The crystal and molecular structure of γ-P4S6

Article abstract of DOI:10.1002/zaac.201100216

The crystal and molecular structure of γ-P₄S₆ was determined from single-crystal X-ray diffraction. It crystallizes monoclinically in the space group P2₁/m (No. 11) with a = 6.627(3) A, b = 10.504(7) A, c = 6.878(3) A, β = 90.18(4)°, V = 478.8(4) A³, and Z = 2. The structure consists of cage-like P₄S₆ molecules with C_S symmetry arranged with the topology of a cubic close packing. Copyright

Full text of DOI:10.1002/zaac.201100216

ARTICLE
DOI: 10.1002/zaac.201100216
The Crystal and Molecular Structure of γ-P4S6
Thomas Rödl[a] and Arno Pfitzner*[a]
In Memory of Professor Hans Georg von Schnering
Keywords: Phosphorus; Sulfur; Phosphorus sulfides; Cage molecules
Abstract. The crystal and molecular structure of γ-P4S6 was deter-
10.504(7) Å, c = 6.878(3) Å, β = 90.18(4)°, V = 478.8(4) Å3, and Z =
mined from single-crystal X-ray diffraction. It crystallizes monoclin- 2. The structure consists of cage-like P4S6 molecules with CS sym-
ically in the space group P21/m (No. 11) with a = 6.627(3) Å, b = metry arranged with the topology of a cubic close packing.
Introduction
In general the phosphorus sulfides consist of small cage-like
molecules with the composition P4Sn (n = 3–10). The struc-
tures of α-P4S3,[1] γ-P4S3,[1,2] α-P4S4,[3] α-P4S5,[4] β-P4S5,[5] β-
P4S6,[6] α-P4S7,[4,7] β-P4S7,[8] P4S9-II,[9] P4S9-III,[10] and
P4S10[4,7,11] were determined from single-crystal X-ray diffrac-
tion. Other phosphorus sulfides like P4S8 have been charac-
terized by 31P NMR spectroscopy.[12] They all have in com-
mon, that their molecular structures can be derived from the
P4 tetrahedron of white phosphorus by either insertion of sulfur
atoms into P–P bonds or exocyclic addition to phosphorus
atoms. Due to the possible combinations a large number of
constitution isomers is suggested for each composition. Ad-
ditionally, different crystal structures of the same molecule are
conceivable. In the case of e.g. P4S6 five isomers are known,
see Figure 1. Among these, only the crystal structure of β-P4S6
was determined by X-ray diffraction analysis.[6] On the con-
trary the structures of α-P4S6,[13] γ-P4S6,[14] δ-P4S6, and ε-
Figure 1. Known molecular structures of P4S6.[6,13–15]
[15]
P4S6
have been characterized only spectroscopically.
γ-P4S6 has first been observed by Jason as a product in the
oxidation of phosphorus by sulfur at low temperatures
(Ͻ 100 °C) and in the sulfurization of α-P4S5 by triphenylarse-
nic sulfide.[14] Based on the signals in the corresponding solu-
tion 31P NMR spectra he was able to assign a molecular struc-
ture. Herein, we confirm the molecular structure assigned by
Jason, and in addition, present the crystal structure of γ-P4S6.
tallizes as a pseudomerohedral twin in the monoclinic space
group P21/m (No. 11) with a = 6.627(3) Å, b = 10.504(7) Å,
c = 6.878(3) Å and β = 90.18(4)°. The monoclinic angle is
very close to 90° and mimics a metrically orthorhombic cell.
Analyzing the reflection data with XPREP[16] revealed that the
true metric is monoclinic: whereas the internal R-value is poor
for the higher symmetry (Rint = 0.297) it is very good for the
lower symmetry (Rint = 0.032). In the monoclinic setting only
the reflection condition for 21||b was fulfilled indicating the
possible space groups P21 (No. 4) and P21/m (No. 11). Due to
pseudomerohedral twinning the E statistics (|E2–1| = 0.814)
were no real criterion for (non-)centrosymmetry. For this
reason the structure solution was performed in the higher- and
centrosymmetric space group P21/m (No. 11). The structure
solution using direct methods was successful and after a few
refinement cycles a reasonable structural model was obtained.
However, the R values were unusually high at this stage and
Results and Discussion
The crystal and molecular structure of γ-P4S6 was deter-
mined by single-crystal X-ray diffraction. The compound crys-
* Prof. Dr. A. Pfitzner
Fax: +49-941-943-814551
E-Mail: arno.pfitzner@chemie.uni-regensburg.de
[a] Institut für Anorganische Chemie
Universität Regensburg
Universitätsstraße 31
93040 Regensburg, Germany
Z. Anorg. Allg. Chem. 2011, 637, 1507–1510
© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
1507

T. Rödl, A. Pfitzner
ARTICLE
pseudomerohedral twinning had to be taken into account. The Table 2. Atomic coordinates and equivalent isotropic displacement pa-
rameters Ueq (in Å2) for γ-P4S6.
a)
possible twin laws were derived from symmetry reduction
starting from the apparent Laue class 2/m 2/m 2/m and ending
up with the true Laue class 2/m. Thus, a mirror plane perpen-
dicular to the a axis could be used as a twin element in the
refinement procedure. By doing this, the R values dropped sig-
nificantly from R1 = 0.1311 and wR2 0.3174 to R1 = 0.0703
and wR2 = 0.1758 (for all data). Table 1 shows the results of
the refinement for γ-P4S6. The atomic coordinates and aniso-
tropic displacement parameters are listed in Table 2 and
Table 3.
Atom Wyck.
x
y
z
Ueq
P(1)
P(2)
P(3)
S(1)
S(2)
S(3)
S(4)
4f
0.2485(3)
0.2046(5)
0.6795(5)
0.1055(3)
0.5638(3)
0.1533(6)
0.4878(5)
0.1118(2)
0.25
0.25
0.5460(2)
0.0890(2)
0.25
0.2612(4)
0.5084(5)
0.3851(6)
0.2492(4)
0.2396(4)
0.0562(6)
0.6368(6)
0.040(1)
0.044(1)
0.053(1)
0.051(1)
0.053(1)
0.054(1)
0.053(1)
2e
2e
4f
4f
2e
2e
0.25
a) Ueq is defined as one third of the trace of the orthogonalized Uij
tensor.
Table 1. Crystallographic data for γ-P4S6.a)
Table 3. Anisotropic displacement parameters Uij (in Å2 ϫ 103) for
γ-P4S6.
Compound
γ-P4S6
Formula Weight /g·mol–1
Colour
316.24
Atom
U11
U22
U33
U23
U13
U12
yellow
Crystal system, space group
Lattice constants
a /Å
b /Å
c /Å
monoclinic, P21/m (No.11)
P(1)
P(2)
P(3)
S(1)
S(2)
S(3)
S(4)
35(1)
39(2)
30(2)
47(1)
35(1)
59(2)
45(2)
39(1)
41(2)
55(2)
43(1)
48(1)
45(2)
58(2)
46(1)
52(2)
74(3)
63(2)
75(2)
59(2)
58(2)
–2(1)
0
0
0(1)
–8(1)
0
–1(1)
5(1)
0(2)
–8(1)
3(1)
–23(2)
–12(2)
–2(1)
0
0
7(1)
5(1)
0
6.627(3)
10.504(7)
6.878(3)
90.18(4)
478.8(4)
β /°
Volume V /Å3
0
0
Number of formula units Z
Calculated density ρcalc /g·cm–3
Temperature T /K
Diffractometer
Wavelength λ /Å
Absorption coeff. μ(Mo-Kα) /mm–1
θ range of data collection /°
Index ranges
2
2.194
293(2)
ment with those in other phosphorus sulfides. The distance
P(1)–P(2) is 2.255(4) Å. The exocyclic phosphorus sulfur dis-
tance d(P(1)–S(1)) = 1.912(3) Å is as expected shorter than the
distances between phosphorus and bridging sulfur atoms which
vary in the range from 2.071(5) Å to 2.151(6) Å.
Stoe IPDS I
0.71073 (Mo-Kα)
2.018
2.96–25.19
–7 Յ h Յ 7
–12 Յ k Յ 12
–8 Յ l Յ 8
numerical, X-RED[17]
and X-SHAPE[18]
6288
Absorption correction
No. of reflections collected
(independent)
(905)
Rσ, Rint
0.0353, 0,0525
99.6%
Completeness to θ = 25.19°
Structure solution
Structure refinement
No. of refined parameters
No. of restraints
SIR92[19]
SHELXL-97[20]
53
0
GooF
1.142
Twin law
–1 0 0, 0 1 0, 0 0 1
0.138(4)
0.0604, 0.1705
0.0703, 0.1758
1.635 and –0.418
Figure 2. Single γ-P4S6 molecule. Ellipsoids are drawn at 75% prob-
ability level.
Batch scale factor BASF
R1, wR2 [I Ͼ 2σ (I)]
R1, wR2 [all data]
Largest diff. peak & hole /e·Å–3
Table 4. Selected interatomic distances (in Å) and angles (in °) in
γ-P4S6.
a) Further details on the crystal structure investigations may be ob-
tained from the Fachinformationszentrum Karlsruhe, 76344 Egg-
enstein-Leopoldshafen, Germany (Fax: +49-7247-808-666; E-Mail:
crysdata@fiz-karlsruhe.de), on quoting the depository number CSD-
423037.
P(1)–S(1)
P(1)–S(2)
P(1)–S(3)
P(1)–P(2)
P(2)–S(4)
P(3)–S(2)
P(3)–S(4)
1.912(3)
2.109(3)
2.118(4)
2.255(4)
2.071(5)
2.108(4)
2.151(6)
S(1)#1–P(1)–S(2)
S(1)#1–P(1)–S(3)
S(2)–P(1)–S(3)
S(1)#1–P(1)–P(2)
S(2)–P(1)–P(2)
S(3)–P(1)–P(2)
S(4)–P(2)–P(1)
P(1)–P(2)–P(1)#1
S(2)–P(3)–S(2)#1
S(2)–P(3)–S(4)
P(3)–S(2)–P(1)
P(1)#1–S(3)–P(1)
P(2)–S(4)–P(3)
112.9(1)
114.8(2)
108.9(2)
121.7(2)
104.8(2)
91.3(1)
101.7(2)
80.1(2)
106.7(2)
99.6(2)
As it is common for phosphorus sulfides the structure of γ-
P4S6 consists of discrete cage-like molecules. The molecular
structure can be derived from the P4 tetrahedron of white phos-
phorus by introducing four bridging and two terminal sulfur
atoms, see Figure 2. A single γ-P4S6 molecule exhibits only
one symmetry element, a mirror plane through the atoms P(2),
P(3), S(3) and S(4). Thus, the molecules are achiral and belong
to the point group Cs. The intramolecular distances and angles
103.6(1)
86.5(2)
101.1(2)
#1 symmetry transformation used to generate equivalent atoms: x,
in γ-P4S6 are summarized in Table 4. They are in good agree- –y+½, z
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Z. Anorg. Allg. Chem. 2011, 1507–1510

The Crystal and Molecular Structure of γ-P4S6
Each unit cell contains two equivalent γ-P4S6 molecules re-
lated by a 21 screw axis along b. The shortest intermolecular
distances are 3.58(3) Å for P(2)···P(3), 3.41(4) Å for
P(2)···S(1) and 3.45(4) Å for S(1)···S(3). Hence, weak van der
Waals forces are present between adjacent molecules. Figure 3
shows a section of the crystal structure of γ-P4S6 illustrating
the molecular arrangement. Considering the cages to be almost
spherical it is strongly related to a cubic closest packing of
spheres. The symmetry relations are explained with the help
of a Bärnighausen tree, see Figure 4. The low symmetry of the
molecules enforces a reduction of the space group symmetry.
Due to the non-ideal spherical shape of the molecules there are
deviations from a perfect fcc packing resulting in a slight shift
of the molecular centre from the ideal position and a signifi-
cant distortion of the lattice. This finding is not surprising
since α-P4S3, γ-P4S3, α-P4Se3 and α-As4S3 show quite similar
deviations, albeit this time from a hexagonal packing of
spheres.
Figure 4. Bärnighausen tree relating a cubic closest packing of spheres
with the molecular arrangement in γ-P4S6. Only the centre of the mole-
cule (C) is displayed.
argon atmosphere for eight weeks. The solvent was then removed by
slow evaporation under inert gas conditions at room temperature,
yielding some crystals of γ-P4S6, together with larger amounts of unre-
acted starting materials. The air- and moisture-sensitive yellow crystals
of γ-P4S6 were manipulated under argon atmosphere in a glovebox and
a crystal suitable for the X-ray diffraction analysis was sealed in a
glass capillary. The measurement was carried out on a STOE IPDS I
diffractometer with λ = 0.71073 Å (Mo-Kα). Further details on the data
collection are shown in Table 1.
Figure 3. Section of the crystal structure of γ-P4S6 with view along c.
Note added in proof: In the meantime, the crystal structures
of polymeric phosphorus polysulfides α-P2S7 and β-P2S7 were
determined. They show a ratio of P:S Ͻ 4:10 and are the first
well-characterized crystalline polymeric phosphorus polysul-
fides.[21]
References
[1] a) Y. C. Leung, J. Waser, S. van Houten, A. Vos, G. A. Wiegers,
E. H. Wiebenga, Acta Crystallogr. 1957, 10, 574–582; b) T. K.
Chattopadhyay, W. May, H. G. von Schnering, G. S. Pawley, Z.
Kristallogr. 1983, 165, 47–64; c) I. Raabe, S. Antonijevic, I.
Krossing, Chem. Eur. J. 2007, 13, 7510–7522.
[2] H. Gruber, U. Müller, Z. Kristallogr. 1997, 212, 662–664.
[3] a) A. M. Griffin, P. C. Minshall, G. M. Sheldrick, J. Chem. Soc.,
Chem. Commun. 1976, 809–810; b) P. C. Minshall, G. M. Sheld-
rick, Acta Crystallogr., Sect. B 1978, 34, 1326–1328; c) C.-C.
Chang, R. C. Haltiwanger, A. D. Norman, Inorg. Chem. 1978, 17,
2056–2062.
[4] a) S. van Houten, E. H. Wiebenga, Acta Crystallogr. 1957, 10,
156–160; b) A. Vos, R. Olthof, F. van Bolhuis, R. Botterweg, Acta
Crystallogr. 1965, 19, 864–867.
Experimental Section
P4S3 was prepared by reaction of stoichiometric amounts of the ele-
ments, phosphorus (Hoechst, 99.999%) and sulfur (Chempur,
99.999%) in an evacuated silica ampoule at 300 °C and purified by
recrystallization from toluene (Merck, p.A.). Commercial FeCl3
(Fluka, Ͼ98%) was purified by sublimation in a stream of chlorine
gas at 250 °C.
[5] A. M. Griffin, G. M. Sheldrick, Acta Crystallogr., Sect. B 1975,
31, 2738–2740.
Synthesis of γ-P4S6. Equimolar amounts of P4S3 and anhydrous FeCl3
were dissolved in a 2:1 solvent mixture of dry carbon disulfide and
[6] R. Blachnik, U. Peukert, A. Czediwoda, B. Engelen, K. Boldt, Z.
Anorg. Allg. Chem. 1995, 621, 1637–1643.
chloroform. The reaction mixture was kept in a Schlenk flask under [7] A. Vos, E. H. Wiebenga, Acta Crystallogr. 1955, 8, 217–223.
Z. Anorg. Allg. Chem. 2011, 1507–1510
© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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T. Rödl, A. Pfitzner
ARTICLE
[8] D. T. Dixon, F. W. Einstein, B. R. Penfold, Acta Crystallogr. [15] H. Nowottnick, R. Blachnik, Z. Anorg. Allg. Chem. 1999, 625,
1966–1968.
1965, 18, 221–225.
[16] XPREP, Reciprocal Space Exploration, Ver. 2005/2, Bruker AXS,
2005.
[17] X-RED32, STOE & Cie GmbH, 2004.
[18] X-SHAPE, STOE & Cie GmbH, 1999.
[19] A. Altomare, M. C. Burla, M. Camalli, G. Cascarano, C. Giacov-
azzo, A. Guagliardi, G. Polidori, J. Appl. Crystallogr. 1994, 27,
435.
[20] G. M. Sheldrick, Acta Crystallogr., Sect. A 2008, 64, 112.
[21] T. Rödl, R. Weihrich, J. Wack, J. Senker, A. Pfitzner, Angew.
Chem. Int. Ed. 2011, in press. DOI: 10.1002/anie.201103485.
[9] W. Wilmer, Acta Crystallogr., Sect. B 1969, 25, 1229–1232.
[10] B. Wallis, G. U. Wolf, P. Leibnitz, Z. Anorg. Allg. Chem. 1990,
588, 139–146.
[11] R. Blachnik, J. Matthiesen, A. Müller, H. Nowottnick, H. Reuter,
Z. Kristallogr. – New Cryst. Struct. 1998, 213, 233–234.
[12] J.-J. Barieux, M. C. Demarcq, J. Chem. Soc., Chem. Commun.
1982, 176–177.
[13] T. Bjorholm, H. J. Jakobsen, J. Am. Chem. Soc. 1991, 113, 27–
32.
[14] a) M. E. Jason, T. Ngo, S. Rahman, Inorg. Chem. 1997, 36, 2633–
2640; b) M. E. Jason, Inorg. Chem. 1997, 36, 2641–2646.
Received: May 9, 2011
Published Online: August 20, 2011
1510
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© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2011, 1507–1510