03 Å. The ruthenium atom sits
nearly coplanar with the mean plane with a deviation of 0.0030
Å. The angle of 59.02° between the C(3)−S(1)−C(3A) plane
and the equatorial plane consisting of Ru(1) and coordinating
atoms falls in the middle of 45.9° for [NiI(SDPDTP)Cl]19 and
69.5° for [FeII(STPP)Cl].18 Similar to other metal−thiapor-
phyrin complexes, the five-member ring of thiophene in 1 is
puckered with an angle of 16.05° between C(3)−S(1)−C(3A)
and C(3)−C(2)−C(2A)−C(3A)-containing planes. The
ruthenium(II) complex 1 possesses one chloro and one
carbonyl as the axial ligands. The ν(CO) was located at 1956
cm−1. The carbonyl group sits at the opposite side of the
thiophenic sulfur atom with an angle of 173.7(4)° for Ru(1)−
C(1)−O(1). A vector defined by atoms of axial ligands Cl(1),
Ru(1), and C(1) exhibits a tilting angle of 8.07° away from the
normal of the plane defined by the tripyrrin moiety. The
distances of 2.044(3) and 2.077(2) Å for Ru−N are close to an
average of 2.049 Å for RuII−N bonds among reported
ruthenium porphyrin complexes. Furthermore, distances of
1.834(4) and 1.114(5) Å for the bond lengths of Ru(1)−C(1)
and C(1)−O(1), respectively, fall in the range of distances
(1.762−1.959 Å for Ru−C and 0.961−1.188 Å for C−O)
reported for available ruthenium−carbonyl porphyrin com-
plexes. The Ru−Cl distance of 2.469(1) Å in 1 is significantly
longer than the average of 2.398 Å for structurally available
nonporphyrinic RuII complexes containing one chloride, one
carbonyl, and at least three nitrogens in the coordination sphere
deposited in the Cambridge Structural Database (CSD).37
Although there is no precedent for ruthenium porphyrins with
a Cl− and a CO at the trans positions, both the unexpectedly
long Ru−Cl bond and the normal Ru−C and C−O bond
lengths for the Cl−Ru−(CO) moiety of 1 suggest a weakened
interaction between Ru and Cl.
Figure 2. The absorption spectra of 2 (black line), 3 (red line), and 4
(green line).
pseudohalide−ruthenium−carbonyl− thiaporphyrins exhibit
similar UV−vis absorption patterns with an asymmetric Soret
band located at 432 nm for 2 and 3 and 440 nm for 4. The Q-
bands at around 570 and 680 nm for 2−4 are weak and
broadened. Metal-to-ligand charge transfer (MLCT) bands for
porphyrin complexes are generally difficult to identify because
of overlapping with intense porphyrinic π→π* transitions. The
asymmetric character of Soret bands with an observable tailing
at around 500 nm for 2−4 might imply the overlap of the
MLCT absorption with the Soret band. Analyzing the potential
electronic transitions obtained from the theoretical calculations
revealed a charge-transfer band around 480 nm for all
ruthenium−carbonyl−thiaporphyrin complexes, which sup-
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Figure 3. The molecular structures of 2 (a), 3 (b), and 4 (c) in 25% ellipsoids. Only one of the two disordered positions for 2 and 3 was presented.
Hydrogen atoms are omitted for clarity.
ports the speculation that porphyrinic π→π* transitions overlap
with a change-transfer band, resulting in tailing Soret bands. On
the other hand, the UV−vis absorptions of 1−4 are insensitive
to the axial pseudohalides. A similar phenomenon has been
observed in a series of ruthenium−nitrosyl porphyrin
ν(NO), respectively. According to those reported cases, the
unidentate chelating of nitrato in [Ni(en)2(NO3)2] gave a Δ(νa
− νs) = 115 cm−1, while a much larger value of 186 cm−1 was
obtained from the nitrato group with a bidentate chelating
mode in [Ni(en)2(NO3)]ClO4.39 Consequently, the small
Δ(νa − νs) value of 83 cm−1 in the nitrato complex 2
indicates a unidentate coordination mode. The νa(NO2) and
νs(NO2) for the nitro group in complex 3 were located at 1366
and 1323 cm−1, respectively. These values are in the lower
energy regions of 1470−1370 cm−1 for νa(NO2) and 1340−
1320 cm−1 for νs(NO2) and are consistent with stretching
frequencies of a N-bound NO2 . The characteristic IR
frequencies of azido complex 4 were located at 2035 cm−1 for
νa(N3) and 1262 cm−1 for νs(N3). These frequencies fall in the
normal region for these linear triatomic pseudohalogeno groups
but are lower than 2048 and 1291 cm−1 for νa(N3) and νs(N3),
respectively, in the complex [Ru(TTP)(NO)(N3)].38
−
complexes [Ru(porphyrin)(NO)(X)] (X = NO3 , H2O,
27
NCS−, Cl−, NO2 , NSO−, N3 , OH−, OMe−, SH−), and
the insensitivity has been attributed to the dominance of the
strong π-accepting ligand on the interaction between axial
ligands and the ruthenium center.38
−
−
1
In the H NMR spectra of 2−4, singlet resonances at 9.32
40
−
and 8.64 ppm for 2 and at 9.33 and 8.66 ppm for 3 resulted
from β-thiophenic and β-pyrrolic protons, respectively, are all
downfield shifted compared with the corresponding resonances
of 9.26 and 8.57 ppm for 1. The largest downfield shifted meso-
tolyl proton resonance was at 8.06 ppm for 1 and 8.07 ppm for
4, whereas for 2 and 3 unusually downfield shifted doublet
resonances for meso tolyl groups at 8.83 ppm and 8.84 ppm,
respectively, were observed. The extra downfield shifting of ca.
0.75 ppm in 2 and 3 for the meso-tolyl resonance indicates
either an intramolecular or an intermolecular weak hydrogen-
bonding interaction from the nitrato or nitro group to aromatic
protons on tolyl groups.
Since ν(CO) is highly sensitive to the electronic structure of
the carbonyl complex, the ν(CO) values can be used to gauge
the electron-donating ability of the ligand trans to the carbonyl
group. As the electron-donating ability of the trans ligand
increases, the increased π back-bonding from ruthenium to
carbonyl group results in a lower ν(CO). The comparison of
the ν(CO) values among [Ru(STTP)(CO)X] demonstrates a
proportional correlation of the ν(CO) with the electron-
donating ability of trans ligands. Complex 1 with a chloride
trans to CO exhibited the lowest ν(CO) at 1956 cm−1. These
values increased to 1958 cm−1 for the azido complex, 1965
cm−1 for the nitrato complex, and 1977 cm−1 for the nitro
complex, indicating electron-donating ability in a spectrochem-
Characteristic vibrational modes from axial ligands in the
infrared spectra of 2−4 provide fingerprint-like peaks for
understanding the bonding modes of axial ligands. Specifically,
the difference of νa(NO2) and νs(NO2) (Δ(νa − νs)) has been
−
−
used to differentiate chelating modes of NO3 and NO2 in
their metal complexes. The infrared spectrum of nitrato
complex 2 showed characteristic bands of 1468, 1385, and
1279 cm−1, which were assigned to νa(NO2), νs(NO2), and
ical series of Cl− ∼ N3 > NO3 > NO2 for the ruthenium−
−
−
−
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Table 2. Selected Bond Distances and Angles for 1−4
1
2
3
4
5
bond distances
Ru−N(Por)
2.044(3)
2.077(2)
2.050(4)
2.086(3)
2.047(2)
2.071(2)
2.037(2)
2.068(2)
2.070(2)
2.2240(7)
1.149(4)
1.834(3)
2.155(3)
2.013(7)
2.057(5)
Ru−S
C−O
Ru−C(CO)
Ru−Xaxial
2.2453(10)
1.114(5)
2.2436(11)
1.148(6)
1.822(5)
2.120(5)
2.2436(9)
1.137(4)
1.862(3)
2.145(3)
2.251(2)
1.834(4)
2.4694(14)
2.320(2)
2.356(2)
bond angles
N(Por)−Ru−N(Por)
S−Ru−N(Por)
C−Ru−Xaxial
91.26(5)
91.28(6)
91.43(4)
91.43(9)
91.53(9)
176.73(8)
88.65(6)
88.19(6)
169.61(7)
176.06(11)
173.1(3)
15.67(13)
0.0136
91.44(13)
176.0(3)
177.48(10)
177.23(11)
177.14(9)
88.76(5)
88.65(6)
88.58(4)
88.71(13)
171.47(10)
169.86(12)
170.24(8)
174.22(19)
175.78(12)
173.7(4)
16.05(15)
0.0030
178.83(18)
174.9(4)
16.99(21)
0.038
176.32(12)
172.7(3)
15.98(11)
0.0074
177.36(9)d
Ru−C−O
a
Φ
(deg)
16.36(29)
0.0649
0.50
b
Δ(Ru) (Å)
b
Δ(S) (Å)
0.50
0.50
0.52
0.54
c
Λ (deg)
59.02(8)
59.81(9)
58.39(7)
56.85(8)
59.52(21)
a
b
c
Dihedral angle between planes of Cα−Cβ−Cβ−Cα and Cα−S−Cα. Atomic deviation from mean plane defined by the tripyrrin moiety. Angle
between plane of Cα−S−Cα and plane of S−Ru−N(Por).
carbonyl−thiaporphyrins. It is noteworthy that the N-bound
nitro group has been considered an extremely good π-acceptor
in the five coordinated complex [Fe(TpivPP)(NO2)]−
according to the short bond distance of 1.849 Å for Fe−
N(NO2).41 However, the strong π-accepting nature of the nitro
group has been found to substantially diminish in six-
coordinate nitro complexes.42 In conjunction with the longer
Ru−N(NO2) distance and nearly constant bond lengths of
Ru−X (X = O for nitrato and N for nitro and azido) as
described below, we conclude that it is the electron-donating
character but not the π-accepting ability of the ligand trans to
CO which dominates the values of ν(CO).
To corroborate the molecular conformation, the single-
crystal structures of 2, 3, and 4 were obtained and displayed in
Figure 3. Selected bond distances and angles as well as
important structure parameters for complexes 1−4 are listed in
Table 2. Compounds 2 and 3 crystallized in the monoclinic
As listed in Table 2, Ru−N(Por) bond distances for
complexes 2, 3, and 4 are in the range of 2.037(2)−2.086(3)
Å, which are in the normal range for ruthenium porphyrin
complexes. The bond distance of Ru−N(Por) trans to the Ru−
S is significantly shorter than the other two Ru−N(Por) bonds,
presumably due to the weakened Ru−S bond under the
pyramidal coordination geometry. In all ruthenium−thiapor-
phyrin complexes, ruthenium centers are nearly coplanar with
the mean plane of the tripyrrin. Thiophenic sulfur atoms
deviate from the mean-plane of the tripyrrin toward nitrato,
nitro, and azido with values of 0.50, 0.50, and 0.52 Å for 2, 3,
and 4, respectively. The Ru−Onitrato bond distance of 2.120(5)
Å in complex 2 is longer than the reported distance of 2.059 Å
for Ru−Onitrato in cis-[Ru(NO)(NO3)(bpy)2](ClO4)2.43 Also,
the Ru−Nnitro distance of 2.145(3) Å in 3 is longer than those
of 2.066 and 2.071 Å for Ru−Nnitro in [Ru(PC)(NO2)2] (PC =
phthalocyaninato).44 These relatively long Ru−Onitrato and Ru−
Nnitro bonds indicate that the electron density on Ru−O and
Ru−N bonds is outcompeted by the back-bonding from the
ruthenium ion to the carbonyl antibonding orbital. Complex 2,
which has a nitrato axial ligand, gives the shortest Ru−C(CO)
distance, and longer C−O distances are seen in 1−4, implying
the utmost back-bonding interaction among the complexes
studied herein.
A ubiquitous phenomenon in the crystal structures of
ruthenium−carbonyl−thiaporphyrins is that the deviating
thiophenic sulfur is always leaning toward chloride/pseudoha-
lides. Results of theoretical calculations rationalize this
tendency. As listed in Table 3, the total-energy difference
between two scenarios, thiophenic sulfur directed toward axial
chloride/pseudohalides (observed) and the sulfur directed
toward the axial carbonyl group (proposed), clearly indicates
that the former one is always preferable over the latter one,
which is consistent with the observation in solid state
structures. For example, in the case with the largest energy
C2/m space group, while 4 crystallized in triclinic Pı. In the
̅
structure of 2, atoms of Ru, CO, and two of the oxygens from
nitrato group sit on the special positions to generate, from
symmetry operation, not only the other half molecule but also a
−
disordered NO3 with 50% occupancy. The nitro group in
complex 3 is also disordered in two positions with 50%
occupancy on each site. Overall, in addition to the different
pseudohalide coordination, the conformation of the ruthe-
nium−carbonyl−thiaporphyrin moiety for 2, 3, and 4 resembles
that of 1. As predicted from IR spectra, the nitrato ligand in 2
adopted an O-bound monodentate binding mode, while an N-
bound nitro group was observed in the structure of 3. To the
best of our knowledge, complex 3 is the first structurally
characterized N-bound ruthenium nitro porphyrin complex,
and there is no precedent for a crystal structure for a ruthenium
porphyrin complex containing either a nitrato or an azido as the
axial ligand.
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Table 3. Total Electronic Energies (Etotal), Zero Point
Vibrational Energies (Etotal + ZPV), and Their Relative
Differences in Energies between Two Potential Thiophene
Orientations (Erel)
a
compounds
Etotal in Hartree
Etotal + ZPV
Erel in kcal/mol
1
−1997.13186895
−1997.13054609
−1819.35610923
−1819.35014942
−1703.24395868
−1703.24386005
−1996.850819
−1996.849367
−1819.060129
−1819.054025
−1702.951729
−1702.951508
0.0
1a
2
0.91
0.0
2a
4
3.83
0.0
4a
0.13
a
A bend nitrito ligand with an angle of 54° between nitrito O−N−O
plane and the porphyrinic tripyrrin plane was obtained from the
structural optimization of 3. This optimized structure apparently is one
of the stabilization forms but is significantly different from the crystal
structure. Therefore, data obtained for 3 were not included here.
Figure 4. The cyclic voltammogram of 5 in THF with 0.1 M tetra-n-
butylammonium hexafluorophosphate under a scan rate of 50 mV/s.
difference (2 and 2a), the observed conformer with the sulfur
directed toward the nitrato group is 3.83 kcal/mol lower in
energy than the proposed one. Even in the azido case with only
a minute energy difference (4 and 4a), the observed conformer
is 0.13 kcal/mol more stable than the proposed one. Further
analysis on the optimized structures reveals that the stable
conformers exhibit shorter Ru−CO bond distances but longer
C−O and Ru−S bond distances in comparison with the higher
energy ones, suggesting that the observed conformers show a
stronger ruthenium-to-carbonyl back-bonding interaction than
proposed ones.
ligand after electrochemical demetalation of [Cu(STTP)X], a
·STTPH−/STTPH2− redox process.
Single-crystal X-ray structural determination, as shown in
Figure 5, revealed that the neutral complex consists of two Cl−
Synthesis of Higher Valence [RuIII(STTP)Cl2] (5). RuIII−
thiaporphyrin complex [Ru(STTP)Cl2] (5) was synthesized by
treating STTPH with Ru(COD)Cl2 in o-dichlorobenzene in
moderate yield. The absorption spectrum with the Soret band
at 446 nm is slightly red-shifted relative to the RuII
thiaporphyrin complexes 1−4. In contrast to the broad and
asymmetric Soret bands in 1−4, the Soret band in 5 is sharp and
symmetrical, and no obvious Q-band can be observed in the
Figure 5. The molecular structure of 5 under 25% ellipsoids.
Hydrogen atoms are omitted for clarity.
1
lower energy region. H NMR resonances of complex 5 were
ligands coordinating at axial positions and one thiaporphyrin
chelating in a tetradentate mode to give a formally Ru(III)
complex. The bond lengths of Ru−Cl in 5 are 2.320(2) and
2.356 (2) Å, which are shorter than the 2.469(1) Å in 1, as
expected for a complex with the RuIII oxidation state. As shown
in Table 2, the distances of 2.013(7) and 2.057(5) Å for Ru−
N(Por) are also slightly shorter than corresponding distances
for RuII−N(Por). The Ru−S distance and bending angle of the
thiophene ring in 5 are almost identical to those of RuII
thiaporphyrin complexes, implying that a steric constraint
instead of electrostatic interaction dominates the conformation
of the thiophene moiety.
Preparation of Ruthenium Dithiaporphyrin Com-
plexes with Nitrate or Bis(phenylseleno)methane As
Axial Ligands. The free-base 5,10,15,20-tetra-p-tolyl-21,23-
dithiaporphyrin, S2TTP, was prepared via condensation of 2,5-
bis(tolylhydroxylmethyl)thiophene and pyrrole using BF3·OEt2
as an acid catalyst followed by oxidation with DDQ. As
sketched in Scheme 2, the reaction of [Ru(S2TTP)Cl2]25 with a
large excess of AgNO3 or NaSePh isolates [Ru(S2TTP)-
(NO3)2] (6) or [Ru(S2TTP)(PhSeCH2SePh)2] (7), respec-
tively, in 78% yields. Both complexes 6 and 7 were air-sensitive,
and all preparations have been carried out under N2. Complex
6 was stable in CH2Cl2 with no significant decomposition
during the workup; however, passing the toluene or THF
too broad to be observed because of the intrinsic paramagnetic
characteristic. Complex 5 is stable under aerobic conditions in
both solid and solution states, and no demetalation proceeded
under examined conditions. The high stability of 5 allows the
examination of redox processes by cyclic voltammetry. As
shown in Figure 4, two reversible and one irreversible process
were observed in the cyclic voltammogram of 5. The half-wave
potential at +1.083 V, which is close to +1.03 V for the first
oxidation potential of the free-base thiaporphyrin, presumably
resulted from a thiaporphyrin-centered oxidation. The other
reversible process at E1/2 = −0.123 V, which is considerably
different from −1.065 V for a thiaporphyrin-centered reduction
in STTPH, was assigned to the Ru3+/Ru2+ redox couple. The
irreversible process at −1.476 V, which is more negative than
−1.065 V for the STTPH reduction, indicates that a more
electron-rich species might be generated after the RuIII → RuII
reduction process. Since there is no observable redox potential
corresponding to a RuII → RuI process, it is likely that the
[RuII(STTP)Cl2]− is not stable and readily demetalated to
STTP−. A similar reduction-promoting demetalation was
observed in an earlier electrochemical study on [Cu(STTP)X]
(X = Cl− or HCO3 ).45 A reduction potential with an E1/2 value
−
of −1.40 V, which is close to the −1.476 V observed in 5, has
been assigned as the addition of a second electron to the free
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Scheme 2
solution of 6 through Celite in an inert atmospheric drybox
instantly produced 6 and free-base S2TTP with a ratio of 1:1.
The isolation of 7 from the reaction of [Ru(S2TTP)Cl2] and
NaSePh was unexpected. Presumably, a concerted bond-
breaking/formation between the intermediate, [Ru(S2TTP)-
(SePh)2], and CH2Cl2 through a radical pathway results in the
formation of PhSeCH2Cl and simultaneously reduces the
ruthenium(II) complex to ruthenium(0). As PhSeCH2Cl
possesses higher reactivity toward nucleophilic-attack substitu-
tion, the reaction of excess PhSe− and PhSeCH2Cl readily
resulted in the formation of bis(phenylseleno)methane. Control
studies to derive a plausible mechanism are described in detail
in the following paragraphs.
To provide more insight into the formation and coordination
of bis(phenylseleno)methane, control reactions with or without
the presence of [Ru(S2TTP)Cl2] were stoichiometrically and
spectroscopically monitored. At room temperature, the reaction
of NaSePh and CH2Cl2, without any metal complex or base,
under anaerobic conditions for 12 h, isolated diphenyl
diselenide and bis(phenylseleno)methane in low yields (12%).
Noticeably, no reaction was observed when 2.0 equiv of
NaSePh were reacted with [Ru(S2TTP)Cl2]. On the other
hand, the reaction of 4.0 equiv of NaSePh with [Ru(S2TTP)-
Cl2] in CH2Cl2 yielded an electronic absorption pattern with
Soret band at 448 nm and Q-bands at 589 and 814 nm, which
resembles those of [Ru(S2TTP)Cl2] and 6, suggesting that the
reaction might achieve [RuII(S2TTP)(SePh)2] through a
metathesis reaction. Treatment of the reaction mixture with
another 4.0 equiv of NaSePh, the UV−vis spectrum gradually
shifted to that of complex 7. The crude mixture from a reaction
of [Ru(S2TTP)Cl2] and 14.7 equiv of NaSePh was extracted
with hexane, and the GC-mass analysis identified PhSeCH2Cl
(relative intensity: 100%), PhSeSePh (20%), and
PhSeCH2SePh (77%) as three major products. Implications
from the above-mentioned control reactions and the presence
of a large amount of PhSeCH2Cl in the reaction mixture, which
is not observed from the reaction of NaSePh and CH2Cl2 in the
absence of [Ru(S2TTP)Cl2], are as follows: (1) reaction of
[RuII(S2TTP)(SePh)2] and CH2Cl2 might result in a concerted
formation of PhSe−CH2Cl through homolytic cleavage of both
axial RuII−SePh bonds with a concurrent reduction of Ru(II) to
Ru(0); (2) reaction of the more reactive PhSeCH2Cl and
PhSe− readily proceeded to form PhSeCH2SePh via a
nucleophilic-attack pathway; (3) the Ru0 intermediate, resulted
from the reductive elimination of PhSeCH2Cl, was stabilized by
the coordination of bis(phenylseleno)methane, of which the
vacant 3d orbital is a good π acid to stabilize the Ru0 metal
center.
Complex 6 exhibits absorption maxima at 467, 556, 593, and
816 nm (Figure 6) similar to the pattern of [Ru(S2TTP)Cl2],
Figure 6. The absorption spectra of ruthenium dithiaporphyrin
complex 6 (black) and 7 (red).
whereas the formally ruthenium(0) complex 7 gives a broad
and unusually blue-shifted Soret band at 400 nm with no
obvious Q-band. Complex 6 displayed IR absorption peaks at
1467 cm−1 for νa(NO2), 1384 cm−1 for νs(NO2), and 1262
cm−1 for ν(NO) with Δ(νa − νs) of 83 cm−1, which are
consistent with the values for a monodentate nitrato ligand.
The NMR spectrum of 6 in CDCl3 shows sharp peaks for β-
thiophenic and β-pyrrolic protons, and resonances of meso-tolyl
protons were broadened into three humps at 8.30, 7.57, and
7.32 ppm, showing that a twisting thiaporphyrin core results in
a facile dynamic rotation of meso-tolyl rings at room
Complexes 6 and 7 crystallized in space groups of
orthorhombic Pnnm and monoclinic P21/n, respectively. One-
fourth of atoms in the structure of 6 were located from the
electron density map, and the complete molecule can be
generated from the symmetry operation. The axial nitrato
group was disordered in two sites with 50% occupancy for each
one. In the structure of 7, half of the molecule was observed,
and the noncoordinated PhSe moiety on bis(phenylseleno)-
methane was dangling in two positions with a ratio of 4:1 on
site-occupancy factors. The molecular diagrams of 6 and 7 are
illustrated in Figure 7, and the selected bond lengths and angles
are listed in Table 4. With two thiophene moieties in the
macrocycle, the core size of S2TTP is much smaller than that of
1
temperature. The H NMR signals of 7 were extremely broad
between 6.50 and 8.75 ppm for β-thiophenic, β-pyrrolic, and
meso-tolyl protons, and no further efforts were made to assign
the resonances.
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in was 0.84 Å for 6 and 0.94 Å for 7, while the bending angles
of the thiophene ring were 17.11(51)° in 6 and 20.02(24)° in
7. Larger deviations and bending angles in 6 and 7 than those
of 1−5 suggest a larger intrinsic steric constraint in
dithiaporphyrin than in thiaporphyrin core. Although the
vector connecting two axial coordinating atoms was not
perpendicular to the thiophene-excluded dithiaporphyrin
mean plane, it was near orthogonal to the line of S(1)−
Ru(1)−S(1A) in both 6 and 7. The nitrato groups in 6
coordinating to the Ru(II) center in a unidentate O-bound
coordination mode with a Ru−O distance of 2.145(4) Å are
slightly longer than those of 2. Axial PhSe−CH2−SePh
coordinating to the Ru(0) center was unidentate with Ru−Se
distances of 2.4935(8) Å. Intermolecular cross-linking inter-
actions between sulfur atoms were located in the crystal lattices
of 6 and 7 to form a one-dimensional linear chain. The
intermolecular linear chains pack into a three-dimensional
channel-type structure (Figure 8). The dimensions of the
Figure 7. Molecular structures of ruthenium dithiaporphyrin complex
6 (up) and 7 (down, tolyl groups omitted for clarity).
Figure 8. The linear chains packed into channels in the crystal lattice
of 6.
channel in 6 are 9.46 × 9.46 Å2, measured from the distances
between two opposite walls constructed by meso tolyl groups.
With the presence of bulky bis(phenylseleno)methane groups
on the axial positions, channels in 7 are smaller than those in 6.
Table 4. Selected Bond Distances and Angles for 6 and 7
6
7
bond distances (Å)
2.069(4)
2.145(4)
2.2335(11)
bond angles (deg)
90.03(14)
90
Ru(1)−N(1)
Ru(1)−Xaxial
Ru(1)−S(1)
2.103(4)
2.4935(8)
2.2669(16)
CONCLUSIONS
■
In this work, the preparations of stable ruthenium thiaporphyr-
in and dithiaporphyrin complexes have been achieved. The
availability of [Ru(STTP)(CO)Cl] and [Ru(S2TTP)(Cl)2]
provides essential starting complexes for further manipulation
to explore the coordination chemistry of thiaporphyrin and
dithiaporphyrin. Similarly, the stable [Ru(STTP)(Cl)2] can be
used as a precursor for the preparation of other Ru(III)−
thiaporphyrins. According to the ν(CO) values, the spec-
trochemical series of electron-donating abilities for the studied
S(1)−Ru(1)−Xaxial
N(1)−Ru(1)−S(1)
N(1)−Ru(1)−Xaxial
X1−Ru(1)−X2
92.56(4)
90.01(13)
85.79(13)
90
180
180
a
a
Φ
(deg)
17.11(51)
0.84
20.02(24)
0.94
b
Δ(S) (Å)
a
Λ
(deg)
61.86(16)
63.10(18)
a
b
See Table 2 for the define on the angles. Deviation of sulfur atom
ruthenium−carbonyl thiaporphyrins is Cl− ∼ N3 > NO3
>
−
−
from mean-plane defined by two pyrroles and meso carbons.
−
NO2 . Exceptionally, the reaction of NaSePh of [Ru(S2TTP)-
Cl2] in CH2Cl2 resulted in the formation of bis(phenylseleno)-
methane coordinating to a Ru0 center.
STTPH. Therefore, similar to the conformation of Ru(S2TTP)-
Cl2, both thiophene rings of S2TTP in 6 and 7 tilted toward
opposite directions from the S2TTP mean plane in order to
accommodate the ruthenium ion. The ruthenium centers in
both complexes were of six-coordinated octahedral geometry.
The Ru−N and Ru−S bond distances of 2.069(4) and
2.2335(11) Å, respectively, for complex 6 were significantly
shorter than those of 2.103(4) and 2.2669(16) Å for complex 7,
which indicate the distinctively different oxidation state among
two metal centers. The deviation of sulfur atoms from the 14
thiophene-excluded macrocyclic mean planes of dithiaporphyr-
ASSOCIATED CONTENT
■
S
* Supporting Information
Calculated absorption spectra, computed excited energies,
oscillator strengths and electronic transitions configurations,
NMR spectra (PDF). Crystallographic information (CIF). This
material is available free of charge via the Internet at http://
pubs.acs.org.
11956
dx.doi.org/10.1021/ic200977n|Inorg. Chem. 2011, 50, 11947−11957

Inorganic Chemistry
Article
(28) Pople, J. A. et al. Gaussian, Inc.: Wallingford, CT, 2004.
AUTHOR INFORMATION
Corresponding Author
*Phone: 886-2-27898570. Fax: 886-2-27831237. E-mail:
chhung@chem.sinica.edu.tw.
■
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Present Address
⊥Department of Applied Chemistry & Polymer Technology,
Delhi Technological University, Shahbad Daulatpur, Delhi,
India.
ACKNOWLEDGMENTS
We would like to thank the National Science Council (Taiwan)
and Academia Sinica for financial support.
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