Reaction of β-diketiminate copper(II) complexes and Na 2S2

Article abstract of DOI:10.1039/b808678h

Reaction of β-diketiminate copper(ii) complexes and Na ₂S₂ resulted in formation of (μ-η²: η²-disulfido)dicopper(ii) complexes (adduct formation) or β-diketiminate copper(i) complexes (reduction of copper(ii)) depending on the substituents of the supporting ligands. In the case of sterically less demanding ligands, adduct formation occurred to provide the (μ- η²:η²-disulfido)dicopper(ii) complexes, whereas reduction of copper(ii) took place to give the corresponding copper(i) complexes with sterically more demanding β-diketiminate ligands. Spectroscopic examinations of the reactions at low temperature using UV-vis and ESR as well as kinetic analysis have suggested that a 1: 1 adduct LCu^II-S-SNa with an end-on binding mode is initially formed as a common intermediate, from which different reaction pathways exist depending on the steric environment of the metal-coordination sphere provided by the ligands. Thus, with the sterically less demanding ligands, rearrangement of the disulfide adduct from end-on to side-on followed by self-dimerisation occurs to give the (μ- η²:η²-disulfido)dicopper(ii) complexes, whereas such an intramolecular rearrangement of the disulfide co-ligand does not take place with the sterically more demanding ligands. In this case, homolytic cleavage of the Cu^II-S bond occurs to give the reduced copper(i) product. The steric effects of the supporting ligands have been discussed on the basis of detailed analysis of the crystal structures of the copper(ii) starting materials. The Royal Society of Chemistry 2008.

Full text of DOI:10.1039/b808678h

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PAPER
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Reaction of b-diketiminate copper(II) complexes and Na2S2†
Masayuki Inosako,a Atsushi Kunishita,a Chizu Shimokawa,a Junji Teraoka,a Minoru Kubo,b Takashi Ogura,b
Hideki Sugimotoa and Shinobu Itoh*a
Received 22nd May 2008, Accepted 21st August 2008
First published as an Advance Article on the web 1st October 2008
DOI: 10.1039/b808678h
Reaction of b-diketiminate copper(II) complexes and Na2S2 resulted in formation of
2
2
(m-h :h -disulfido)dicopper(II) complexes (adduct formation) or b-diketiminate copper(I) complexes
(reduction of copper(II)) depending on the substituents of the supporting ligands. In the case of
sterically less demanding ligands, adduct formation occurred to provide the
2
2
(m-h :h -disulfido)dicopper(II) complexes, whereas reduction of copper(II) took place to give the
corresponding copper(I) complexes with sterically more demanding b-diketiminate ligands.
Spectroscopic examinations of the reactions at low temperature using UV-vis and ESR as well as
kinetic analysis have suggested that a 1 : 1 adduct LCuII–S–SNa with an end-on binding mode is
initially formed as a common intermediate, from which different reaction pathways exist depending on
the steric environment of the metal-coordination sphere provided by the ligands. Thus, with the
sterically less demanding ligands, rearrangement of the disulfide adduct from end-on to side-on
2
2
followed by self-dimerisation occurs to give the (m-h :h -disulfido)dicopper(II) complexes, whereas such
an intramolecular rearrangement of the disulfide co-ligand does not take place with the sterically more
demanding ligands. In this case, homolytic cleavage of the CuII–S bond occurs to give the reduced
copper(I) product. The steric effects of the supporting ligands have been discussed on the basis of
detailed analysis of the crystal structures of the copper(II) starting materials.
tetradentate N4 ligands such as TPA [tris(2-pyridylmethyl)amine]
Introduction
and its derivatives provide the end-on disulfido dicopper(II)
complex A, whereas tridentate N3 ligands such as PY2 {bis[2-
(2-pyridyl)ethyl]amine} afford the side-on disulfido dicopper(II)
complex B. The core structures obtained in these reactions are
similar to those obtained in the reactions between O2 and the
copper(I) complexes supported by the same ligands.10,11 Namely,
the tetradentate N4 ligands afforded the end-on type (trans-
m-1,2-peroxo)dicopper(II) complexes, whereas the tridentate N3
The reaction of copper(I) complexes and elemental sulfur S8 has
been given much recent attention as an efficient method for the
preparation of several Cu/S clusters.1 So far, disulfido-bridged
dicopper(II) complexes both with an end-on and a side-on binding
mode (A and B in Chart 1, respectively)2–7 and a bis(m3-sulfido)
mixed valent trinuclear copper(II,II,III) complex C8 as well as
∑
a bis(m-1,2-S2 -)dicopper(II) complex D9 have been prepared by
2
2
this method using several nitrogen donor ligands. For instance,
ligands mainly gave the side-on type (m-h :h -peroxo)dicopper(II)
complexes. Formation of the mixed valent trinuclear copper
complex C involving the bis(m3-sulfido) unit in the ethylenediamine
N2 didentate ligand system is also analogous to the formation
of the mixed valent bis(m3-oxo)tricopper(II,II,III) complex in the
oxygenation reaction of copper(I) complex of the same ligand.10–12
More recently, the reaction of copper(II) complexes and sulfides
(reduced sulfur) has also been examined as an alternative method
for the preparation of Cu/S clusters. Tolman and coworkers
recently reported the formation of novel Cu/S cluster complexes
of varying nuclearity (Cu2–6) in the reaction of CuIIX2 (X =
CF3SO3- or Cl-) and Li2S or Na2S2 in the presence of N,N,N¢,N¢-
tetramethyl-trans-(1R,2R)-diaminocyclohexane (Me4chd).13 We
have also demonstrated that the reaction of copper(II) acetate com-
plexes supported by b-diketiminate ligands and Na2S2 afforded the
disulfido dicopper(II) complexes with the side-on binding mode
B.14 The reaction can be regarded as a sulfur version of the
copper(II)-H2O2 reaction, which affords various types of Cu2/O2
complexes.15 However, little is known about the mechanistic details
of the reaction between copper(II) complexes and sulfides. Thus,
in this study, we have investigated the reaction of a series of
Chart 1
aDepartments of Chemistry and Material Sciences, Graduate School of
Science, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka,
558-8585, Japan. E-mail: shinobu@sci.osaka-cu.ac.jp
bPicobiology Research Center, Graduate School of Life Science, University
of Hyogo, 3–2–1 Koto, Kamigori-cho, Ako-gun, Hyogo, 678-1297, Japan
† Electronic supplementary information (ESI) available: Fig. S1: ESR
spectrum of 3a. Fig. S2: ESR spectrum of 1c. CCDC reference numbers
688667 (3a) and 688668 (4a). For ESI and crystallographic data in CIF or
other electronic format see DOI: 10.1039/b808678h
6250 | Dalton Trans., 2008, 6250–6256
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Table 1 Summary of X-ray crystallographic data of the CuII-complexes
3a and 4a
b-diketiminate copper(II) complexes and Na2S2 in order to shed
light on the reaction mechanism and ligand effects on the reaction.
Compound
3a
4a
Results and discussion
Empirical formula
Mr
C31H44CuN2O2
540.25
Monoclinic
C2/c (no. 15)
13.943(5)
14.355(4)
16.170(5)
C27H36CuN2O2
484.14
Structural characterisation of copper(II) acetate complexes
(starting materials)
Crystal system
Space group
Triclinic
¯
P1 (no. 2)
˚
a/A
8.015(6)
8.546(7)
19.929(17)
88.52(2)
83.23(2)
67.57(2)
1252.8(17)
2
514.00
1.283
-160
0.32 ¥ 0.23 ¥ 0.03
8.968
0.077
9984
3586[I > 3.0s(I)]
325
0.0866; 0.1944
1.048
The mononuclear copper(II) acetate complexes (starting mate-
rials) 1a, 2a, 3a and 4a supported by b-diketiminate ligands
L1-, L2-, L3- and L4- (deprotonated form of L1H–L4H, see
Chart 2), respectively, were prepared by treating the ligands and
Cu(OAc)2·H2O in refluxing methanol or ethanol for 48 h as
reported previously.14,16,17 The crystal structures of complexes 3a
and 4a have been determined in this study, and those of 1a and 2a
have already been reported in our previous papers.16,17 The ORTEP
drawings of the cationic parts of 3a and 4a are shown in Fig. 1,
and their crystallographic data are summarised in Table 1.
˚
b/A
˚
c/A
a/◦
b/◦
g /◦
V/A
Z
106.237(7)
3
˚
3107.3(16)
4
1156.00
1.155
23
0.38 ¥ 0.28 ¥ 0.24
7.297
0.048
15213
2331 [I > 2.0s(I)]
193
0.0543; 0.1403
1.003
F(000)
Dc/g cm-3
T/◦C
Crystal size/mm
m(Mo-Ka)/cm-1
Rint
No. reflns measd
No. reflns obsd
No. variables
Ra; wRb
GOF
ꢀ
ꢀ
ꢀ
ꢀ
2
1/2
a R = ꢀFo| - |Fcꢀ/ |Fo|. b Rw = [ w(|Fo|2 - |Fc|2)2/ wFo
] .
Chart 2
Overall structures of 3a and 4a look similar to those of 1a and
2a, exhibiting a mononuclear square planar geometry with the
N2O2 donor set, where two nitrogen atoms and two oxygen atoms
are provided by the b-diketiminate ligand and the didentate acetate
co-ligand, respectively.18 However, more detailed inspection of the
X-ray structures revealed notable structural differences among the
complexes as described below.
Compound 1a exhibits the Cb–N–CAr angles (CAr = C1 carbon
of the 2,6-disubstituted phenyl group) as 116.9(2)◦ and the Cu–N
˚
bond length as 1.944(2) A (see Fig. 2 and Table 2). Introduction
of methyl groups into the b-position of the carbon framework to
give complex 2a resulted in an increase of the Cb–N–CAr angle
to 120.◦ (average value, see Table 2), whereas the average Cu–
˚
N bond length decreased to 1.910 A. The structural change in
going from 1a to 2a may be due to a steric repulsion between
the b-methyl groups and the 2,6-diisopropylphenyl groups of L2.
Namely, the nitrogen atoms are enforced to move inward of the
six-membered chelate ring in order to reduce the steric repulsion
between the N-aromatic substituent and the b-methyl group. Such
an enhanced steric repulsion between the substituents in 2a is also
reflected in the larger torsion angle consisting of Cb–N–CAr–Co(o-
position of Ar group) of 83.1◦ (average value) in 2a as compared
to those in 1a (average value 73.3◦). The dihedral angle defined by
N(1)–Cu(1)–N(2) and O(1)–Cu(1)–O(2) planes of the N2CuO2
core in 2a is 7.0◦, which is also larger than that of 1a (0.0◦). The
Fig. 1 ORTEP drawings of copper(II) acetate complexes 3a and 4a
showing 50% probability thermal ellipsoids. The hydrogen atoms are
omitted for simplicity.
structural features of 3a are similar to those of 2a. Namely, com-
plex 3a has a larger Cb–N–CAr angle of 119.2(2)◦, a shorter Cu–N
˚
bond length of 1.905(2) A, a larger torsion angle Cb–N–CAr–Co
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[eqn (1)].14 Compound 1d exhibited two intense absorption bands
at 333 (e = 24 000 M-1 cm-1) and 432 (12 500), attributable to
the ligand based p–p* and/or S2 to CuII LMCT transitions,
2-
together with a weak d–d band at 867 nm (150 M-1 cm-1).14
The resonance-Raman spectrum of 1d newly obtained in the
present study showed an isotope sensitive band at 446 cm-1, which
shifted to 431 cm-1 upon 34S-substitution using Na234S2 instead of
Na232S2 (Fig. 3). The peak position and its associated isotope
2
2
shift are fully consistent with those of the reported (m-h :h -
disulfido)dicopper(II) complexes.6 Thus, the band can be assigned
to a S–S stretching vibration nS–S of the side-on disulfido ligand.
The additional peaks at 509 and 605 cm-1 also shifted to 506
and 603 cm-1, respectively. Judging from their small isotope shifts,
these Raman bands can be assigned to the stretching vibrations
arising from the b-diketiminate ligand backbone, which may also
be affected slightly by the isotope substitution of the disulfide
moiety. Furthermore, compound 1d was ESR silent and exhibited
a sharp 1H NMR spectrum,14 indicative of the existence of strong
antiferromagnetic coupling interaction between the two CuII ions
through the side-on disulfido bridging ligand.
Fig. 2 ORTEP drawings around the N2CuO2 core of 1a, 2a, 3a and 4a
showing 50% probability thermal ellipsoids. The ORTEP drawings of 1a
and 2a are generated by using the reported data.16,17
(1)
of 80.5◦ and a larger dihedral angle between N(1)–Cu(1)–N(1)*
and O(1)–Cu(1)–O(1)* planes of 10.1◦, as compared with the
respective values of 1a (Table 2).
On the other hand, replacement of the 2,6-diisopropylphenyl
(Dipp) groups in 3a by 2,6-diethylphenyl (Dep) groups to give
˚
4a resulted in an increase of the Cu–N bond length to 1.921 A
(average value) (compare the structural parameters between 3a
and 4a in Fig. 2). Although the torsion angle of Cb–N–CAr–
Co of 82.7◦ (average value) and the Cb–N–CAr angle of 119.2◦
(average value) are similar to those of 2a and 3a, the dihedral
angle between N(1)–Cu(1)–N(2) and O(1)–Cu(1)–O(2) planes is
much smaller (5.0◦) as in the case of 1a. These data clearly indicate
that the steric repulsion between the b-methyl group and the 2,6-
disubstituted phenyl group is reduced by changing the substituents
from isopropyl to ethyl. Overall, it can be concluded that L1- and
L4- are sterically less demanding ligands as compared with L2-
and L3-. These structural features are reflected to the differences
in reactivity of the complexes toward Na2S2 as described below.
Fig. 3 Resonance-Raman spectra of 1d generated by using Na232S2 (A)
and Na234S2 (B) in CH2Cl2 obtained with an excitation wavelength of
441.6 nm at room temperature.
Reaction of the copper(II) complexes and Na2S2
The reaction of 2a having b-methyl groups in addition to the a-
cyano group on the carbon framework with Na2S2 under the same
experimental conditions resulted in precipitation of yellow solid
material, which was insoluble to ordinary organic solvents. The
IR spectrum of the isolated product was identical to that of the
Treatment of 1a with 0.5 equivalent of Na2S2 in CH3CN under
Ar atmosphere gave dark reddish solid material in a 78% yield,
2
2
which was identified as the (m-h :h -disulfido)dicopper(II) complex
1d by the X-ray crystallographic analysis as previously reported
Table 2 Structural parameters of CuII-complexes 1a, 2a, 3a and 4a
Structural parameter
1a
1.944(2)
116.9(2)
73.3
2a
3a
1.905(2)
119.2(2)
80.5
4a
Cu–N/A
1.914(4), 1.905(4) (1.910)c
1.920(5), 1.921(4) (1.921)c
˚
◦
Cb–N–CAr
/
119.7(4), 120.4(4) (120.1)c
118.2(4), 120.2(4) (119.2)c
◦
Torsion anglea,c
/
83.1
7.0
82.7
5.0
Dihedral angleb/◦
0.0
10.1
a Torsion angle consisting of Cb–N–CAr–Co(o–position of Ar). b Dihedral angle between N–Cu–N¢ and O–Cu–O¢ planes. c Average value.
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known copper(I) b-diketiminate coordination polymer complex,
which was previously obtained in the reaction of L2H and
[CuI(CH3CN)4]PF6 in the presence of base.19 Thus, the copper(II)
complex 2a was found to be reduced to the corresponding
copper(I) complex 2e in a 77% yield by the reaction with Na2S2 [eqn
(2)]. Similarly, copper(II) complex 3a without the a-cyano group
but having the b-methyl groups on the carbon framework was
reduced to copper(I) complex 3e by the reaction with Na2S2 under
the same experimental conditions [65% yield, eqn (3)]. The IR and
MS spectra of 3e were identical to those of [CuI(L3)(CH3CN)] in
the literature.20
(2)
Fig. 4 UV-vis spectra of 1a, 1b and 1c in CH2Cl2–CH3OH (2 : 1) at
-80 ◦C. Inset: Titration for the formation of 1b.
copper complex clearly demonstrates that the reaction from 1b to
1c is a unimolecular process with respect to the copper complex.
Intermediate 1c was further converted to the final product, (m-
(3)
2
2
h :h -disulfido)dicopper(II) complex 1d, when the temperature of
the reaction mixture was raised to room temperature, and the UV-
vis spectrum of the final reaction mixture was identical to that of
Interestingly, replacement of the 2,6-diisopropylphenyl (Dipp)
2
2
groups of 3a by 2,6-diethylphenyl (Dep) groups resulted in forma-
the isolated (m-h :h -disulfido)dicopper(II) complex (the spectrum
2
2
is not shown in Fig. 4).14
tion of the (m-h :h -disulfido)dicopper(II) complex 4d exhibiting
similar spectral features to those of 1d [eqn (4)],14 although the
yield was lower (39%).21
Fig. 5 shows the spectral change for the reaction of copper(II)
complex 3a and Na2S2 under the same experimental conditions,
where formation of intermediate 3b exhibiting two intense absorp-
tion bands at lmax = 483 nm (e = 3240 M-1 cm-1) and 625 (3580)
was observed at the initial stage of the reaction. The spectrum of 3b
is fairly close to that of intermediate 1b shown in Fig. 4, suggesting
that both intermediates 1b and 3b have a similar structure. In fact,
the stoichiometry of CuII to Na2S2 for the formation of 3b was also
1 : 1 (inset of Fig. 5) as in the case of the formation of 1b (inset of
Fig. 4). In contrast to the case of the adduct formation reaction
of 1a to give 1d, intermediate 3b was reduced to the copper(I)
compound 3e having a featureless UV-vis spectrum in the visible
(4)
Reaction pathway
In order to get insight into the ligand effects on the reactivity
of the copper(II) complexes toward Na2S2 (adduct formation vs.
reduction), the reactions of 1a leading the adduct formation and 3a
causing the reduction of copper(II) were examined in more detail at
low temperature. Fig. 4 shows the spectral change for the reaction
of 1a (2.0 ¥ 10-4 M) and Na2S2 (1 equiv.) in CH2Cl2–CH3OH
(2 : 1) at -80 ◦C. At the initial stage of the reaction, intermediate 1b
exhibiting absorption bands at 520 nm (e = 1310 M-1 cm-1) and 640
(1210) immediately appeared (within a few seconds after mixing).
Titration for the formation of this intermediate from 1a with Na2S2
(inset of Fig. 4) clearly demonstrated that the intermediate 1b is a
1 : 1 adduct between the copper(II) complex and Na2S2.
Intermediate 1b was then gradually converted to another
intermediate 1c exhibiting absorption bands at 424 nm (e =
3070 M-1 cm-1) and 610 (845). Notably, the conversion of 1b
to 1c obeyed first-order kinetics, and the first-order dependence
of this process was confirmed by the fact that the first-order
rate constants obtained from the reactions with different initial
concentration of 1a were nearly identical; kobs = 9.4 ¥ 10-3 s-1,
9.0 ¥ 10-3 s-1, 9.5 ¥ 10-3 s-1, and 8.5 ¥ 10-3 s-1, at [1a] = 0.2, 0.4,
0.6 and 0.8 mM, respectively. The first-order dependence on the
Fig. 5 UV-vis spectra of 3a and 3b in CH2Cl2–CH3OH (2 : 1) at
-80 ◦C. Inset: Titration for the formation of 3b.
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region at the elevated temperature (the spectrum is not shown in
Fig. 5).
In the case of 1b supported by the sterically less demanding
ligand L1-, intramolecular rearrangement of the disulfide co-
ligand may occur from end-on to side-on to give another inter-
All these results can be interpreted by the reaction pathway
shown in Scheme 1. In the initial stage of the reaction, both
copper(II) starting materials 1a and 3a (LCuIIOAc) react with
Na2S2 to form similar 1 : 1 adducts 1b and 3b, respectively. The
ESR spectrum of 3b shown in Fig. 6, which is different from that of
starting material 3a shown in Fig. S1 (see ESI†), is very close to that
of Tolman’s three-coordinate copper(II)-thiolate complex with b-
diketiminate ligand L3-.22 This strongly suggests that intermediate
3b has a similar three coordinate structure with N2S donor set,
where disulfide co-ligand binds to the copper ion in an end-
on fashion. Despite our great efforts, however, Raman data of
intermediate 3b has yet to be obtained.
2
2
mediate 1c, from which (m-h :h -disulfido)dicopper(II) complex
1d can be generated by self-dimerisation. The first-order kinetics
observed in the conversion of 1b to 1c is consistent with this
mechanism. Furthermore, the ESR spectrum of 1c shown in Fig.
S2 (ESI†) supports the mononuclearity of 1c. Another sterically
less demanding ligand L4 may follow the same reaction pathway
2
2
to give (m-h :h -disulfido)dicopper(II) complex 4d.
On the other hand, with sterically more demanding ligand
L3-, such an intramolecular rearrangement of the sulfide co-
ligand from end-on to side-on may be prohibited due to the
steric congestion around the coordination sphere, thus CuII–S
bond homolysis predominates to give the copper(I) product 3e.
Similarly, the reduction of copper(II) to copper(I) occurred in the
case of another sterically demanding ligand L2-. The different
reactivity between the 1a/4a-system and the 2a/3a-system could
not be attributed to a difference in the reduction potential of the
copper(II) complexes, since regardless of the presence or absence
of the strong electron withdrawing substituent a-CN both the
adduct formation and the reduction of copper(II) occur.23
In summary, we have demonstrated that the reaction of b-
diketiminate copper(II) complexes and Na2S2 leads to formation of
a mononuclear LCuII–S–SNa end-on adduct as a key intermediate,
2
2
from which both the (m-h :h -disulfido)dicopper(II) complexes
and the copper(I) complexes are generated depending on the
substituents of supporting ligand. The results can be interpreted
by taking into account of the steric congestion around the metal-
coordination sphere as discussed above. Similar steric effects by the
substituents of b-diketiminate ligand system have been reported
in Cu(I)/O2 chemistry.24 Thus, the present results provide further
insight into the ligand effects on the reactivity of the b-diketiminate
complexes toward small molecules.
Experimental
Scheme 1
General
The reagents and the solvents used in this study except the ligands
and the complexes were commercial products of the highest
available purity and were further purified by the standard methods,
if necessary.25 Na2S2 was prepared according to the reported
procedures,26 and the purity of the Na2S2 sample (~98%) was
confirmed by the reported method.26 The isotope labeled Na234S2
was prepared by the reaction of Na and 34S8 (isotope content
is 99%, purchased from Euriso-top) according to the reported
procedures.26 The ligand precursors L1H, L2H, L3H and L4H (see
Chart 2) were prepared by the reported methods.19,27–29 Copper(II)
acetate complexes 1a, 2a, 3a and 4a were prepared according to
the reported procedures.14,17 FT-IR spectra were recorded on a
Jasco FTIR-4100 and UV-visible spectra were taken on a Hewlett
Packard 8453 photo diode array spectrophotometer equipped with
1
a Unisoku thermostated cell holder USP-203. H NMR spectra
Fig. 6 Experimental ESR spectrum of 3b in CH2Cl2 at -150 ◦C
(Exp); microwave frequency 9.40 GHz, modulation frequency 100 kHz,
modulation amplitude 5 G, microwave power 0.097 mW, and its computer
simulation spectrum (Sim) with the ESR parameters g1 = 2.210, g2 = 2.035,
g3 = 2.046, ACu1 = 180 G, ACu2 = 15 G, ACu3 = 15 G, AN1 = 15 G, AN2 = 15
G, AN3 = 13.5 G, W1 = 13 G, W2 = 30 G, W3 = 7 G.
were recorded on a JEOL FT-NMR GX-400 spectrometer. Mass
spectra were recorded on a JEOL JMS-700T Tandem MS-station
mass spectrometer. Raman scattering was excited by a He/Cd laser
(Kinmon Electrics, CDR80SG) and the resonance-Raman light
was dispersed with a JEOL 400D Raman spectrometer equipped
6254 | Dalton Trans., 2008, 6250–6256
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with a modified cryostat cell holder USP-203 for the Raman
measurements. Elemental analyses were recorded with a Perkin-
Elmer or a Fisons instruments EA1108 Elemental Analyzer.
(0.6–2.0 equivalent). For each addition of Na2S2, a new solution
of the copper(II) complex was used.
X-Ray structure determination. The single crystals of 3a and
4a were obtained by solvent vaporization from a CH3OH solution
containing the complex in a glove-box ([O2] <1 ppm, [H2O]
<1 ppm). A crystal suitable for X-ray analysis was mounted
on a glass-fiber. Data of X-ray diffraction were collected by a
Rigaku CCD area detector with graphite-monochromated Mo-
14
Reaction of 1a and Na2S2
.
To a CH3CN solution (40 mL) of
1a (165.5 mg, 0.30 mmol) was added Na2S2 (17.6 mg, 0.16 mmol)
suspended in CH3CN (5 mL), and the mixture was stirred for
60 min under anaerobic conditions (Ar). The resulting dark
reddish solid was immediately collected by filtration and dried
to give compound 1d in a 78% yield (114.7 mg). 1H NMR (CDCl3,
400 MHz); d 0.93 (d, J = 6.8 Hz, 24 H, CH3), 1.04 (d, J =
6.8 Hz, 24 H, CH3), 2.80 (q, J = 6.8 Hz, 8 H, CH), 6.98 (d,
Ka radiation (l = 0.71070 A) to 2qmax of 55◦. All the crystal-
˚
lographic calculations were performed by using Crystal Structure
software package of the Molecular Structure Corporation [Crystal
Structure: Crystal Structure Analysis Package version 3.8.0,
Molecular Structure Corp. and Rigaku Corp. (2005)].30 The crystal
structures were solved by the direct methods using SIR200231
and refined by the full-matrix least squares against F2. All non-
hydrogen atoms were refined anisotropically. Hydrogen atoms
were located at calculated positions and not refined.
J = 8.0 Hz, 8 H, HAr-3), 7.18 (t, J = 8.0 Hz, 4 H, HAr-4), 7.37 (s,
-1
4 H, CH); IR (KBr): 2207 cm-1 (C N), 1563 cm (C N); HRMS:
m/z 1019.3955, calc. for C56H73Cu2N6S2 1019.4130; Anal. Calc.
for C56H72Cu2N6O2·H2O: C, 64.77; H, 7.18; N, 8.09. Found: C,
65.07; H, 7.01; N, 8.12%; UV-vis (THF); lmax/nm (e/M-1 cm-1);
333 (24 000), 432 (12 500), 867 (150). Single crystals of 1d were
obtained by slow diffusion of methanol into a CH2Cl2 solution
of 1d.
∫
=
Acknowledgements
Reaction of 2a and Na2S2. To a CH3CN solution (5 mL) of
2a (42.5 mg, 0.08 mmol) was added Na2S2 (4.6 mg, 0.04 mmol)
suspended in CH3CN (3 mL), and the mixture was stirred for
30 min under anaerobic conditions (Ar). The resulting yellow
solid was immediately collected by filtration and dried to give
compound 2e in a 77% yield (29.2 mg). The IR and mass spectra
of the product were identical with those of the authentic sample
of 2e.19
This work was financially supported in part by Grants-in-Aid for
Scientific Research on Priority Area (Nos. 18033045, 19020058,
19027048 and 19028055 for S. I.) from MEXT, Japan.
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˚
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The Royal Society of Chemistry 2008
Dalton Trans., 2008, 6250–6256 | 6255
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