Low-temperature preparation of tungsten halide clusters: Crystal structure of the adduct W5Br12 · SbBr31

Article abstract of DOI:10.1134/S1070328412020078

Single-crystals of a new compound W₅Br₁₂ · SbBr₃ (I) were isolated as a reaction product from the reduction of WBr₆ with elemental antimony at 250°C. The crystal structure was determined by single-crystal X-ray diffraction analysis. The structure contains square-pyramidal tungsten clusters being linked into infinite [(W ₅Br₈ⁱ)Br₃^aBr _2/2^a-a] chains through shared W-Br^a- ^a-W contacts of adjacent clusters. The structure of the adduct I can be viewed as an intercalation compound composed of double-layers of cluster chains alternating with mono-layers of SbBr₃ molecules. Pleiades Publishing, Ltd., 2012.

Full text of DOI:10.1134/S1070328412020078

ISSN 1070ꢀ3284, Russian Journal of Coordination Chemistry, 2012, Vol. 38, No. 3, pp. 178–182. © Pleiades Publishing, Ltd., 2012.
Dedicated to Professor Vladimir Fedorov
on the occasion of his 75th birthday
LowꢀTemperature Preparation of Tungsten Halide Clusters:
1
Crystal Structure of the Adduct W5Br12 · SbBr3
M. Ströbele and H.ꢀJ. Meyer*
Abteilung für Festkörperchemie und Theoretische Anorganische Chemie, Institut für Anorganische Chemie,
Auf der Morgenstelle 18, EberhardꢀKarlsꢀUniversität Tübingen, Dꢀ72076 Tübingen, Germany
*eꢀmail: juergen.meyer@uniꢀtuebingen.de
Received August 20, 2011
Abstract
reduction of WBr6 with elemental antimony at 250
Xꢀray diffraction analysis. The structure contains squareꢀpyramidal tungsten clusters being linked into infiꢀ
—Singleꢀcrystals of a new compound W5Br12
⋅ SbBr3 (I) were isolated as a reaction product from the
°C. The crystal structure was determined by singleꢀcrystal
i
a
nite [(W
)
a−a] chains through shared W–Bra–a–W contacts of adjacent clusters. The structure of the
5Br8 Br3 Br2 2
adduct I can be viewed as an intercalation compound composed of doubleꢀlayers of cluster chains alternating
with monoꢀlayers of SbBr3 molecules
.
DOI: 10.1134/S1070328412020078
1
Recent studies have demonstrated a great potenꢀ preparation of known tungsten halides (i.e., W6Cl18
tial of soft solidꢀstate reduction routes for the prepꢀ
aration of metalꢀrich tungsten halide compounds.
Preparations may depart from tungsten hexachloride
by using nonꢀconventional reduction reagents, as
has been described for the highꢀyield preparation of
W6Cl12 [1, 2]. In the meantime, the use of various
reduction agents has emerged as a synthetic strategy
for the preparation of novel tungsten halide cluster
compounds.
and W6CCl18) compared to other routes reported in
the literature. In addition, the novel compounds
W30C2(Cl,Br)68 and W6CCl15 were discovered followꢀ
ing this synthesis, revealing that reactions with carbon
halides involve oxidations (chlorinations) at lower
temperatures and reductions at more elevated temperꢀ
atures [12].
When following all these reactions, it turns out that
more than one reaction products or even a cascade of
reaction products can occur with increasing temperaꢀ
ture. Such a sequence of products was also obtained
when reducing WCl6 with iron or cobalt metal (M).
Only the structures of two compounds (MW2Cl10 and
MW6Cl14) are fully characterized so far, out of several
ones being obtained [13].
The employment of bismuth as a reduction agent
has brought up constitution isomers of BiW6Cl15 apꢀ
pearing as (BiCl)[W6Cl14] [3] and (BiCl2)[W6Cl13] [4].
Corresponding reduction experiments were carried
out with tungsten hexabromide to yield Bi2W6Br18 [5].
When elemental red phosphorous was used as a reducꢀ
ing agent the interstitially stabilized phosphido cluster
compound W6PCl17 was obtained [6], which appears
with an intermediate structure inꢀbetween cluster arꢀ
After reactions of tungsten hexahalide with eleꢀ
mental phosphorous, arsenic, and bismuth were inꢀ
vestigated in some detail, the exploration of reacꢀ
tions with elemental antimony as a reduction agent
was missing. Preliminary experiments of reactions
between tungsten hexachloride and antimony yieldꢀ
chitectures of triprismoꢀW6CCl18 [7] and octahedroꢀ
W6Cl18 [8–10]. A chlorophosphinidene compound
W4(PCl)Cl10 [6] and a chlorocarbyne compound
W2Cl7(CCl) [11] were also obtained via reduction with
phosphorous and arsenic, the latter under solvotherꢀ
mal conditions.
ed W6Cl12 and SbCl3 above 300°C, and some yet unꢀ
known products below this temperature. Therefore,
we decided to use the slightly less reactive WBr6.
Herein we describe the first reaction product obꢀ
tained from the reduction of WBr6 with elemental
antimony.
Reactions of the reduced cluster compound W6Cl12
with reactive carbon halide (i.e., C2Cl6) sources have
turned out to be an interesting way for the highꢀyield
1
The article is published in the original.
178

LOWꢀTEMPERATURE PREPARATION OF TUNGSTEN HALIDE CLUSTERS
EXPERIMENTAL
179
Synthesis of WBr6 [14]. Tungsten hexabromide was
prepared by reacting W(CO)6 with an excess of eleꢀ
mental bromine. The W(CO)6 (9.1 g, 0.0259 mol;
Strem, 99%) was ground in an agate mortar under
W
argon atmosphere (glovebox) and brought into a
250ꢀmL Schlenk vessel. Afterwards 12.5 mL of eleꢀ
mental bromine (39 g, 0.488 mol) were injected into
the vessel under a flow of argon and external cooling
with liquid nitrogen. The mixture was allowed to heat
up to room temperature during 60 min. After room
temperature was reached and the evolution of gas
(mostly CO) was finished the vessel was heated up to
Br
90°C to remove the excess of bromine (absorbed with
a concentrated alkaline sodium sulfite solution). The
greyꢀblack residue was handled in argon atmosphere
(glovebox) and examined by powder Xꢀray diffraction
(XRD) measurement. The reaction yielded 16.8 g
(0.0253 mol) WBr6 (estimated 95–98% pure), 98% of
theory. A small amount of WOBr4 was obtained as
a sideꢀphase, well separated from the WBr6 bulk mateꢀ
rial.
Fig. 1. Structure of the [(W Br8i
)
Br5a
tained in the crystal structure of W Br
]
cluster anion conꢀ
–
5
⋅
SbBr .
5
12
3
Some results of the crystal structure refinements, inꢀ
cluding the final values are provided in the table.
Atomic coordinates and other structure data are availꢀ
able at the FIZ Karlsruhe (CSD nos. 423460 for
423461 for WBr4, and 423462 for WBr5).
R
Synthesis of W5Br12 ⋅ SbBr3. Reactions of WBr6 with
I,
variable amounts of elemental antimony were explored at
various temperatures. The formation of products was conꢀ
trolled visually and by powder XRD. During the early stagꢀ
es of reactions, singleꢀcrystals of WBr4 and WBr5 were
formed besides SbBr3. The composition SbW6Br15 was atꢀ
tempted following to the known BiW6Cl15. For this reacꢀ
tion WBr6 (150 mg, 0.226 mmol) and elementary antimoꢀ
ny (36.7 mg, 0.301 mmol; Aldrich, 99%) where mixed unꢀ
der argon atmosphere (glovebox) and sealed into an
evacuated silica tube:
RESULTS AND DISCUSSION
The reduction of WBr6 with antimony yields a numꢀ
ber of compounds of which the new W5Br12 SbBr3 (I)
has been identified by singleꢀcrystal Xꢀray diffraction.
The other compounds being systematically detected by
powder XRD with increasing reaction temperature were
·
WBr4, compound
up to 300 C, before W6Br12 was formed above 350
Powder patterns of compounds , and
vestigated by means of Rietveld structure refinements
leading to structures having the compositions W4Br10
2SbBr3, W4Br10 for compounds , respectively, and
W5Br12 for compound , but more studies are necessary
A
, compound
B
,
I
, and compound
C
6WBr6 + 8Sb
→ SbW6Br15 + 7SbBr3.
°
°C.
The reaction mixture was heated in a tube furnace
at 250°C for 72 h. The resulting black powder conꢀ
tained darkꢀgreen crystals of (estimated yield 15%)
along with a main phase identified as W4Br10, accordꢀ
ing to a Rietveld refinement.
Xꢀray diffraction analysis. All reaction products
were inspected by XRD, collected with a Stadi P
(STOE, Darmstadt) powder diffractometer, using gerꢀ
A
,
B
C have been inꢀ
I
⋅
A, B
C
to settle these preliminary results.
Singleꢀcrystals of WBr4 and WBr5 were obtained as
sideꢀphases of reactions, and their crystal structures
were refined because no structural data were available
manium monochromated CuKα radiation. A darkꢀ
green singleꢀcrystal of I was selected and fixed on the
1
tip of a glass fiber for a singleꢀcrystal Xꢀray diffraction to us [16].
measurement (Stoe IPDS diffractometer, graphite
monochromatized Mo α radiation, = 0.71073 ) at
The characteristic motif of the crystal structure of
I
K
λ
Å
i
is the [(W
)
a]– anion which can be derived from
5Br8 Br5
room temperature (293(2) K). Intensities were corꢀ
rected for Lorentz factors, polarisation and absorption
effects. The structure solution was performed with diꢀ
rect methods (SHELXS) and fullꢀmatrix least square
i
a
an octahedral (W
W–Bra unit (Fig. 1). A corresponding [(W ) ]– fragꢀ
ment is contained in the structure of W15I47 [17] which
contains outer monoꢀiodide and triꢀiodide ligands,
)
moiety by removing one
i
6Br8 Br6
a
5I8 I5
refinements on
F
2 using SHELXL [15].
Intensity measurements and structure refinements
were also performed for singleꢀcrystals of WBr4 and and in [(W5I8i
)
I5a
]
(n
= 1, 2) [18]. Moreover, similar
WBr5 sealed in glass capillaries. Due to the large monoꢀ cluster compounds with a square pyramidal metal core
were reported for molybdenum halides, such as for
n–
clinic angle in the space group
C2/m
(β
= 131.05(3)
°) of
–
WBr4, the nonꢀstandard space group
I2/m
was used. [Mo5Cl13]n
(n
= 1–3) [19–21].
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 38
No. 3
2012

180
STRÖBELE, MEYER
, WBr4, and WBr5
Crystal data and structure refinements of
Parameter
I
Value
Br4W
Empirical formula
Crystal system
Br15SbW5
Triclinic
2239.65
Br5W
Triclinic
583.40
Monoclinic
503.49
Formula weight
I
2/m
Space group
P
1
P1
Unit cell dimensions:
a
, Å
, Å
9.329(2)Å
15.002(3)
18.601(7)
91.45(4)
99.74(4)
90.00(3)
2565(1)
4
8.519(3)
6.839(1)
9.384(3)
90
6.446(2)
6.978(2)
9.540(2)
108.67(3)
90.69(3)
116.29(3)
358.4(2)
2
b
c, Å
, deg
, deg
, deg
α
β
92.16(4)
90
γ
Volume, Å3
546.3(3)
4
Z
ρcalcd, g/cm3
5.800
6.121
50.225
856
5.406
Absorption coefficient, mm–1
46.728
43.862
498
F
(000)
Crystal size, mm
Range, deg
3784
0.02
×
0.02
×
0.01
0.04
×
0.04
×
0.45
0.12
× 0.2 × 0.1
θ
2.30–26.17
3.17–26.1
2.29–26.11
Index ranges
–11
–18
–15
≤
≤
≤
h
k
l
≤
≤
≤
11
18
15
–10
–7
–11
≤
≤
≤
h
k
≤
≤
11
1
7
–7
–8
–11
≤
≤
≤
h
k
l
≤
≤
≤
7
8
11
l
≤
Reflections collected
Independent reflections
Refinement method
Data/parameters
23164
int = 0.0380)
3037
int = 0.043)
3984
1314 (Rint = 0.058)
7757 (
R
555 (
R
Fullꢀmatrix leastꢀsquares on F2
7757/379
1.021
555/27
1.018
1314/55
0.919
Goodnessꢀofꢀfit on F2
Final
R
indices (
I
> 2
σ(
I
))
R
1 = 0.0387
R
1 = 0.0264
wR2 = 0.0642
1 = 0.0285
R
1 = 0.0302
wR2 = 0.0659
1 = 0.0789,
wR2 = 0.0653
1 = 0.0391
R
indices (all data)
R
R
R
wR2 = 0.0724
wR2 = 0.0653
wR2 = 0.0671
Largest diff. peak and hole,
e
Å–3
1.117 and –1.019
1.741 and –1.426
1.292 and –1.559
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 38
No. 3
2012

LOWꢀTEMPERATURE PREPARATION OF TUNGSTEN HALIDE CLUSTERS
181
a−a
Br3aBr
2 2
Fig. 2. Section of an infinite chain of (W Br8i
)
clusters running parallel to the
y
axis direction in the structure of
5
W Br
⋅ SbBr .
12 3
5
y
z
Fig. 3. Unit cell content of the W Br
ecules along the z axis direction.
⋅
SbBr structure, showing doubleꢀlayers of cluster chains and singleꢀlayers of SbBr molꢀ
5
12
3
3
tacts between adjacent clusters along the chain (via Bra–a
anions) involve angles of 125.01(3) and 127.15(3) , and
W–Br distances of 2.605(1) and 2.634(1) . The SbBr3
molecules clearly deviate from planarity with Br Sb Br
angles ranging from 88.1(1) to 106.1(1) . Average Sb–
Br distances (2.506 ) are similar to those in solid SbBr3
(2.503 ) [24]. The cluster chains in are neutral, and the
compound can be considered as an intercalation comꢀ
pound containing SbBr3 molecules. The existence of
pure W5Br12 or conditions for the removal of SbBr3 is not
yet fully explored.
i
a
The two slightly distinct [(W
)
a−a] units in
5Br8 Br3 Br2 2
°
°
the structure of I alternate along the oneꢀdimensional
chain direction (Fig. 2), similar to the connectivity patꢀ
Å
⎯
⎯
i
a
tern obtained for octahedral [(Mo
)
a−a]– clusꢀ
6Cl8 Cl4Cl2 2
°
°
Å
ters in the structure of LiMo6Cl13 [22]. The complete
crystal structure of contains an arrangement of cluster
chains running along the axis direction, forming layers
in the ꢀplane. Two of these layers alternate with one
layer of SbBr3 molecules along the axis direction
(Fig. 3). Tungsten–tungsten distances in square pyramiꢀ
dal tungsten clusters of (ranging from 2.6081(9) to
2.674(1) ) and W–Br distances (ranging from 2.509(1)
to 2.692(1) ) are in good agreement with corresponding
distances in W6Br12 [23]. The bridging W–Br–W conꢀ and is isotypic to the reported structure of NbCl4 [25].
Å
I
I
y
x,y
z
I
The refined crystal structure of WBr4 contains
chains of edgeꢀsharing WBr2Br4/2 octahedra having alꢀ
ternating W–W distances of 2.794(1) and 4.044(1) Å,
Å
Å
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 38
No. 3
2012

182
STRÖBELE, MEYER
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14. Shchukarev, S.A and Kokovin, G.A., Russ. J. Inorg.
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triclinic modification after a monoclinic modification
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No. 3
2012