New insight into the reduction of rhenates(VII) with hydrogen chloride and into the structure of the ReOCl5- product

Article abstract of DOI:10.1016/j.ica.2009.01.035

Rhenate(VII) anion is reduced by gaseous HCl to yield pentachloridooxidorhenate(VI) anion. Several pentachloridooxidorhenate(VI) salts have been crystallized and the anion structure has been investigated in detail. The ReOCl₅^- anion

Full text of DOI:10.1016/j.ica.2009.01.035

Inorganica Chimica Acta 362 (2009) 3019–3024
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New insight into the reduction of rhenates(VII) with hydrogen chloride
ꢀ
and into the structure of the ReOCl5 product
*
´
Małgorzata Hołynska , Tadeusz Lis
Faculty of Chemistry, University of Wrocław, 14 Joliot-Curie St, 50-383 Wrocław, Poland
a r t i c l e i n f o
a b s t r a c t
Article history:
Rhenate(VII) anion is reduced by gaseous HCl to yield pentachloridooxidorhenate(VI) anion. Several pen-
tachloridooxidorhenate(VI) salts have been crystallized and the anion structure has been investigated in
detail. The ReOCl5 anion structure has been compared with the ReOCl5 structure and conclusions con-
cerning the influence of the central atom d electrons number on the anion geometry have been drawn.
Ó 2009 Elsevier B.V. All rights reserved.
Received 14 November 2008
Received in revised form 18 December 2008
Accepted 28 January 2009
ꢀ
2ꢀ
Available online 6 February 2009
Keywords:
Crystal structure
Pentachloridooxidorhenate(VI)
1. Introduction
Yatirayam and Singh [4] reported the preparation and proper-
ties of pentachloridooxidorhenates(VI) obtained during bubbling
It was reported in literature that hydrogen chloride could not
act as a reducing agent towards rhenate(VII) anions, contrary to
the well-known reaction with manganates(VII) used already by
Scheele [1] as a laboratory method of obtaining chlorine. This
gaseous HCl through the suspension of potassium rhenate(VII) in
acetic acid with addition of acetic anhydride. This procedure led
to the rhenate(VII) dissolution and
a red-coloured mixture
formation. The red mixture contained pentachloridooxidorhe-
nate(VI) anions, which could be precipitated in form of tetraphen-
ylphosphonium and tetraphenylarsonium salts. No attempt was
made to explain the formation of these compounds.
Other investigations of the products obtained in the reaction of
rhenates(VII) with HCl led to crystallization of such compounds as
Cs2[ReO3Cl3] [5,6]; bpy[ReO3Cl] [7]; (H2phen)[ReCl2(H2O)O3]Cl [8].
Apart from that, reaction of rhenate(VII) with acetyl chloride
yielded Cs[ReO2Cl4] and Cs[ReOCl5] salts [9].
_
seems to be confirmed by the work of Jezowska-Trzebiatowska
[2]. As part of that research, gaseous HCl was bubbled through rhe-
nates(VII) with simple inorganic cations such as K+, dissolved in
concentrated HCl acid. The mixture underwent a colour change
from yellow to red. A mechanism for this process was proposed
ꢀ
assuming that the yellow colour results from the ReO2Cl4
formation:
ReO4ꢀ þ 4HCl ! ReO2Cl4ꢀ þ 2H2O
The systematic research, this work being a part of it, was begun
_
It was reported, that these anions could easily be reduced; however,
not by HCl but by other reducing agents, such as HI. It is to note that
the study of Astheimer and Schwochau [3] on the electrolytic reduc-
tion of rhenates(VII) revealed, that the first reduction step involves
by Lis and Jezowska-Trzebiatowska [10]. The authors bubbled a
slow stream of HCl through the suspensions of [AsPh4]ReO4 and
[PPh4]ReO4 in various solvents. They observed colour changes sim-
ilar to those noticed by other authors and, furthermore, reported
precipitation of the relevant pentachloridooxidorhenate(VI) crys-
tals in form of red tetragonal needles, which were stable in air
when obtained from acetone or chloroform. However, when the
red crystals prepared in ethanol, together with the reaction mix-
ture, were exposed to air, rhenium(V) oxocomplexes were ob-
tained. The authors did not offer explanation whether the
rhenium (V) compounds were products of reduction or rather
disproportionation.
_
one-electron reduction to Re(VI). Contrary to Jezowska-Trzebia-
towska, the authors used rhenate(VII) of bulky tetrabutylammo-
nium cation, dissolved in organic solvents. The relevant
rhenate(VI) could be obtained; however the attempt to obtain the
analogous potassium salt failed.
Other authors also confirmed the possibility to stabilize Re(VI)
complexes obtained in the reaction of rhenates(VII) with HCl. The
published results therefore seem to contradict the initial conclu-
_
sions of Jezowska-Trzebiatowska [2].
It should be noted, that although the processes described above
play an important role in inorganic syntheses (e.g. as one of first
stages in the synthesis of rhenium potential radiopharmaceuticals
[11]), they remain unexplained in detail.
* Corresponding author.
E-mail address: holynska@wcheto.chem.uni.wroc.pl (M. Hołyn´ ska).
0020-1693/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2009.01.035

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M. Hołynska, T. Lis / Inorganica Chimica Acta 362 (2009) 3019–3024
3020
This work is intended to fill this gap, as well as to gain further
chloride) or prepared in the reactions of the relevant alkyl/aryl ha-
lide with the selected phosphine in toluene1
insight into the structure of their products, pentachloridooxidorh-
enates(VI). In comparison to the analogous Re(V) oxidocomplexes,
the central metal atom lacks one d electron, therefore the influence
of this additional electron on the geometric parameters can be
.
In the course of this work many pentachloridooxidorhe-
nates(VI) have been investigated by X-ray diffraction studies
(Fig. 1). Very frequently problems connected with anion disorder
or the presence of impurities, occured. A series of phosphonium
salts structures was obtained (the methyltriphenylphosphonium
salt, two polymorphs of the benzyltriphenylphosphonium salt,
two polymorphs of the (4-methylbenzyl)triphenylphosphonium
salt, the ethyltriphenylphosphonium salt, the 1,1,4,4-tetraphenyl-
1,4-diphosphoniacyclohexane salt, (4-chloromethylbenzyl)tri-
phenylphosphonium salt). Three structures were chosen. The crite-
rion of choice was based on the X-ray data quality and indicators of
the possible crystal structure disorder affecting the observed
_
assessed. The first such analysis was published by Lis and Jezows-
ka-Trzebiatowska [10], who compared bond lengths and angles for
ꢀ
ReOCl4 and ReOCl4 (from AsPh4[ReOCl4] later shown by Müller
[12] to be in fact AsPh4[ReOCl4H2O] [13]). The relevant differences
appear to be significant and affect the IR spectra parameters. The
ꢀ
Re–Cl bond length increase in ReOCl4 was explained assuming,
that one additional d electron is present on the antibonding orbital,
the same as the one occupied by the unpaired electron in ReOCl4
according to Al-Mowali and Porte [14]. Pentachloridooxidorhe-
ꢀ
_
nates(VI) obtained by Lis and Jezowska-Trzebiatowska [10] were
ReOCl5 anion geometry or impurity (e.g. the final difference Fou-
affected by disorder due to the highly symmetric (tetraphenyl-
phosphonium and tetraphenylarsonium) counterions. Accordingly,
in this study it was decided to use phosphonium cations of lower
symmetry (such as: methyltriphenylphosphonium, benzyltriphen-
rier map). The selected structures include the 1,1,4,4-tetraphenyl-
1,4-diphosphoniacyclohexane salt (A, containing also hydrogen
dichloride anions), the ethyltriphenylphosphonium salt (B) and
one polymorph of the benzyltriphenylphosphonium salt (C). The
three chosen data sets provide the structure of pentachloridooxi-
dorhenate(VI) anion not affected significantly by detectable
artifacts.
ylphosphonium, (4-methylbenzyl)triphenylphosphonium
– see
Fig. 1), that would allow to limit the crystal structure disorder.
As a result, the pentachloridooxidorhenate(VI) anion geometrical
parameters have been obtained, which then could be compared
with the parameters reported for the analogous Re(V) compounds.
2.2. 1,1,4,4-Tetraphenyl-1,4-diphosphoniacyclohexane
pentachloridooxidorhenate(VI) hydrogen dichloride (A)
2. Experimental
Gaseous HCl was bubbled through suspension of the corre-
sponding rhenate(VII) (0.05 g) in 0.5 ml of methanol. The solid rhe-
nate(VII) dissolved and the reaction mixture changed from yellow
through orange to red.
At this stage (red homogenous mixture) the bubbling of the HCl
gas through the reaction mixture was stopped and 0.05 g of rhe-
nate(VII) was added under HCl atmosphere to the mixture. The
vessel with the mixture was sealed and stored in a freezer at about
ꢀ10 °C. After a few days crystals in form of red needles began to
appear. The crystals, which were very unstable, were quickly fil-
tered off and covered with polyfluoroalkylether. One monocrystal
was chosen for X-ray data collection.
2.1. General
All compounds used for syntheses and preparations were ob-
tained commercially and not purified further.
The preparative procedure was as follows. The starting rhe-
nate(VII) salt was placed in a flow reactor and the relevant solvent
was added. Gaseous HCl obtained in reaction of concentrated
H2SO4 with solid NaCl was bubbled through the rhenate(VII) sus-
pension in the flow apparatus.
The relevant rhenate(VII) salts were prepared in the reaction of
ammonium rhenate(VII) with phosphonium halide in aqueous
solution. The obtained precipitates were filtered and washed with
cold water until no halide ions were present in the filtrate [38].
The phosphonium halides were obtained commercially (ethyl-
triphenylphosphonium bromide, benzyltriphenylphosphonium
2.3. Ethyltriphenylphosphonium pentachloridooxidorhenate(VI) (B)
Ethyltriphenylphosphonium rhenate(VII) (0.05 g) was sus-
pended in 0.5 ml of ethanol. Gaseous hydrogen chloride was bub-
bled through the suspension. Similar colour changes as in case of
(A) were observed. At this stage (red homogenous mixture) the
bubbling of HCl gas through the reaction mixture was stopped
and 0.01 g of rhenate(VII) was added under HCl atmosphere to
the mixture. The vessel with the mixture was sealed and stored
in a freezer at about ꢀ10 °C. As a result, red crystals in the form
of plates were obtained after a few days. The crystals were filtered
1
Beilstein’s Handbook of Organic Chemistry, 16, 759. The 1,1,4,4-tetraphenyl-1,4-
diphosphoniacyclohexane bromide used in the preparation of the starting rhe-
nate(VII) for A was obtained in the reaction of ethane-1,2-bis(triphenylphosphine)
with the excess of 1,2-dibromoethane in toluene. The compound is known [23];
however, the present authors could not retrieve the synthesis description, which was
published in Ph. D. thesis cited in the paper on the crystal structure [23]. Therefore
the here applied procedure is described. 1 g of PPh2CH2CH2PPh2 was placed in a 50 ml
flask. 25 cm3 of toluene and 3 cm3 of ethylene bromide were added. The mixture was
heated under reflux over 2 h. A white precipitate was obtained, comprising 1,1,4,4-
tetraphenyl-1,4-diphosphoniacyclohexane bromide (yield: 70%). Elemental Anal. Calc.
10.6% P; obs.: 10.2% P. IR (KBr pellet): 443.2 (w), 500 (vs), 657.0 (w), 688.6 (m), 728.2
(vs), 761.5 (m), 780.1 (w), 844.4 (m), 928.2 (vw), 995.6 (w), 1026.3 (vw), 1112.4 (m),
1133.0 (s), 1198.7 (vw), 1340.9 (vw), 1403.7 (w), 1415.8 (w), 1439.1 (s), 1487.6 (vw),
1584.4 (w), 1623.7 (w), 2088.5 (vw), 2241.5 (vw), 2582.2 (vw), 2788.0 (m), 2851.4 (s),
2913.7 (w), 3007.7 (m), 3036.8 (m), 3069.4 (w), 3431.9 (s). MS spectrum obtained for
solution in methanol – m/z (I, a. u.) – positive ions: (Mꢀ2) 213.1 (3.6ꢁ104), 213.6
(8ꢁ103), 214.1 (103); 314.1 (103), 399.1 (9ꢁ102), 453.1 (103).
Fig. 1. The phosphonium cations used as counter-ions in this study. The cations
from (A), (B) and (C) are provided with the corresponding letters.

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M. Hołynska, T. Lis / Inorganica Chimica Acta 362 (2009) 3019–3024
off, covered with polyfluoroalkylether and next one monocrystal
was chosen for X-ray data collection.
from that of a complexing agent, also as the reducing agent. In
all the syntheses involving various phosphonium rhenates(VII)
suspended in different solvents as starting materials the precipi-
tated red crystals contained pentachloridooxidorhenates(VI). HCl
was at the same time oxidised to chlorine what would be demon-
strated when bubbling the gas coming out from the flow reaction
vessel through KI aqueous solution, which would turn brown as
a result of free iodine formation. Therefore, the process could be
2.4. Benzyltriphenylphosphonium pentachloridooxidorhenate(VI), one
of the monoclinic modifications (C)
Reaction of gaseous HCl was performed using as starting mate-
rial 0.1 g of benzyltriphenylphosphonium rhenate(VII) suspended
in 3 ml of isopropyl alcohol. Similar reaction as in case of (A) led
to precipitation of red crystals. However, the quality of the crystals
was very bad, therefore the mixture was sealed in the reaction ves-
sel and left for recrystallization. After a few days the crystals were
filtered and their examination showed them to be a mixture of two
polymorphs: in form of needles (majority, compound (C)) and
blocks. Both polymorphs were unstable and on exposure to air
underwent decomposition to yellow polycrystalline products.
_
summarized as follows. In the first stage in accordance to Jezows-
ka-Trzebiatowska [2] the yellow complex [ReO3Cl3]2ꢀ and subse-
quently [ReO2Cl4]ꢀ ions are formed according to the following
scheme:
HCl—H2
!
HCl—H2
!
ꢀ
2ꢀ
ꢀ
ReO4
O ReO3Cl
O ReO2Cl
3
4
Subsequently, the colour changes to red as a result of reduction
process:
2½ReO2Cl4ꢂꢀ þ 4HCl ¼ 2ReOCl5ꢀ þ Cl2 þ 2H2O
2.5. X-ray data collection
It is possible to isolate the relevant Re(VI) oxidocomplexes as bulky
phosphonium cations present in the reaction environment facilitate
their precipitation [15].
Selected crystallographic data for compounds (A), (B) and (C)
are given in Table 1. Data were collected on KM4CCD diffractome-
ter [39] with graphite-monochromatised Mo K
a radiation. All
structures were solved by Patterson method using SHELXS97 and re-
fined using SHELXL software [40]. All cation H atoms positions were
calculated from geometry and their displacement parameters were
constrained as 1.2Ueq(parent atom). In (A) the H6 atom in the
[HCl2]ꢀ anion (containing Cl5 and Cl6 atoms) was found on the dif-
ference Fourier map closer to the Cl6 atom. All parameters of H6
were first refined and then constrained. The difference Fourier
peak near the Cl5 atom was interpreted as sign of slight disorder.
As a result, Cl5 atom was modelled as disordered between two
positions (with occupancies of 0.972(8) and 0.028(8), respectively).
3.2. The pentachloridooxidorhenate(VI) anion structure. ReVIOCl5
ꢀ
versus ReVOCl5
2ꢀ
In the pentachloridooxidorhenate(VI) anion the central Re atom
is surrounded by five chloride ligands and one oxide ligand, placed
in vertices of a distorted octahedron (Fig. 2). The Re–O bond may
be regarded as a triple bond [16] and should be expected to influ-
ence the Re–Cltrans bond length (see Scheme 1), which is longer
than the Re–Clcis bonds. The overall anion distortion with the O–
Re–Clcis bond angles greater than 90° should also be expected. All
2ꢀ
these features occur in the ReOCl5 anion [17] (in the potassium
3. Results and discussion
salt).
The Re–O and Re–Cl distances are collected in Table 2 ((A), (B)
and (C) as well as K2ReOCl5). In (B) and (C) the anions occupy gen-
eral positions. In the crystal structure of K2ReOCl5 [17] the
3.1. The reduction of rhenates(VII) with hydrogen chloride
2ꢀ
Based on the experimental data collected in this study, the role
of HCl in its reaction with rhenates(VII) could be defined, apart
ReOCl5 anion lies in special position of m site symmetry. A sim-
ꢀ
ilar situation is observed in case of the ReOCl5 anion in (A). There-
Table 1
Crystal and refinement data for (A), (B) and (C)
(A)
(B)
(C)
Formula
Formula weight
T (K)
[PPh2(CH2CH2)2PPh2] [ReOCl5][HCl2]
877.80
100(2)
[PPh3CH2CH3] [ReOCl5]
670.79
100(2)
[PPh3CH2Ph][ReOCl5]
732.85
100(2)
k (Å)
0.71073
orthorhombic
Pnma
8.504(3)
16.666(5)
22.976(7)
0.71073
orthorhombic
Pbca
16.500(5)
16.240(5)
17.414(5)
0.71073
monoclinic
P21/c
10.984(3)
17.906(5)
14.069(4)
108.60(3)
2623(2)
Crystal system
Space group
a (Å)
b (Å)
c (Å)
b (Å)
V (Å3)
3256(2)
4, 1.791
4.43
1716
4666(2)
8, 1.910
5.86
2584
Z, qcalc (g cmꢀ3
)
4, 1.856
5.22
1420
l
(mmꢀ1
F(000)
)
Crystal size (mm)
h Range (°)
Reflections total/unique
Rint
0.29 ꢃ 0.05 ꢃ 0.017
2.8–36.9
55633/8259
0.0829
0.20 ꢃ 0.08 ꢃ 0.04
2.8–35.0
65037/10054
0.0725
0.15 ꢃ 0.12 ꢃ 0.09
3.0–38.5
45819/13560
0.0943
Absorption correction
Minimum, maximum transmission factors
Data/restraints/parameters
Goodness-of-fit on F2
analytical
0.417, 0.822
8259/0/191
1.018
analytical
0.387, 0.829
10054/0/253
1.016
analytical
0.553, 0.639
13560/0/298
0.928
R1 [I > 2
r
(I)]a
0.036
0.032
0.052
wR2 (all data)
Maximum, minimum
0.039
1.48/ꢀ1.42
0.035
1.76/ꢀ1.68
0.055
1.55/ꢀ1.55
D
qelect (e Åꢀ3
)
P
P
a
R = ||Fo| ꢀ |Fc||/ |Fo|.

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3022
Fig. 2. Pentachloridooxidorhenate(VI) anion in (A) and (B), (C) (on example of (B)) with atom labelling scheme (for the sake of comparison the anion labelling scheme in A
2ꢀ
corresponds to the labelling scheme used for the ReOCl5 anion by Głowiak et al. [17], see article text). The thermal ellipsoids have been drawn at 30% probability level.
Symmetry code: [i] x, 0.5 ꢀ y, z.
ꢀ
fore a comparison of the two data sets gives a good opportunity to
compare the influence of the additional d electron on the overall
ReOCl5 (n = 1 or 2) anion geometry. Table 2 shows, that in both
cases the Re–O bond length is comparable within the experimental
error. This bond length is similar to the triple Re–O bond length re-
ported for other Re(VI) oxidocomplexes [18], as well as the value
fitted by Pyykkö et al. [16] as the sum of the O and Re covalent radii
in a triple bond.
The most striking difference between the ReOCl5 anion in A
2ꢀ
and the ReOCl5 anion in K2ReOCl5 is connected with the Re–Cl
bond lengths, in particular the Re–Clcis bond lengths. All these
bonds are longer in case of the ReOCl5 anion. The Re–Cltrans bond
length is longer by 0.034(2) Å and the average Re–Clcis bond
lengths differ by 0.054(5) Å. This may be explained based on the
available theoretical studies on Re(V) and Re(VI) oxidocomplexes.
A general molecular orbital diagram for the X–M–L moiety in com-
plex molecules (where M – metal, X – ligand imposing trans influ-
ence on the ligand L) was provided by Shustorovich et al. [19].
nꢀ
2ꢀ
_
Natkaniec and Jezowska-Trzebiatowska [20] reported the molecu-
2ꢀ
lar orbital diagram for the ReOCl5 anion based on theoretical cal-
culations, as well as spectroscopic, magnetic and EPR
measurements. The authors carried out theoretical calculations
2ꢀ
assuming C4v symmetry of the ReOCl5 anion. However, still their
results are helpful in the analysis of the here reported data. The
2ꢀ
authors explain the trans-effect in the ReOCl5 anion (elongation
of the Re–Cl bond placed in the trans position with respect to the
oxide ligand) as a result of decrease in the total
tion in the affected bond. This decrease corresponds to the fact,
p overlap popula-
nꢀ
Scheme 1. Labelling in the ReOCl5 anion (where n = 1 or 2) often used in the
general considerations concerning the bond lengths in this paper.
that the bonding and antibonding b2
(p) orbitals are filled with
Table 2
The pentachloridooxidorhenate(VI) anion (in (A), (B) and (C)) versus the pentachloridooxidorhenate(V) anion [17] geometrical parameters
Salt
Anion
A
B
C
2ꢀ
ꢀ
ꢀ
ꢀ
ReOCl5
ReOCl5
ReOCl5
ReOCl5
Re–O
Re–Cl1
1.655(6)
2.379(2)
1.675(2)
2.322(1)
Re–O
Re–Cl1
Re–Cl4
Re–Cl2
Re–Cl3
Re–Cl5
O–Re–Cl1
O–Re–Cl4
O–Re–Cl2
O–Re–Cl3
O–Re–Cl5
Cl1–Re–Cl4
Cl1–Re–Cl2
Cl1–Re–Cl3
Cl1–Re–Cl5
Cl2–Re–Cl3
Cl2–Re–Cl5
Cl3–Re–Cl5
1.686(2)
2.314(1)
2.351(1)
2.316(1)
2.408(1)
2.341(1)
94.7(1)
91.8(1)
95.8(1)
176.7(1)
92.9(1)
173.4(1)
89.9(1)
87.6(1)
90.1(1)
86.6(1)
171.3(1)
84.8(1)
1.668(3)
2.325(2)
2.330(1)
2.327(2)
2.405(1)
2.344(2)
93.2(1)
94.7(1)
93.7(1)
179.2(1)
93.8(1)
171.9(1)
91.4(1)
86.0(1)
88.8(1)
85.9(1)
172.4(1)
86.5(1)
Re–Cl2
Re–Cl3
Re–Cl4
O–Re–Cl1
2.371(2)
2.502(2)
2.382(2)
94.7(2)
2.314(2)
2.468(2)
2.336(2)
95.6(1)
O–Re–Cl2
O–Re–Cl3
O–Re–Cl4
97.2(2)
179.4(2)
95.1(2)
170.6(1)
89.3(1)
85.3(1)
89.7(1)
83.4(1)
167.7(1)
84.3(1)
96.0(1)
175.5(1)
92.2(1)
168.8(1)
89.0(1)
84.4(1)
90.2(1)
88.5(1)
171.8(1)
83.3(1)
Cl1–Re–Cl1a
Cl1–Re–Cl2
Cl1–Re–Cl3
Cl1–Re–Cl4
Cl2–Re–Cl3
Cl2–Re–Cl4
Cl3–Re–Cl4
a
Symmetry code: [i] x, 0.5 ꢀ y, z.

´
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M. Hołynska, T. Lis / Inorganica Chimica Acta 362 (2009) 3019–3024
electrons. The authors imply, that if the magnitudes of the trans ef-
fect for d2 and d1 electron central ion are different, this provides an
indirect evidence, that the second d electron of the central ion is
also in the antibonding 2b2 (dxy) orbital. The here reported data
are probably an experimental proof for this conclusion. Also, e.g.
Neuhaus et al. [21] reported as a result of a theoretical study that
the Re–Cl bonds should involve the d orbitals of Re.
the crystal (A) is the presence of [HCl2]ꢀ anions. Such anions have
been subject to spectroscopic [24,25], as well as theoretical [26],
neutron [27] and X-ray diffraction studies [28–36]. It was shown,
based on IR spectra analysis [24,25], that the [HCl2]ꢀ anion should
be linear. Two spectroscopically distinguishable cases were de-
scribed: (1) non-centrosymmetric case (asymmetric stretching
mode at 1540–1700 cmꢀ1), (2) centrosymmetric case (broad band
at 690–810 cmꢀ1). The H atom of the [HCl2]ꢀ anion in (A) was
localized on the difference Fourier map nearer to one of the Cl
atoms. Moreover, preliminary IR spectra indicate the presence of
a broad band at 1500–1800 cmꢀ1, what suggests the former possi-
bility [25,26].
For the ethyltriphenylphosphonium cation both in (B) and in
the corresponding rhenate(VII) [37] the P atom of nearly tetrahe-
dral environment deviates from the phenyl rings planes (the max-
imum deviation values: 0.261(4) and 0.138(4) Å for (B) and the
corresponding rhenate(VII), respectively). The methyl group devia-
tion from the phenyl group in trans position in (B) (ꢀ0.153(7) Å) is
not as significant as in case of the rhenate(VII) (ꢀ0.879(6) Å). Thus
the cation in (A) adopts the other possible ethyltriphenylphospho-
nium cation geometry [37].
The phosphonium cation conformation is not strictly the same
in case of (C) in comparison to the corresponding rhenate(VII)
[38]. The differences concerning the interplanar angles for phenyl
rings from the –PPh3 moiety as well as C–P–C–C torsion angles
with respect to the benzyltriphenylphosphonium cation in the cor-
responding rhenate(VII) [38] could be found. The P atom with
nearly tetrahedral environment in each case deviates from the
phenyl rings planes (0.064(5) and either 0.203(4) or 0.201(4) Å in
two symmetry-independent cations in (C) and for the correspond-
ing rhenate(VII) [38], respectively).
In (A), the cations are arranged in layers perpendicular to [010].
Between the layers the pentachloridooxidorhenate(VI) and hydro-
gen dichloride anions are located, forming columns (one set of col-
umns consisting of pentachloridooxidorhenate(VI) anions and the
other set of columns comprising hydrogen dichloride anions) along
[100] (Fig. 3). The crystals (B) and (C) are built from cation and an-
ꢀ
The symmetries of the ReOCl5 anions in (A) and (B), (C) are dif-
ferent. The difference is connected with a slight change at bond an-
gles values, e.g. in (C) the O–Re–Cltrans bond angle is closer to 180°,
2ꢀ
as in the ReOCl5 anion [17] (Table 2). However, the main differ-
ence concerns the Re–Cltrans bond length, which in (B) and (C) is
shorter than in (A) (the values for (B) and (C) are essentially equal).
This leads to the conclusion, that the main effect of the Re d1 elec-
tron is connected with the Re–Clcis bond lengths and the Re–Cltrans
bond length may to a higher extent be an effect of the crystal struc-
ture packing.
In case of the anions in (A)–(C) and K2ReOCl5 [17] the equatorial
Cl ligands lie in one plane and the Re atom is shifted from this
plane towards the O ligand. It is to be noted, that these shifts are
different: in case of K2ReOCl5 the value calculated based on the
available atom coordinates [17] is 0.255(1) Å, whereas in case of
(A) it is 0.196(1) Å, in case of (B): 0.155(1) Å and for (C): 0.158(1) Å.
3.3. The crystal structure packing in (A), (B) and (C)
It would be justified to take a closer look on the crystal structure
packing, that allowed to capture the ReOCl5ꢀ anions selectively and
to stabilize their positions. For all crystal structures (A)–(C) the
crystal packing is cation-dominated with numerous phenyl rings
embrace interactions [22,38], with weak C–HꢁꢁꢁCl or C–HꢁꢁꢁO hydro-
gen bonds and without any phenyl rings stacking interactions.
(A) is the second determined crystal structure with the 1,1,4,4-
tetraphenyl-1,4-diphosphoniacyclohexane cation. In the bromide
structure published by Brown and Trefonas [23] the core 1,4-
diphosphoniacyclohexane ring adopts a chair conformation, a sim-
ilar conformation is observed in (A). Another uncommon feature of
Fig. 3. Packing in the crystals (A), (B) and (C). The minor component of the disordered part (Cl51; in case of A) and H atoms (in all cases) are omitted for clarity.

´
3024
M. Hołynska, T. Lis / Inorganica Chimica Acta 362 (2009) 3019–3024
_
[2] B. Jezowska-Trzebiatowska, Trav. Soc. Sci., Wrocław, Ser. B 36 (1951) 1.
[3] L. Astheimer, K. Schwochau, J. Inorg. Nucl. Chem. 38 (1976) 1131.
[4] V. Yatirayam, H. Singh, J. Inorg. Nucl. Chem. 37 (1975) 2006.
[5] D.E. Grove, N.P. Johnson, G. Wilkinson, Inorg. Chem. 8 (1969) 1196.
[6] T. Lis, Acta Crystallogr., Sect. C 39 (1983) 961.
ion columns extending along the [010] and [001] direction,
respectively (Fig. 3).
4. Conclusion
[7] W.S. Sergiyenko, M. Porai-Koshits, T.S. Khodashova, G.K. Babeshkina, L.A.
Butman, Koord. Khim. 1 (1975) 1282.
The results obtained in this study verify the state-of-the-art
view on the reduction of rhenates(VII) with gaseous hydrogen
chloride. It has been proved that the reaction is possible and that
hydrogen chloride may act there not only as the complexing agent,
but also as the reducing agent. One of the products formed is pen-
tachloridooxidorhenate(VI) anion. A series of phosphonium salts
with this anion was obtained and investigated using X-ray diffrac-
tion. The obtained data sets were analyzed. Three crystals were
chosen to obtain pentachloridooxidorhenate(VI) anions geometri-
cal parameters not affected by such phenomena as disorder or
co-crystallization of other rhenium complexes. A comparison of
the obtained data with the analogous data reported previously
[17] for the pentachloridooxidorhenate(V) anion allowed to draw
[8] T. Lis, Acta Crystallogr., Sect. B 35 (1979) 1230.
´
[9] M. Hołynska, T. Lis, Acta Crystallogr., Sect. C 64 (2008) i18.
_
[10] T. Lis, B. Jezowska-Trzebiatowska, Acta Crystallogr., Sect. B 33 (1977) 1248.
[11] A. Marchi, A. Duatti, R. Rossi, L. Magon, U. Mazzi, A. Pasquetto, Inorg. Chim.
Acta 81 (1984) 15.
[12] U. Müller, Acta Crystallogr., Sect. C 40 (1984) 571.
[13] M. Siczek, T. Lis, Acta Crystallogr., Sect. E 62 (2006) m358.
[14] A.H. Al-Mowali, A.L. Porte, J. Chem. Soc., Dalton Trans. (1975) 50.
[15] B.J. Brisdon, D.A. Edwards, Inorg. Chem. 7 (1968) 1898.
[16] P. Pyykkö, S. Riedel, M. Patzschke, Chem. Eur. J. 11 (2005) 3511.
_
[17] T. Głowiak, B. Jezowska-Trzebiatowska, T. Lis, Acta Crystallogr., Sect. C 47
(1991) 177.
[18] W. Noh, G.S. Girolami, Dalton Trans. (2007) 674.
[19] E.M. Shustorovich, M.A. Porai-Koshits, Yu.A. Buslaev, Coord. Chem. Rev. 17
(1975) 1.
_
[20] L. Natkaniec, B. Jezowska-Trzebiatowska, Bull. Acad. Polon. Sci. 19 (1971) 129.
[21] A. Neuhaus, A. Veldkamp, G. Frenking, Inorg. Chem. 33 (1994) 5278.
[22] I. Dance, M. Scudder, J. Chem. Soc., Dalton Trans. (2000) 1579.
[23] J.N. Brown, L.M. Trefonas, J. Heterocycl. Chem. 9 (1972) 35.
[24] J.C. Evans, Y.-S. Lo, J. Phys. Chem. 70 (1966) 11.
[25] J.W. Nibler, G.C. Pimentel, J. Chem. Phys. 47 (1967) 710.
[26] W.D. Chandler, K. Johnson, B.D. Fahlman, E. Campbell, Inorg. Chem. 36 (1997)
776.
[27] J.M. Williams, S.W. Peterson, Am. Cryst. Assoc. Progr. Abs., Ottawa, Canada 31
(1970). cited after [29].
[28] J.S. Swanson, J.M. Williams, Inorg. Nucl. Chem. Lett. 6 (1970) 271.
[29] L.W. Schroeder, J.A. Ibers, Inorg. Chem. 7 (1968) 594.
[30] H. Thonnessen, P.G. Jones, R. Schmutzler, Z. Anorg. Allg. Chem. 629 (2003)
1265.
the following conclusion. Upon going over from the ReOCl5 (d1
ꢀ
system) to the ReOCl5 (d2 system) the additional d electron does
2ꢀ
not affect significantly the Re–O bond length, but mainly the Re–Cl
bond lengths, above all in the Re–Clcis bonds (the Re–Cltrans bond
length may depend on the crystal structure packing). These results
provide new insight into the Re(VI) chemistry, which is still under-
investigated due to the Re(VI) compounds instability.
Acknowledgements
[31] D. Mootz, W. Poll, H. Wunderlich, H.G. Wussow, Chem. Ber. 114 (1981) 3499.
[32] A. Deeg, T. Dahlems, D. Mootz, Z. Kristallogr. – New Cryst. Struct. 212 (1997)
401.
[33] B.H. Ward, G.E. Granroth, K.A. Abboud, M.W. Meisel, D.R. Talham, Chem. Mater.
10 (1998) 1102.
Financial support from Ministry of Science and Higher Educa-
tion (project number N204 130 32/3318).
[34] R. Boese, N. Augart, Z. Kristallogr. 182 (1988) 32.
[35] J.L. Atwood, S.G. Bott, M. Means, A.W. Coleman, H. Zhang, M.T. May, Inorg.
Chem. 29 (1990) 467.
[36] A. Habtemariam, B. Watchman, B.S. Potter, R. Palmer, S. Parsons, A. Parkin, P.J.
Sadler, J. Chem. Soc., Dalton Trans. (2001) 1306.
Appendix A. Supplementary material
CCDC 706455, 706456 and 706457 contain the supplementary
crystallographic data for this paper. These data can be obtained
free of charge from The Cambridge Crystallographic Data Centre
via www.ccdc.cam.ac.uk/data_request/cif. Supplementary data
associated with this article can be found, in the online version, at
doi:10.1016/j.ica.2009.01.035.
[37] M. Hołyn´ ska, T. Lis, Acta Crystallogr., Sect. C 60 (2004) m648.
´
[38] M. Hołynska, T. Lis, J. Chem. Crystallogr. 37 (2007) 275.
[39] Kuma, KM-4 CCD Software, 1995–1999, Version 1.161. Kuma Diffraction,
Wrocław, Poland.
[40] G.M. Sheldrick, Acta Crystallogr., Sect. A 64 (2008) 112.
References
[1] Early history of chlorine: Papers by Carl Wilhelm Scheele (1774), C.L. Berthollet
(1785), Guyton de Morveau (1787), J.L. Gay-Lussac and L.J. Thenard (1809).
Alembic Club, Edinburgh, 1905.