MnO3Cl, isolation and crystal structure

Article abstract of DOI:10.1002/zaac.200600186

MnO₃Cl is prepared from KMnO₄ und ClSO₃H. The thermally very unstable compound is identified by its Raman spectrum and a single crystal structure determination: a = 715.4(5), b = 1008.3(7), c = 500.9(4) pm, space group CmC

Full text of DOI:10.1002/zaac.200600186

DOI: 10.1002/zaac.200600186
MnO3Cl, Isolation and Crystal Structure
Johann Spandl*, Joanna Supeł, Thomas Drews, and Konrad Seppelt*
Berlin, Institut für Chemie und Biochemie der Freien Universität
Received July 6th, 2006.
Abstract. MnO3Cl is prepared from KMnO4 und ClSO3H. The
thermally very unstable compound is identified by its Raman spec-
trum and a single crystal structure determination: a ϭ 715.4(5),
b ϭ 1008.3(7), c ϭ 500.9(4) pm, space group Cmc21. Solid MnO3Cl
consists of molecules with only weak intermolecular interactions.
The MnϪCl bond length is 209.9(4) pm. The crystal structure is
compared to those of MnO3F, CrO2Cl2, and ReO3Cl, the X-ray
crystal structure determinations of which are also submitted in
this article.
Keywords: Manganese; Manganese trioxide chloride; Crystal struc-
ture
Introduction
Ϫ
All manganese(VII) compounds except the salts of MnO4
are unstable. This is particularly true for the covalent de-
rivatives Mn2O7, MnO3F, and especially MnO3Cl. The lat-
ter two represent the only cases of MnVIIϪhalogen bonds.
MnO3F has been prepared in quite large amounts from
KMnO4 and FSO3H [1] (a warning against this preparation
follows in the experimental part). It is therefore quite well
characterized, including a structure determination by mi-
crowave spectroscopy in the gaseous state [2].
Our knowledge about MnO3Cl is much less complete.
This is certainly due to the high instability of the latter. It
has been prepared at first by reacting KMnO4 in H2SO4
with gaseous HCl [3]. Soon later the preparation from
KMnO4 and ClSO3H was published, and all subsequent
work with MnO3Cl is based on this preparation [4]. The
absorption spectrum of it has been discussed in some detail
[5Ϫ8], also in combination with theoretical considerations
[9Ϫ11]. An incomplete IR spectrum is known. The Raman
bands have been derived from a Raman resonance spectrum
[12]. Quite recently the reaction between MnO3Cl and olef-
ines has been studied by matrix isolation and density func-
tional theory [13]. Modern techniques of low temperature
isolation, crystallization, and spectroscopy allow now a
much more detailed description of this elusive compound.
Figure 1 Raman spectrum of MnO3Cl, liquid, at Ϫ120 °C.
Upper trace: parallel orientation, lower trace: perpendicular orien-
tation.
x ϭ chlorine impurity.
Results and Discussion
The preparation of MnO3Cl from KMnO4 and ClSO3H is
certainly the method of choice [4]. In order to handle the
extreme sensitive compound safely, solutions in CCl4 have
been used previously. We, however, isolated the compound
and kept it at low temperatures all the time. MnO3Cl can
be handled at Ϫ100 °C without decomposition, if moisture
and reducing materials are excluded. The Raman spectrum
of the liquid is shown in Figure 1. Besides some inevitable
amounts of Cl2 the assignment of the six strong bands is
very straightforward, see table 1. The assignment has been
confirmed by a DFT calculation, values are also included
in table 1. MnO3Cl melts at about Ϫ130 °C. In a glass capil-
* Dr. J. Spandl, Prof. Dr. K. Seppelt
Freie Universität Berlin, Institut für Chemie und Biochemie
Fabeckstraße 34Ϫ36
D-14195 Berlin
Fax: ϩϩ4930 83853310
E-mail: jspand@chemie.fu-berlin.de
seppelt@chemie.fu-berlin.de
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MnO3Cl, Isolation and Crystal Structure
Table 2 Bond lengths/pm and angles/° of oxide halides.
MnO3Cl
MnϪO1
MnϪO2
MnϪCl
158.4(12) O1ϪMnϪO1Ј
158.8(8) O1ϪMnϪO2
209.9(4)
110.2(7)
110.3(5)
MnO3F
MnϪ(O,F)1
MnϪ(O,F)2
162.0(2) (O,F)1ϪMnϪ(O,F)1Ј 109.5(1)
162,2(2) (O,F)1ϪMnϪ(O,F)2 109.5(1)
(O,F)2ϪMnϪ(O,F)2 109.3(1)
MnO3F
(microwave, gas [2])
MnϪO
MnϪF
158.6(5) OϪMnϪF
172.4(10)
108.5(10)
CrO2Cl2
CrϪO1
CrϪO2
CrϪCl1
CrϪCl2
ReO3Cl
157.3(7) O1ϪCrϪO2
157.5(4) OϪCrϪCl
211.8(2)
108.5(2)
109.5, 108.5
108.1, 109.0(2)
113.1(1)
211.4(2) Cl1ϪCrϪCl2
ReϪO1
ReϪO2
ReϪO3
ReϪCl
169.9(6) O1ϪReϪO2
169.9(7) O1ϪReϪO3
170.7(5) O2ϪReϪO3
221.9(2) ClϪReϪO
108.4(3)
107.5(3)
108.3(3)
111.5, 112.1, 108.9(2)
Figure 2 Structure of MnO3Cl in the crystal, ORTEP representa-
tion, 50 % probability plot.
Table 3 Crystallographic data
Compound
M
T/°C
space group
a/pm
b/pm
c/pm
MnO3Cl
138.4
Ϫ150
Cmc21
715.4(5)
1008.3(7)
500.9(4)
MnO3F
121.8
Ϫ120
C2/c
916.3(10)
434.9(4)
841.7(11)
116.78(3)
299.5
4
2.705
4.23
30.5
2364
457
CrO2Cl2
154.2
Ϫ150
P21
644.5(3)
497.1(3)
717.5(4)
106.58(1)
220.4
2
2.334
3.63
35.5
895
841
ReO3Cl
69.7
Table 1 Raman spectrum of MnO3Cl, values in cmϪ1, in brak-
kets: intensity
Ϫ100
P21/n
562.3(2)
896.4(4)
764.4(2)
94.68(2)
383.9
4
4.665
32.17
30.5
4675
1163
exp.
calcd.
assignment
948 (20,dp)
887 (100,p)
535, 544 (Cl2)
457 (35,p)
365 (50,dp)
306 (25,p)
1060 (15)
1013 (40)
ν MnO3, E
ν MnO3, A1
β/°
V/106pm3
361.3
4
2.544
4.20
26.4
730
352
29
0.142
0.0415
Z
ρcalcd/103kjcmϪ1
471 (6)
403(5)
336(5)
233(7)
ν MnCl, A1
δ MnO3, E
δ MnO3, A1
δ MnO2Cl, E
µ/mmϪ1
θmax/°
217 (80,dp)
reflections, collected
reflections, independent
refined parameters
wR2
25
0.064
0.024
48
0.154
0.049
47
0.1054
0.047
lary we grew a single crystal and subjected it to a single
crystal structure determination. As expected, the crystal
structure shows monomeric units. Bond lengths, and angles,
including calculated values, are collected in table 2.
We have prepared also MnO3F [1], CrO2Cl2 [14, 15], and
ReO3Cl [16] by literature methods and subjected them to
single crystal structure determinations. Crystals of CrO2Cl2
have been grown in a glass capillary at Ϫ110 °C, those of
ReO3Cl by recrystallizations from CFCl3 at Ϫ80 °C, and
those of MnO3F by recrystallization from HF at Ϫ78 °C.
The results are summarized in table 2 also.
The crystal structures of MnO3Cl, MnO3F, CrO2Cl2, and
ReO3Cl are based on molecules that have only weak inter-
molecular interactions. Bond distances and angles within
the MnO3 group in MnO3Cl agree well with those observed
in gaseous MnO3F [2] and crystalline Mn2O7 [17]. The
MnϪCl bond length in MnO3Cl of 209.9(4) pm is the first
determined MnVIIϪCl bond length, and agrees well with
the expectation, e.g. if compared to the CrϪCl bond lengths
of 211.4 Ϫ 211.8 pm in CrO2Cl2. The instability of the com-
pound is therefore not a result of a particularly weak
MnϪCl bond, but rather a result of the energy gain by the
internal redox process. Intermolecular O···Cl and Cl···Cl
R(Fo>,4σ(Fo)
contacts are in the vicinity of the sum of the van der Waals
radii of these atomic combinations. Nevertheless the pack-
ing seems to be governed by the zig zag chain chlorine-
chlorine interactions of 360.4 pm lengths, as indicated by
dotted lines in figure 2. 350 pm is considered a typical dis-
tance for Cl···Cl contacts [18]. Possibly the shortest Cl···Cl
contact of 307.0 pm is observed in crystalline ClF [19]. As
in ClF the chlorine atom in MnO3Cl bears a positive charge
of 0.2 according to the Mullikan charge analysis.
In contrast to this the fluorine atom in MnO3F bears a
negative charge (Ϫ0.2) The lack of such weak interactions
in solid MnO3F may be the reason for the complete dis-
order of the oxygen and fluorine atoms, so that no individ-
ual bond lengths and angles can be given. Only the averaged
bond lengths of 160.0 Ϫ 160.2(2) pm lie in the expected
region, when they are compared to the weighed average of
three MnϭO bonds with 158.6 and one MnϪF of 172.4 pm
lengths from the microwave structure.
In the second publication on MnO3Cl also MnO2Cl2 and
MnOCl3 have been reported [4]. We have also tried to ob-
Z. Anorg. Allg. Chem. 2006, 2222Ϫ2225
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J. Spandl, J. Supeł, Th. Drews, K. Seppelt
HF is slowly pumped off, and green crystals of MnO3F are formed.
These were immediately transferred to the diffractometer. The yield
of MnO3F is very low, estimated to be 1-3 %.
tain these elusive compounds, but they turned out to be so
unstable that attempts to grow single crystals remained
futile.
CrO2Cl2 is prepared from K2Cr2O7, NaCl, and H2SO4 [5].
ReO3Cl [16]: 3 g (8.25 mmol) freshly sublimed ReCl5 is suspended
in 10 ml CFCl3. The temperature is kept at 10 °C during the entire
reaction time. Cl2O is prepared in situ from Cl2 and HgO dried by
passage through P2O5 and slowly added to the reaction mixture.
After about 6 hrs. the green solution turns red (ReOCl4), finally
colorless. The solvent is pumped away at Ϫ60 °C and 10Ϫ3 mbar,
yield 90 %, based on ReCl5. Mp 4.5 °C, bp 128 °C. Raman spec-
trum: 1001, 435, 344, 335, 303, 196 cmϪ1. Also ReOCl4 can be re-
acted with Cl2O. This reaction is finished within 2 hrs, the yield is
similarly high.
Experimental Part
All manipulations were carried out under vacuum or in an Argon
atmosphere with standard Schlenk techniques.
Raman spectra were measured on Bruker RFS 100 spectrometer
(with 1064 nm line of Nd:YAG laser) at Ϫ120 °C. Single crystals
were obtained by annealing samples in a glass capillary (MnO3Cl,
CrO2Cl2) directly on the diffractometer.
Single crystals grown from solution (MnO3F, ReO3Cl) were
handled in a special device [20], cut to an appropriate size, and
mounted on a Bruker SMART CCD 1000 TU diffractometer. This
works with MoKͰ irradiation, a graphite monochromator, a scan
width of 0.3° in ω, and a measuring time of 20 s per frame. After
semi empirical absorption corrections (SADABS) by equalizing
symmetry-equivalent reflections, the SHELX programs were used
for solution and refinement [21]. Experimental details are laid
down in table 3, results in table 2. Crystallographic data (excluding
structure factors) for the structures reported in this paper have been
deposited with the Fachinformationszentrum Karlsruhe, Gesellsch-
aft für wissenschaftliche technische Zusammenarbeit mbH, D-
76344 Eggenstein-Leopoldshafen, under the CSD numbers 416749
(MnO3Cl), 416748 (MnO3F), 416750 (CrO2Cl2), and 416751 (Re-
O3Cl). Details can be obtained on quoting the depository numbers,
names of authors and the journal citation.
DFT-calculations are done with the GAUSSIAN package [22], the
Becke 3 parameter hybrid functional [23], and the correlation func-
tional of Lee, Yang, and Parr [24]. Basis sets used throughout: 6-
311ϩG(d,p).
We thank the Deutsche Forschungsgemeinschaft and the Fonds der
Chemischen Industrie for support of this work, also the H. C. Stark
Co., Germany, for a generous gift of rhenium powder.
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