Structure and spectroelectrochemical response of arene-ruthenium and arene-osmium complexes with potentially hemilabile noninnocent ligands

Article abstract of DOI:10.1021/om5002815

Nine of the compounds [M(L^2-)(p-cymene)] (M = Ru, Os, L^2- = 4,6-di-tert-butyl-N-aryl-o-amidophenolate) were prepared and structurally characterized (Ru complexes) as coordinatively unsatu-rated, formally 16 valence electron species.

Full text of DOI:10.1021/om5002815

Article
pubs.acs.org/Organometallics
Structure and Spectroelectrochemical Response of Arene−
Ruthenium and Arene−Osmium Complexes with Potentially
Hemilabile Noninnocent Ligands
Martina Bubrin,† David Schweinfurth,†,‡ Fabian Ehret,† Stanislav Zalis,§ Hana Kvapilova,§ Jan Fiedler,§
́
̌
́
Qiang Zeng,∥ Frantisek Hartl,*,∥ and Wolfgang Kaim*,†
̌
†Institut fur Anorganische Chemie, Universitat Stuttgart, Pfaffenwaldring 55, D-70550 Stuttgart, Germany
̈
̈
‡Institut fur Chemie und Biochemie, Freie Universitat Berlin, Fabeckstraße 34-36, D- 14195 Berlin, Germany
̈
̈
§J. Heyrovsky Institute of Physical Chemistry, v.v.i., Academy of Sciences of the Czech Republic, Dolejsk
̌
ova 3, CZ-18223 Prague,
́
Czech Republic
∥Department of Chemistry, University of Reading, Whiteknights, Reading RG6 6AD, United Kingdom
S
* Supporting Information
ABSTRACT: Nine of the compounds [M(L2−)(p-cymene)] (M = Ru,
Os, L2− = 4,6-di-tert-butyl-N-aryl-o-amidophenolate) were prepared and
structurally characterized (Ru complexes) as coordinatively unsatu-
rated, formally 16 valence electron species. On L2−-ligand based
oxidation to EPR-active iminosemiquinone radical complexes, the
compounds seek to bind a donor atom (if available) from the N-aryl
substituent, as structurally certified for thioether and selenoether
functions, or from the donor solvent. Simulated cyclic voltammograms
and spectroelectrochemistry at ambient and low temperatures in
combination with DFT results confirm a square scheme behavior (ECEC mechanism) involving the Ln ligand as the main
electron transfer site and the metal with fractional (δ) oxidation as the center for redox-activated coordination. Attempts to
crystallize [Ru(Cym)(QSMe)](PF6) produced single crystals of [RuIII(QSMe•−)2](PF6) after apparent dissociation of the arene
ligand.
Chart 1. Reversible Intramolecular 1e Oxidation-Induced
Addition5
INTRODUCTION
■
In 2008 Ringenberg, Rauchfuss, et al. reported the organo-
metallic system [Ir(C5Me5)Q′]+/0 ((Q′)2− = 4,6-di-tert-butyl-2-
(2-trifluoromethyl)amidophenolate), which was shown1 to
catalyze the “hydrogenase-type” conversion of H2 to H+ via
electron transfer based on the noninnocent2 amidophenolate/
iminobenzosemiquinone ligand redox system.3 While an
extension of this work focusing on the role of external base
was provided later,4 including a brief reference to a related
(inactive) areneruthenium species, we have studied the under-
lying reactivity in the form of a reversible single-electron
oxidation-induced addition in an intramolecular arrangement
(Chart 1) for [Ir(C5Me5)Qy]+/0,5 making use of the hemilabile6
character of this previously introduced7 ligand Qy2− = 4,6-di-tert-
butyl-2-(2-methylthio)amidophenolate.
In this report we describe the synthesis, partial structural
characterization, cyclic voltammetry, and spectroelectrochemis-
try at ambient and low temperatures9 of neutral and cationic
complexes of (η6-Cym)M (Cym = p-cymene, M = Ru, Os) with
the noninnocent ligands in Chart 2 (iminosemiquinone forms
shown).
Spectroscopic (EPR) and DFT investigations revealed an
activation involving minor (ca. 8%) but non-negligible spin
density transfer from the ligand to the metal as a crucial feature.5
Modifications including rhodium analogues and the effect of
thioether/ether (S/O donor) substituent exchange were
studied,8 using the noninnocent7 amidophenolate/iminosemi-
quinone/iminobenzoquinone redox systems3 as represented by
Arene−ruthenium and −osmium complexes have been widely
used in catalysis10 and in the development of metallodrugs.11
Special Issue: Organometallic Electrochemistry
Received: March 17, 2014
o-iminosemiquinonate ligand intermediates QSMe•− and QOMe
•−
(see Chart 2).
© XXXX American Chemical Society
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Chart 2. o-Iminosemiquinonate Ligands
spectroelectrochemically (EPR, UV−vis−NIR) earlier.13
A
RESULTS AND DISCUSSION
Synthesis and Characterization. The neutral compounds
1−9 (Chart 3) were obtained from the reaction of the
■
structural comparison will be made below between [Ru-
(QSMe)2]+ (10) and the neutral precursor [Ru(QSMe)2], aimed
at assignment of the oxidation states of the metal center and of
the noninnocent ligands.
Chart 3. Compounds Investigated
Structure. In the crystallographically characterized (Table 1
and Table S1 (Supporting Information), Figures 1−5 and
Figures S1−S4 (Supporting Information)) neutral compounds
1−6 the metal exhibits a formal 16-valence-electron count. Such
coordinative unsaturation was observed before for metal
catecholate compounds of, e.g., Cr, W, Mn, Re, Rh, and
Ir;5,8,14−16 it is attributable to the strong σ and π donation from
the catecholate dianion. The bond parameters of the neutral
compounds are very similar (Table 1) and are well reproduced
for 1−5 by DFT calculations (Tables S2 and S3 (Supporting
Information)). No unusual intermolecular interactions have
been observed (Figure S4). The neutral compounds 1 and 3 are
isostructural (S/Se exchange). The p-cymene ligands adopt
different orientations in the crystals, as illustrated in Figure S5.
The N-aryl substituents are substantially twisted relative to the
amidophenolate chelate ring (cf. the angle ω in Table 1),
illustrating the lack of conjugation as well as the nonbonded
interactions (Ru- - -E ≥ 3.95 Å) of the chalcogen heteroatoms O
(2), S (1), and Se (3).
The redox pairs 1/1+ and 3/3+ illustrate the structural effect of
oxidation: the Ru−N and, to a lesser extent, the Ru−O distances
increase. The o-monoiminoquinones have become popular17−19
due to their strong metal binding even in the neutral form while
offering easy access to all three oxidation states in the
conventional redox potential region. In contrast to the Ru−N
and Ru−O bond lengths, the C−O and C−N distances decrease
by about 0.02 Å, indicating electron loss from the amidopheno-
late ligand. In fact, the EPR data for all cations (see below) show
an o-iminosemiquinone spin distribution. The C−C distances in
the aromatic rings correspond to averaged values for the
amidophenolate compounds but reveal the onset of bond
alternation in the semiquinone complexes.
corresponding o-aminophenol precursors and [M(Cym)Cl2]2
under basic conditions. The ruthenium compounds 1−6 are
more stable than the osmium complexes 7−9, which is attributed
to more facile dissociation of the neutral aromatic cymene ligand.
All compounds proved to be air sensitive and slowly reacted
(within days) with dichloromethane; crystallization was thus
performed from other solvents (see the Experimental Section).
Oxidation using Fc(BArF) (BArF− = tetrakis(3,5-bis-
(trifluormethyl)phenyl)borate)12 was successful for the ruthe-
nium compounds 1 and 3 to yield structurally characterized salts
with the noncoordinating BArF− anion. Similar attempts to
oxidize other complexes such as 2 resulted in noncrystalline
material, probably due to the lack of strong intramolecular
addition (2, 4−6) or because of the generally higher lability in the
case of the osmium analogues 7−9. During the attempted
crystallization of [Ru(Cym)(QSMe)](PF6) the formation of
[10](PF6) was observed, as confirmed by a single-crystal X-ray
analysis. This reaction involves dissociation of neutral arene and
produces a paramagnetic cation which had been characterized
Most significantly, the oxidized complexes complement their
coordination by binding the S (1+) or Se (3+) donor atoms at a
normal bond length of about 2.4 Å. A twist is necessary to effect
this, the dihedral angles between the N-aryl substituents relative
to the aminophenolate chelate ring being forced to decrease to
<60°.
As noted earlier,5,8 the oxidation of the complex may affect
predominantly the noninnocent ligand (see below) but the
fractional amount δ of the charge change at the metal results in
additional coordination of the hemilabile ligand. The additional
binding of the thio- and selenoether donors in systems 1/1+ and
3/3+, respectively, appears reasonable but raises further
questions: How does an O-ether function respond, are
coordination situations comparable for solids and dissolved
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Table 1. Selected Atom−Atom Distances (Å) and Dihedral Angles (deg)
1
1+
2
3
3+
4
5
6
Ru−N
Ru−O
C−O
1.963(5)
2.043(2)
2.048(2)
2.049(2)
2.048(2)
1.309(3)
1.309(3)
1.372(3)
1.373(3)
1.426(4)
1.425(4)
1.406(4)
1.405(4)
1.368(4)
1.375(4)
1.421(4)
1.420(4)
1.378(4)
1.383(4)
1.438(4)
1.432(4)
2.3820(8)
2.3806(8)
53.62
1.952(2)
1.967(5)
2.045(2)
1.949(2)
1.952(2)
2.005(2)
2.006(2)
1.339(3)
1.338(3)
1.398(3)
1.393(3)
1.405(3)
1.412(3)
1.402(3)
1.407(3)
1.387(3)
1.381(3)
1.415(3)
1.412(3)
1.396(3)
1.395(3)
1.415(3)
1.412(3)
1.951(1)
1.967(4)
1.963(4)
2.017(3)
2.022(3)
1.330(6)
1.337(5)
1.383(6)
1.386(6)
1.398(6)
1.396(6)
1.413/(7)
1.409(6)
1.384(6)
1.388(6)
1.409(6)
1.415(7)
1.388(7)
1.392(6)
1.425(6)
1.420(6)
2.003(3)
1.327(6)
1.395(6)
1.401(8)
1.401(8)
1.388(7)
1.412(7)
1.388(8)
1.421(7)
3.949(3)
81.27
2.022(2)
1.341(3)
1.396(3)
1.402(4)
1.398(4)
1.377(4)
1.405(4)
1.387(4)
1.419(3)
4.094(2)
72.45
2.005(5)
1.332(8)
1.411(9)
1.415(9)
1.394(9)
1.379(9)
1.410(9)
1.385(9)
1.424(9)
4.002(2)
80.61
2.048(1)
1.312(3)
1.369(3)
1.424(4)
1.409(4)
1.371(4)
1.431(4)
1.375(4)
1.434(4)
2.508(0)
58.43
2.000(1)
1.336(2)
1.393(2)
1.410(2)
1.403(2)
1.388(2)
1.416(2)
1.389(2)
1.424(2)
C−N
C1−C2
C2−C3
C3−C4
C4−C5
C5−C6
C1−C6
a
Ru−E
b
ω
85.65
88.09
63.56
81.59
79.95
59.24
a
b
E = S, O. Dihedral angle between N-aryl substituent and chelate ring.
Figure 1. Molecular structure of 1 in the crystal. Thermal ellipsoids are
given at the 50% probability level.
Figure 2. Molecular structure of the cation in the crystal of [1](BArF).
Thermal ellipsoids are given at the 50% probability level.
complexes, and which options are there in the absence of suitable
complementary donor atoms within the noninnocent ligand?
The DFT calculations on 1/1+ and 7/7+ confirm the lower
energy of the S-noncoordinated form for the neutral species and
the S-coordinated arrangement for the cations; the alternatives,
S-coordinated neutral and S-dissociated cation (Scheme 1), have
been calculated at significantly higher energies. In vacuo DFT
calculated selected bond lengths and angles of complexes are
given in Tables S2−S4 (Supporting Information). The calculated
bonding parameters agree with the experimental structural data
for the ruthenium compounds (Table 1). Both configurations,
i.e., the N,O-bonded (form A, Chart 4) and N,O,S-coordinated
alternatives (form B), were examined for the complexes 1 and 7.
In the case of the neutral species the calculations indicate that
form A is more stable; free energy differences, ΔG, of 0.407 and
0.506 eV have been obtained for the neutral Ru (1) and Os (7)
complexes, respectively. Form B is more stable for the
monooxidized species, where ΔG values of 0.339 and 0.324 eV
have been obtained for Ru (1+) and Os (7+) complexes,
respectively.
Attempts to crystallize [Ru(Cym)(QSMe)](PF6) from di-
chloromethane led to the formation of single crystals of the
compound [10](PF6) (Table S5 (Supporting Information)).
Apparently, dissociation of the neutral arene ligand has taken
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Figure 3. Molecular structure of 2 in the crystal. Thermal ellipsoids are
given at the 50% probability level.
Figure 5. Molecular structure of 4 in the crystal (one of the two
independent molecules in the unit cell). Thermal ellipsoids are given at
the 50% probability level.
mechanism and the cyclic voltammetric response depend on
the coordination capabilities of the iminosemiquinonate ligands.
Compounds 4−6 without a hemilabile ligand, i.e., without
intramolecularly accessible donors, exhibit in CH2Cl2 only one
discernible wave (see Figure 6, top, for system 4n), comprising
two potentially close 1e steps (cf. detection of cation radicals by
EPR). Simple charge transfers without a coupled chemical
reaction can be expected in the absence of the auxiliary
coordinating functionality and in noncoordinating CH2Cl2. In
a coordinating solvent the situation is changed, as illustrated in
Figure 6. The use of coordinating CH3CN results in a larger
separation between the anodic oxidation waves and the shifted
reverse cathodic waves for the first redox step, 4/4+, obviously
coupled with CH3CN coordination. The second redox process,
4+/42+, displays normal Nernstian behavior, indicating un-
changed coordination of the 18-valence-electron species (Figure
6, bottom).
The compounds 1−3 and 7−9 with potential for intra-
molecular chalcogen coordination exhibit in the first step a
response characteristic of a square redox scheme (Figures 7−9
and Figures S7−S10 (Supporting Information)) with a strongly
shifted reverse cathodic wave (Scheme 3, Table 2), as has been
presented for the related redox system [Ir(C5Me5)Qy]+/0 (11/
11+). The follow-up reaction with an electrochemically
manifested structural change accompanying the first electron
transfer process (neutral/cation) contrasts markedly with the
Nernstian behavior of the second oxidation step (cation/
dication), suggesting the absence of significant structural changes
in this case.
Apparently, the initial electron withdrawal of an electron from
neutral, coordinatively unsaturated 16-VE species at virtually
substituent-independent potentials (Table 2) leads to an
unstable cationic complex which tends to achieve coordinative
saturation either by an intramolecular process (1−3, 7−9) or
through the binding of coordinating solvent molecules (4−6).
On second oxidation, the “piano-stool” coordination arrange-
ment remains unchanged, as illustrated by the apparently
reversible waves.
Figure 4. Molecular structure of the cation in the crystal of [3](BArF).
Thermal ellipsoids are given at the 50% probability level.
place (Scheme 1). While the neutral precursor 10, identified
structurally as [RuIV(QSMe2−)2], had been characterized spec-
troelectrochemically (EPR, UV−vis−NIR) earlier,13 the pres-
ently feasible structural comparison of 10 and 10+ (Table S6 and
Figure S6 (Supporting Information)) reveals that the oxidation
to 10+ produces a situation best described as [RuIII(QSMe•−)2]+.
Accordingly, a redox-induced electron transfer (RIET)20 has
effected metal reduction as a consequence of double ligand
oxidation (Scheme 2), evident especially by shortened CO and
CN bonds. Another structural difference between [10](PF6) and
the neutral precursor 10 involves the CC bonds in the six-
membered ring, which change from average values around 1.40 Å
to more alternating bond lengths, as may be expected for
semiquinones (Table S6).
Cyclic Voltammetry. All neutral compounds 1−9 undergo
two-step oxidation processes in the accessible potential range in
CH2Cl2/0.1 M Bu4NPF6 solution. However, the redox
D
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Scheme 1. Anodic Conversion of Compound 1 to Radical Cation 10+
Chart 4. Bonding Alternatives for Hemilabile Noninnocent
Ligands
Scheme 2. Redox Series of [Ru(QSMe)2]n
Figure 6. Cyclic voltammograms of 4 in CH2Cl2 (top) and CH3CN
(bottom), with each complex in 0.1 M Bu4NPF6/CH2Cl2 at 298 K.
7 and 8). The derived parameters in Table 3 reveal reasonable
differences: the small values of equilibrium constants K1 (for the
cations) and K2 (for the neutral species) confirm the weak
bonding for the ether complex. Even at lower temperatures (253
K) the O-donor system 2x still exhibits K1 constants considerably
smaller than those of the other systems investigated. However, a
much increased constant K2 was determined for 2x at low
temperature, reflecting the absence of O-coordination.
The rate constants k1 obtained from simulations also reflect
more rapid association of the E-donor functionality to the metal
after oxidation for 2x in comparison to the thio- and selenoether
analogues 1x and 3x; the osmium complexes 7x and 9x are
After the first cycling the cyclic voltammograms of the isolated
oxidized compounds [1](BArF) and [3](BArF) showed the same
response (Figure 8) as those of the neutral precursors.
The forward anodic and reverse cathodic voltammetric
responses of complexes 1−3, 7, and 9 were simulated (Figures
E
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Figure 7. Cyclic voltammograms of 1 (left) and 3 (right) in 0.1 M Bu4NPF6/CH2Cl2 at 298 K with simulation (for parameters see Scheme 3 and text).
crystallized: the osmium systems are distinguished by a distinctly
lower g factor due to the very high spin−orbit coupling constant
of the 5d transition metal21,22 and by large metal hyperfine
splitting due to the high Aiso value of 4710 G.21 The radical
complex 8+ could not be investigated due to its lability. The
deviation to smaller g values reflects the proximity of empty
orbitals near the singly occupied MO (SOMO),23,24 and the
relatively small a/Aiso ratios of <0.010 point to decreased
covalent nature of the metal−ligand bonding. The a(H) constant
from H5 at the amidophenolate ring reflects, like the 14N
splitting, variable spin distribution as caused by different binding
Figure 8. Cyclic voltammogram of 7 in 0.1 M Bu4NPF6/CH2Cl2 at 298
K with simulation (for parameters see Scheme 3 and text).
of O, S, or Se “arms” (intramolecularly) or by the solvent. Rather
large differences between a(99,101Ru) values are attributed to the
weaker bonding of the ether (2+) or solvent ligands (4+−6+,
smaller values <6 G) with respect to thio- or selenoether groups,
which leads to higher metal splitting constants (>8.0 G).
Table S7 (Supporting Information) gives G09/PBE0/PCM
calculated spin densities for all cationic species. The spin density
distribution in both forms of the radical cation 1+ is depicted in
Figure 11. Ruthenium spin densities are calculated at 0.07 and
0.16 for forms B and A, respectively. The calculations on the
complex 7+ (form B) give a spin density of 0.095 on the Os atom.
As for the reported iridium complex ion 11+, the DFT
calculations thus suggest relatively low spin densities on the
Figure 9. Cyclic voltammograms of [1](BArF) at 100 mV/s at 298 K in
0.1 M Bu4NPF6/CH2Cl2.
metals (Ru or Os), in agreement with the observed EPR
characteristics. Calculated spin densities show higher metal
contribution for radical complexes 2+−5+ and 7+ lacking the
thioether coordination. Larger metal and smaller ligand spin
distinguished by slower reactions.3 The k2 values for dissociation
densities were calculated for the S-noncoordinated structure A of
of the E-donor functions are invariably much larger than k1.
1+ (see Figure 11).
EPR Spectroscopy. The one-electron-oxidized intermedi-
While the EPR results confirm that a small (“δ”) ligand-to-
ates 1+−9+ are paramagnetic and thus susceptible to investigation
metal spin transfer can effect a significant change in the
by EPR. The recorded experimental and corresponding
coordination behavior, the related ruthenium system [Ru(Cym)-
simulated spectra are shown in Figure 10; the EPR data are
(Q′)]0/+, as described and characterized by Ringenberg et al.,4a
given in Table 4.
showed no catalytic activity toward dihydrogen conversion.
All spectra indicate predominant oxidation of the amidophe-
UV−Vis−NIR Spectroelectrochemistry. Both oxidation
nolate to the iminosemiquinonato ligand, exhibiting
processes of the compounds 1−9 could be monitored by
• high EPR resolution at room temperature in solution
• isotropic g factors close to the free electron value of 2.0023
• unresolved small g anisotropy g1 − g3 in the glassy frozen
spectroelectrochemistry at 293 and 223 K using OTTLE cells
(see the Experimental Section). Figures 12 and 13 and Figures
S11−S13 (Supporting Information) show representative
responses, and Table 5 summarizes the observed absorptions.
Low-temperature spectroelectrochemistry was utilized to
generate unstable dications from the osmium complexes. The
cations 72+ and 82+ obtained by fast electrolysis at the second
oxidation peak have then been rereduced in the reverse potential
scan to monocations and subsequently to the neutral original
complexes (Figure 13 and Figure S13 (Supporting Informa-
tion)).
state
1
•
14N and H hyperfine coupling constants typical for o-
iminosemiquinones
• metal isotope hyperfine splitting at only a fraction
(<0.012) of the corresponding isotropic hyperfine
coupling constant (Aiso = −629.4 G for 99Ru (12.7%
natural abundance), −705.2 G for 101Ru (17.0% natural
abundance), 4710 G for 189Os (16.1% natural abundan-
ce)).21
The neutral precursor molecules exhibit LMCT bands at about
500 nm (M = Ru) or 400 nm (M = Os). A representative TD
DFT calculation of 1 yields an intense transition at 427 nm, the
While the values do not vary excessively, there are revealing
differences which pertain also to those species which could not be
F
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Scheme 3. Redox Cycle As Derived from Cyclic Voltammetry
a
Table 2. Redox Potentials from Cyclic Voltammetry in
MLCT band is shifted and a broad absorption appears in the vis−
NIR border region (700−1000 nm). This feature is assigned to a
weak mixed intraligand/metal centered (IL/MC) transition
(Figure S15 (Supporting Information)), calculated for 1+ at 784
nm.
CH2Cl2/0.1 M Bu4NPF6 at 100 mV/s Scan Rate
first oxidation
redox system
Epa
Epc
second oxidation E1/2
1n
2n
3n
4n
5n
6n
7n
8n
9n
−0.07
−0.05
−0.04
−0.54
−0.40
−0.74
−0.14
−0.13
−0.09
−0.20
−0.08
−0.40
0.18
0.10
0.11
CONCLUSIONS
■
The crystallographically characterized redox pairs 1/1+ and 3/3+
involving ruthenium show behavior similar to that of the related
iridium-based system 11/11+ and that of the corresponding
osmium analogues 7/7+ and 9/9+. Reversible intramolecular
one-electron oxidative addition to effect a tridentate coordina-
tion of the respective hemilabile noninnocent ligands takes place
with predominant, albeit not exclusive, spin concentration at the
semiquinone part of the ligand. The small amount δ of charge
transferred from the metal is apparently sufficient to cause
binding of S (1, 11), Se (3), or external H2 ligands.1 The
simulated cyclic voltammetric response and the spectroelec-
trochemical characterization allowed us to analyze the
mechanism of Scheme 3 in quantitative detail. The situation in
the oxidized O-ether compound 2+, in the complexes 4+−6+ with
pendant donor-free bidentate ligands, and in the osmium
analogues 7+−9+ was not accessible by structure determination
in the solid. However, the (spectro)electrochemical results point
to similar behavior of more weakly bonded OMe substituents
(2+, 8+), coordinating solvent molecules (4+−6+), or analogously
appended thio- and selenoether functions (7+, 9+). The
corresponding equilibrium constants, which also reflect possible
differences between dissolved molecules and those packed in the
crystal, have been determined for representative cases through
simulation of voltammograms. In the absence of additional
donor functions from the ligand or the solvent, two one-electron
reversible oxidations at close potentials are observed, merged
into a single wave in the cyclic voltammetry experiment. In all
cases, the EPR information about g factors and about metal and
b
b
b
−0.07
0.12
0.19
0.06
0.19
−0.01
a
b
In V vs Fc/Fc+. E1/2
.
Table 3. Equilibrium Constants and Rates Obtained from
Simulations of Cyclic Voltammograms
a
Keq(1);
Keq(2); kf(2)/ het rate constant
diffusion
kf(1)/s−1
s−1
ks/cm s−1
coeff/cm2 s−1
1
3
2
4.6 × 104; 4.5 4.1 × 104; 1.66
0.1
9 × 10−5
7 × 10−5
7 × 10−5
n.d.
× 108
4.5 × 105; 3.0 1.6 × 105; 1.2
× 1010
0.005
0.02
n.d.
58.2; 380
2.016; 5.7 ×
1010
2 (253 K) 2.42 × 102;
8.4 × 105; 1.1
0.16
× 109
7
9
1.7 × 104;
1.2 × 105; 5.8
× 109
0.005
0.02
5.4 × 10−5
7 × 10−5
0.48
4.2 × 104;
2.8 × 104; 3.9
0.95
× 107
a
See Scheme 3 and Figures 6 and 7; Rint = 800 Ω. T = 293 K unless
noted otherwise.
MLCT character of which is illustrated in Figure S14
(Supporting Information). On the first oxidation to the
semiquinone state (see EPR Spectroscopy), the diminished
G
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Figure 10. EPR spectra (with simulations) of 1+ (top left), 2+ (top right), 3+ (center), 4+ (center left), 5+ (center right), 7+ (bottom left), and 9+ (bottom
right) at 298 K in CH2Cl2 (from oxidation with FcPF6; 1 G = 10−4 mT).
a
Table 4. EPR Parameters of Radical Complex Cations
1+
2+
3+
4+
6+
5+
7+
9+
g
1.992
8.7
2.002
7.6
1.989
8.7
2.000
8.0
1.999
8.6
2.000
8.2
1.965
10.0
1.962
8.9
a(14N)
a(1H)
a(99,101Ru)
3.3
4.0
3.8
4.3
5.3
4.2
<3.5
<8.0
b
c
c
8.0
3.5
8.6
5.8
5.7
5.6
39
41.7
a
b
From oxidation of precursors with Fc(PF6) in CH2Cl2 at 298 K; coupling constants in G (1 G = 0.1 mT or10−4 T). 99Ru, 12.7% natural
c
abundance, I = 5/2; 101Ru, 17.0% natural abundance, I = 5/2; gyromagnetic ratio 1.12. 189Os hyperfine coupling (189Os, 16.1% natural abundance, I =
3/2).
instrument; solid-state IR measurements were performed with an ATR
unit (smart orbit with diamond crystal). UV−vis−NIR absorption
spectra were recorded on J&M TIDAS and Shimadzu UV 3101 PC
spectrophotometers. Cyclic voltammetry was carried out in 0.1 M
Bu4NPF6 solutions using a three-electrode configuration (glassy-carbon
working electrode, Pt counter electrode, Ag/AgCl reference electrode)
and a PAR 273 potentiostat and function generator. The ferrocene/
ferrocenium (Fc/Fc+) couple served as internal reference. Simulation
ligand hyperfine structure served to assess the electronic
structure of the potentially active radical intermediates.
EXPERIMENTAL SECTION
■
Instrumentation. X-band EPR spectra were recorded with a Bruker
System EMX instrument. 1H NMR spectra were taken on a Bruker AC
250 spectrometer. IR spectra were obtained using a Nicolet 6700 FT-IR
H
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Figure 11. DFT (G09/PBE0/PCM) calculated spin densities for forms B (left) and A (right) of 1+.
Figure 12. UV−vis−NIR spectroelectrochemical responses of compounds 1 and 2 to their stepwise one- and two-electron oxidations in CH2Cl2/0.1 M
Bu4NPF6 at 298 K.
curves were acquired using the DigiElch 7.0 version25 to investigate the
redox mechanism and to establish the kinetic parameters for
electrochemical and chemical steps. Diffusion coefficients were
determined by Cottrell type plots (Figure S16 (Supporting
Information)). Spectroelectrochemistry was performed using an
optically transparent thin-layer electrode (OTTLE) cell at room
temperature and a cryostated cell at low temperatures.9 Thin-layer
cyclic voltammograms were recorded in the course of the spectroelec-
trochemical monitoring. A two-electrode capillary served to generate
intermediates for X-band EPR studies.26
Synthesis. All reactions were conducted using Schlenk equipment.
Reagents and solvents were obtained commercially and were purified by
standard methods. Ru2Cym2Cl4 was obtained from ABCR; Os2Cym2Br4
was prepared according to ref 27.
2-Methylselenoaniline. To a solution of dimethyl diselenide (5
mmol, 0.47 mL) in 25 mL of ethanol was added NaBH4 (10.9 mmol,
0.41 g). The solution was stirred until the color disappeared, and then
0.97 mL (9.2 mmol) of 2-fluoronitrobenzene was added. The solution
was stirred for 12 h at room temperature, after which the solvent was
removed, water (20 mL) was added, and the product was extracted with
dichloromethane. The organic phase was dried over MgSO4, and the
crude product was reacted for the next step without further purification.
A suspension of methylseleno-2-nitrobenzene (8 mmol), zinc powder
(75 mmol, 4.9 g), and ammonium chloride (48 mmol, 2.6 g) in THF (70
mL) were stirred for 20 h at reflux under an argon atmosphere. The
resulting suspension was filtered and the solid washed with dichloro-
methane. The organic phase was dried over MgSO4, the solvent was
removed, and the product was purified over a silica column (hexane/
ethyl acetate 1/1). Yield: 53% (4.24 mmol) of an orange oil. Anal. Calcd
for C7H9NSe: C, 45.17; H, 4.87; N, 7.53. Found: C, 45.66; H, 4.96; N,
7.70. 1H NMR (250 MHz, CD2Cl2): δ 7.49 (dd, J = 7.7, 1.6 Hz, 1H),
7.13 (ddd, J = 8.0, 7.3, 1.6 Hz, 1H), 6.77 (dd, J = 8.0, 1.3 Hz, 1H), 6.67
(td, J = 7.5, 1.4 Hz, 1H), 4.34 (s, 2H), 2.25 (t, 3H, J = 5.7 Hz zu 77Se).13C
NMR (63 MHz, CD2Cl2): δ 147.9, 135.8, 129.3, 118.5, 115.3, 114.3, 7.8.
77Se NMR (47.7 MHz, CD2Cl2): δ 100.54.
Q
SeMe. Procedure as described for QSMe,7 using 2-methylselenoaniline.
Anal. Calcd for C13H29NOSe: C, 64.60; H, 7.49; N, 3.59. Found: C,
64.55; H, 7.50; N, 3.52. 1H NMR (250 MHz, C6D6): δ 7.54 (dd, J = 7.6,
I
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solvent was removed to obtain a dark red, air-sensitive residue. Yields: 1,
68% (63 mg); 2, 77% (69 mg); 3, 70% (70 mg); 4, 82% (69 mg); 5, 86%
(78 mg); 6, 69% (64 mg); 7, 51% (54 mg); 8, 59% (61 mg); 9, 48% (55
mg).
Compound 1. Anal. Calcd (found) for 1, C31H41NORuS (576.78):
C, 64.22; H, 7.16; N, 2.43. Found: C, 65.20; H, 7.55; N, 2.59. 1H NMR
(250 MHz, C6D6): δ 7.37 (d, J3 = 2.2 Hz, 1H, Ar-H), 7.10 (m, 3H, Ar-
H), 6.84 (d, J3 = 2.1 Hz, 1H, Ar-H), 5.18 (d, J3 = 5.5 Hz, 1H, Cym-H),
5.04 (d, J3 = 5.5 Hz, 1H, Cym-H), 4.74 (d, J3 = 5.7 Hz, 1H, Cym-H), 4.70
(d, J3 = 5.8 Hz, 1H, Cym-H), 2.58 (sep, J = 2.2 Hz, 1H, CH(CH3)2) 1.88
(s, 9H, C(CH3)3), 1.87 (s, 3H, SCH3)), 1.56 (s, 3H, CH3), 1.32 (s, 9H,
C(CH3)3), 1.25 (d, J = 3.1 Hz, 3H, CH(CH3)2), 1.23 (d, J = 3.2 Hz, 3H,
CH(CH3)2). ESI-MS: m/z calcd for C31H41NORuS + H+ (found)
577.195 (577.195).
Compound 2. Anal. Calcd (found) for 2, C31H41NO2Ru (560.72): C,
1
66.40; H, 7.37; N, 2.50. Found: C, 66.70; H, 7.50; N, 2.49. H NMR
(250 MHz, C6D6): δ 7.35 (d, J = 2.2 Hz, 1H, Ar-H), 7.28 (dd, J = 7.6, 1.7
Hz, 1H, Ar-H), 7.10 (dd, J = 8.0, 1.7 Hz, 1H, Ar-H), 6.95 (dd, J = 7.5, 1.3
Hz, 1H, Ar-H), 6.91 (d, J = 2.2 Hz, 1H, Ar-H), 6.75 (dd, J = 8.1, 1.1 Hz,
1H, Ar-H), 5.05 (d, J = 5.6 Hz, 1H, Cym-H), 4.98 (d, J = 5.7 Hz, 1H,
Cym-H), 4.76 (d, J = 5.7 Hz, 1H, Cym-H), 4.64 (d, J = 5.7 Hz, 1H,Cym-
H), 3.18 (s, 3H, OCH3), 2.44 (sep, J = 6.6 Hz, 1H, CH(CH3)2), 1.86 (s,
9H, C(CH3)3), 1.62 (s, 3H, CH3), 1.33 (s, 9H, C(CH3)3), 1.19 (dd, J =
6.6 Hz, 6H, CH(CH3)2). ESI-MS: m/z calcd for C31H41NO2Ru + H+
(found) 561.220 (561.219).
Compound 3. Anal. Calcd (found) for 3, C31H41NORuSe (625.69):
C, 59.70; H, 6.63; N, 2.25. Found: C, 60.01; H, 6.77; N, 2.20. 1H NMR
(400 MHz, C6D6): δ 7.35 (d, J = 2.2 Hz, 2H, Ar-H), 7.11−7.00 (m, 4H,
Ar-H), 6.84 (d, J = 2.2 Hz, 2H, Ar-H), 5.21 (d, J = 5.6 Hz, 1H, Cym-H),
5.03 (d, J = 5.4 Hz, 1H, Cym-H), 4.75 (d, J = 5.8 Hz, 1H, Cym-H), 4.70
(d, J = 5.6 Hz, 1H, Cym-H), 2.60 (sept, 6.6 Hz, 1H, CH(CH3)2), 1.86 (s,
9H, C(CH3)3), 1.73 (s, 3H, SeCH3), 1.54 (s, 3H, Ar-CH3), 1.30 (s, 9H,
C(CH3)3), 1.24 (d, 6.6 Hz, 6H, CH(CH3)2), 1.21 (d, 6.6 Hz, 6H,
CH(CH3)2). ESI-MS: m/z calcd for C31H41NORuSe+ (found) 625.1
(625.2).
Compound 4. Anal. Calcd (found) for 4, C30H39NORu (530.70): C,
1
69.08; H, 8.08; N, 2.44. Found: C, 68.97; H, 8.07; N, 2.33. H NMR
(250 MHz, C6D6): δ 7.37 (d, J = 2.2 Hz, 1H, Ar-H), 7.29−7.16 (m, 2H,
Ar-H), 7.07 (dt, J = 4.7, 2.0 Hz, 1H, Ar-H), 7.03 (d, J = 2.1 Hz, 1H, Ar-
H), 4.97 (d, J = 6.0 Hz, 1H, Cym-H), 4.62 (d, J = 6.0 Hz, 1H, Cym-H),
2.38 (sep, J=6.9 Hz, 1H, CH(CH3)2), 1.88 (s, 9H, C(CH3)3), 1.50 (s,
3H, CH3), 1.30 (s, 9H, C(CH3)3), 1.14 (d, J = 6.9 Hz, 6H, CH(CH3)2),
ESI-MS: m/z calcd for C30H39NORu+ (found) 531.208 (531.208).
Compound 5. Anal. Calcd (found) for 5, C31H38F3NORu (598.69):
C, 63.63; H, 7.07; N, 2.18. Found: C, 63.17; H, 7.15; N, 2.17. 1H NMR
(250 MHz, C6D6): δ 7.60 (m, 1H, Ar-H), 7.37 (d, J = 2.1 Hz, 1H, Ar-H),
7.27 (d, J = 7.8 Hz, 1H, Ar-H), 7.23 (d, J = 8.6 Hz, 1H, Ar-H), 6.99 (t, J =
7.8 Hz, 1H, Ar-H), 6.90 (d, J = 2.1 Hz, 1H, Ar-H), 4.91 (m,2H, Cym-H),
4.59 (d, J = 5.7 Hz, 1H, Cym-H), 4.54 (d, J = 5.7 Hz, 1H, Cym-H), 2.31
(sept, J = 6.9 Hz, 1H, CH(CH3)2), 1.88 (s, 9H,C(CH3)3), 1.41 (s,
3H,CH3), 1.28 (s, 9H, C(CH3)3), 1.09 (d, J = 6.9 Hz, 6 H, CH(CH3)2).
ESI-MS: m/z calcd for C31H38F3NORu+ (found) 599.19 (599.19).
Compound 6. Anal. Calcd (found) for 6, C32H43NORu (558.75): C,
Figure 13. UV−vis−NIR spectroelectrochemical responses of 7 to its
one- and two-electron oxidations and reverse reductions in CH2Cl2/0.1
M Bu4NPF6 at 298 K (top) and 223 K (bottom). See the main text for an
explanation.
1
68.78; H, 7.76; N, 2.51. Found: C, 68.53; H, 7.85; N, 2.38. H NMR
(250 MHz, CD2Cl2): δ 7.41 (dd, J = 5.1, 4.1 Hz, 1H, Ar-H), 7.35−7.20
(m, 3H, Ar-H), 6.92 (d, J = 2.2 Hz, 1H, Ar-H), 6.34 (d, J = 2.1 Hz, 1H,
Ar-H), 5.42 (d, J = 5.7 Hz, 1H, Cym-H), 5.07 (d, J = 5.7 Hz, 1H, Cym-
H), 5.00 (d, J = 5.7 Hz, 1H, Cym-H), 2.80−2.65 (sep, 1H, CH(CH3)2),
2.52−2.33 (quint, 2H, Ar-CH2CH3), 1.54 (s, 9H, C(CH3)3), 1.43−1.31
(m, 6H, CH(CH3)2), 1.16−1.06 (m, 11H, Ar-CH2CH3 and C(CH3)3).
ESI-MS: m/z calcd for C32H43NORu+ (found) 559.24 (559.24).
Compound 7. Anal. Calcd (found) for 7, C31H41NOOsS (665.96):
C, 55.91; N, 6.21; H, 2.10. Found: C, 55.45; N, 6.21; H, 2.20. 1H NMR
(250 MHz, C6D6): δ 7.23 (d, J = 2.2 Hz, 1H, Ar-H), 7.06−6.99 (m, 4H,
Ar-H), 6.86 (d, J = 2.1 Hz, 1H, Ar-H), 5.67 (d, J = 5.4 Hz, 1H, Cym-H),
5.46 (d, J = 5.4 Hz, 1H, Cym-H), 5.25 (d, J = 5.4 Hz, 1H, Cym-H), 5.16
(d, J = 5.4 Hz, 1H, Cym-H), 2.49 (sep, J = 6.9 Hz, 1H, CH(CH3)2),
1.87−1.82 (m, J = 4.1 Hz, 12H, SCH3, C(CH3)3), 1.66 (s, 3H, Cym-
CH3), 1.33 (s, 9H, C(CH3)3), 1.24 (d, J = 3.2 Hz, 3H, CH(CH3)2), 1.21
1.4 Hz, 1H), 7.47 (d, J = 2.3 Hz, 1H), 7.02 (d, J = 2.7 Hz, 1H), 6.94−6.80
(m, 1H), 6.65−6.50 (m, 2H), 6.33 (s, 1H), 6.02 (s, 1H), 1.75 (s, 3H),
1.65 (s, 9H), 1.23 (s, 9H). 13C NMR (63 MHz, C6D6): δ 150.0, 148.0,
142.3, 136.1, 135.4, 129.9, 122.1, 122.0, 120.1, 117.5, 113.9, 35.0, 34.1,
31.4, 29.5, 7.8. 77Se (47.7 MHz, CD2Cl2): δ 94.9.
General Procedure for the Synthesis of 1−9. M2Cym2X4 (0.08
mmol) and H2Q (0.16 mmol)7 were dissolved in 10 mL of
dichloromethane/n-hexane (1/1). To this solution was added 0.5 mL
(3.5 mmol) of Et3N. The orange solution turned dark red immediately.
The reaction mixture was stirred for 1 h, and then the solvent was
evaporated under reduced pressure. The red residue was extracted into
100 mL of n-hexane and the solid Et3NHCl removed by filtration. The
J
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Table 5. UV−Vis Absorption Maxima λmax/nm (ε/M−1 cm−1) from Spectroelectrochemistry in CH2Cl2/0.1 M Bu4NPF6
compound
λmax/nm (ε/M−1 cm−1
)
1
344 (1870), 480 (11870)
1+
12+
2
298 (4470), 355 (4010), 552 (3860), 700−1000 (<670)
309 (3830), 404 (3040), 513 (5580), 674 (1680)
343 (11000), 481 (1650)
2+
22+
3
284 (7850), 343 (3580), 500 (4380), 540 (4090), 654 (2400), 700−1000 (<590)
294 (5080), 505 (5630)
343 (2350), 481 (12500)
3+
32+
4
296 (4960), 354 (4730), 542 (4490), 593 (3390), 700−1000 (<960)
392 (3630), 517 (7760), 709 (1150)
347 (1980), 478 (13610)
4+
42+
5
301 (4700), 367 (3550), 486 (6520), 700−1000 (<670)
305 (3750), 480 (6270), 636 (1590)
348 (2430), 480 (13810)
5+
52+
6
293 (5510), 358 (3860), 488 (7160), 700−1000 (<520)
304 (4140), 481 (7590), 641 (1110)
339 (2180), 478 (11000)
6+
62+
7
306 (2290), 356 (3840), 488 (5120), 700−1000 (<660)
379 (1920), 540 (5278)
395 (8240)
7+
72+
8
351 (4980), 535 (3650), 582 (4010), 700−1000 (<550)
397 (3760), 517 (8390)
391 (8260)
8+
82+
9
354 (3290), 518 (7580), 700−100 (<780)
364 (3860), 513 (5380)
395 (7810)
9+
92+
361 (3870), 526 (3600), 581 (4500), 700−1000 (<700)
398 (2940), 515 (8540)
(d, J = 3.2 Hz, 3H, CH(CH3)2). ESI-MS: m/z calcd for C31H41NOOsS+
(found) 667.25 (667.25).
Crystallography. Crystals suitable for X-ray diffraction were
prepared by slow crystallization from pentane or diethyl ether solutions
at −34 °C in the case of the neutral metal compounds and from benzene
at 8 °C for the cationic forms. Crystals of [10](PF6) suitable for X-ray
diffraction were obtained from a dichloromethane solution at 8 °C. X-
ray diffraction data were collected using a Bruker Kappa Apex2duo
diffractometer. The structures were solved and refined by full-matrix
least-squares techniques on F2 using the SHELX-97 program.28 The
absorption corrections were done by the multiscan technique or by
numeric means (see the Supporting Information). All non-hydrogen
atoms were refined anisotropically, except for the partially occupied split
F atom positions in the BArF anions. Hydrogen atoms were included in
the refinement process as per the riding model. The structures of
[1](BArF), [3](BArF), and [10](PF6) contain large voids which contain
highly disordered solvent molecules (benzene in the case of [1](BArF)
and [3](BArF) or dichloromethane in the case of [10](PF6)). Since the
solvent molecules could not be located, the PLATON/SQUEEZE
procedure29 was used. In the structure of 6 one of the two independent
molecules has an isopropyl group, which was modeled with 50%
occupied split positions (C139 and C140).
Compound 8. Anal. Calcd (found) for 8, C31H41NO2Os (649.89): C,
1
57.29; N, 6.36; H, 2.16. Found: C, 59.68; N, 7.45; H, 2.06. H NMR
(250 MHz, C6D6): δ 7.23−7.16 (m, J = 8.1, 2.0 Hz, 1H, Ar-H), 7.07−
6.99 (m, 1H, Ar-H), 6.93−6.84 (m, 1H, Ar-H), 6.73−6.66 (m, 1H, Ar-
H), 5.52 (d, J = 5.4 Hz, 1H. Cym-H), 5.40 (d, J = 5.4 Hz, 1H, Cym-H),
5.23 (d, J = 5.4 Hz, 1H, Cym-H), 5.07 (d, J = 5.4 Hz, 1H, Cym-H), 3.15
(s, 3H, OCH3), 2.31 (sep, J = 6.9, 1H, CH(CH3)2), 1.81 (s,9H,
C(CH3)3), 1.73 (s, 3H, CH3), 1.35 (s, 9H, C(CH3)3), 1.20−1.14 (m,
6H, CH(CH3)2). ESI-MS: m/z calcd for C31H41NO2Os+ (found)
651.27 (651.27).
Compound 9. Anal. Calcd (found) for 9, C31H41NOOsSe (712.85):
C, 52.23; N, 5.81; H, 1.96. Found: C, 51.79; N, 5.74; H, 1.90. 1H NMR
(250 MHz, C6D6): δ 7.27 (d, J = 2.2 Hz, 1H, Ar-H), 7.03 (m, 4H, Ar-H),
6.93 (d, J = 2.2 Hz, 1H, Ar-H), 5.76 (d, J = 5.4 Hz, 1H, Cym-H), 5.48 (d,
J = 5.4 Hz, 1H, Cym-H), 5.31 (d, J = 5.5 Hz, 1H, Cym-H), 5.18 (d, J = 5.4
Hz, 1H, Cym-H), 2.53 (sept, J = 13.7, 6.8 Hz, 1H, CH(CH3)2), 1.87 (s,
9H, C(CH3)3), 1.66 (d, J = 3.5 Hz, 6H, SeCH3), 1.38 (d, J = 3.2 Hz, 9H,
C(CH3)3), 1.31−1.23 (m, 6H, CH(CH3)2). ESI-MS: m/z calcd for
C31H41NOOsSe+ (found) 715.19 (715.19).
DFT Calculations. The electronic structures of the complexes
[Ru(Cym)Q]n and [Os(Cym)Q]n in the neutral and the monooxidized
states were calculated by density functional theory (DFT) methods
using the Gaussian 0930 (G09) program package.
[1](BArF). A 75 mg amount (0.13 mmol) of 1 was dissolved in
CH2Cl2 (8 mL). To this solution was added Fc(BArF) (0.13 mmol, 133
mg).12c The red solution turned purple immediately and was
subsequently stirred for 1 h at room temperature. The solvent was
removed, and the purple solid was washed three times with 6 mL of n-
hexane. The complex was dissolved in diethyl ether, precipitated with
hexane, and filtered. The complex was crystallized from benzene at 8 °C.
Anal. Calcd for C63H53BF24NORuS (1440.00): C, 52.55; N, 0.97; H,
3.71; S, 2.23. Found: C, 52.42; N, 1.04; H, 3.69; S, 2.36. ESI-MS: m/z
Within the G09 calculations, quasi-relativistic effective core
pseudopotentials and the corresponding optimized set of basis functions
for Ru and Os31 and 6-311G(d) polarized triple-ζ basis sets32 for the
remaining atoms were employed. G09 calculations employed the hybrid
exchange and correlation functional by Perdew, Burke, and
Ernzerhof.33,34 The solvent was described by the polarizable calculation
model (PCM).35 The geometry optimizations were performed both in
vacuo and with PCM correction. Geometry optimizations were followed
by vibrational analysis; no imaginary frequencies were found for the
optimized structures. Electronic excitations were calculated by the time-
dependent DFT (TD DFT) method.
−
calcd for C31H41NORuS+ (found): 577.20 (577.20) and C32H12BF24
(found): 863.06 (863.07).
[3](BArF). The procedure was analogous to that for [1](BArF), using
3. Anal. Calcd for C63H53BF24NORuSe (1486.90): C, 50.89; N. 0.94; H,
3.59. Found: C, 51.18; N, 0.89; H, 3.70. ESI-MS: m/z calcd for
C31H41NORuSe+ (found): 625.1 (625.1).
K
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(2) (a) Kaim, W. Inorg. Chem. 2011, 50, 9752. (b) Praneeth, V. K. K.;
Ringenberg, M. R.; Ward, T. R. Angew. Chem. 2012, 124, 10374; Angew.
Chem., Int. Ed. 2012, 51, 10228.
(3) Poddel’sky, A. I.; Cherkasov, V. K.; Abakumov, G. A. Coord. Chem.
Rev. 2009, 253, 291.
(4) (a) Ringenberg, M. R.; Nilges, M. J.; Rauchfuss, T. B.; Wilson, S. R.
Organometallics 2010, 29, 1956. (b) Ringenberg, M. R.; Rauchfuss, T. B.
Eur. J. Inorg. Chem. 2012, 490.
ASSOCIATED CONTENT
■
S
* Supporting Information
CIF files giving crystallographic data for [Ru(Cym)(QSMe)],
[Ru(Cym)(QSMe)]+, [Ru(Cym)(QOMe)], [Ru(Cym)(QSeMe)],
[Ru(Cym)(QSeMe)]+, [Ru(Cym)(QH)], [Ru(Cym)(Q3‑CF3)],
and [Ru(Cym)(QEt)], crystallographic data (Table S1), selected
atom−atom distances (Å) and dihedral angles (deg) in
[Ru(Cym)Q]n complexes, comparison of experimental and
DFT calculated results (Table S2), selected bond lengths (Å)
and dihedral angles (deg) in complex 5, comparison of
experimental and DFT calculated results (Table S3), DFT
calculated selected atom−atom distances (Å) and dihedral angles
(deg) in osmium complexes (Table S4), crystallographic and
refinement data of [Ru(QSMe)2](PF6) (Table S5), bond
parameters for 10+ and 10 (Table S6), DFT (G09/PBE0/
PCM) calculated spin densities in oxidized Ru and Os complexes
(Table S7), molecular structure of 3 in the crystal (Figure S1),
molecular structure of 5 in the crystal (Figure S2), molecular
structure of 6 in the crystal (one of two independent molecules)
(Figure S3), structure of [1](BArF) in the crystal (Figure S4),
different orientations of the p-cymene ligand in the crystals of 4,
2, and 1 (Figure S5), molecular structure of [Ru(QSMe)2](PF6)
([10](PF6)) in the crystal (Figure S6), cyclic voltammograms of
2 in 0.1 M Bu4NPF6/CH2Cl2 at different scan rates (253 K)
(Figure S7), cyclic voltammograms of 5 in 0.1 M Bu4NPF6/
CH2Cl2 (top) and 0.1 M Bu4NPF6/CH3CN (bottom) (Figure
S8), cyclic voltammograms of 6 in 0.1 M Bu4NPF6/CH2Cl2
(top) and 0.1 M Bu4NPF6/CH3CN (bottom) (Figure S9),
differential pulse voltammogram of 1 in 0.1 M Bu4NPF6/
CH2Cl2, scan rate 100 mV/s (Figure S10), UV−vis spectroelec-
trochemical response of 4 in 0.1 M Bu4NPF6/CH2Cl2 at 298 K
(Figure S11), UV−vis−NIR spectroelectrochemical response of
5 in 0.1 M Bu4NPF6/CH2Cl2 at 298 K (Figure S12), UV−vis
spectroelectrochemical response of 7 in 0.1 M Bu4NPF6/CH2Cl2
at 223 K (Figure S13), cyclic voltammograms (left) of 1 at
different scan rates in 0.1 M Bu4NPF6/CH2Cl2 and the Cottrell
plot (right) (Figure S14), and an xyz file for the calculated
structures in the paper. This material is available free of charge via
the Internet at http://pubs.acs.org.
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AUTHOR INFORMATION
̌
k, A., Jr. Inorg.
■
Corresponding Authors
*E-mail for F.H.: f.hartl@reading.ac.uk.
*E-mail for W.K.: kaim@iac.uni-stuttgart.de.
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Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS
■
Support from the Land Baden-Wurttemberg and the EU COST
̈
action programme CM1202 is gratefully acknowledged. S.Z.
thanks the Ministry of Education of the Czech Republic (grant
LD14129) for support. Q.Z. and F.H. acknowledge EPSRC
funding (grant EP/K00753x/1) for the development of the
Spectroelectrochemistry Laboratory in Reading. We also thank
Dr. Wolfgang Frey (Stuttgart) for crystallographic measure-
ments.
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