A simple synthetic route to the formation of tetracopper(1) 2-mercaptothiazoline compounds - The crystal structures of [Cu 4(S-thiaz)4(PEt2Ph)2], [Cu 4(S-thiaz)4(PEt3)2], [Cu 4(S-thiaz)4]2, and [Cu4(S-thiaz) 4]4

Article abstract of DOI:10.1139/V06-003

Reactions of copper(I) acetate with 2-mercaptothiazoline (HS-thiaz) in the presence of tertiary phosphines lead to the formation of tetranuclear sulphur-bridged copper complexes. Depending on the reaction conditions, isolated clusters ([Cu₄(S-thiaz)₄(PR₃)₂] (PR₃ = PPh₃ (1), PEt₂Ph (2), PEt₃ (3)), oligomeric compounds ([Cu₄(S-thiaz)₄] (4) and [Cu₄(S-thiaz)₄]₄ (5)), or a one-dimensional polymer ([Cu₄(S-thiaz)₄]∞ (6)) are formed. The structures of the compounds 2-5 have been determined by single crystal X-ray analysis.

Full text of DOI:10.1139/V06-003

251
A simple synthetic route to the formation of
tetracopper(I) 2-mercaptothiazoline compounds —
The crystal structures of [Cu4(S-thiaz)4(PEt2Ph)2],
[Cu4(S-thiaz)4(PEt3)2], [Cu4(S-thiaz)4]2, and [Cu4(S-
1
thiaz)4]4
Olaf Fuhr, Lucia Fernandez-Recio, and Dieter Fenske
Abstract: Reactions of copper(I) acetate with 2-mercaptothiazoline (HS-thiaz) in the presence of tertiary phosphines
lead to the formation of tetranuclear sulphur-bridged copper complexes. Depending on the reaction conditions, isolated
clusters ([Cu4(S-thiaz)4(PR3)2] (PR3 = PPh3 (1), PEt2Ph (2), PEt3 (3)), oligomeric compounds ([Cu4(S-thiaz)4]2 (4) and
[Cu4(S-thiaz)4]4 (5)), or a one-dimensional polymer ([Cu4(S-thiaz)4]∞ (6)) are formed. The structures of the compounds
2–5 have been determined by single crystal X-ray analysis.
Key words: copper, 2-mercaptothiazoline, single crystal X-ray analysis.
Résumé : Les réactions de l’acétate de cuivre(I) avec la 2-mercaptothiazoline (HS-thiaz), en présence de phosphines
tertiaires, conduisent à la formation de complexes de cuivre tétranucléaires comportant des ponts de soufre. Suivant les
conditions réactionnelles, il y a formation d’agrégats isolés, ([Cu4(S-thiaz)4(PR3)2] (PR3 = PPh3 (1); PEt2Ph (2); PEt3
(3)), des composés oligomères, ([Cu4(S-thiaz)4]2 (4) ou [Cu4(S-thiaz)4]4 (5)), ou d’un polymère unidimensionnel,
[Cu4(S-thiaz)4]∞ (6). Les structures des composés 2, 3, 4 et 5 ont été déterminées par diffraction des rayons X sur un
cristal unique.
Mots clés : cuivre, 2-mercaptothiazoline, diffraction des rayons X par un cristal unique.
[Traduit par la Rédaction] Fuhr et al. 256
Introduction
2-mercaptothiazoline compounds. Those that were unknown
so far were characterized by single crystal X-ray analysis.
The chemistry of copper(I) in combination with chalcogen
derivatives provides a large variety of compounds. Many
clusters with increasing numbers of metal atoms have been
synthesized, the biggest cluster to date being [Cu146Se73(PPh3)30]
(1). Typically, such clusters reflect the transition from sepa-
rated molecules or complexes to the infinite bulk phase. Not
only structural aspects are of interest, but many polynuclear
d10 compounds also show interesting photophysical features
(2). A third aspect is the fact that many enzymes contain
copper–sulphur clusters (3). Therefore, researchers have spent
considerable effort on the synthesis of copper(I) complexes
with 2-mercaptothiazoline and its derivatives as ligands (4–9).
In this work, we describe a simple route to tetracopper(I)
Experimental
All reactions were performed in a dry, oxygen-free nitro-
gen atmosphere using standard Schlenk techniques. Solvents
were dried with sodium/benzophenone and freshly distilled.
Copper(I) acetate (CuOAc) was synthesized by reduction of
copper(II) acetate with copper tunings in acetonitrile (10),
PEt3, P-n-Pr3, and PEt2Ph by common Grignard reactions
(11). PPh3 and 2-mercaptothiazoline were used as received
from the commercial source (Sigma-Aldrich).
IR-spectra were recorded as KBr pellets using a FT-IR
spectrometer Spectrum GX from PerkinElmer.
Received 28 September 2005. Published on the NRC Research Press Web site at http://canjchem.nrc.ca on 17 March 2006.
Dedicated to Professor Arthur J. Carty.
O. Fuhr2 and L. Fernandez-Recio. Forschungszentrum Karlsruhe, Institut für Nanotechnologie, Postfach 36 40, D-76021
Karlsruhe, Germany.
D. Fenske. Universität Karlsruhe (TH), Institut für Anorganische Chemie, Engesserstraße 15, Geb. 30.45D-76128 Karlsruhe,
Germany.
1This article is part of a Special Issue dedicated to Professor Arthur Carty.
2Corresponding author (e-mail: olaf.fuhr@int.fzk.de).
Can. J. Chem. 84: 251–256 (2006)
doi:10.1139/V06-003
© 2006 NRC Canada

252
Can. J. Chem. Vol. 84, 2006
Table 1. Crystallographic data for 2–5.
Compound
2
3·C7H8
4
5·2C7H8
Empirical formula
C32H46Cu4N4P2S8
C31H54Cu4N4P2S8
C24H32Cu8N8S16
C62H80Cu16N16S32
Formula mass
Colour, habit
Crystal system
Space group
1 059.31
1 055.36
1 453.86
3 091.98
Colourless, block
Monoclinic
C2/c
Colourless, block
Tetragonal
P43212
Colourless, plate
Monoclinic
P21/c
Colourless, block
Monoclinic
P21/c
Z
4
4
4
2
a (Å)
b (Å)
c (Å)
23.672(5)
11.354(2)
16.063(3)
90
94.99(3)
90
12.278(2)
12.278(2)
29.192(6)
90
90
90
16.846(3)
11.234(2)
24.336(5)
90
110.01(3)
90
20.363(4)
11.296(2)
21.928(4)
90
95.11(3)
90
α (°)
β (°)
γ (°)
Volume (Å3)
Dcalcd (g cm–3)
4 300.8(15)
1.636
4 400.7(12)
1.593
4 327.4(15)
2.232
5 023.8(18)
2.044
Temperature (K)
180
200
180
180
µ(MoKα) (mm–1)
2θ range of data collection (°)
F(000)
2.443
2.0–54.2
2 160
10 770
2.387
3.6–52
2 168
11 516
4.659
2.3–52
2 880
18 544
4.020
3.8–52
3 080
23 594
Observed reflections
Independent reflections
4 687 (Rint = 0.0403) 4 273 (Rint = 0.0528)
8 272 (Rint = 0.0475) 9 709 (Rint = 0.0905)
Independent reflections with I > 2σ(I) 3 439
3 603
12, 209
0.963
6 832
0, 506
1.172
R1 = 0.0756
5 268
0, 571
0.831
R1 = 0.0444
Restraints/parameters
0, 228
Goodness of fit on F²
Final R indices [I > 2σ(I)]
0.912
R1 = 0.0386
R1 = 0.0395
wR2 = 0.0950
R1 = 0.0542
wR2 = 0.0994
0.601, –0.684
wR2 = 0.0945
R1 = 0.0475
wR2 = 0.0973
wR2 = 0.1941
R1 = 0.0847
wR2 = 0.1967
2.037, –1.078
wR2 = 0.0767
R1 = 0.1051
wR2 = 0.0904
0.805, –0.727
R indices (all data)
Largest diff. peak and hole (e Å–3)
Flack parameter
0.613, –0.666
0.00(2)
(380 mg, 3.18 mmol) in THF (5 mL). Within 4 days, colour-
less plates of 1·2THF crystallized. Yield: 1.1 g (98%). IR
(KBr, cm–1): 3049 (m), 2941 (m), 2850 (m), 1958 (w), 1585
(w), 1571 (w), 1523 (vs), 1480 (s), 1448 (m), 1434 (s), 1304
(s), 1261 (w), 1189 (m), 1157 (w), 1093 (s), 1067 (m), 1026
(vs), 968 (vs), 934 (s), 852 (w), 746 (s), 694 (s), 619 (w),
574 (w), 518 (s), 432 (m). Anal. calcd. for
C56H62Cu4N4O2P2S8: C 48.19, H 4.48, N 4.01, S 18.38;
found: C 48.53, H 4.60, N 4.16, S 18,61.
X-ray structure determination
Crystals were removed from the reaction flask under a
stream of N2 gas and immediately covered with a layer of
perfluoropolyether oil (Riedel de Häen). A suitable crystal
was selected, attached to a glass fibre, and immediately
placed in the low-temperature nitrogen stream. The data
were collected with a STOE IPDS II diffractometer using
MoKα (λ = 0.710 73 Å) radiation produced by a common X-
ray tube (2 kW). Structure solution and refinement against
F² were carried out using SHELXS and SHELXL software
(12). Molecular drawings were prepared with Diamond 2.1
(13) and PaintShopPro 7AE (14).
Synthesis of [Cu4(S-thiaz)4(PEt2Ph)2] (2)
Copper(I) acetate (150 mg, 1.22 mmol), PEt2Ph (0.21 mL,
1.22 mmol), and 2-mercaptothiazoline (145 mg, 1.22 mmol)
were dissolved in DME (60 mL). After stirring for 1 day, the
volume of the reaction mixture was reduced to 10 mL and n-
heptane (15 mL) was added. From this solution 2 crystal-
lized within 2 h as colourless blocks. Yield: 80 mg (25%).
IR (KBr, cm–1): 3084 (w), 2958 (m), 2927 (m), 2870 (m),
2850 (m), 2361 (m), 2342 (m), 1522 (vs), 1453 (m), 1433
The crystal and refinement data of 2–5 are summarized in
Table 1.3
Synthesis of [Cu4(S-thiaz)4(PPh3)2] (1)
A solution of copper(I) acetate (390 mg, 3.18 mmol) and
triphenylphosphine (830 mg, 3.18 mmol) PPh3 in THF
(30 mL) was layered with a solution of 2-mercaptothiazoline
3 Supplementary data for this article are available on the journal Web site (http://canjchem.nrc.ca) or may be purchased from the Depository
of Unpublished Data, Document Delivery, CISTI, National Research Council Canada, Ottawa, ON K1A 0R6, Canada. DUD 5006. For more
information on obtaining material refer to http://cisti-icist.nrc-cnrc.gc.ca/irm/unpub_e.shtml. CCDC 290083–290086 contain the crystallo-
graphic data for this manuscript. These data can be obtained, free of charge, via http://www.ccdc.cam.ac.uk/conts/retrieving.html (Or from
the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax +44 1223 336033; or de-
posit@ccdc.cam.ac.uk).
© 2006 NRC Canada

Fuhr et al.
253
Scheme 1.
+ PPh3
THF
[Cu4(S-thiaz)4(PPh3)2] (1)
+ PEt2Ph
DME
CuOOCCH3
+ PEt3
THF
+
[1]
S
+ P-n-Pr3
methanol
HS
N
+ P-n-Pr3
methanol/toluene
+ PEt3
toluene
Fig. 1. Principal drawing of the [Cu4(S-thiaz)4] cage found in
compounds 1–6.
(s), 1375 (w), 1306 (m), 1259 (w), 1187 (w), 1101 (w), 1023
(vs), 967 (vs), 933 (s), 855 (w), 767 (m), 755 (m), 734 (m),
699 (m), 669 (m), 574 (w), 490 (w), 432 (w), 418 (w). Anal.
calcd. for C32H46Cu4N4P2S8: C 36.28, H 4.38, N 5.29, S
24.21; found: C 36.51, H 4.29, N 5.16, S 23.74.
Synthesis of [Cu4(S-thiaz)4(PEt3)2] (3)
Copper(I) acetate (312 mg, 2.55 mmol) was dissolved in
THF (60 mL) by adding triethylphosphine (0.38 mL,
2.55 mmol) to give a light yellow solution. After addition of
2-mercaptothiazoline (300 mg, 2.55 mmol), the reaction
mixture turned colourless and was stirred for 6 h. All vola-
tile compounds were removed under reduced pressure and
the resulting oily residue was recrystallized from toluene.
The product was isolated as big colourless crystals of
3·C7H8. Yield: 175 mg (26%). IR (KBr, cm–1): 2954 (m),
2929 (m), 2872 (m), 1525 (vs), 1450 (m), 1376 (m), 1304
(m), 1259 (w), 1194 (w), 1025 (vs), 970 (s), 933 (s), 768
(m), 729 (w), 669 (w), 576 (w), 433 (w). Anal. calcd. for
C31H54Cu4N4P2S8: C 35.28, H 5.16, N 5.31, S 24.31; found:
C 34.94, H 5.31, N 5.62, S 23.78.
Within a short time a white precipitate was formed, which
was redissolved by mild heating. After several hours the
product crystallized as colourless bars as 6·C7H8. Yield:
280 mg (45%). IR (KBr, cm–1): 2852 (w), 1524 (vs), 1447
(m), 1304 (m), 1189 (w), 1025 (s), 970 (s), 937 (s), 737 (m),
697 (w), 676 (w), 469 (w), 427 (w). Anal. calcd. for
C19H24Cu4N4S8: C 27.86, H 2.95, N 6.84, S 31.32; found: C
27.81, H 2.88, N 6.55, S 33.20.
Synthesis of [Cu4(S-thiaz)4]2 (4)
A solution of 2-mercaptothiazoline (80 mg, 0.7 mmol) in
methanol (10 mL) was added at room temperature to a solu-
tion of CuOAc (86 mg, 0.7 mmol) and P-n-Pr3 (0.07 mL,
0.35 mmol) in methanol (20 mL). After 30 min, the pale yel-
low solution was separated from a white precipitate. Within
several days compound 4 crystallized from the filtrate as
colourless plates. Yield: 50 mg (39%). IR (KBr, cm–1): 3430
(w), 1636 (m), 1532 (s), 1505 (m), 1309 (m), 1026 (s), 970
(m), 931 (m). Anal. calcd. for C24H32Cu8N8S16: C 19.83, H
2.22, N 7.71, S 35.29; found: C 20.47, H 1.81, N 7.34, S
35.81.
Results and discussion
When 2-mercaptothiazoline (HS-thiaz) reacts with cop-
per(I) acetate it is deprotonated and sulphur-bridged copper
clusters are formed. The main structural motif of these com-
pounds is a [Cu4(S-thiaz)4] cage, which is shown in Fig. 1.
The four copper atoms of this unit are bridged by the four
exocyclic sulphur atoms of the 2-mercaptothiazoline ligands
forming an eight-membered, folded ring. In addition, the
heterocycles coordinate via the lone pairs of the nitrogen at-
oms to the copper atoms of the Cu4S4 core. Depending on
the reaction conditions — especially the solvent used — dif-
ferent substances can be synthesized: compounds with iso-
lated [Cu4(S-thiaz)4] cages (1–3), as well as oligomeric (4,
5) and polymeric (6) products (Scheme 1). All reactions
have been carried out in the presence of tertiary phosphines
as additional donor components.
Synthesis of [Cu4(S-thiaz)4]4 (5)
A solution of 2-mercaptothiazoline (160 mg, 1.31 mmol)
in methanol (10 mL) was added at room temperature to a so-
lution of CuOAc (161 mg, 1.31 mmol) and P-n-Pr3
(0.13 mL, 0.66 mmol) in methanol (40 mL). After 30 min,
the pale yellow solution was separated from a white precipi-
tate. Toluene (30 mL) was added to the filtrate; within the
next 2 weeks, compound 4 and 5 crystallized from this solu-
tion.
In ethereal solvents two phosphine molecules are coordi-
nated to one Cu4 unit forming clusters of the type [Cu4(S-
thiaz)4(PR3)2] (PR3 = PPh3 (1), PEt2Ph (2), PEt3 (3)). 1 has
been synthesized before starting from copper(II) acetate un-
der reductive conditions (4); the crystallographic data pub-
Synthesis of [Cu4(S-thiaz)4]∞ (6)
2-Mercaptothiazoline (360 mg, 3.06 mmol) was added to
a solution of copper(I) acetate (375 mg, 3.06 mmol) and
triethylphosphine (0.45 mL, 3.06 mmol) in toluene (60 mL).
© 2006 NRC Canada

254
Can. J. Chem. Vol. 84, 2006
Fig. 2. Molecular structure of 2 (H atoms are omitted for clarity).
Fig. 3. Molecular structure of 4 (H atoms are omitted for clarity).
Fig. 4. A section of the layer structure of 4 showing the Cu—Sendo interactions (dashed lines).
© 2006 NRC Canada

Fuhr et al.
255
Fig. 5. Molecular structure of 5 (H atoms are omitted for clarity).
lished could be proven by our samples. Using methanol as
solvent, a dimer, [Cu4(S-thiaz)4]2 (4), is formed, a mixture
of methanol and toluene leads to the formation of a tetramer,
[Cu4(S-thiaz)4]4 (5). Finally, in pure toluene a one-
dimensional polymer, [Cu4(S-thiaz)4]∞ (6), is formed, which
is also already described in the literature, obtained via an
electrochemical synthesis (5). Again the crystallographic
data published there fit with our sample.
carry one negative charge, we assume that the description as
a copper(I) compound is the right one.
Compound 4 crystallizes as colourless plates in the
monoclinic space group P21/c with four formula units per el-
ementary cell. Figure 3 shows one dimeric unit of 4; another
crystallographically independent molecule is found in the
asymmetric unit having, within experimental errors, the
same bonding parameters.
4 consists of two [Cu4(S-thiaz)4] clusters connected via
the atoms Cu4 and S5. There is an inversion centre in the
middle of the so formed Cu2S2 ring. Cu—S distances within
a Cu4S4 cycle range from 223.7(4) to 244.8(3) pm, the
Cu4—S5′ bond is slightly longer (255.4(3) pm). This kind of
cluster agglomeration is also found in 6 where the Cu4 units
form infinite strands (5). In contrast to 1–3 and 6 where no
intermolecular bonds are present, the dimers in 4 are inter-
connected by donor bonding of two endocyclic sulphur at-
oms (S6, S6′) to copper atoms of neighbouring molecules. In
this way layers are formed and this is illustrated in Fig. 4.
Therefore, Cu2 is shifted out of the centre of the triangle
formed by S1, S3, and N3, whereas Cu1 and Cu3, which
have no intermolecular contacts, are nearly in plane with
their neighbouring atoms. The average Cu—Sendo distances
are 289.7 pm, which is significantly shorter than the sum of
the van der Waals radii of copper and sulphur (320 pm (17)).
The same kind of intermolecular linking was also found in
the compound [Cu4(S-thiaz)4(NC5H5)] (4).
In 5 (Fig. 5) four [Cu4(S-thiaz)4] units are bound together
forming a tetramer. Compound 5 crystallizes in the mono-
clinic space group P21/c with two molecules per elementary
cell and two molecules of toluene per formula unit.
The middle part of 5 is identical with 4: two [Cu4(S-
thiaz)4] units being connected via two Cu—S bonds (Cu1—
S1′ and Cu1′—S1, 279.0(2) pm). The two additional subunits
are both bonded to this inner part by one Cu—S bond
(Cu5—S3, 253.6(2) pm). Altogether, the tetramer has a
length of 2.16 nm. As in 4 the molecules are agglomerated
by interactions between copper atoms (Cu2) and endocyclic
Crystal structures of 2–5
The colourless compound 2 (Fig. 2) crystallizes in the
monoclinic space group C2/c with four molecules per unit
cell. There is a twofold axis running through each molecule.
The Cu—S distances in the Cu4S4 cycle range between
220.2(1) pm (Cu2—S1) and 250.3(1) pm (Cu1—S3′); Cu—
N distances are Cu1—N1′, 203.4(3) pm, and Cu2—N2′,
201.4(3) pm. Cu2 and Cu2′ have a nearly trigonal planar co-
ordination sphere (the sum of the bond angles is 358.8°).
Both Cu1 and Cu1′ are additionally bonded to a phosphine
ligand (Cu1—P1, 227.0(1) pm), whereby these copper atoms
achieve a distorted tetrahedral coordination.
3 crystallizes as colourless blocks in the tetragonal space
group P43212 with four molecules per unit cell and one tolu-
ene molecule per formula unit. The molecular structure of 3
is analogous to 2 except for the different phosphine ligands.
Therefore, further discussions of the structure are unneces-
sary.
There is one example in the literature of a similar tetra-
nuclear copper compound with no further coordinating
ligands or aggregation of cages, where chiral benzyl-
substituted 2-mercaptothiazoline is used as chelating ligand.
Indeed, this compound has been published twice, once dis-
cussed as a copper(II) species (CCDC no. 174127) (15) and
1 year later as a copper(I) compound (CCDC no. 174125)
(16). Though the compounds have been synthesized in dif-
ferent ways, the crystallographic parameters are the same.
As both are described as colourless, and each ligand should
© 2006 NRC Canada

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Can. J. Chem. Vol. 84, 2006
Fig. 6. A section of the layer structure of 5 showing the Cu—Sendo interactions (dashed lines).
5. E.S. Raper, J.R. Creighton, and W. Clegg. Inorg. Chim. Acta,
237, 87 (1995).
6. E.S. Raper, J.R. Creighton, W. Clegg, L. Cucurull-Sanchez,
M.N.S. Hill, and P.D. Akrivos. Inorg. Chim. Acta, 271, 57
(1998).
sulphur atoms (S14) of neighbouring molecules (Cu—Sendo
302.6(1) pm). Layers are also formed in this case as illus-
trated in Fig. 6.
,
Conclusion
7. P. Aslanidis, S.K. Hadjikakou, P. Karagiannidis, and P.J. Cox.
Inorg. Chim. Acta, 271, 243 (1998).
Tetranuclear copper(I) 2-mercaptothiazoline complexes
can be easily synthesized starting from copper(I) acetate by
deprotonation of the ligand. Depending on the reaction con-
ditions the [Cu4(S-thiaz)4] cages are either monomeric (1–3)
with two additional phosphine ligands, or they form
oligomeric (4, 5) or polymeric (6) aggregates. In 4 and 5 ad-
ditional intermolecular interactions between endocyclic sul-
phur atoms and copper atoms of neighbouring molecules are
found.
8. J.-M. Du, H.-Y. Zeng, Z.-C. Dong, G.-C. Guo, and J.-S.
Huang, Acta Crystallogr. Sect. C, C58, M396 (2002).
9. P. Aslanidis, P.J. Cox, P. Karagiannidis, S.K. Hadjikakou, and
C.D. Antoniadis. Eur. J. Inorg. Chem. 2216 (2002).
10. D.A. Edwards and R. Richards. J. Chem. Soc. Dalton Trans.
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Sheldrick. SHELXL-97 [computer program]. University of
Göttingen, Göttingen, Germany. 1997.
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© 2006 NRC Canada