Synthesis and structure determination of two neutral cadmium thiophenolate clusters

Article abstract of DOI:10.1002/zaac.201200302

The polynuclear complexes [Cd₈S(SPh)₁₄(DMF) ₃] (1) and [Cd₁₇S₄(SH)₂(SPh) ₂₄(PPh₃)₂] (2) were prepared by an organometallic synthesis route. X-ray diffraction on single-crystals revealed a hexagonal closed packing of the cluster unit in 1 in the triclinic space group P1. Compound 2 crystallized in the monoclinic space group C2/c. In contrast to related cluster compounds, the ligand sphere of 1 is expanded resulting in an unusual trigonal-bipyramidal coordination of one of the cadmium ions. The heterogeneous composition of the ligand sphere of 2 results in the formation of individual cluster molecules. Copyright

Full text of DOI:10.1002/zaac.201200302

Job/Unit: Z12302
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Date: 06-09-12 10:09:05
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SHORT COMMUNICATION
DOI: 10.1002/zaac.201200302
Synthesis and Structure Determination of Two Neutral Cadmium
Thiophenolate Clusters
Franziska Gruber*[a]
Keywords: Cadmium; Cluster compounds; Sulfide ligands; Quantum dots; Semiconductors
Abstract. The polynuclear complexes [Cd8S(SPh)14(DMF)3] (1) and contrast to related cluster compounds, the ligand sphere of 1 is ex-
[Cd17S4(SH)2(SPh)24(PPh3)2] (2) were prepared by an organometallic panded resulting in an unusual trigonal-bipyramidal coordination of
synthesis route. X-ray diffraction on single-crystals revealed a hexago- one of the cadmium ions. The heterogeneous composition of the ligand
nal closed packing of the cluster unit in 1 in the triclinic space group
P1. Compound 2 crystallized in the monoclinic space group C2/c. In
sphere of 2 results in the formation of individual cluster molecules.
¯
However, one additional DMF molecule is found in the ligand
sphere of 1. This DMF molecule coordinates to one of the
cadmium ions of the central Cd4S tetrahedron, whereby the
coordination sphere of this cadmium ion is expended from a
tetrahedral to a trigonal-bipyramidal arrangement (highlighted
in Figure 1). The angles of the trigonal bipyramid are
117.4(1)–121.7(1)° between equatorial ligands and 86.9(3)–
91.3(3)° to the axial ligands. The unusual coordination of the
cadmium ion causes also an elongation of the bond to the cen-
tral sulfur ion of around 10 percent. Behrens and Fenske[4]
found a similar cluster structure in [Cd8Se(SePh)14(DMF)3]
which was recrystallized from [Cd8Se(SePh)14(PPh3)2] in
Introduction
Polynuclear transition metal chalcogenide compounds exhi-
bit a high diversity of core sizes and cluster structures, where-
bythey serve as model system for the study of size-depen-
dent electronic and optical properties.[1] In the series of cad-
mium sulfide compounds the smallest cluster is [Cd4(SR)10]2–
(R = alkyl, phenyl etc.), followed by [Cd8S(SR)16]2– over
[Cd17S4(SR)26)] and [Cd32S14(SR)40]4– to [Cd54S32(SR)48]4–.
Depending on the cluster charge and the ligand molecules dif-
ferent structure motives appear: individual clusters, ionic pack-
ings of cluster units or two- or three-dimensional networks.[2]
In this article two new, neutral representatives of the Cd–S-
series are presented: [Cd8S(SPh)14(DMF)3] (1) (with DMF =
dimethylformamide) and [Cd17S4(SH)2(SPh)24(PPh3)2] (2).
Their synthesis, structure and properties are discussed.
¯
DMF. Compound 1 crystallizes in the triclinic space group P1
(no. 2) with two formula units in the unit cell. The overall
packing of the cluster molecules can also be described as a
hexagonal closed packing. A feature that very often occurs
in cluster compounds crystallized from solutions are voids or
channels filled with small solvent molecules. The solvent ac-
cessible volume of 1 was calculated to be 2.1% (PLATON[5]).
Compound 2 was synthesized in two steps. First Cd(acetate)2
reacted with triphenylphosphine and thiophenol in tetra-
hydrofuran to a mixed salt. After separation the product was
redissolved, in the second step, in a mixture of DMF/CS2 and
layered with methanol. After two weeks colorless plate-like
crystals of 2 were obtained.
The cluster molecule of 2 contains a central CdS4 tetrahe-
dron at each of which the corners three Cd(μ2-SPh)3 tetrahedra
are attached to. The linkage of these tetrahedra is comparable
with the cubic lattice of CdS, however, the cluster is more
distorted. To the outside the cluster is terminated by two
Cd(μ2-SPh)2(SH) groups and two Cd(μ2-SPh)2(PPh3) groups.
The bond lengths for Cd–(μ2-S) range from 2.51(2) to 2.58(1)
Å, which is in agreement with literature.[3] The bond from
cadmium to the –SH group is significantly shorter (2.48(1) Å).
The Cd–P bond is 2.61(1) Å long. The hydrogen atoms of
the –SH groups were not found crystallographically but due to
Results and Discussion
[Cd8S(SPh)14(DMF)3] (1) was synthesized by the reaction
of Cd(acetate)2 with thiophenol and CS2 in a two phase system
of dimethylformamide and methanol at ambient temperature.
The molecular structure of 1, shown in Figure 1, contains a
central Cd4S tetrahedron of which each face is capped by a
Cd(μ2-SPh)3 group. The tetrahedral coordination of the outer
Cd ions is completed in two cases by a terminal –SPh group
and in two cases by DMF molecules. The bond lengths range
from 2.45(1) to 2.60(1) Å for Cd–S and from 2.28(1) to
2.30(1) Å for Cd–O, which is in agreement with literature.[3]
This arrangement would sum up to [Cd8S(SPh)14(DMF)2] and
would be comparable to known clusters like [Cd8S(SPh)16]2–.
* Dr. F. Gruber
Fax: +49-351-463-33244
E-Mail: franziska.gruber@chemie.tu-dresden.de
[a] Department of Chemistry and Food Chemistry
Dresden University of Technology
01062 Dresden, Germany
Z. Anorg. Allg. Chem. 0000, ᭿,(᭿), 0–0
© 0000 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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F. Gruber
SHORT COMMUNICATION
a few seconds. A single crystal structure determination of dried
crystals of 2 showed the Cd17S28 core, but due to a high disor-
der of ligand molecules, an entire structure refinement was not
possible.
The solid-state absorption spectrum of 1 was recorded by
the diffuse reflectance method over the range of 300–800 nm
and is shown in Figure 3. Compared with the corresponding
absorptions of (NEt4)[Cd8S(SPh)16] the spectrum of 1 is red-
shifted. Interestingly, an analogue effect was found in Cd8
clusters where thiophenyl ligands were substituted with other
molecules.[6] Preliminary time-dependent density functional
molecular orbital calculations of 1 based on the structure solu-
tion from X-ray diffraction, were performed. The calculations
reveal a HOMO–LUMO transition energy of 3.17 eV which
equals 391 nm. Thus the calculated wavelength is also red-
shifted. Further investigation of the nature of the HOMO –
LUMO transition which correlates the contribution of the dif-
ferent ligand molecules to the individual orbitals are in pro-
gress.
Figure 1. Schematic drawing of the structure of 1 (ligand molecules
are omitted for clarity). The trigonal-bipyramidal coordination of the
cadmium ion is shown in polyhedral representation. The ellipsoids rep-
resent the probability level of 50%.
the charge equalization and the missing of any counterion it is
assumed that the two sulfur atoms belong to –SH groups. A
bridging between the cluster units was not found, hence 2 con-
sist of individual cluster molecules (see Figure 2).
Figure 3. Solid-state absorption spectra of [Cd8S (SPh)14(DMF)3] (1).
Conclusions
Due to the constitutions of their cluster core, the two com-
pounds presented in this article fit in the well-known series of
cadmium sulfide cluster compounds. At the same time the five-
fold coordination of one Cd ion in 1 facilitate further reactions
by exchange of the additional DMF molecule. Compound 2 is
one of the few examples of Cd17 compounds that consist of
individual cluster molecules.
Experimental Section
Figure 2. Polyhedral representation of the structure of 2 without
phenyl molecules. The terminal ligands –SH and –PPh3 are high-
lighted.
Synthesis: All manipulations were performed under an inert argon
atmosphere using standard Schlenk techniques or in a glove box. Sol-
vents were dried according to standard procedures and freshly distilled
prior to use. Anhydrous Cd(ac)2 was prepared from Cd(ac)2·2H2O,
which was heated to 150 °C in dynamic vacuum overnight. PPh3
(99%, Acros) and thiophenol (99%, Merck) were used without further
treatment.
Compound 2 crystallizes monoclinic in space group C2/c
(no. 15) with 4 formula units per unit cell. The solvent access-
ible volume of 14.3%.[5], located in four voids of 741 Å3 each
per unit cell. The solvent molecules are heavily disordered and
could not be located during the crystal structure determination.
As a consequence, the crystals easily liberate the solvent mole-
1: In a Schlenk flask a mixture of Cd(ac)2 (0.8 mmol) was dissolved
cules upon removal of the mother liquid and turn white within in tetrahydrofurane (5 mL). Thiophenol (1 mmol) was added and the
2
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Two Neutral Cadmium Thiophenolate Clusters
solution was stirred for 2 h. Afterwards the solution was layered with the Becke three-parameter hybrid exchange functional[11] with the Per-
hexane (5 mL). After 24 h, the solvent was removed in vacuo yielding dew-Wang correlation functional[12], in addition, a contribution to ex-
a white crystalline powder. The powder and CS2 (0.3 mmol) were
change energy calculated according to Hartree-Fock (HF) was used.
mixed in dimethylformamide (3mL). When the solution becomes clear, The SBKJC basis set[13] was used for cadmium atoms. The structures
it is layered with methanol (3 mL). After one week, colorless plate- were used as received from diffraction experiment and all calculations
like single crystals of 1 were obtained (yield 106 mg) .
were performed with the programs GAMESS 2011[14]
.
2: In a Schlenk flask a mixture of Cd(ac)2 (461 mg, 2 mmol) and PPh3
(530 mg, 2 mmol) was dissolved in tetrahydrofurane (10 mL). Thi-
ophenol (0.2 mL, 2 mmol) was added and the solution was stirred for
2 h. Afterwards the solution was layered with hexane (10 mL). After
24 h, the solvent was removed in vacuo yielding a white crystalline
powder. The white powder (200 mg) was dissolved in a mixed solvent
dimethylformamide/CS2 (6 g, weight ratio = 2:1) and layered with
methanol. After one week, colorless single crystals of 1 were obtained.
After 2 weeks colorless plate-like crystals of 2 were grown (yield
110 mg).
Acknowledgments
F. G. thanks Prof. Dr. M. Ruck and Prof. Dr. T. Doert for their support.
References
[1] a) N. Herron, J. C. Calabrese, W. E. Farneth, Y. Wang, Science
1993, 259, 1426–1428; b) T. Vossmeyer, G. Reck, L. Katasikas,
E. T. K. Haupt, B. Schulz, H. Weller, Science 1995, 267, 1476–
1479; c) V. N. Soloview, A. Eichhöfer, D. Fenske, U. Banin, J.
Am. Chem. Soc. 2001, 123, 2354–2364; d) J. F. Corrigan, O. Fuhr,
D. Fenske, Adv. Mater. 2009, 21, 1867–1871.
[2] a) I. G. Dance, A. Choy, M. L. Scudder, J. Am. Chem. Soc. 1984,
106, 6285–6295; b) S. Behrens, D. Fenske, Ber. Bunsenges. Phys.
Chem. 1997, 101, 1588–1592; c) X.-L. Yang, J. Zhang, S.-B. Ren,
Y.-Z. Li, W. Hoang, H.-B. Du, X.-Z. You, Inorg. Chem. Commun.
2010, 13, 1337–1339.
[3] a) I. G. Dance, R. G. Garbutt, D. C. Craig, Inorg. Chem. 1987,
26, 3732–3740; b) T. Vossmeyer, G. Reck, B. Schulz, L. Katsikas,
H. Weller, J. Am. Chem. Soc. 1995, 117, 12881–12882; c) M.
Bendova, M. Puchberger, U. Schubert, Eur. J. Inorg. Chem. 2010,
3299–3306.
[4] S. Behrens, D. Fenske, Ber. Bunsenges. Phys. Chem. 1997, 101,
1588–1592.
[5] A. L. Spek, Utrecht University, 2005.
[6] M.-L. Fu, R. D. Adams, D. Cristancho, P. Leon-Plata, J. M. Sem-
inario, Eur. J. Inorg. Chem. 2011, 660–665.
[7] SAINT(V7.60A), Bruker AXS Inc., Madison, Wisconsin, USA,
2009.
[8] SADABS(V2008/1), Bruker AXS Inc., Madison, Wisconsin, USA,
2008.
[9] a) G. M. Sheldrick, SHELX-97, Program for Crystal Structure De-
termination, University of Göttingen, Germany 1997; b) G. M.
Sheldrick, Acta Crystallogr., Sect. A 2008, 64, 112.
[10] a) Y. Tawada, T. Tsuneda, S. Yanagiswa, Y. Yanai, K. Hirao, J.
Chem. Phys. 2004, 120, 8425–8433; b) M. Chiba, T. Tsuneda, K.
Hirao, J. Chem. Phys. 2006, 124, 144106.
[11] A. D. Becke, J. Chem. Phys. 1993, 98, 1372–1377.
[12] J. P. Perdew, Electronic Structure of Solids (Eds.: P. Ziesche, H.
Eschrig), Berlin, Akademie Verlag, 1991, pp.11–20.
[13] a) W. J. Stevens, H. Bassch, M. Krauss, J. Chem. Phys. 1984, 81,
6026–6033; b) W. J. Stevens, M. Krauss, H. Basch, P. G. Jasien,
Can. J. Chem. 1992, 70, 612–630; c) T. R. Cundari, W. J. Stevens,
J. Chem. Phys. 1993, 98, 5555–5565.
For single-crystal X-ray diffraction experiments, the crystals of both
compounds were separated from the reaction mixture and transferred
into inert oil.
X-ray Diffraction: Intensity data of single crystals were collected at
296 K with a four-circle diffractometer Kappa APEX II (Bruker AXS)
with CCD detector using graphite-monochromated Mo-Kα radiation.
The frames were integrated with the Bruker SAINT software pack-
age[7] using a narrow-frame algorithm. Data were corrected for absorp-
tion effects using the multiscan method with the SADABS program.[8]
All structures were solved by direct methods[9] and subsequent differ-
ence Fourier syntheses. All atoms, except C-atoms, were refined with
anisotropic thermal parameters. Hydrogen atoms were placed in geo-
metrically idealized positions and included as standard riding atoms
during the least-squares refinements. The elevated agreement values
(R values) found in both structures are caused by the disorder of the
surface –SPh ligands and the solvent molecules.
¯
Crystal data for 1: [C93H91Cd8N13O3S15], M = 2678.8, triclinic, P1,
a = 13.907(1) Å, b = 18.848(2) Å, c = 21.175(2) Å, α = 95.144(5), β
= 95.926(5), γ = 106.400(5)°, V = 5255.1(9) Å3, Z = 2, T = 296(2) K,
46044 reflections measured, 20417 unique (Rint = 0.071), 475 param-
eters, final R1 (9492 Fo Ͼ 4σ(Fo)) = 0.077, R1 (all) = 0.171, wR2 (all)
= 0.259. Solvent accessible volume 2.1%.
Crystal data for 2: [C180H152Cd17P2S30], M = 5249.56, monoclinic,
C2/c, a = 34.854(3) Å, b = 19.479(2) Å, c = 32.33(2) Å, β =
105.038(4)°, V = 21198(3) Å3, Z = 4, T = 296(1) K, 75089 reflections
measured, 11509 unique (Rint = 0.117), 402 parameters, final R1 (6499
Fo Ͼ 4σ(Fo)) = 0.078, R1 (all) = 0.152, wR2 (all) = 0.275. Solvent
accessible volume: 14.3%.
CCDC-895024 contains the supplementary crystallographic data of 1
and CCDC-895025 the data of compound 2. These data can be ob-
tained free of charge from The Cambridge Crystallographic Data Cen-
tre via www.ccdc.cam.ac.uk/data_request/cif.
[14] M. W. Schmidt, K. K. Baldridge, J. A. Boatz, S. T. Elbert, M. S.
Gordon, J. H. Jensen, S. Koseki, N. Matsunaga, K. A. Nguyen,
S. J. Su, T. L. Wind, M. Dupuis, J. A. Montgomery, J. Comput.
Chem. 1993, 14, 1347–1363.
Computational Details: Time-dependent DFT calculations[10] at the
Received: June 29, 2012
B3PW91 level of theory were performed. This level of theory includes
Published Online: ᭿
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F. Gruber
SHORT COMMUNICATION
F. Gruber* ......................................................................... 1–4
Synthesis and Structure Determination of Two Neutral Cad-
mium Thiophenolate Clusters
4
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