Reversible intramolecular single-electron oxidative addition involving a hemilabile noninnocent ligand

Article abstract of DOI:10.1021/om100969q

Using the noninnocent ligand Q [= 4,6-di-tert-butyl-(2- methylthiophenylimino)-o-benzoquinone] with a thioether group as potential coordination function, it has been possible to substantiate a single-electron transfer induced oxidative addition within the

Full text of DOI:10.1021/om100969q

ARTICLE
pubs.acs.org/Organometallics
Reversible Intramolecular Single-Electron Oxidative Addition
Involving a Hemilabile Noninnocent Ligand
Ralph H€ubner,† Sebastian Weber,† Sabine Strobel,† Biprajit Sarkar,† Stanislav Zꢀaliꢁs,‡ and Wolfgang Kaim*,†
†Institut f€ur Anorganische Chemie, Universit€at Stuttgart, Pfaffenwaldring 55, D-70550 Stuttgart, Germany
‡J. Heyrovskꢀy Institute of Physical Chemistry, v.v.i., Academy of Sciences of the Czech Republic, Dolejꢁskova 3, CZ-18223 Prague,
Czech Republic
S Supporting Information
b
ABSTRACT: Using the noninnocent ligand Q [= 4,6-di-tert-
butyl-(2-methylthiophenylimino)-o-benzoquinone] with
a
thioether group as potential coordination function, it has been
possible to substantiate a single-electron transfer induced
oxidative addition within the complex [IrCp*Q]0/þ (Cp* =
C5Me5) via structural characterization (catecholato f semi-
quinonato transition coupled with reversible SfIr coor-
dination), via cyclic voltammetry, EPR, and DFT (semiquin-
one formulation with about 8% Ir participation). The intramolecular rearrangement of the 16-electron precursor [IrCp*Q] triggered
by electron removal illuminates the complementary activities of the substrate binding metal and the electron-buffering ligand as was
recently employed by Ringenberg et al. in dihydrogen activation (Organometallics 2010, 29, 1956).
’ INTRODUCTION
to react in the radical state (n = 1) with H2 to produce Hþ. In
contrast, the related complex [IrCp*(RNCHCHNR)], R = 2,6-
dimethylphenyl, cannot be oxidized completely reversibly under
these conditions, i.e., in CH2Cl2.9 To understand this reactivity,
we have now prepared [IrCp*Q] and its oxidized form
[IrCp*Q](PF6) and studied their structures and spectroscopic
and electrochemical properties.
The oxidative addition-reductive elimination sequence con-
tinues to be one of the most useful and most frequently applied
reaction patterns in transition metal chemistry.1 Metal-based
electron configuration changes such as the d8/d6 two-electron
interchange have been employed to provide very different
coordination situations for substrate binding, conversion, and
release.2
Noninnocent3 ligands, which provide an electron reservoir,
have been employed lately not only for spectroscopic studies4
but also in schemes involving chemical transformations.5,6
Among such ligands, the 1,2-dioxolene (o-quinone/catecholate)
redox system has been favored due to its stability (via chelate
binding) and variability (e.g., substitution of O by NR functions
and of H through substituents).4-6 While the aromatic catecho-
late forms are σ- and π-electron rich, the semiquinones and
especially the quinones are π-electron accepting.
’ RESULTS AND DISCUSSION
Separately prepared and characterized [IrCp*Q] and its
oxidized form [IrCp*Q](PF6) were found to be connected via
an irreversible processs before a reversible second oxidation for
the couple [IrCp*Q]2þ/þ takes place (Figures 1 and S1, S2).
Structural evidence, supported by DFT calculations, was then
obtained to clarify this reactivity: The neutral [IrCp*Q]
(Figure 2) exhibits coordinative unsaturation (16 valence elec-
tron situation) because the electron deficit at the trivalent metal
is mitigated by strong σ- and π-electron donation from what is
clearly an iminocatecholate ligand with average and little variable
C-C distances of about 1.39 Å in the aromatic ring (Table 1).
Such coordinative unsaturation for d6 systems has been found
also for the related [IrCp*Q0]6 and [IrCp*(RNCHCHNR)]9 as
well as for RhCp*(cat), [Cr(CO)3(cat)]2-, and [Mn(CO)3(cat)]-
(cat = catecholate).10 Consequently, there is no bonding inter-
action between Ir and S at 4.0033(7) Å distance, and the metric
Herein we describe an established6,7 organometallic species,
pentamethylcyclopentadienyliridium(III), [IrCp*]2þ, in connec-
tion with a potentially tridentate noninnocent ligand Q [= 4,
6-di-tert-butyl-(2-methylthiophenylimino)-o-benzoquinone].
This ligand was shown8 to form a semiquinone that can provide a
thioether sulfur donor for additional coordination. In a bis-
(semiquinone)copper(II) complex Cu(Q)2 this has led to
structural effects modulating the intramolecular three-spin interac-
tion.8 The related 4,6-di-tert-butyl-(2-trifluoromethylphenylimino)-
o-benzoquinone Q0 was presented recently in connection with
[IrCp*]2þ in a system displaying redox-switched oxidation of
H2.6 That reversibly oxidizable system [IrCp*(Q0)]nþ was shown
Received: October 6, 2010
Published: February 22, 2011
r
2011 American Chemical Society
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|

Organometallics
ARTICLE
Figure 1. Cyclic voltammograms of [IrCp*Q] (ca. 10-3 M) in 0.1 M
Bu4NPF6/CH2Cl2 at 15, 25, 50, 75, 100, 125, 150, 175, 200, 225, and
250 mV/s scan rate vs Fcþ/0 (quasi-steady-state voltammograms). Peak
potentials in V vs Fcþ/0 at 100 mV/s: Epa = -0.06, þ0.30; Epc = þ0.23,
-0.50 V.
Figure 3. Molecular structure of the cation in the crystal of
[IrCp*Q](PF6) CH2Cl2.
3
Figure 4. Electronic paramagnetic resonance spectrum and simulation
of [IrCp*Q](PF6) in CH2Cl2 at 110 K (9.5 GHz). Simulation was
carried out using the data from the text.
g3 = 1.951, the latter with notable 14N hyperfine splitting of
1.7 mT (Figure 4). This observation reveals non-negligible metal
contributions (DFT: about 8%, see below) from iridium with its
high spin-orbit coupling constant, but otherwise an anion
radical complex,12 corresponding to a semiquinone/IrIII
description.9 UV-vis spectroelectrochemistry shows absorption
features (Figure S3) that agree with those of previously described
analogues.6,9 Apparently, the one-electron oxidation of the
iminocatecholate to the iminobenzosemiquinonate is already
sufficient to remove the tolerance of coordinative unsaturation
in the 16 valence electron species, resulting in binding of either
weakly donating thioether-S, dihydrogen,6 or halogen species.9
Scheme 1 illustrates the square scheme for the present case,
showing calculated structures and energy differences. The calcu-
lations confirm that this indirect oxidative addition at the metal
involving one-electron exchange1,13 on the ligand is made possible
through the participation of a noninnocently behaving3b ligand
while maintaining a formally invariant metal oxidation state.
Two stable configurations, A, corresponding to N,O coordi-
nation, and B, characterized by N,O,S coordination, were found
by DFT (G09/PBE0) geometry optimization for both neutral
and oxidized [IrCp*Q]nþ (Scheme 1). The forms corresponding
to the experimental structures (A, Bþ) have the lowest energies.
The free energy differences, ΔG, are 0.500 and 0.191 eV in the
case of the neutral (A, B) and oxidized forms (Aþ, Bþ),
respectively. The DFT-optimized bond lengths and angles of
neutral [IrCp*Q] and its radical cation agree with the experi-
mental crystal structures (Table 2).
Figure 2. Molecular structure of [IrCp*Q] in the crystal.
Table 1. Selected Atom-Atom Distances [Å] for Complexes
[IrCp*Q]
[IrCp*Q]þa
Ir-S
4.0033(7)
2.3754(15)
Ir-N
Ir-O
N-C6
O-C1
C-Cb
1.947(2)
2.062(4)
2.010(2)
2.072(4)
1.396(4)
1.366(7)
1.337(3)
1.318(6)
1.386(4)-1.407(4)
a In the crystal of [IrCp*Q](PF6) CH2Cl2. b Intraring distances of Q.
1.364(7)-1.448(8)
3
parameters of the ligand reveal not only an aromatic ring but also
C-O and C-N single bonds (Table 1).
On one-electron oxidation, the structure rearranges character-
istically (Figure 3): Iridium-sulfur coordination occurs with a
standard11 bond length of 2.354(15) Å, leading to coordinative
saturation (piano-stool configuration). The dihedral angle be-
tween the two C6 rings decreases from 89° to 56° in the cation.
The metric parameters of the noninnocent ligand reveal bond
alternacy within the benzo-semiquinone ring as well as shortened
C-O and C-N bonds (Table 1). ESR spectroscopy shows DFT
confirmed g tensor components at g1 = 1.996, g2 = 1.985, and
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Organometallics
ARTICLE
Scheme 1. DFT-Calculated Structural Changes Involving
Electron Transfer Effected S(thioether) Coordination
(Hysteresis)a
Figure 5. Spin density plots for the two configurations Bþ (left) and Aþ
(right) of the radical complex cation [IrCp*Q]þ.
the paramagnetic intermediate can bind not only weakly donat-
ing thioether-S as shown here but also H26 or halogen species.9
Under electrochemical aspects, the different reversibility pat-
terns for the two-step oxidation processes are remarkable: While
the [IrCp*Q0]n system exhibits two conventional waves in the
cyclic voltammogram,6 the [IrCp*(RNCHCHNR)]n redox sys-
tem with R = 2,6-dimethylphenyl showed a reversible first but
irreversible second oxidation in propylene carbonate.9 In yet
another variant, the example [IrCp*Q]0/þ/2þ described here is
distinguished by an irreversible first oxidation process involving
fast intramolecular thioether coordination after initial electron
transfer. On the return scan in the cyclic voltammogram, the
wave at about -0.5 V is due to reduction of N,O,S-coordinated
[IrCp*Q]þ, which can also undergo a fully reversible one-
electron oxidation (Bþ/B2þ) to the [IrCp*Q]2þ state at 0.26 V.
a The ΔG differences between A and B configurations are 0.500 eV
(neutral forms) and 0.191 eV (cations).
Table 2. Comparison of Selected Experimental and DFT-
Calculated Bond Lengths (Å) and Angles (deg) for
[IrCp*Q]nþ, n = 0, 1a
n = 0
n = 1
’ EXPERIMENTAL SECTION
exptl
calcd
calcd
exptl
calcd
calcd
conf A conf B
conf B conf A
Materials. CH2Cl2 and CD2Cl2 were dried over CaH2; hexane was
dried over sodium. All solvents were degassed and placed under vacuum
before use. [Cp*IrCl2]2 and AgPF6 were purchased from Strem;
2-methylthioaniline and 3,5-di-tert-butylcatechol were purchased from
Aldrich and used without further purification. 3,5-Di-tert-butyl-2-hydro-
xy-1-(2-methylthioanilido)benzene (H2Q) was prepared from
2-methylthioaniline and 3,5-di-tert-butylcatechol.14
Ir-N
Ir-O
Ir-S
1.947(2)
2.010(2)
1.951 2.056 2.062(4)
1.987 2.072 2.072(4)
2.064 2.003
2.062 2.026
4.0033(7) 3.885 2.339 2.3754(15) 2.406 3.939
b
Ir-Ccp
2.153
2.155 2.171 2.173
78.74 77.65 77.61(17)
83.20 77.47(14)
2.166 2.150
76.72 78.42
77.30
N-Ir-O
N-Ir-S
79.24(8)
Instrumentation. UV/vis spectra including spectroelectrochem-
istry were recorded on a TIDAS diode array spectrometer using an
O-Ir-S
92.48 97.85(11)
97.93
1
OTTLE cell. H NMR spectra were measured on a Bruker AV 250
relative free
0.000 0.500
0.000 0.191
spectrometer. EPR spectra were measured on a Bruker ESP 300 system
at 9.5 GHz. Cyclic voltammograms were recorded as described below.
Syntheses. [IrCp*Q]. A solution of 80 mg (0.1 mmol) of
[Cp*IrCl2]2 and 68 mg (0.2 mmol) of H2Q26 in 25 mL of CH2Cl2
was stirred. After 5 min an excess of K2CO3 (500 mg) was added, and the
reaction was stirred for 48 h at room temperature, during which the
solution turned from yellow to orange. The orange solution was filtered
to remove excess K2CO3, and the solvent was removed under reduced
pressure, resulting in an orange solid. The air-stable solid was triturated
with 10 mL of hexane, and the mixture was filtered through a medium-
porosity frit. This process was repeated four times in order to ensure
removal of excess H2Q. Residual solvent was removed by evacuation at
0.01 mmHg for 12 h at 80 °C. Yield: 120 mg (1.80 mmol, 90%). Anal.
Calcd for C31H42IrNOS (found): C, 55.66 (55.59); H, 6.33 (6.28); N,
2.09 (2.05). 1H NMR (CD2Cl2): δ 1.14 (s, 9H), 1.54 (s, 9H), 1.71 (s,
15H), 6.28 (d, 1H), 6.75 (d, 1H), 7.08 (d, 1H), 7.23 (t, 1H), 7.26 (t,
1H), 7.30 (d, 1H). ESI-MS: m/z = 669.12 (Mþ). UV-vis (CH2Cl2):
450 (ε = 1.4 ꢀ 104 M-1 cm-1), 291 (sh) nm.
energy (eV)
a Configuration A corresponds to N,O coordination and configuration B
to N,O,S coordination. b Symmetry averaged.
Figure 5 depicts spin densities for configurations Aþ and Bþ of
[IrCp*Q]þ. ADF/BP86 calculations for B yield a metal spin
density of 0.084 and negligible spin density at Cp*. This approach
yields g tensor components of g1 = 2.0028, g2 = 1.9878, and g3 =
1.9541, in good agreement with experimental values of g1 =
1.996, g2 = 1.985, and g3 = 1.951. Calculated hyperfine coupling
values for 14N are A1 = 0.02 mT, A2 = 0.03 mT, and A3 = 1.47 mT.
Summarizing, the results observed for the structurally char-
acterized redox pair [IrCp*Q]0/þ, connected via an irreversible
processs, have demonstrated how an indirect oxidative addition
at the metal coupled with a one-electron exchange on the ligand
can occur via participation of a noninnocently behaving ligand
while the metal oxidation state remains invariant. Remarkably,
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Organometallics
ARTICLE
Table 3. Crystallographic Parameters
(SHELXL-97).17 All non-hydrogen atoms in the structures were refined
with anisotropic displacement parameters. Selected crystal data and
structure refinement details for both compounds are given in Table 3.
Quantum Chemical Calculations. The electronic structures of
[IrCp*Q] and of its oxidized form were calculated by density functional
theory (DFT) methods using the Gaussian 0918 and Amsterdam
Density Functional (ADF2009.01)19,20 program packages.
[IrCp*Qy]
[IrCp*Q](PF6) CH2Cl2
3
formula
fw
C31H42IrNOS
668.92
C32H44Cl2F6IrNOPS
898.81
cryst syst
space group
a (Å)
monoclinic
P21/c
monoclinic
P21/n
G09 calculations employed the Perdew, Burke, Ernzerhof21,22 PBE0
hybrid functional (G09/PBE0). The geometry of the cationic form was
calculated by the UKS approach. Geometry optimization was followed
by vibrational analysis. For H, C, O, S, and N atoms polarized triple-ζ
basis sets 6-311G(d) were used,23 together with quasirelativistic effective
core pseudopotentials and a corresponding optimized set of basis
functions for Ir.24,25
10.71340(10)
22.2774(3)
13.2353(2)
113.096(1)
2905.64(6)
4
9.67850(10)
11.6660(4)
31.090(2)
96.01(1)
3491.1(2)
4
b (Å)
c (Å)
β (deg)
V (Å3)
Z
Within the ADF program Slater-type orbital (STO) basis sets of
triple-ζ quality with two polarization functions for Ir, C, N, O, and S
atoms and of double-ζ quality with one polarization function for the H
atoms were employed. Inner shells were represented by the frozen core
approximation (1 s for C, N, and O, 2p for S, and 1s-4d for Ir were kept
frozen) within calculations of the g tensor; core electrons were included
in the calculation of the A tensor. Within ADF the functional including
Becke’s gradient correction to the local exchange expression in conjunc-
tion with Perdew’s gradient correction to local density approximation
(LDA) with VWN parametrization of electron gas data was used (ADF/
BP86).26,27 A and g tensors were obtained by first-order perturbation
theory from a ZORA Hamiltonian in the presence of a time-independent
magnetic field.28,29 The g tensor was obtained from a spin-nonpolarized
wave function after incorporating the spin-orbit (SO) coupling.
F(000)
Dcalced (g cm-3
μ(Mo KR) (mm-1
cryst size (mm)
temp (K)
1344
1788
)
1.529
1.710
)
4.690
4.142
0.09 ꢀ 0.06 ꢀ 0.04 0.35 ꢀ 0.33 ꢀ 0.1
100(2)
100(2)
θ limits (deg)
index ranges
2.28 - 28.38
-14 e h e 14
-29 e k e 29
-17 e k e 17
14 102
1.32 - 27.83
-12 e h e 12
-15 e k e 15
-40 e k e 40
15 187
no. of collected reflns
no. of unique reflns
7238
8201
no. of reflns with I > 2σ(I) 5917
5499
no. of params/restraints
GOF (on F2)
317/0
407/0
1.039
0.986
’ ASSOCIATED CONTENT
R1 (on F, I > 2σ(I))
wR2 (on F2, all data)
0.0255
0.0469
S
Supporting Information. X-ray crystallographic files in
0.0512
0.1096
b
max./min. ΔF (e Å-3
)
1.411/-0.980
1.311/-2.679
CIF format for [IrCp*Q] and [IrCp*Q](PF6) CH2Cl2, cyclo-
3
voltammograms, and spectroelectrochemical results. This ma-
terial is available free of charge via the Internet at http://pubs.acs.
org.
[IrCp*(Q)](PF6). A solution of 100 mg (0.15 mmol) of [IrCp*Q] in 5
mL of CH2Cl2 was added to a suspension of 38 mg (0.15 mmol) of
AgPF6 in 15 mL of CH2Cl2. An immediate color change from orange to
dark was observed. After 3 h of stirring, the reaction mixture was filtered
through Celite 500 to remove precipitated silver. The solvent was
evaporated from the filtrate, and the resulting solid triturated with 20
mL of hexane. The hexane was then removed via a filter cannula fitted
with a G6 glass fiber filter. This precipitation process was repeated until
the oily residue converted to a brown powder. Residual solvent was
removed by evacuation at 0.01 mmHg for 12 h. Yield: 105 mg (85%).
Anal. Calcd for C31H42F6IrNOPS (found): C, 45.75 (45.65); H, 5.20
(5.23); N, 1.72 (1.74). ESI-MS: m/z = 813.95 (Mþ). UV-vis
(CH2Cl2): 850 (ε = 0.8 ꢀ 103 M-1 cm-1), 620 (sh) 500 (5 ꢀ 103),
355 (5.5 ꢀ 103) 300 (6 ꢀ 103) nm. Single crystals were obtained by slow
evaporation of solutions in CH2Cl2 ([IrCp*Q]) or CH2Cl2/hexane
’ AUTHOR INFORMATION
Corresponding Author
*E-mail: kaim@iac.uni-stuttgart.de.
’ ACKNOWLEDGMENT
Support from the Deutsche Forschungsgemeinschaft, the EU
(COST D35), the Grant Agency of the Academy of Sciences of
the Czech Republic (KAN 100400702), and the Ministry of
Education of the Czech Republic (Grant No. LD 11086) is
gratefully acknowledged.
(3:1) ([IrCp*Q](PF6) CH2Cl2).
3
Electrochemical Experiments. A 10-3 M solution of [IrCp*Q] in 5
mL of CH2Cl2 was prepared and saturated with Ar for cyclic voltam-
metry analysis using a M 273 A potentiostat from EG&G. The setup was
a platinum working electrode, a platinum wire counter electrode, a Ag/
Agþ reference electrode, and 0.1 M Bu4NPF6 as a supporting electrolyte.
The Fc/Fcþ couple was used as internal standard.
’ REFERENCES
(1) Crabtree, R. H. The Organometallic Chemistry of the Transition
Metals, 5th ed.; Wiley: Weinheim, 2009; Chapter 6.
(2) Cornils, B.; Herrmann, W. A., Eds. Applied Homogeneous Cata-
lysis with Organometallic Compounds, 2nd ed.; Wiley-VCH: Weinheim
(Germany), 2002.
(3) (a) Jorgensen, C. K. Coord. Chem. Rev. 1966, 1, 164. (b) Ward,
M. D.; McCleverty, J. A. J. Chem. Soc., Dalton Trans. 2002, 275.
(4) (a) Kaim, W.; Wanner, M.; Kn€odler, A.; Zꢀaliꢁs, S. Inorg. Chim.
Acta 2002, 337, 163. (b) J€ustel, T.; Bendix, J.; Metzler-Nolte, N.;
Weyherm€uller, T.; Nuber, B.; Wieghardt, K. Inorg. Chem. 1998,
37, 35. (c) Haga, M.; Dodsworth, E. S.; Lever, A. B. P. Inorg. Chem.
1986, 25, 447.
Spectroelectrochemistry. UV-vis spectroelectrochemistry was
measured in an OTTLE15 (optically transparent thin-layer electrolytic
cell) using CH2Cl2 and Bu4NPF6 as supporting electrolyte. The
measurements were carried out with a TIDAS diode array spectrometer.
Crystal Structure Determination. The samples were studied on a
Bruker-Nonius Kappa CCD with graphite-monochromatized Mo KR
(0.71073 Å) radiation. The structures were solved by direct methods
using SHELXL-9716 and refined using full-matix least-squares on F2
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ARTICLE
(5) (a) Blackmore, K. J.; Ziller, J. W.; Heyduk, A. F. Inorg. Chem.
2005, 4, 5559. (b) Mason, R. H.; Heyduk, A. F. J. Am. Chem. Soc. 2006,
128, 8410. (c) Boyer, J. L.; Cundari, T. R.; DeYonker, N. J.; Rauchfuss,
T. B.; Wilson, S. R. Inorg. Chem. 2009, 48, 638.
(6) (a) Ringenberg, M. R.; Kokatam, S. L.; Heiden, Z. M.; Rauchfuss,
T. B. J. Am. Chem. Soc. 2008, 130, 788. (b) Ringenberg, M. R.; Nilges,
M. J.; Rauchfuss, T. B.; Wilson, S. R. Organometallics 2010, 29, 1956.
(7) Ogo, S.; Uehara, K.; Abura, T.; Watanabe, Y.; Fukuzumi, S. J. Am.
Chem. Soc. 2004, 126, 16520.
(8) Ye, S.; Sarkar, B.; Lissner, F.; Schleid, Th.; van Slageren, J.;
Fiedler, J.; Kaim, W. Angew. Chem. 2005, 117, 2140; Angew. Chem., Int.
Ed. 2005, 44, 2103.
(9) Kaim, W.; Sieger, M.; Greulich, S.; Sarkar, B.; Fiedler, J.; Zꢀaliꢁs, S.
J. Organomet. Chem. 2010, 695, 1052.
(10) (a) Espinet, P.; Bailey, P. M.; Maitlis, P. M. J. Chem. Soc., Dalton
Trans. 1979, 1542. (b) Darensbourg, D. J.; Klausmeyer, K. K.; Reibens-
pies, J. H. Inorg. Chem. 1995, 34, 4676. (c) Hartl, F.; Vlꢁcek, A., Jr.;
deLearie, L. A.; Pierpont, C. G. Inorg. Chem. 1990, 29, 1073. (d) Hartl.,
F.; Stufkens, D. J.; Vlꢁcek, A. Inorg. Chem. 1992, 31, 1687.
(11) Heilmann, O.; Hornung, F. M.; Fiedler, J.; Kaim, W.
J. Organomet. Chem. 1999, 589, 2.
(12) Kaim, W. Coord. Chem. Rev. 1987, 76, 187.
(13) Tejel, C.; Ciriano, M. A.; Lꢀopez, J. A.; Jimꢀenez, S.; Bordonaba,
M.; Oro, L. A. Chem.—Eur. J. 2007, 13, 2044.
(14) Ye, S.; Sarkar, B.; Lissner, F.; Schleid, T.; van Slageren, J.;
Fiedler, J.; Kaim, W. Angew. Chem., Int. Ed. 2005, 44, 2103.
(15) Krejcik, M.; Danek, M.; Hartl, F. J. Electroanal. Chem. 1991,
317, 179.
(16) Sheldrick, G. M. Acta Crystallogr. 2008, A64, 112.
(17) Sheldrick, G. M. SHELXL-97: Program for Crystal Structure
Determination; University of G€ottingen: Germany, 1997.
(18) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.;
Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci, B.;
Petersson, G. A.; Nakatsuji, H.; Caricato, M.; Li, X.; Hratchian, H. P.;
Izmaylov, A. F.; Bloino, J.; Zheng, G.; Sonnenberg, J. L.; Hada, M.;
Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima,
T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven, T.; Montgomery, J. A., Jr.;
Peralta, J. E.; Ogliaro, F.; Bearpark, M.; Heyd, J. J.; Brothers, E.; Kudin,
K. N.; Staroverov, V. N.; Kobayashi, R.; Normand, J.; Raghavachari, K.;
Rendell, A.; Burant, J. C.; Iyengar, S. S.; Tomasi, J.; Cossi, M.; Rega, N.;
Millam, J. M.; Klene, M.; Knox, J. E.; Cross, J. B.; Bakken, V.; Adamo, C.;
Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.;
Cammi, R.; Pomelli, C.; Ochterski, J. W.; Martin, R. L.; Morokuma, K.;
Zakrzewski, V. G.; Voth, G. A.; Salvador, P.; Dannenberg, J. J.; Dapprich,
S.; Daniels, A. D.; Farkas, O.; Foresman, J. B.; Ortiz, J. V.; Cioslowski, J.;
Fox, D. J. Gaussian 09, Revision A.02; Gaussian, Inc.: Wallingford, CT,
2009.
(19) te Velde, G.; Bickelhaupt, F. M.; van Gisbergen, S. J. A.; Fonseca
Guerra, C.; Baerends, E. J.; Snijders, J. G.; Ziegler, T. J. Comput. Chem.
2001, 22, 931.
(20) ADF2009.01; SCM, Theoretical Chemistry, Vrije Universiteit:
Amsterdam, The Netherlands, http://www.scm.com.
(21) Perdew, J. P.; Burke, K.; Ernzerhof, M. Phys. Rev. Lett. 1996,
77, 3865.
(22) Adamo, C.; Barone, J. Chem. Phys. 1999, 110, 6158.
(23) Curtiss, L. A.; McGrath, M. P.; Blaudeau, J.-P.; Davis, N. E.;
Binning, R. C., Jr.; Radom, L. J. Chem. Phys. 1995, 103, 6104.
(24) Andrae, D.; Haussermann, U.; Dolg, M.; Stoll, H.; Preuss, H.
Theor. Chim. Acta 1990, 77, 123.
(25) Martin, J. M. L.; Sundermann, A. J. Chem. Phys. 2001, 114, 3408.
(26) Becke, A. D. Phys. Rev. A 1988, 38, 3098.
(27) Perdew, J. P. Phys. Rev. B 1986, 33, 8822.
(28) van Lenthe, E.; van der Avoird, A.; Wormer, P. E. S. J. Chem.
Phys. 1997, 107, 2488.
(29) van Lenthe, E.; van der Avoird, A.; Wormer, P. E. S. J. Chem.
Phys. 1998, 108, 4783.
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