Mono- and dinuclear (o-thioetherphenolato)-copper(II) complexes. Structural models for galactose oxidase

Article abstract of DOI:10.1016/S0020-1693(01)00756-3

Three new o-thioetherphenol ligands have been synthesized: 1,2-bis(3,5-di-tert-butyl-2-hydroxyphenylsulfanyl)ethane (H₂bse), 1,2-bis(3,5-di-tert-butyl-2-hydroxyphenylsulfanyl)benzene (H₂bsb), and 4,6-di-tert-butyl-2-phenylsulfanylphe

Full text of DOI:10.1016/S0020-1693(01)00756-3

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Inorganica Chimica Acta 331 (2002) 81–89
Mono- and dinuclear (o-thioetherphenolato)-copper(II) complexes.
Structural models for galactose oxidase
Tobias Kruse, Thomas Weyhermu¨ller, Karl Wieghardt *
Max-Planck-Institut fu¨r Strahlenchemie, Stiftstrasse 34-36, D-45470 Mu¨lheim an der Ruhr, Germany
Received 29 June 2001; accepted 14 August 2001
Dedicated to Professor A.G. Sykes
Abstract
Three new o-thioetherphenol ligands have been synthesized: 1,2-bis(3,5-di-tert-butyl-2-hydroxyphenylsulfanyl)ethane (H2bse),
1,2-bis(3,5-di-tert-butyl-2-hydroxyphenylsulfanyl)benzene (H2bsb), and 4,6-di-tert-butyl-2-phenylsulfanylphenol (Hpsp). Their
complexes with copper(II) were prepared and investigated by UV–Vis-, EPR-spectroscopy; their electro- and magnetochemistry
have also been studied: [CuII(psp)2] (1), [CuI2I(bse)2] (2), [Cu2II(bsb)2] (3), [CuII(bsb)(py)2] (4). The crystal structures of the ligands
H2bse, H2bsb, Hpsp and of the complexes 1, 2, 3, 4 have been determined by X-ray crystallography. © 2002 Elsevier Science B.V.
All rights reserved.
Keywords: o-Thioetherphenols; Copper complexes; Galactose oxidase models; Magnetochemistry
form is readily oxidized by dioxygen to produce reac-
tive (phenoxyl)copper(II) species.
1. Introduction
Here we report an attempt to systematically vary the
structural features and thereby the coordinating ability
of similar o-thioetherphenol ligands. To this end, we
have synthesized the ligands and complexes shown in
Scheme 1.
In the resting state of the enzyme galactose oxidase, a
single Cu(II) ion is coordinated in a distorted square-
based pyramidal fashion to two histidine N-donor
atoms (His 496, His 581), two tyrosinato oxygen atoms
(Tyr 495, Tyr 272) and a labile water molecule [1]. Tyr
272 exhibits a peculiar post-translational modification.
It forms in the ortho position, a thioether linkage to a
neighboring cystein residue (Cys 228). The thioether
sulfur is only weakly, if at all, coordinated to the Cu(II)
2. Results and discussion
,
ion (Cu···S 3.58 A). In a number of model studies, the
2.1. Syntheses
role of this o-thioetherphenolato moiety has been inves-
tigated [2] since this is the locus where one-electron
oxidation generating the active form of the enzyme,
namely a coordinated CuII-tyrosyl radical moiety, oc-
curs [3].
The three new o-thiophenol ligands were synthesized
following the general route displayed in Scheme 2.
2,4-Di-tert-butylphenol was brominated in chloroform
at ambient temperature affording 2-bromo-4,6-di-tert-
butylphenol in excellent yields. This compound was
lithiated in two successive 1 equiv. steps in tetrahydro-
furan at −50 °C by using commercially available n-
butyllithium in n-hexane solutions. After addition of
the second equivalent, the solution was allowed to
slowly warm-up to 20 °C. The success of this prepara-
tion critically depends on the rigorous absence of water
and on the purity of reagents and solvents. Excess
We have previously shown [4] that it is possible to
synthesize a functional model for the aerobic oxidation
of alcohols by using
a
(2,2%-thio-bis(2,4-di-tert-
butylphenolato)copper(II) complex, which in its dimeric
* Corresponding author. Tel.: +49-208-306 3609/10; fax: +49-
208-306 3952.
E-mail address: wieghardt@mpi-muelheim.mpg.de (K. Wieghardt).
0020-1693/02/$ - see front matter © 2002 Elsevier Science B.V. All rights reserved.
PII: S0020-1693(01)00756-3

82
T. Kruse et al. / Inorganica Chimica Acta 331 (2002) 81–89
Scheme 1.
Scheme 2.

T. Kruse et al. / Inorganica Chimica Acta 331 (2002) 81–89
83
The green–brown complexes [CuI2I(bse)2] (2) and
[CuI2I(bsb)2] (3) were obtained from the reaction of
H2bse, or H2bsb and CuCl (1:1) in THF in the presence
of air upon addition of 2 equiv. of NEt3. Both 2 and 3
are bis(m-phenolato)dicopper(II) species. It is well es-
tablished chemistry of such dinuclear species [2c–e] that
they can form penta- and even hexadentate mononu-
clear complexes via addition of coordinating ligands
such as pyridine (Eqs. (1) and (2)).)
[Cu2II(bse)2]+X2py2[CuII(bse)py]+X2py2[CuII(bse)(py)2] (1)
−2py
−2py
[CuI2I(bsb)2]+X2py2[CuII(bsb)py]+X2py2[CuII(bsb)(py)2]
−2py
−2py
(2)
Mononuclear [Cu(bsb)(py)2] (4) has been isolated as
crystalline material and its crystal structure has been
determined (see below).
Fig. 4 displays the electronic spectra of 2 and 3 in
CH2Cl2 solution. Both display an intense absorption
maximum at 450 nm (m=3.3×103 l mol−1 cm−1) for 2
and at 470 (2.3×103) for 3. A second maximum which
is assigned to a predominantly d–d transition is ob-
served at 645 nm (m=1.45×103 l mol−1 cm−1) for 2
and at 620 (630) for 3. Upon addition of 2 equiv./dimer
of pyridine, the spectra change dramatically; a color
change from brown to violet is observed. Both absorp-
tion maxima in the visible of 2 and 3 are less intense
and they are shifted to longer wavelengths:
[CuII(bse)py]: umax=464 nm (m=1.2×103 l mol−1
cm−1) and 769 (680); [CuII(bsb)py]: 517 (580) and 743
(250). Upon addition of a further 2–4 equiv. of pyri-
dine to these solutions, the spectra do not change
significantly. Thus, the spectra of the hexacoordinate
species resemble closely those of the five-coordinate
intermediates.
Fig. 1. Molecular structures of H2bse (top), H2bsb (middle), and
Hpsp (bottom).
2.2. Crystal structures
n-butyllithium must be avoided. To these solutions was
added exactly 1 or 1.5 equiv. of the corresponding
sulfenyl- or disulfenyl chloride yielding the o-thiophe-
nol ligands and LiCl. The sulfenyl chlorides were pre-
pared by the reaction of the starting thiol with SO2Cl2
in CH2Cl2 solution at temperatures in the range −30
to 0 °C [5]. Effervescence of HCl is observed until 1.5
equiv. of SO2Cl2 has been added. In the case of a
dithiol starting material, the formation of insoluble
polymers containing disulfide bridges occurred. After
addition of the second half equivalent of SO2Cl2 these
redissolved with formation of the desired disulfenyl
dichlorides.
The synthesis of the copper(II) complexes containing
monoanionic (psp)1−, or dianionic (bse)2− and (bsb)2−
ligands is straightforward. Thus, the reaction of 2
equiv. of Hpsp with 1 equiv. of CuICl and 2 equiv. of
the base triethylamine in the presence of air in
methanol yields brown crystals of [CuII(psp)2] (1).
The molecular structures of the ligands H2bse,
H2bsb, Hpsp have been determined by X-ray crystallog-
raphy at cryogenic temperatures (100(2) K). Fig. 1
shows the structures of these organic molecules. Bond
distances and angles are available in the supplementary
material; they do not show any unusual features. The
molecular structures of complexes 1–4 have also been
determined. Crystallographic data of all structure deter-
minations are summarized in Table 1; Table 2 gives
selected bond distances and angles of the complexes.
Fig. 2 displays the structures of the neutral mononu-
clear species in crystals of 1 and 4 whereas Fig. 3 shows
those of the dinuclear complexes in crystals of 2 and 3.
The copper(II) ion in 1 is O,S-coordinated to two
bidentate (psp)1− monoanions; it is in a nearly planar
O2S2-coordination sphere with a slight distortion to-
ward a tetrahedron. The two (psp)1− ligands are in
trans-position relative to each other. The average CuꢀO

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T. Kruse et al. / Inorganica Chimica Acta 331 (2002) 81–89
and CuꢀS distances are short at 1.848(2) and 2.345(1)
ligands forms a m-phenolato bridge to the respective
second CuII ion. Thus, both CuII ions are five-coordi-
nate in a distorted square-based pyramidal environ-
ment. One thioether sulfur donor is always in an apical
position whereas the second occupies a basal coordina-
,
A, respectively. In the solid state, two mononuclear
[Cu(psp)2] entities form a dimer via two very weak
CuꢀS···Cu* interactions. The S1···Cu* distance is
,
3.131(1) A and the ‘intramolecular’ Cu···Cu* distance is
,
,
4.371(1) A.
tion site. The Cu···Cu distance in 2 is at 2.814(1) A but
,
In contrast, the Cu(II) ion in 4 is six-coordinate in a
S2O2N2 donor environment composed of two thioether
S-donors in cis-position relative to each other and two
pyridine N-donors also in cis-position, whereas the two
phenolato O-donor atoms are trans relative to each
other. The two CuꢀS and CuꢀN bonds are not equidis-
slightly longer at 2.904(2) A in 3 and, concomitantly,
the CuꢀOꢀCu angle at 90.8(1)° in 2 is smaller by 5.3°
than in 3.
2.3. Magnetic susceptibility and EPR spectroscopic
data
,
tant whereas the two CuꢀO bonds at an av. 1.930(3) A
are equivalent within experimental error. The
N1ꢀCuꢀS2 axis clearly defines a Jahn Teller axis of a
tetragonally elongated distorted O2N2S2Cu octahedron
(static Jahn Teller distortion).
As shown in Fig. 3 crystals of 2 and 3 contain the
centrosymmetric dinuclear species [CuI2I(bse)2] and
[CuI2I(bsb)2], respectively. The dianionic ligands (bse)2−
and (bsb)2− are each coordinated to one of the CuII
ions via two Cu-thioether and a terminal Cu-phenolato
bond. In addition, the second phenolate group of both
The temperature dependent magnetic susceptibilities
of complexes have been measured in the range 2–298 K
by using a SQUID magnetometer and an external
magnetic field of 1 T. The raw magnetic susceptibility
data were corrected for underlying diamagnetism by the
use of tabulated Pascal’s constants (Fig. 4).
In the solid state the two didentate ligands of 1 are in
trans-position relative to each other and two such
entities form a weakly S-bridged dimer [CuII(psp)2]2 as
shown in Fig. 2 (top). In excellent agreement with this
Table 1
Crystallographic data for H2(bse), H2(bsb), and H(psp), 1, 2, 3, and 4
H2(bse)
H2(bsb)
H(psp)
1
2
3
4
Chemical
formula
Formula weight 502.79
C30H46O2S2
C34H46O2S2
550.83
C20H26OS
314.47
C40H50CuO2S2
C60H88Cu2O4S4
C68H88Cu2O4S4
C
44H54CuN2O2S2
690.46
1128.62
1224.70
770.55
Crystal size
(mm)
0.52×0.42×0.12 0.3×0.2×0.2 0.4×0.4×0.3 0.28×0.18×0.06 0.26×0.24×0.06 0.60×0.07×0.06 0.14×0.11×0.07
Space group
P21/c
P21/n
P21/c
C2/c
C2/c
P21/c
P21/n
,
a (A)
16.148(3)
10.006(2)
9.060(2)
98.44(3)
1448.0(5)
2
16.175(3)
12.580(3)
17.102(3)
112.88(3)
3206.1(11)
4
8.619(2)
12.585(3)
17.367(4)
102.55(3)
1838.8(6)
4
29.729(4)
13.875(2)
21.983(3)
125.12(2)
7417(2)
8
19.145(2)
10.486(1)
31.250(3)
105.83(2)
6035.8(10)
4
12.384(3)
15.218(3)
17.624(4)
94.06(3)
3313.1(13)
2
9.804(2)
18.357(4)
22.535(5)
90.76(2)
4055(2)
4
,
b (A)
,
c (A)
i (°)
V (A )
3
,
Z
T (K)
z calcd (g
100(2)
1.153
100(2)
1.141
100(2)
1.136
100(2)
1.237
100(2)
1.242
100(2)
1.228
100(2)
1.262
cm−3
)
Number of
data/2qmax
(°)
10 771/50.00
12 814/49.98
17 296/60.00
54 186/55.00
20 023/46.52
14 140/45.00
13 568/45.00
Number of
unique data
Number of
parameters/res
traints
2524
5182
5258
8502
4305
4286
5264
178/0
436/0
238/15
418/0
328/0
346/16
460/0
v (Mo Ka)
2.08
1.93
1.76
7.33
8.86
8.12
6.79
(cm−1
)
a
R1
0.0649
0.0451
0.1105
0.930
0.0900
0.2375
1.099
0.0529
0.1635
1.049
0.0450
0.0865
0.971
0.0795
0.2073
1.072
0.0531
0.1074
0.963
b
wR2 (all data) 0.1683
Goodness-of-fit c1.094
a Observation criterion: I\2|(I). R1=SꢀꢀFoꢀ−ꢀFcꢀꢀ/SꢀFoꢀ.
b wR2=[[Sw(Fo2−Fc2)2]/S[w(Fo2)2]]1/2 where w=1/|2(Fo2)+(aP)2+bP, P=(Fo2+2Fc2)/3.
c GooF=[Sw(Fo2−Fc2)2/(n−p)]1/2 where n=number of reflections and p=number of parameters.

T. Kruse et al. / Inorganica Chimica Acta 331 (2002) 81–89
85
Table 2
following parameters were established: 2: g1=g2=2.0;
J= +36.5 cm−1, TIP=142×10−6 cm−3 mol−1; 3:
g1=g2=2.1; J= +58.7 cm−1, TIP=50×10−6 cm−3
mol−1. These data are in excellent agreement with
published magneto-structural correlations for bis(m-
phenolato)dicopper complexes [6]. According to these
analyses, the main structural parameter responsible for
ferromagnetic exchange coupling is the CuꢀOꢀCu an-
gle. At 90° the magnetic orbitals are orthogonal and
maximum stabilization of the S=1 ground state is
achieved. In 2 this CuꢀOꢀCu angle is 90.8(1) and
96.1(2)° in 3, and, consequently, the coupling is ferro-
magnetic in both cases.
The X-band EPR spectra of mononuclear 4 and
dinuclear 3 in frozen CH2Cl2 solutions measured at 10
K are shown in Fig. 7. The spectrum of 4 confirms the
S=1/2 and that of 3 the S=1 ground state, respec-
tively. The spectrum of 4 is most probably that of the
square-based pyramidal species [CuII(bsb)py]; it dis-
plays an axial signal with Cu hyperfine coupling. A
simulation of this spectrum gives the parameters: gx=
2.06, gy=2.11, gz=2.22 (giso=2.13), Ax=Ay=0 and
Az(Cu)=15 mT with line widths Wx=19, Wy=23,
Wz=10 mT. This spectrum is in excellent agreement
with those reported for similar mononuclear complexes
[7].
,
Selected bond distances (A) and angles (°)
Complex 1
CuꢀO1
CuꢀO2
CuꢀS1
CuꢀS2
1.846(2)
1.851(2)
2.351(1)
2.340(1)
S1ꢀC6
S1ꢀC7
S2ꢀC27
S2ꢀC26
O1ꢀC1
O2ꢀC21
1.773(4)
1.789(3)
1.777(3)
1.779(3)
1.343(4)
1.335(4)
O1ꢀCuꢀO2
O1ꢀCuꢀS2
O2ꢀCuꢀS2
165.4(1)
95.3(1)
87.2(7)
O1ꢀCuꢀS1
O2ꢀCuꢀS1
S2ꢀCuꢀS1
87.5(1)
94.8(1)
161.05(3)
Complex 2
CuꢀO2
CuꢀO1
CuꢀO1*
CuꢀS2
1.861(3)
1.927(3)
2.023(3)
2.373(1)
2.622(1)
S1ꢀC1
1.778(4)
1.829(4)
1.351(4)
1.778(4)
1.818(4)
1.340(4)
S1ꢀC29
O1ꢀC2
S2ꢀC15
S2ꢀC30
O2ꢀC16
CuꢀS1
Cu···Cu*
2.814(1)
CuꢀO1ꢀCu*
90.8(1)
Complex 3
CuꢀO1
CuꢀO2
CuꢀO2*
CuꢀS1
1.877(5)
1.943(5)
1.961(5)
2.308(2)
2.766(2)
S1ꢀC6
S1ꢀC7
O1ꢀC1
S2ꢀC12
S2ꢀC13
O2ꢀC14
1.774(8)
1.815(8)
1.325(9)
1.761(9)
1.781(8)
1.371(8)
CuꢀS2
Cu···Cu*
2.904(2)
CuꢀO2ꢀCu*
96.1(2)
In contrast, the rhombic signal of 3 confirms the
triplet ground state of this dinuclear species. From a
satisfactory simulation for an S=1 system, the follow-
ing parameters were obtained: gx=2.15, gy=2.107,
gz=2.02 (giso=2.09), Ax(Cu)=12, Ay(Cu)=0, Az=
2.5 mT; D= −0.006 cm−1 and E=0.002 cm−1 (E/
D=1/3).
Complex 4
CuꢀO1
CuꢀO2
CuꢀN2
CuꢀN1
CuꢀS1
1.929(3)
1.932(3)
2.067(4)
2.394(4)
2.422(2)
2.696(2)
S1ꢀC2
1.777(5)
1.796(5)
1.793(4)
1.794(5)
1.334(5)
1.323(5)
S1ꢀC15
S2ꢀC21
S2ꢀC20
O1ꢀC1
O2ꢀC22
CuꢀS2
The asterisk denotes atoms, which are related by a crystallographic
inversion center in a given molecule.
2.4. Electrochemistry
structure the temperature dependence of the magnetic
moment of 1 displays a very weak, intramolecular
ferromagnetic coupling. Fig. 5 displays the temperature
dependence of the magnetic moment of 1 calculated per
dimer. By using the spin Hamiltonian Eq. (3), an
excellent fit of the data was obtained: g1=g2=2.07,
J= +0.5 cm−1 and a temperature-independent mag-
netic susceptibility, (TIP), of 51×10−6 cm−3 mol−1
per dimer.
The electrochemistry of complexes has been investi-
gated by square-wave (swv) and cyclic voltammetry (cv)
on CH2Cl2 solutions containing 0.10 M [(n-bu)4N]PF6
as supporting electrolyte at 20 °C; ferrocene was added
as internal standard. The cv of 1 displays four irre-
versible, ligand-centered oxidations at Eopx=0.50, 0.57,
0.80, and 0.95 V versus ferrocenium/ferrocene (Fc+/Fc)
at 20 °C and 100 mV s−1 scan rate. Two of these
oxidations occur at very similar potentials, respectively.
We interpret the observation of four oxidations as
follows. In solution, a dynamic equilibrium of the cis-
and trans-[Cu(psp)2] forms exist. This has been proven
for the Pd and Pt analogs and will be reported else-
where [8]. Each of the coordinated o-thioetherpheno-
lato(1−) ligands can then undergo a ligand-centered,
H= −2JS1S2+gvBSB S1=S2=1/2
(3)
The electronic spectrum of 1 in CH2Cl2 solution dis-
plays absorption maxima at u=245 nm (m=4.0×104 l
mol−1 cm−1), 290 (1.7×104), 320 (1.25×104), 360
(0.5×104), 440 (0.3×104), 520 (broad tail).
Fig. 6 shows the temperature dependence of the
magnetic moment/dimer of 2 (top) and 3 (bottom).
Clearly, in both cases a relatively strong intramolecular
ferromagnetic coupling prevails. Both data sets were
satisfactorily fitted to the Hamiltonian Eq. (3). The
one-electron oxidation yielding neutral, coordinated
0
’
phenoxyl radicals (psp ) .
−e
II
II
+
’
cis-,trans-[Cu (psp)2] X [Cu (psp )(psp)]
+e
−e
2+
’
X [Cu(psp )2]
(4)
+e

86
T. Kruse et al. / Inorganica Chimica Acta 331 (2002) 81–89
These radical complexes are not stable on the time scale
of a swv.
3. Experimental
Complex 2 displays two irreversible one-electron oxi-
dations at 0.52 and 0.71 versus Fc+/Fc at 20 °C and
100 mV s−1 scan rate which correspond to the genera-
tion of one and two coordinated phenoxyl radicals
which are also not stable on the time scale of a swv.
Similarly, complex 3 exhibits two irreversible one-elec-
tron oxidations at 0.62 and 0.99 V versus Fc+/Fc at
20 °C and 100 mV s−1 scan rate.
These experiments show that the o-thioetherpheno-
lates can be oxidized but the oxidized species are very
unstable and do not allow further spectroscopic
characterizations.
3.1. Syntheses of ligands and complexes
3.1.1. 1,2-Bis(3,5-di-tert-butyl-2-hydroxyphenyl-
sulfanyl)ethane (H2bse)
To a solution of 2-bromo-4,6-di-tert-butylphenol
(5.71 g; 20 mmol) in dry diethylether (25 ml) a solution
of 1.6 M n-butyllithium in n-hexane (25 ml) was added
at −50 °C. The immediately formed precipitate redis-
solved upon increasing the temperature to 20 °C. The
pale yellow solution was stirred for 30 min. After
cooling to −65 °C,
a
solution of ethane-1,2-
disulfenylchloride (1.63 g; 10 mmol) in dry diethylether
Fig. 2. Molecular structures of the neutral mononuclear complexes in crystals of 1 (top) and 4 (bottom).

T. Kruse et al. / Inorganica Chimica Acta 331 (2002) 81–89
87
(10 ml) was added dropwise. The reaction mixture was
stirred for 12 h during which time the temperature was
slowly increased to 25 °C. Water (20 ml) was carefully
added and a colorless precipitate, which had formed,
was collected by filtration. Additional product was
obtained upon separation of the liquid phases and
extraction of the aqueous phase with diethylether (2×
50 ml) and CH2Cl2. After drying the combined organic
Fig. 5. Temperature-dependence of the magnetic moment, veff/vB, of
1 (calculated per dimer) and best fit (solid line) using parameters
given in the text.
Fig. 3. Molecular structures of the dinuclear species in crystals of 2
(top) and 3 (bottom).
Fig. 6. Temperature-dependence of the magnetic moment/dimer of 2
(top) and 3 (bottom). The solid lines represent best fits using parame-
ters given in the text.
Fig. 4. Electronic spectra of 2 (top) and 3 (bottom) in CH2Cl2 (solid
lines) and after addition of two equivalents of pyridine (broken lines).

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T. Kruse et al. / Inorganica Chimica Acta 331 (2002) 81–89
13C NMR (100 MHz, CDCl3): l=29.42; 31.51; 34.42;
35.34; 115.82; 126.97; 126.99; 127.75; 130.91; 135.02;
136.03; 143.01; 153.45.
3.1.3. 4,6-Di-tert-butyl-2-phenylsulfanylphenol (Hpsp)
To a solution of 2-bromo-4,6-di-tert-butylphenol
(5.71 g; 20 mmol) in dry diethylether (25 ml) was added
a solution of 1.6 M n-butyllithium in n-hexane (25 ml)
at −50 °C. After stirring for 30 min and at 20 °C and
cooling to −65 °C, a solution of benzenesulfenyl chlo-
ride (2.89 g; 20 mmol) in dry diethylether was added
dropwise with dropwise. The work-up was the same as
described for H2bse and H2bsb. Distillation of the
residual yellow oil at 115 °C and 10−2 mbar yielded
3.40 g (54%) of Hpsp. C20H26OS (314.5): Anal. Calc.: C,
76.38; H, 8.33; S, 10.20. Found: C, 76.1; H, 8.6; S,
1
10.1%. EI-mass spectrum: m/z=314 [M]+. H NMR
(250 MHz; CDCl3): l=1.28 (9H, s); 1.40 (9H, s); 6.83
(1H, s); 7.00–7.25 (7H, m). 13C NMR (63 MHz,
CDCl3): l=29.41; 31.49; 34.36; 35.27; 115.70; 125.71;
126.30; 126.82; 129.07; 131.03; 135.73; 136.46; 142.77;
153.39.
Fig. 7. X-band EPR spectra of frozen CH2Cl2 solutions of 4 (top) and
3 at 10 K. Conditions: 4, frequency: 9.4368 GHz; power: 10.1 mW;
modulation 1.25 mT; 2, frequency: 9.4365 GHz; power 100.8 mW;
modulation 0.99 mT.
3.1.3.1. [CuII(psp)2] (1). To a solution of the ligand
Hpsp (0.63 g; 2.0 mmol) in dry methanol (30 ml) was
added under an argon atmosphere CuICl (98 mg; 1.0
mmol) and 280 ml of triethylamine. The mixture was
heated to reflux for 3 h. After removal of a colorless
precipitate by filtration in the presence of air, brown
needle shaped crystals precipitated from the solution in
the presence of air. Yield: 255 mg (37%). C40H50CuO2S2
(690.5): Anal. Calc.: C, 69.58; H, 7.30; S, 9.29. Found:
C, 69.2; H, 7.4; S, 9.5%. EI-mass spectrum: m/z=689
[M+].
phases over MgSO4, the solvent was removed by evapo-
ration under reduced pressure. The product was recrys-
tallized from n-pentane at −20 °C. Yield: 3.62 g
(72%). C30H46O2S2 (502.8): Anal. Calc.: C, 71.66; H,
9.22; S, 12.75. Found: C, 71.9; H, 9.4; S, 12.6%. EI-
1
mass spectrum: m/z=502 [M]+. H NMR (400 MHz;
CDCl3): l=1.25 (18H, s); 1.37 (18H, s); 2.78 (4H, s);
7.03 (2H, s); 7.28 (2H, d); 7.30 (2H, d). 13C NMR (100
MHz, CDCl3): l=29.42; 31.51; 34.29; 35.20; 36.24;
117.44; 126.10; 130.30; 135.31; 142.35; 153.18.
3.1.3.2. [CuI2I(bse)2] (2). CuICl (49 mg; 0.5 mmol) and
140 ml of triethylamine were added to a solution of the
ligand H2bse (251 mg; 0.5 mmol) in dry tetrahydro-
furan (25 ml). After heating to reflux for 60 min under
an argon atmosphere, the solution was exposed to air
and cooled to 20 °C. The then dark blue solution was
stored at 0 °C for 12 h whereupon colorless crystals of
[NEt3H]Cl formed, which were filtered off and dis-
carded. Removal of the solvent by evaporation under
reduced pressure yielded a green microcrystalline mate-
rial, which was recrystallized from acetone. Yield: 60
mg (21%). C60H88Cu2O4S4 (1128.7): Anal. Calc.: C,
63.85; H, 7.86; S, 11.36. Found: C, 63.8; H, 8.0; S,
11.1%. EI-mass spectrum: m/z=1128 [M]+.
3.1.2. 1,2-Bis(3,5-di-tert-butyl-2-hydroxyphenyl-
sulfanyl)benzene (H2bsb)
A solution of 1.6 M n-butyllithium in n-hexane (25
ml) was added to a solution of 2-bromo-4,6-di-tert-
butylphenol in dry diethylether at −50 °C. The imme-
diately formed precipitate redissolved upon increasing
the temperature to 20 °C. After stirring of this solution
for 30 min and subsequent cooling to −65 °C, a
solution of benzene-1,2-disulfenyl dichloride (2.11 g; 10
mmol) in dry diethylether (10 ml) was added dropwise.
After stirring at ambient temperature for 12 h with slow
increase of the reaction temperature to 20 °C, a color-
less precipitate formed. The following work-up was the
same as described above for H2bse. The product was
recrystallized from acetone at −20 °C. Yield: 3.45 g
(63%). C34H46O2S2 (550.9): Anal. Calc.: C, 74.13; H,
8.42; S, 11.64. Found: C, 75.0; H, 8.5; S, 11.4%. EI-
3.1.3.3. [CuI2I(bsb)2] (3). This complex was prepared as
described above for 2 using the ligand H2bsb as starting
material. One hundred and eighty milligrams of green–
brown crystals (29%) were obtained after recrystalliza-
tion of the crude product from CH2Cl2. C68H88Cu2O4S4
(1224.8): Anal. Calc.: C, 66.68; H, 7.24; S, 10.47.
1
mass spectrum: m/z=550 [M]+. H NMR (400 MHz;
CDCl3): l=1.30 (18H, s); 1.40 (18H, s); 6.77 (2H, q);
6.83 (2H, s); 6.97 (2H, q); 7.41 (2H, d); 7.43 (2H, d).

T. Kruse et al. / Inorganica Chimica Acta 331 (2002) 81–89
89
Found: C, 66.4; H, 7.2; S, 10.4%. EI-mass spectrum:
Acknowledgements
m/z=1224 [M]+.
We thank the Fonds der Chemischen Industrie for
financial support. Heike Schucht is thanked for skillful
help with the X-ray data collections.
3.1.3.4. [CuII(bsp)(py)2] (4). A solution of 3 (0.61 g; 0.5
mmol) and pyridine (0.08 g; 1.0 mmol) in dry CH2Cl2
(20 ml) was allowed to stand in an open vessel for 12 h.
Slow evaporation of the solvent yielded violet crystals
of 4 (0.19 g; 26%). C44H54CuN2O2S2 (770.6): Anal.
Calc.: C, 68.58; H, 7.06; S, 8.32. Found: C, 68.3; H, 7.0;
S, 8.5%. EI-mass spectrum: m/z=611 [M−2py]+.
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Crystallographic data for H2(bse), H2(bsb), H(psp),
1, 2, 3, and 4 have been deposited with the Cambridge
Crystallographic Data Centre as supplementary publi-
cations no. CCDC 165316–165322. Copies of the data
can be obtained free of charge on application to
CCDC, 12 Union Road, Cambridge CB2 1EZ, UK
(fax: +44-1223-336 033; e-mail: deposit@ccdc.
cam.ac.uk or www: http://www.ccdc.cam.ac.uk).