A new thioether-based (N2S2)copper(II/I) complex exhibiting a high redox potential

Article abstract of DOI:10.1002/ejic.200300073

From the new ligand bis[2-(tert-butylthio)benzyl](2-pyridyl-methyl)amine [N₂(StBu)₂], the corresponding complexes [Cu^I{N₂(StBu)₂}]CF₃SO₃ (1) and [Cu^II{N₂(StBu)₂}] (H₂O)-(CF₃SO₃)]CF₃SO₃ (2) were synthesized and characterized by X-ray crystallography. The Cu-S bonds are unusually shortened in 1 and elongated for the axial thioether in 2. Redox studies show that 1 and 2 interconvert during the electron transfer with a high Cu^II/I potential of 0.79 V vs. SCE in CH₂Cl₂. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.

Full text of DOI:10.1002/ejic.200300073

FULL PAPER
A New Thioether-Based (N2S2)Copper(II/ ) Complex Exhibiting a High Redox
I
Potential
[a]
[a]
[a]
[a]
´
Stephane Torelli, Catherine Belle,* Christian Philouze, Jean-Louis Pierre,
Wassim Rammal,[a] and Eric Saint-Aman[b]
Keywords: S ligands / N ligands / Tripodal ligands / Copper / Redox chemistry
From the new ligand bis[2-(tert-butylthio)benzyl](2-pyridyl- Redox studies show that 1 and 2 interconvert during the
methyl)amine [N2(StBu)2], the corresponding complexes
[CuI{N2(StBu)2}]CF3SO3 (1) and [CuII{N2(StBu)2}](H2O)-
(CF3SO3)]CF3SO3 (2) were synthesized and characterized by
X-ray crystallography. The Cu−S bonds are unusually
electron transfer with a high CuII/I potential of 0.79 V vs. SCE
in CH2Cl2.
( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
shortened in 1 and elongated for the axial thioether in 2. Germany, 2003)
Introduction
Blue (type 1) copper proteins involved in electron-trans-
fer processes have, in their active site, a single Cu atom
bound to two histidine nitrogen atoms and to one cysteine
thiolate group.[1,2] One additional axial thioether ligand (of
methionine) is usually found in the coordination sphere of
the copper ion (e.g plastocyanin[3] or azurin[4,5]). The posi-
tive CuII/I redox potential, found in the range of 0.2Ϫ0.8 V
Scheme 1
vs. NHE,[1] has long held the interest of bioinorganic chem-
ists. Model complexes, described by Kitajima[6] and more
recently by Tolman,[7] present structural and spectroscopic
features close to those of the type 1 site, but significant dif-
ferences in electrochemical properties are observed. Syn-
Results and Discussion
thetic copper complexes, for which both CuII and CuI struc-
tures are available, could provide information about the
structure/redox properties relationships.[8Ϫ10]
By adding 1 equiv. of Cu(CF3SO3), Cu(CF3SO3)2 or
Cu(ClO4)2·6H2O to the ligand N2(StBu)2 {bis[2-(tert-butyl-
thio)benzyl](2-pyridylmethyl)amine}, the CuI (1) and CuII
(2 and 3) complexes were obtained (Scheme 1).
The X-ray structures of the cationic units are depicted in
Figures 1 (for 1 and 2) and 2 (for 3). Selected bond lengths
and angles are reported in Table 1.
The structure of 1 (Figure 1, A) shows a copper() center
in a distorted tetrahedral geometry. The CuϪS distances in
1 are similar [CuϪS1 ϭ 2.2421(7) A and CuϪS2 ϭ
We present herein the preparation and characterization,
in both the CuI and CuII oxidation states, of a copper com-
plex from a new tripodal N2S2 donor ligand (Scheme 1).
The CuII/I redox potential is as high as that found in blue
copper proteins. We focused our attention on the role of the
thioether ligand; few structurally characterized CuII and
CuI complexes involving a long axial CuϪS(thioether)
bond have been studied electrochemically.[11,12]
˚
I
˚
2.2492(7) A], although shorter than the usual Cu ϪSR2
bond of 2.33(9) A.
[10]
˚
The X-ray crystal structure of 2 reveals an elongated oc-
tahedral complex for the CuII redox state (Figure 1, B). Two
nitrogen atoms, a thioether group and the water molecule
are in the equatorial plane [a deviation of 0.007(3) A from
the mean plane for the copper atom is observed]. Two axial
[a]
´
´
LEDSS, Chimie Biomimetique, UMR CNRS 5616, Universite
J. Fourier,
B. P. 53, 38041 Grenoble Cedex, France
Fax: (internat.) ϩ 33-4/76514836
˚
E-mail: Catherine.Belle@ujf-grenoble.fr
LEOPR, Laboratoire d’Electrochimie Organique et de
[b]
groups complete the octahedron: one StBu [CuϪS ϭ
´
Photochimie Redox, UMR CNRS 5630, Universite J. Fourier,
˚
B. P. 53, 38041 Grenoble, France
2.758(1) A] and one oxygen atom of a CF3SO3 anion
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 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
DOI: 10.1002/ejic.200300073
Eur. J. Inorg. Chem. 2003, 2452Ϫ2457

New Thioether-Based (N2S2)Copper(II/I) Complex Exhibiting a High Redox Potential
FULL PAPER
˚
[CuϪO ϭ 2.457(3) A] at semi-coordinating distances. Inter-
estingly, 2 involves both an equatorial CuϪS(thioether)
II
˚
bond [2.354(1) A], shorter than usual Cu ϪSR2 bond
[10]
˚
lengths of 2.42 A,
CuϪS(thioether) bond [2.758(1) A].
and one much longer axial
˚
Complex 3 was obtained in a similar manner to complex
2 using Cu(ClO4)2·6H2O as the metallic salt. The coordi-
nation sphere of the copper center in 3, as in 2, is described
by an octahedral geometry (see Figure 2) with an oxygen
atom of the perchlorate anion coordinated in an axial posi-
tion. The structural data for the molecular entity 3 is close
to that of 2 (see Table 1), except that the axial distances are
˚
longer in 3 [CuϪStBu ϭ 2.822(1) A and CuϪO ϭ 2.546(3)
A] than in 2.
Figure 1. ORTEP view showing 50% displacement ellipsoids with
partial atomic labeling for the cation (A) [CuI(N2(StBu)2]ϩ of 1 and
(B) [CuII{N2(StBu)2}(H2O)(CF3SO3)]ϩ of 2; hydrogen atoms have
been omitted for clarity
˚
Such an octahedral coordination with unequal
CuIIϪS(thioether) bond lengths is unusual and has only
been reported in complexes of non-tripodal ligands.[13,14]
The CuϪS distances in 2 (or 3) can be compared to those
found for the oxidized azurin,[4,5] characterized by two axial
groups, an S(thioether) atom and a carbonyl oxygen atom
of Gly45 in weak interaction with a copper() ion (near 3.1
˚
˚
A). The equatorially bound S(thiolate) ligand (Cys) is 2.12
A apart from the copper ion.
In CH2Cl2, the UV/Vis spectrum of 2 is characterized
by a band at 345 nm (ε ഠ 2250 Ϫ1·cmϪ1) assigned to the
S(thioether)ǞCuII LMCT band and a copper() dϪd tran-
sition at 721 nm (ε ഠ 130 Ϫ1·cmϪ1).[15] In ethanolic solu-
tion, the LMCT band appears at 332 nm (ε ഠ 2180
Ϫ1·cmϪ1) and the dϪd band is shifted up to 685 nm (ε ഠ
70 Ϫ1·cmϪ1). The changes observed in the UV/Vis spectra
suggest the displacement of at least one ligand by a solvent
molecule in the copper coordination sphere. In a frozen
Figure 2. ORTEP view showing 50% displacement ellipsoid with
partial atomic labeling for the cation [CuII{N2(StBu)2}-
(H2O)(ClO4)]ϩ of 3; hydrogen atoms have been omitted
˚
Table 1. Selected bond lengths [A] and angles [°] for 1, 2 and 3
1
2
3
CuϪS1
CuϪS2
CuϪN1
CuϪN2
2.2421(7)
2.2492(7)
2.023(2)
2.123(2)
CuϪS1
CuϪS2
CuϪN1
CuϪN2
CuϪO1
CuϪO2
N1ϪCuϪN2
N1ϪCuϪS1
N1ϪCuϪS2
N1ϪCuϪO1
N1ϪCuϪO2
N2ϪCuϪO1
N2ϪCuϪO2
N2ϪCuϪS1
N2ϪCuϪS2
O1ϪCuϪO2
O1ϪCuϪS1
O1ϪCuϪS2
O2ϪCuϪS1
O2ϪCuϪS2)
S1ϪCuϪS2
2.354(1)
2.758(1)
2.007(4)
2.037(4)
1.995(3)
2.457(3)
82.7(1)
179.1(1)
85.9(1)
90.4(1)
82.6(1)
173.1(1)
90.8(1)
96.7(1)
92.9(1)
CuϪS1
CuϪS2
CuϪN1
CuϪN2
CuϪO1
CuϪO2
N1ϪCuϪN2
N1ϪCuϪS1
N1ϪCuϪS2
N1ϪCuϪO1
N1ϪCuϪO2
N2ϪCuϪO1
N2ϪCuϪO2
N2ϪCuϪS1
N2ϪCuϪS2
O1ϪCuϪO2
O1ϪCuϪS1
O1ϪCuϪS2
O2ϪCuϪS1
O2ϪCuϪS2
S1ϪCuϪS2
2.359(1)
2.822(1)
1.987(4)
2.026(3)
1.958(3)
2.546(3)
83.8(1)
176.87(8)
82.43(8)
91.4(1)
87.6(1)
174.8(1)
87.8(1)
95.6(1)
91.16(8)
90.0(1)
N1ϪCuϪN2
N1ϪCuϪS1
N1ϪCuϪS2
N2ϪCuϪS1
N2ϪCuϪS2
S1ϪCuϪS2
83.77(8)
118.16(7)
119.74(7)
104.13(6)
100.27(9)
118.71(2)
88.3(1)
90.23(9)
86.62(9)
98.06(9)
167.34(9)
93.55(4)
89.3(1)
90.27(9)
95.48(9)
169.99(9)
94.53(4)
Eur. J. Inorg. Chem. 2003, 2452Ϫ2457
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 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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S. Torelli, C. Belle, C. Philouze, J.-L. Pierre, W. Rammal, E. Saint-Aman
FULL PAPER
solution of CH2Cl2/toluene (1:1) at 100 K, 2 displays a typi-
cal axial EPR spectrum (Figure 3, A), in agreement with
the X-ray structure, with g|| ϭ 2.19, gЌ ϭ 2.04, A|| ϭ 181 ϫ
10Ϫ4 cmϪ1. In EtOH/toluene (1:1), two sets of overlapping
signals centered at roughly g1|| ϭ 2.17, A1|| ϭ 176 ϫ 10Ϫ4
cmϪ1 and g2|| ϭ 2.29, A2|| ϭ 171 ϫ 10Ϫ4 cmϪ1 are observed
(Figure 3, B). These features indicate that solvent molecules
are involved in the coordination sphere of the metal center,
giving rise to the formation of a mixture of complexes.
Figure 3. EPR spectrum at 100 K of 2, at a microwave frequency
of 9.419 GHz as a frozen solution, 3 m in (A) CH2Cl2/toluene
(1:1, v/v); (B) EtOH/toluene (1:1, v/v)
Thus, the electrochemical behaviors of 1 and 2 have been
examined in coordinating solvents (MeOH or EtOH) and
in a noncoordinating solvent (CH2Cl2) by CV and RDE
experiments. In CH2Cl2 ϩ TBAP (0.1 ) solution, the same
CV features were found starting either from isolated 1 or
from isolated 2, i.e. compound 2 is the final product of the
oxidation of 1 and vice versa (Scheme 1). The CV curve is
characterized by a pair of peaks whose potentials depend
strongly on the scan rate: their peak-to-peak separation in-
creases from 0.21 V at 5 mVsϪ1 to 1.07 V at 5 VsϪ1 (Fig-
Figure 4. Voltammetric curves of 2 (A) and 1 (C), 1.2 m, recorded
in CH2Cl2 ϩ TBAP (0.1 ), WE: glassy carbon (␾ ϭ 3 mm), E vs.
Fc/Fcϩ; (A) CV at 0.03 (curve a) and 0.3 VsϪ1 (curve b), nor-
malized current vs. E; (B) anodic (Epa), cathodic (Epc) peak poten-
tial and peak-to-peak (∆Ep) separation vs. scan rate; (C) RDE vol-
tammetry, N ϭ 600 rpm, initial (curve a), after oxidative electrolysis
(0.8 exchanged electron, curve b), after re-reduction (curve c, the
increase in the limiting current between curves a and c is due to a
partial evaporation of CH2Cl2)
ure 4). At low scan rates, Epa and Epc tend towards constant transfer implies changes in coordination and geometry dur-
values of 0.41 V and 0.20 V vs. Fc/Fcϩ. The RDE wave ing the redox cycle. The overall mechanism can thus be best
recorded in a CH2Cl2 solution of 1 is characterized by described by the classic square scheme[2] in which the elec-
E1/2 ϭ 0.54 V (N ϭ 600 rpm).
tron-transfer steps are followed by coordinate bond forma-
Upon exhaustive potentiostatic electrolysis at 0.75 V (one tions (or ruptures) accounting for the change in the coordi-
exchanged electron), the RDE wave recorded in the re- nation mode of the copper center according to its redox
sulting solution (Figure 4) matches well with that recorded state, i.e. the electron transfer leads to an unstable inter-
in an electrolytic solution of 2, E1/2 ϭ 0.14 V (N ϭ mediate which undergoes a fast rearrangement to yield the
600 rpm). Additionally, the UV/Vis features of both solu- stable corresponding complex. Due to their very fast kine-
tions are very close. The starting solution is fully restored tics, the electroactivity of the intermediates could not be
upon further exhaustive reduction at Ϫ0.2 V. It can be seen seen on the CV curves, the anodic and cathodic processes
that the anodic and cathodic E1/2 values determined from remaining electrochemically irreversible, even at high scan
RDE experiments performed in solution of 1 or 2 are differ- rate (10 VsϪ1). This precluded any precise determination of
ent.
the kinetic constants by electrochemical simulations.
These results can be analyzed as the simple one-electron
Intervention of a coupled chemical reaction is further
transfer depicted in Scheme 1. Simulations of the exper- confirmed by examining the electrochemical response of 1
imental CV curves allowed the determination of the appar- or 2 in coordinating solvents. In an electrolytic EtOH solu-
ent formal potential and the apparent heterogeneous elec- tion of 2, when scanning towards negative potentials (0.1
tron-transfer rate constant of the overall mechanism: E1/2 ϭ VsϪ1), the CV curve displays a main cathodic peak at Epc ϭ
0.30 Ϯ 0.01V and k0 ϭ 2.0 Ϯ 0.9 ϫ 10Ϫ4 cm sϪ1. The low 0.14 V and a peak of low intensity at Epc ϭ Ϫ0.15 V. On
value of k0 suggests that the overall electrochemical mecha- the reverse scan, only one anodic peak is seen at Epa ϭ 0.38
nism involves coupled chemical reactions, i.e. the electron V (Figure 5). After an exhaustive reduction/re-oxidation cy-
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Eur. J. Inorg. Chem. 2003, 2452Ϫ2457

New Thioether-Based (N2S2)Copper(II/I) Complex Exhibiting a High Redox Potential
cle, the final CV curve displays the same signals but with
FULL PAPER
Experimental Section
different intensities (Figure 5). This results in an ill-behaved
RDE wave for 2 characterized by an apparent E1/2 ϭ 0.23
V (N ϭ 600 rpm), while a more resolved RDE wave for 1
is seen at apparent E1/2 ϭ 0.35 V (N ϭ 600 rpm). It can be
assumed that in coordinating solvents, solvent molecules
are involved in the coordination sphere of the metal center
giving rise to the formation of different complexes in equi-
librium [as previously observed in UV/Vis and EPR spectra
measured in ethanol (see above)].
General: All chemicals were obtained from commercial sources and
used as received. Solvents were purified by standard methods be-
fore use. Caution: Although no problems were encountered during
the preparation of perchlorate salts, suitable care should be taken
when handling such potentially hazardous compounds.
Spectrometry: Fast-atom bombardment (FAB) mass spectra in the
positive mode were recorded with a Nermag R 1010C apparatus
equipped with an M scan (Wallis) atom gun (8 kV, 20 mA). ESI
mass spectra were obtained with a Bruker Esquire 3000 plus spec-
trometer with an ion trap. UV/Vis spectra were recorded using a
PerkinϪElmer Lambda 2 spectrophotometer equipped with 1.0-cm
matched quartz cells and operating in the range 200Ϫ900 nm; ε
1
values are given in Ϫ1·cmϪ1. H and 13C NMR spectra were re-
corded with a Bruker Avance 300 spectrometer and a Bruker AC
200; chemical shifts (ppm) were referenced to residual solvent
peaks. EPR spectra were recorded at 100 K with a Bruker ESP 300
spectrometer operating at 9.4 GHz (X-band), with 3 m solutions.
Electrochemistry: Electrochemical experiments were carried out
using a PAR model 273 potentiostat equipped with a Kipp-Zonen
x-y recorder. All experiments were run at room temperature under
argon. A standard three-electrode cell was used, with 0.1  tetra-
n-butylammonium perchlorate (TBAP) as supporting electrolyte.
All potentials are referred to the regular Fc/Fcϩ redox couple used
as internal reference. Vitreous carbon disc electrodes for cyclic vol-
tammetry (CV) (5 mm diameter) and rotating disc electrode (RDE)
(3 mm diameter) were polished with 1 µm diamond paste.
Figure 5. CV curves of 2, 1.1 m, recorded in EtOH ϩ TBAP (0.1
), WE: glassy carbon (␾ ϭ 3 mm), E vs. Fc/Fcϩ, v ϭ 0.1 VsϪ1
;
curve (a): initial; curve (b): after an oxidation/reduction cycle
Taking into account E1/2 (Fc/Fcϩ) ϭ 0.49 V or 0.44 V vs.
SCE, in CH2Cl2 or EtOH respectively, under our exper-
imental conditions, the 1/2 electrochemical system presents [2-(tert-Butylthio)benzyl](2-pyridylmethyl)amine: A solution of (2-
pyridylmethyl)amine (477 µL, 4.54 mmol) in dry MeOH (10 mL)
was added at room temperature to a solution of 2-(tert-butylthio)b-
enzaldehyde (1 g, 5 mmol) in dry MeOH (100 mL) under Ar. After
3 h, NaBH4 (455 mg, 11.5 mmol) was slowly added as a solid and
the mixture stirred for an additional 2 h. After acidic treatment
(HCl, 4 ), the solvent was removed under reduced pressure. The
resulting product was dissolved in H2O (50 mL) and extracted with
CH2Cl2 to remove the excess of reduced aldehyde. The aqueous
solution was then neutralized with saturated NaHCO3 and ex-
tracted with CH2Cl2 (2 ϫ 100 mL). The combined organic layers
a very high redox potential, similar to that of blue copper
proteins (a value of 0.78 V vs. NHE is reported for fungal
laccase).[16] As a consequence, whereas 1 is stable in CH2Cl2
or alcohol solution, 2 is partially reduced to the CuI state
even in the presence of air (40% of CuII is reduced after 1
d in ethanol). High redox potential values have been re-
ported for a few small CuII/I molecular systems[17] but are
rare for related copper systems involving tripodal li-
gands.[18,19] Compared to other redox couples involving
tripodal N2S2 ligands, the 1/2 electrochemical system de- were washed with saturated NaCl, dried with Na2SO4 and concen-
trated under reduced pressure to give a brown oil. Yield: 1.2 g
(91%). 1H NMR (200 MHz, CDCl3, TMS): δ ϭ 8.51 (d, J ϭ
4.8 Hz, 1 H, Py-H), 7.51Ϫ7.63 (m, 3 H, Py-H), 7.07Ϫ7.36 (m, 4
H, Ar-H), 4.11 (s, 2 H, NCH2Ar), 3.92 (s, 2 H, NCH2Py), 3.02 (s,
1 H, NH), 1.25 (s, 9 H, tBu) ppm. 13C NMR (50 MHz, CDCl3,
TMS): δ ϭ 159.3, 148.9, 144.3, 138.5, 136.0, 131.8, 129.4, 128.8,
126.7, 122.0, 121.6, 54.0, 51.6, 46.9, 30.8 ppm. FABϩ MS: m/z ϭ
286 [Mϩ ϩ Hϩ]. C17H21N2S (285): calcd. C 67.80, H 7.58, N 9.44,
S 11.86; found C 68.00, H 7.74, N 9.78, S 11.19.
scribed herein displays a shift towards higher potentials by
0.2 V.[10]
Conclusion
The high redox potential of the 1/2 couple could result
from a combination of: (i) the lower donating character of
the aromatic thioether group compared to an aliphatic thi- Bis[2-(tert-butylthio)benzyl](2-pyridylmethyl)amine [N2(StBu)2]: 2-
oether group, (ii) the stabilization of the CuI redox state, as
(tert-Butylthio)benzaldehyde (847 mg, 4.23 mmol) and glacial
acetic acid (878 µL, 15.36 mmol) were added to a solution of [2-
judged from the short CuIϪSR2 bonds, (iii) the long axial
CuIIϪSR2 bond leading to a weaker interaction, likely to
(tert-butylthio)benzyl](2-pyridylmethyl)amine (1.1 g, 3.84 mmol) in
dry MeOH (100 mL) under Ar. After 1 h, NaBH3CN (1.016 g,
be due to (iv) the geometric constraint afforded by the tBu
group. The present study may provide insights into the elec-
15.36 mmol) was added and the mixture stirred overnight. Then,
an acid treatment (HCl, 4 ) was performed and the solvent was
tron-transfer mechanism of the blue copper proteins.
removed under reduced pressure. The resulting product was dis-
Further studies are in progress to understand the relation-
solved in H2O and extracted with CH2Cl2 to remove the excess
ship between the subtle changes of the ligand and the deep
changes induced in the redox properties of the related com-
plexes.
of reduced aldehyde. The aqueous solution was neutralized with
saturated NaHCO3 and extracted with CH2Cl2 (2 ϫ 100 mL). The
combined organic layers were washed with saturated NaCl, dried
Eur. J. Inorg. Chem. 2003, 2452Ϫ2457
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S. Torelli, C. Belle, C. Philouze, J.-L. Pierre, W. Rammal, E. Saint-Aman
FULL PAPER
Table 2. Crystallographic experimental details for 1Ϫ3
1·0.985CH2Cl2
2·C4H8O
3
Empirical formula
Formula mass
Symmetry
C29H36CuF3N2O3S3·0.985CH2Cl2
C30H38CuF6N2O7S4·C4H8O
C28H38Cl2CuN2O9S2
745.19
monoclinic
760.99
915.54
triclinic
orthorhombic
Morphology
pale brownish prism
0.18 ϫ 0.15 ϫ 0.10
10.271(1)
12.192(1)
14.829(1)
74.43(1)
86.80(1)
70.97(1)
1690(1)
turquoise prism
0.32 ϫ 0.26 ϫ 0.18
12.0120(9)
16.2009(5)
21.616(2)
90
90
90
blue-green platelet
0.22 ϫ 0.15 ϫ 0.08
32.86(1)
11.906(4)
23.806(5)
90
129.55(3)
90
Crystal dimension [mm]
˚
a [A]
˚
b [A]
˚
c [A]
α [°]
β [°]
γ [°]
3
˚
V [A ]
4206.6(4)
7181(5)
T [K]
Space group
Z
100.2
P1
2
150
P212121
4
293
C2/c
8
¯
Diffractometer
Monochromator
EnrafϪNonius Kappa CCD
EnrafϪNonius Kappa CCD
EnrafϪNonius CAD-4
graphite
0.7107 (Mo-Kα)
1.038
graphite
0.7107 (Mo-Kα)
0.793
graphite
0.7107 (Mo-Kα)
0.922
˚
Wavelength [A]
µ [mmϪ1
]
No. of reflections (measured)
No. of reflections (unique)
11234
4349
32320
7043
6910
6729
No. of reflections
Rint.
R
3704 (I Ͼ 1σ)
0.039
0.038
4763 (I Ͼ 2σ)
0.067
0.056
4030 (I Ͼ 2σ)
0.034
0.055
R(w)
0.059
0.057
0.065
with Na2SO4 and concentrated under reduced pressure. Addition of 2. FAB MS (NBA matrix): m/z ϭ 678 [N2(StBu)2 ϩ 1 Cu2ϩ
Ϫ
of pentane afforded the product as a pale beige powder. Yield: 1.2 g
H2O ϩ 1 CF3SO3 ϩ 1 Hϩ]. C30H38CuF6N2O7S4 (844): calcd.
C 42.67, H 4.54, Cu 7.53, F 13.5, N 3.32, S 15.19; found C 42.31,
1
(68%), m.p. 95 °C. H NMR (200 MHz, CDCl3, TMS): δ ϭ 8. 53
(d, J ϭ 4.8 Hz, 1 H, Py-H), 7.50Ϫ7.60 (m, 3 H, Py-H), 7.07Ϫ7.36 H 4.56, Cu 7.31, N 3.31, S 15.85.
(m, 8 H, Ar-H), 4.15 (s, 4 H, NCH2Ar), 3.92 (s, 2 H, NCH2Py),
[CuII{N2(StBu)2}(H2O)(ClO4)](ClO4) (3): Copper() perchlorate
1.25 (s, 18 H, tBu) ppm. 13C NMR (50 MHz, CDCl3, TMS): δ ϭ
hexahydrate (0.271 g, 0.715 mmol) was added to a solution of
N2(StBu)2 (0.3 g, 0.65 mmol) in EtOH (20 mL). The solution was
stirred for 10 min and diethyl ether/THF added (10 mL). After 24 h
at Ϫ20 °C, 3 was obtained as a polycrystalline green-blue powder.
Yield: 45% (0.218 g). Crystals of 3 suitable for X-ray crystallogra-
phy were obtained by vapor diffusion of diethyl ether into an aceto-
nitrile solution of 3. FAB MS (NBA matrix): m/z ϭ 628 [N2(StBu)2
160.6, 148.9, 145.0, 139.0, 136.5, 132.7, 129.1, 129.6, 126.6, 122.9,
121.9, 60.7, 57.0, 47.3, 31.3 ppm. FABϩ MS: m/z ϭ 465 [Mϩ
ϩ
Hϩ]. C28H36N2S2 (464): calcd. C 71.86, H 7.88, N 5.92, S 13.68;
found C 72.37, H 7.81, N 6.03, S 13.80.
[CuI{N2(StBu)2}](CF3SO3) (1): Copper() trifluoromethanesulfon-
ate (0.230 g, 0.43 mmol, toluene complex) was added to a solution ϩ 1 Cu2ϩ Ϫ H2O ϩ 1 ClO4 ϩ 1 Hϩ]. UV/Vis (CH2Cl2): λ (ε) ϭ
of N2(StBu)2 (0.2 g, 0.43 mmol) in CH2Cl2 (20 mL). The solution 357 (4146), 706 nm (392 Ϫ1·cmϪ1); (EtOH): λ ϭ 338 (3954), 655
was stirred for 10 min and diethyl ether added (10 mL). After 24 h,
1 was obtained as a polycrystalline pale powder. Yield: 65%
nm (149 Ϫ1·cmϪ1). EPR (9.6 GHz, 100 K, 3 m, CH2Cl2/toluene,
1:1): g|| ϭ 2.22, gЌ ϭ 2.06, A|| ϭ 175 ϫ 10Ϫ4 cmϪ1; (EtOH/toluene,
(0.188 g). Crystals of 1 suitable for X-ray crystallography were ob- 1:1) main features at: g|| ϭ 2.22, gЌ ϭ 2.02, A|| ϭ 170 ϫ 10Ϫ4 cmϪ1
tained by layering hexane onto a CH2Cl2 solution of 1. ESI MS:
.
X-ray Crystallographic Studies: Crystal data and crystallographic
experimental data for complexes 1Ϫ3 are listed in Table 2. In both
structures, collected reflections were corrected for Lorentz and pol-
arization effects but not for absorption. The structures were solved
by direct methods and refined using the TEXSAN software pack-
age.[20] All non-hydrogen atoms were refined with anisotropic ther-
mal parameters. Hydrogen atoms were generated in idealized posi-
m/z ϭ 527 [N2(StBu)2 ϩ 1 Cuϩ]. 1H NMR (300 MHz, CD3CN,
TMS): δ ϭ 8. 68 (d, J ϭ 4.7 Hz, 1 H, Py-H), 7.79 (t, J ϭ 7.0 Hz,
1 H, Py-H), 7.81Ϫ7.37 (m, 5 H, Ar-H ϩ Py-H), 7.27 (d, 1 H, Ar-
H), 3.89 (s, 4 H, NCH2Ar), 3.78 (s, 2 H, NCH2Py), 1.17 (s, 18 H,
tBu) ppm.
[CuII{N2(StBu)2}(H2O)(CF3SO3)](CF3SO3) (2): Copper() trifluoro- tions, riding on the carrier atoms, with isotropic thermal param-
methanesulfonate (0.155 g, 0.43 mmol) was added to a solution of
N2(StBu)2 (0.2 g, 0.43 mmol) in EtOH (20 mL). The solution was
stirred for 10 min and diethyl ether added (10 mL). After 24 h at
Ϫ20 °C, 2 was obtained as a polycrystalline blue powder. Yield:
eters. CCDC-203164 (1), -203165 (2) and -203166 (3) contain the
supplementary crystallographic data for this paper. These data can
be obtained free of charge at www.ccdc.cam.ac.uk/conts/retriev-
ing.html [or from the Cambridge Crystallographic Data Centre, 12
70% (0.250 g). Crystals of 2 suitable for X-ray crystallography were Union Road, Cambridge CB2 1EZ, UK; Fax: (internat.) ϩ 44-
obtained vapor diffusion of diethyl ether into an ethanol solution 1223/336-033; E-mail: deposit@ccdc.cam.ac.uk].
2456
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
Eur. J. Inorg. Chem. 2003, 2452Ϫ2457

New Thioether-Based (N2S2)Copper(II/I) Complex Exhibiting a High Redox Potential
FULL PAPER
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Received February 6, 2003
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Eur. J. Inorg. Chem. 2003, 2452Ϫ2457
www.eurjic.org
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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