Decomposition of pentachloridooxidorhenates(VI) - A still underinvestigated source of rhenium complexes at different oxidation states

Article abstract of DOI:10.1016/j.ica.2014.04.041

Studies on decomposition of pentachloridooxidorhenates(VI) are described. The products are rhenium(V) salts with anions [Re^VOCl ₄X]^- (X = solvent molecule) or [Re^VOCl ₄Re^VIIO₄]^2- or, under proper conditions, hexachloridorhenates(IV), as well as salts with [ReOCl ₅]^2- or [ReOCl₄]^- anions. The products are listed and characterized by X-ray diffraction studies, or TGA/IR in the selected cases.

Full text of DOI:10.1016/j.ica.2014.04.041

Accepted Manuscript
Decomposition of pentachloridooxidorhenates(VI) - a still underinvestigated
source of rhenium complexes at different oxidation states
Małgorzata Hołyńska, Tadeusz Lis
PII:
S0020-1693(14)00246-1
http://dx.doi.org/10.1016/j.ica.2014.04.041
ICA 15980
DOI:
Reference:
Inorganica Chimica Acta
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Received Date:
Revised Date:
Accepted Date:
7 February 2014
28 April 2014
30 April 2014
Please cite this article as: M. Hołyńska, T. Lis, Decomposition of pentachloridooxidorhenates(VI) - a still
underinvestigated source of rhenium complexes at different oxidation states, Inorganica Chimica Acta (2014), doi:
http://dx.doi.org/10.1016/j.ica.2014.04.041
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Decomposition of pentachloridooxidorhenates(VI) - a still
underinvestigated source of rhenium complexes at different oxidation states
Synopsis
Structure and properties of the products of pentachloridooxidorhenates(VI) decomposition
under air are presented.
1

Decomposition of pentachloridooxidorhenates(VI) - a still
underinvestigated source of rhenium complexes at different oxidation states
Małgorzata Hołyńska*a,b and Tadeusz Lisa
aDepartment of Chemistry, Wrocław University, 14 F. Joliot-Curie St., Wrocław, Poland.
bFachbereich Chemie, Wissenschaftliches Zentrum für Materialwissenschaften, Philipps-
Universität Marburg, Hans-Meerwein-Strasse, D-35043 Marburg, Germany. E-mail:
holynska@staff.uni-marburg.de
Abstract
Studies on decomposition of pentachloridooxidorhenates(VI) are described. The products
are rhenium(V) salts with anions [ReVOCl4X]- (X = solvent molecule) or
[ReVOCl4ReVIIO4]2- or, under proper conditions, hexachloridorhenates(IV), as well as
salts with [ReOCl5]2- or [ReOCl4]- anions. The products are listed and characterized by
X-ray diffraction studies, or TGA/IR in the selected cases.
Keywords: rhenium(V), mixed-valent complexes, X-ray diffraction studies, TGA, IR.
1. Introduction
Our recent studies on the system where rhenate(VII) anions react with hydrogen
chloride led to the following description [1]:
HCl
HCl
−H2O
−H2O
ReO4 →ReO3Cl32− →ReO2Cl4
−
−
−
−
2[ReO2Cl4 ] + 4HCl = 2ReOCl5 + Cl2 + 2H2O
The first stages comprise complexation of the rhenate(VII) anions with hydrogen
chloride to yield yellow chloridooxidocomplexes. Subsequently, these transition products are
reduced with hydrogen chloride to pentachloridooxidorhenates(VI).
We also managed to obtain remarkably stable rhenium(VI) binuclear complexes
utilizing the following reaction [2]:
2

1
−
−
ReOCl5 + ReO4 + 4HCl → [ReOCl4OReOCl4 ]2− + Cl2 + 2H2O
2
The present and the previous [3] studies indicate, that pentachloridooxidorhenates(VI)
decompose under air. In this paper we show that this decomposition may lead to a variety of
rhenium-containing anions with Re atom at different oxidation states (Scheme 1).
Among the decomposition products, examples of species with alcohol molecule
coordinating to ReV atom are present. Also, under proper conditions, it is possible to isolate
salts of mixed-valent [ReVOCl4ReVIIO4]2- ions. These results are important as there are related
synthetic routes leading to Re(V) potential radiopharmaceuticals [4]. In the first stages of
these processes a mixture obtained by bubbling hydrogen chloride and then nitrogen gas
through a suspension of tetrabutylammonium rhenate(VII) in methanol is used. It is claimed,
that thus solely a [ReOCl4]- salt is obtained.
The present paper sheds more light on these processes and focuses on listing of the
possible products of decomposition of pentachloridooxidorhenates(VI) under air in different
solvents. Structural aspects of these compounds are discussed, being of importance for the
general coordination chemistry and crystalochemistry of rhenium.
2. Experimental
Preparation descriptions
Caution
The preparations involve irritating and corrosive gaseous hydrogen chloride and
should be carried out employing the relevant safety measures.
A ([PPh3CH2CH3][ReOCl4(H2O)])
A suspension of 0.3 g ethyltriphenylphosphonium rhenate(VII) in 3.5 ml of
isopropanol was prepared and placed in a flow apparatus. Gaseous hydrogen chloride
obtained in a reaction of concentrated (96%) sulfuric acid with sodium chloride was bubbled
through this suspension. Under a continuous flow of hydrogen chloride, as a result of an
exothermal reaction, the solid rhenate(VII) dissolved to form a clear solution, which
subsequently underwent colour changes from yellow, through orange to red with precipitation
of some red crystals (confirmed previously to contain pentachloridooxidorhenate(VI) salts
[1]). The obtained mixture was moved to a separate open vessel. Under air the mixture
underwent slow colour changes from red to orange. After about fifteen minutes crystals in
form of yellow plates (A) were observed to crystallize from the reaction mixture (the crystals
3

tend to form hexagonal twins). The crystallization vessel was covered with parafilm and left
for slow evaporation overnight. As a result, a mixture of different kind of crystals was
obtained, comprising, as evidenced by preliminary X-ray measurements, A, light-green or
light-yellow
crystals
of
impure
orange
(containing
also
rhenium(V)
complexes)
hexachloridorhenate(IV),
blocks containing
trans-tetrachloridooxido(O-
rhenate(VII))rhenate(V) (probably also with cocrystallizing rhenium(V) impurities, therefore
the formally identical F salt was obtained by a different method).
IR bands (nujol/NaCl): 666.8 (m), 686.5 (vs), 695.2 (s), 711.4 (w), 722.4 (vs), 737.9
(vs), 754.9 (m), 771.7 (w), 883.3 (vw), 926.1 (vw), 999.0 (vs), 1012.0 (vw), 1034.7 (vw),
1113.9 (vs), 1165.1 (vw), 1189.3 (w), 1240.3 (vw), 1262.1 (vw), 1333.9 (w), 1378.1 (s),
1436.8 (vs), 1458.3 (vs), 1585.5 (w), 1613.4 (m), 1923.4 (vw), 1986.0 (vw), 2688.4 (w),
2854.8 (vs), 2924.8 (vs), 3314.6 (m).
B ([PPh3CH2CH2PPh3][ReOCl4(CH3OH)]2)
A suspension of 0.3 g ethane-1,2-bis(triphenylphosphonium) rhenate(VII) in 3.5 ml of
methanol was prepared and placed in a flow apparatus. Gaseous hydrogen chloride was
bubbled through this suspension. Under continuous flow of hydrogen chloride, as a result of
an exothermal reaction, the solid rhenate(VII) dissolved to form a clear solution, which
subsequently underwent colour changes from yellow, through orange to red with precipitation
of some red crystals (confirmed previously to contain pentachloridooxidorhenate(VI) salts
[1]). The obtained mixture was moved to a separate open vessel. Under air the mixture
underwent slow colour changes from red to orange. After about fifteen minutes crystals in
form of orange blocks (B) were observed to crystallize from the reaction mixture. The
crystallization vessel was covered with parafilm and left for slow evaporation overnight. As a
result, further crop of crystalline B was obtained. The crystals left under air gradually loose
methanol.
IR bands (nujol/NaCl): 669.3 (w), 688.4 (vs), 728.3 (vs), 739.7 (vs), 749.2 (m), 810.5
(vw), 871.8 (vw), 907.7 (w), 918.8 (w), 932.8 (w), 957.5 (vw), 979.8 (s), 995.1 (vs), 1028.4
(vw), 1112.8 (vs), 1146.6 (m), 1165.9 (w), 1192.3 (w), 1220.0 (w), 1276.8 (vw), 1322.4 (w),
1338.0 (w), 1377.3 (m), 1403.3 (w), 1437.8 (vs), 1462.7 (s), 1483.1 (m), 1587.1 (s), 1824.5
(vw), 1905.5 (vw), 1976.1 (vw), 2854.7 (vs), 2928.0 (vs), 3053.0 (s), 3314.3 (s).
C ([PPh3CH2CH3][ReOCl4(C2H5OH)])
A suspension of 0.3 g ethyltriphenylphosphonium rhenate(VII) in 3.5 ml of methanol
was prepared and placed in a flow apparatus. Gaseous hydrogen chloride was bubbled
through this suspension. Under continuous flow of hydrogen chloride, as a result of an
4

exothermal reaction, the solid rhenate(VII) dissolved to form a clear solution, which
subsequently underwent colour changes from yellow, through orange to red with precipitation
of some red crystals (previously confirmed to contain pentachloridooxidorhenate(VI) salts
[1]). The obtained mixture was moved to a separate open vessel. Under air the mixture
underwent slow colour changes from red to orange. After about fifteen minutes crystals in
form of orange green plates (C) were observed to crystallize from the reaction mixture. The
crystallization vessel was covered with parafilm and left for slow evaporation overnight. As a
result, further portion of crystalline C was obtained. The crystals left under air gradually loose
ethanol.
IR bands (nujol/NaCl): 668.9 (w), 690.1 (vs), 696.1 (s), 723.1 (vs), 739.4 (vs), 747.8
(s), 757.8 (s), 777.1 (m), 804.1 (vw), 877.7 (m), 922.1 (vw), 993.2 (vs), 1031.6 (s), 1091.3 (w),
1115.2 (vs), 1166.4 (vw), 1190.9 (vw), 1265.5 (vw), 1340.7 (w), 1378.7 (m), 1417.6 (w),
1438.0 (vs), 1457.3 (s), 1485.0 (w), 1588.2 (w), 1616.0 (vw), 1653.0 (vw), 1684.5 (vw),
1829.3 (vw), 1922.3 (vw), 1977.4 (vw), 2854.1 (vs), 2923.8 (vs), 3042.3 (m), 3059.0 (m),
3084.2 (m), 3508.2 (s).
D (2([PPh3CH2C6H4CH3][ReOCl4(nPrOH)])•nPrOH)
0.05 g of (4-methylbenzyl)triphenylphosphonium rhenate(VII) was suspended in 0.5
ml of n-propanol. A stream of gaseous hydrogen chloride was bubbled through the
suspension. An exothermal reaction occurred, as a result of which rhenate(VII) underwent
dissolution with formation of a yellow solution, which subsequently turned orange and finally
red. The hydrogen chloride stream was stopped at this point. 0.05-0.06 g of solid (4-
methylbenzyl)triphenylphosphonium rhenate(VII) was added to the mixture. The reaction
vessel was closed and stored in freezer at the temperature of about -10 °C. After 3-4 days the
red solution changed its colour to orange and crystals of D in form of yellow plates were
obtained.
E ([PPh3CH2C6H4CH3][ReOCl4(iPrOH)])
A suspension of 0.3 g (4-methylbenzyl)triphenylphosphonium rhenate(VII) in 3.5 ml
of methanol was prepared and placed in a flow apparatus. Gaseous hydrogen chloride was
bubbled through this suspension. Under continuous flow of hydrogen chloride, as a result of
an exothermal reaction, the solid rhenate(VII) dissolved to form a clear solution, which
subsequently underwent colour changes from yellow, through orange to red with precipitation
of some red crystals (previously confirmed to contain pentachloridooxidorhenate(VI) salts
[1]). Through thus prepared red reaction mixture gaseous nitrogen was bubbled. As a result,
5

the reaction mixture changed its colour to orange and subsequently to yellow. On slow
evaporation in the nitrogen stream crystals of E in form of yellow plates were obtained.
IR bands (Nujol/NaCl): 687.9 (vs), 705.3 (w), 714.6 (m), 720.2 (s), 739.6 (s), 744.9
(s), 759.1 (w), 809.8 (w), 824.5 (s), 837.2 (m), 848.2 (vw), 909.5 (m), 919.7 (s), 975.7 (vw),
1000.1 (s), 1006.1 (m), 1021.3 (vw), 1089.3 (s), 1109.1 (vs), 1141.0 (vw), 1161.0 (w), 1187.9
(vw), 1288.8 (w), 1318.1 (w), 1339.1 (w), 1375.8 (s), 1437.2 (vs), 1462.0 (vs), 1513.4 (w),
1586.7 (w), 1616.1 (vw), 1684.0 (vw), 1743.2 (vw), 2726.9 (w), 2854.5 (vs), 2925.9 (vs),
3382.4 (m).
F ([PPh3CH2CH3]2[ReOCl4ReO4])
0.05 g of ethyltriphenylphosphonium rhenate(VII) was suspended in 1 ml of
chloroform. A stream of gaseous hydrogen chloride was bubbled through the suspension. An
exothermal reaction occurred, as a result of which rhenate(VII) underwent dissolution with
formation of a yellow solution, which subsequently turned orange and finally red. The
hydrogen chloride stream was stopped at this point. 0.05-0.06
g
of solid
ethyltriphenylphosphonium rhenate(VII) was added to the mixture. The reaction vessel was
closed and stored in freezer at the temperature of about -10 °C. After 3-4 days the red solution
changed its colour to violet. Further, the reaction mixture steadily lost the violet colour and
became yellow with formation of stable crystals of D in form of yellow plates.
IR bands (Nujol/NaCl): 667.5 (m), 689.9 (vs), 697.1 (vs), 712.7 (m), 724.2 (vs), 736.6
(vs), 750.3 (vs), 772.7 (s), 860.5 (s), 882.0 (vs), 926.1 (vs), 978.0 (w), 996.2 (s), 1009.9 (vw),
1026.8 (vw), 1034.9 (w), 1074.9 (vw), 1114.0 (vs), 1161.1 (w), 1191.5 (vw), 1235.2 (vw),
1275.4 (vw), 1318.3 (m), 1343.4 (m), 1380.2 (m), 1404.1 (m), 1437.9 (vs), 1456.2 (s), 1481.7
(m), 1587.1 (m), 1613.5 (w), 1904.7 (w), 1983.2 (w), 2691.4 (m), 2854.7 (vs), 2922.4 (vs),
3041.0 (s), 3056.7 (s), 3082.1 (s).
X-ray diffraction measurements
X-ray diffraction data were collected by means of either KM4CCD diffractometer or
of Xcalibur PX diffractometer, both equipped with CCD detectors and graphite-
monochromatized MoKα radiation. The measurements were carried out at 100 K or at 120 K
(see Table 1 for basic experimental data).
Refinement
All structures were solved by direct methods in SHELXS and refined with the aid of
SHELXL software [5]. Where possible, H atoms were generated based on known molecular
geometry and refined with Ueq at nUeq(parent atom), where n = 1.5 for methyl groups, 1.2 for
phenyl/methylene groups. The treatment of other H atoms was dependent mainly on the
6

quality of the recorded X-ray diffraction data. For A water H atoms were found on difference
Fourier map, refined with a DFIX restraint setting O-H bond lengths at 0.840(2) Å and
subsequently their parameters were constrained with Ueq = 1.5Ueq(O atom). For B/C the
coordinated alcohol H atoms were found on a difference Fourier map and refined with DFIX
restraint setting O-H bond lengths at 0.840(2) Å as well as Ueq = 1.5Ueq(O atom). For D the
coordinated n-propanol H atoms were found on a difference Fourier map, refined with DFIX
restraint setting O-H bond lengths at 0.840(2) Å and subsequently their parameters
constrained with “AFIX 147 0.8400” constraint and Ueq = 1.5Ueq(O atom). High difference
Fourier peaks in the neighbourhood of the Re1-containing anion indicated it to be disordered
or that its site contains impurity with other Re complex. The latter possibility seems to be
more probable. Re1 atom and Cl1, Cl4 atoms were split into two components and their
occupancies were refined to sum up to unit (the final refined occupancies: 0.88(1) and 0.22(1)
for higher- and lower-occupancy components, respectively). It seems, that the impurity anion
is also charged mononegatively and containing four Cl ligands with two O-Re-Cl bond angles
greater than 90° and two O-Re-Cl bond angles smaller than 90°. Based on our previous
studies [6] on the reaction of rhenate(VII) anions with hydrogen chloride the impurity could
be trans-tetrachloridooxido(n-propoxido)rhenate(VI) anion. For
E
the coordinated
isopropanol H atoms were found on a difference Fourier map, refined with a DFIX restraint
setting O-H bond lengths at 0.840(2) Å and subsequently their parameters were constrained
with “AFIX 43 0.8400” constraint and Ueq = 1.5Ueq(O atom), assuming an electrostatic mode
of coordination of the alcohol molecule to Re central atom.
On the final difference Fourier maps the following maxima/minima were observed:
3.31 e/Å3 at 0.76 Å from Re2 for A, 3.66 e/Å3 at 1.04 Å from Re2 for B, 0.84 e/Å3 at 0.76 Å
from Re1 for C, 1.67 e/Å3 at 0.81 Å from Re2 for D, 1.81 e/Å3 at 0.74 Å from Re2 for E, 3.25
e/Å3 at 0.15 Å from Re2 for F.
CCDC reference numbers: 985323-985328.
Other measurements
Thermogravimetric measurements were carried out on Setsys TG-DTA 16 device
under nitrogen atmosphere in Al2O3 crucible for samples of B (6.79 mg), C (9.95 mg), E
(12.06 mg), F (13.31 mg) with a heating rate of 5 ºC/min.
Absorption spectra were collected in the standard IR (500-400 cm-1, NaCl window)
and FIR (50-650 cm-1, polyethylene window) wavelength range on a BRUKER
spectrophotometer. The samples were prepared in form of suspensions in nujol mull.
7

3. Results and discussion
Decomposition of pentachloridooxidorhenates(VI) in different solvents
Exposure of the red mixture obtained in the reaction of phosphonium rhenates(VII)
with gaseous hydrogen chloride leads not only to contact with atmospheric oxygen, but also to
a slow decrease of hydrogen chloride concentration in the reaction mixture.
In case of such solvents as acetone it is possible, that interaction of hydrogen chloride
with the solvent itself may be present. This is confirmed by our preliminary GC-MS studies.
Furthermore, the rhenium compounds present in the reaction mixture may act as catalysts of
the reaction of the corresponding solvent with hydrogen chloride. On the other hand, in e.g.
chloroform, such processes should not be relevant. In acetonitrile large quantities of
crystalline acetamide chloride (identified based on the unit cell constants crystallographic
measurement as [7]) are formed. In the concentrated hydrochloric acid, apparently chlorine
formed as a product also of secondary reactions on exposure to air reacts with water to yield
an oxidizing agent, making it possible to reverse the reaction and again to obtain crystalline
phosphonium rhenate(VII). Such solvents as carbon tetrachloride, aromatic or aliphatic
hydrocarbons, do not dissolve very well the products of the reaction of rhenates(VII) with
hydrogen chloride, which limits their suitability.
Summary of the possible decomposition products concluded from this study is shown
in Scheme 1. Usually the decomposition products include a [ReVOCl4]- unit with a solvent
molecule (e.g. water, alcohol molecule) coordinated in trans position to the short Re-Oterminal
bond. It is also possible to obtain mixed-valence [ReOCl4ReO4]2- anions, formally comprising
-
a [ReVOCl4]- unit with a ReO4 anion coordinated in trans position to the short Re-Oterminal
bond.
Structure of the Re(V) products
The investigated system provides new insights into the crystalochemistry of
rhenium(V) compounds.
The structure of all Re(V)-containing anions isolated from the investigated system is
illustrated on Fig. 1 (a)-(f). Below a detailed description of the anions structural aspects is
provided. Different bulky phosphonium cations used as counterions allow to limit the anion
disorder affecting the other previously reported structures [3]. The structure of these cations is
described in detail in SI.
The trans-[ReVOCl4(H2O)]- anion (as in A, Fig. 1a) structure is known from X-ray
diffraction studies performed for its tetraphenylarsonium salt [8], as well as for its
dithiobis(formamidinium) chloride monohydrate [9] and (18-crown-6)hydroxonium salts [10].
8

The corresponding anion geometric parameters are comparable in A (there are two symmetry-
independent anions) and in the former reports [8, 9, 10] (Table 2). Similar trans-
[MOCl4(H2O)]- complexes are also known for niobium [11] and molybdenum [12]. In all
these complexes the central metal ion is bonded to the terminal oxido ligand to form a short
multiple bond, which imposes a trans influence on the Re-O(water coordinated in trans
position) bond. The sum of bond angles around the water atom should be indicative of the
degree of covalency in the M-O(water) bond. Although the H atoms position determination in
A is by no means reliable, it might be expected, that the degree of covalency in Re-O(water)
bond is considerable.
The complex anions in A form two kinds of hydrogen-bonded pairs (Fig. S1a): Re1-
containing anion - Re1i-containing anion (symmetry code (i) -x+2, -y+1, -z+1); Re2-
containing anion - Re2ii-containing anion (symmetry code (ii) -x+2, -y+2, -z). The anions
within each pair interact via O-H…Cl hydrogen bonds (Table S1), in which the coordinated
water molecules act as donors and the Cl ligands act as acceptors with formation of two
R2 (6) and two R2 (8) graph set motifs [13]. The hydrogen-bonded anion pairs are arranged in
2
2
columns parallel to [100]. The phosphonium cations also form columns along [100], which
are further organized in layers parallel to (110) (Fig. S2a).
B-E are unprecedented examples of salts containing [ReVOCl4(ROH)]- anions with
different alcohols molecules coordinated trans to the terminal oxido ligand in a [ReVOCl4]-
unit (B: CH3OH, C: C2H5OH, D: nPrOH, E: iPrOH, Fig. 1 b-e). The reported X-ray structures
of Re complexes with trans-coordinated alcohol molecule are scarce. Data collected for the
analogous alkoxidocomplexes are available (e.g. [14-15]). On the other hand, the Mo
analogues are known [16-17]. In B-E the bonding of the alcohol molecule to the Re ion seems
to be of mainly ion-dipol interaction character. The relevant Re-Otrans bond lengths are
comparable in case of C-E (see Table 2). It is interesting to note, that in the case of B this
bond is slightly longer and comparable to the Re-Otrans bond length in the [ReOCl4(H2O)]-
anion in A. The variability in the Re-Clcis bond lengths observed in some particular cases
could be attributed to the steric effect of alcohol R moiety presence as well as to involvement
in hydrogen bonds. The short terminal Re-O bond length in B-E adopts values characteristic
for the formally triple Re-O bond [18]. All Re-Cl bond lengths are equivalent (see Table 2).
As expected, based on the trans effect theory, all Ot-Re-Clcis angles are greater than 90°. All
these observations correspond well to the structure of the [ReOCl4] moiety in the [ReOCl5]-
and the [ReOCl5]2- anion [1]. The Ot-Re-Otrans bond angle is in each case close to 180°. The
9

[ReOCl4(ROH)]- anions are capable of participating in hydrogen bonds, which, as illustrated
below, leads to the formation of a variety of structural motifs.
In B both symmetry-independent anions comprise a [ReOCl4] moiety with methanol
molecule coordinated trans to the short Re-Ot bond. The Re-Clcis bond lengths within the
[ReOCl4] moiety differ slightly, which corresponds to their involvement in hydrogen bonds.
Within the Re1-containing anion two intramolecular hydrogen bonds are formed (Table S1),
however, no participation in intermolecular hydrogen bonds is observed. On the other hand,
the Re2-containing anion participates in the formation of similar intermolecular hydrogen-
bonded structural motifs (Fig. S1b) as in A, stabilized by two kinds of O-H…Cl hydrogen
bonds involving hydroxyl groups of the coordinated methanol molecules as donors, resulting
in a R2 (8) graph set motif presence [13]. Thus defined anion pairs occupy spaces formed
2
between the columns of phosphonium cations extending along [010] (Fig. S2b). Probably the
tendency to form hydrogen-bonded anion pairs may be of importance in the field of crystal
engineering.
In C the complex anion comprises a [ReOCl4] moiety with ethanol molecule
coordinated trans to the triple Re-Ot bond. The ethyl moiety of the ethanol molecule adopts
apparently a low-energy arrangement with respect to the [ReOCl4] moiety with C21E-C11E-
O1E-Cln (n = 1 to 4) torsion angles of -50.7(2), -93.5(2), -160.2(2) and 155.8(2)°,
respectively. The hydroxyl group from the coordinated ethanol molecule is hydrogen-bonded
to the O atom from the ethanol molecule of solvation (Table S1). The hydroxyl group from
the ethanol molecule of solvation is further involved in a weaker O-H…Cl hydrogen bond to
another anion. Thus defined hydrogen-bonded units (Fig. S1c) along with the phosphonium
cations form layers parallel to (110) (Fig. S2c).
D contains two symmetry-independent anions, comprising a [ReOCl4] moiety with n-
propanol molecule coordinated trans to the short Re-Ot bond. One of these anions is affected
by disorder described in the Refinement section. The position of the n-propyl moiety with
respect to the [ReOCl4] moiety in the ordered Re2-containing anion is illustrated by the
corresponding C-C-C-O and Cl-Re-O-C torsion angles (-175.6(5), 56.3(4), -33.4(4), -122.1(4)
and 146.6(4)°, respectively). The ordered Re2-containing anion forms part of an interesting
hydrogen-bonded unit comprising two anions and two n-propanol molecules of solvation (Fig.
S1d). Hydroxyl groups of each of the two n-propanol molecules of solvation are donors to
bifurcated O-H…Cl hydrogen bonds to the anion Cl22 and Cl32 atoms with formation of
R2 (4) motifs. These hydroxyl groups are also acceptors to O-H…O hydrogen bonds
1
involving n-propanol molecules coordinated to the interacting anions to close a characteristic
10

double-decker hydrogen-bonded structure (Fig. S1d). The Re1-containing anion is not
involved in any hydrogen bonds, occupying considerable spaces between the columns of
phosphonium cations extending along [010] (Fig. S2d). The hydrogen-bonded anionic units
described above also occupy these spaces. Further, double layers parallel to (110) could be
distinguished, comprising the hydrogen-bonded units surrounded by phosphonium cations
columns and the Re1-containing anions in the outer parts. No involvement in specific
interactions apparently makes it possible for the other anions to be built into the site occupied
by the Re1-anions. Therefore apparently part of the anions is probably substituted with trans-
tetrachloridooxido(n-propoxido)rhenate(VI) anions, which was accounted for during the
corresponding crystal structure refinement (see Experimental section).
In E there are two symmetry-independent anions with isopropanol molecules
coordinated trans to the [ReOCl4] moiety. The two anions differ slightly by the distribution of
the Re-Cl bond lengths, which can be explained in terms of the hydrogen bonding scheme.
The two anions interact via O-H…Cl hydrogen bonds with the anion-coordinated isopropanol
molecule hydroxyl group acting as a hydrogen bond donor (Fig. S1e). Thus an R2 (8) graph
2
set motif is formed. These units form columns along [100], isolated by columns of the
analogous phosphonium cations (Fig. S2e).
Structure of the mixed-valence Re(V)-Re(VII) products
Mixed-valence Re complexes are rare. Examples include e.g. salts of the arguable
[Re2O3Cl10]3- anion [19] or binuclear phosphinotiolate Re(VII)-Re(V) complex [20].
Moreover, coordination of the rhenate(VII) anion to Re atom at different oxidation states (I,
II, III, V, VI, VII) is well established, also leading to formally mixed-valence compounds (e.g.
[21-39]).
The mixed-valence anion in F (Fig. 1f) could formally be regarded as a [ReVOCl4]-
-
unit with a ReO4 anion coordinated trans to the terminal oxido ligand. In the [ReOCl4]- unit a
short, formally triple [18] Re-O bond is present, imposing trans influence as shown by the O-
Re-Clcis bond angles deformation (Table 2). The Re-Cl bond lengths are comparable to the
-
Re-Clcis bond lengths in the [ReOCl5]2- anion [40] (Table 2). The ReO4 unit is nearly
-
tetrahedral as in a non-coordinated ReO4 anion [41, 42] (Table 2). The Re2-O12 bond,
through which this unit is coordinated to the [ReOCl4]- unit, is longer than the remaining Re-
O bonds of equivalent lengths (Table 2) with order lower than for a formally double Re-O
bond (e.g. 1.723(4) Å for KReO4 [43]). Similar observation could be made in case of other
-
compounds where the ReO4 anion is coordinated to the ReV atom (e.g. [44]). The ReV-
-
O12(from the coordinated ReO4 unit) is shorter than in the case of Re-O(from water ligand)
11

bond for A, also located in trans position to a triple Re-O bond. This shows, that the division
into two anionic units within the mixed-valence anion in F is only formal and a more correct
treatment would be considering the anion as a whole binuclear unit. The Re-Oµ-Re bond angle
-
value (Table 2) is closer to 180° in F than in the reported systems with a ReO4 unit
coordinated to the ReV atom (e.g. 146.5(4)° for a ReV phtalocyaninate complex reported in
[44]).
In F no specific hydrogen bonds could be distinguished, which results in an increased
-
mobility of the anion (as shown by thermal ellipsoids of O atoms belonging to the ReO4
unit). The phosphonium cations are arranged in columns parallel to [010] (Fig. S2f). The
complex anions occupy spaces between these columns.
Thermal decomposition of the selected Re(V) salts
The thermal decomposition studies carried out for samples of phosphonium salts with
a [ReOCl4(ROH)]- anion show, that all these salts apparently decompose following a similar
pattern. First step, as easily concluded from the experimental data, is evolution of the alcohol
molecule coordinated to the [ReOCl4] moiety (along with the alcohol molecules of solvation,
if present). This is in accordance with the conclusion from X-ray diffraction studies (see
above), that the alcohol molecules are very weakly coordinated to the [ReOCl4] moiety and
interact with the Re centre mainly via dipole-ion interaction. Then, as a second step,
apparently the organic part (the phosphonium cations) is decomposed. As the third step, most
of the chlorine/oxygen contents from the remaining part are lost. In the case of B the first
decomposition step (evolution of the coordinated methanol contents) is endothermal and
occurs at 100-150 °C. At 260-270 °C another endothermal process occurs. At 150-350 °C a
gradual decomposition of the organic part occurs. The last, clearly resolved decomposition
step starts at about 350 °C and leads to the loss of most of the remaining chlorine/oxygen
contents. In the case of C only two well resolved decomposition steps visible on the TG curve
could be distinguished. The first step, leading to an evolution of the ethanol molecules
coordinated to the [ReOCl4] moiety, as well as of ethanol of solvation, occurs up to 400 °C
(apparently the process is endothermal and gradual, however, at about 103 °C and 123 °C two
sharp endothermal peaks are present on the heating curve). From about 400 °C the second
decomposition step starts, in fact comprising two poorly resolved process stages: the loss of
the organic part and of the chlorine/oxygen contents. A very similar decomposition pattern is
observed in the case of E (clearly visible evolution of the coordinated isopropanol up to about
300 °C with two overlapping sharp endothermal peaks at about 133 °C; the loss of the organic
part and of part of the chlorine/oxygen contents starting from 300 °C). F shows a completely
12

different decomposition pattern with a sharp endothermal peak on the heating curve at about
148-155 °C, resulting from melting with decomposition, proceeding smoothly from this
temperature, apparently leading to pure metallic rhenium as the final product.
IR spectra
On the recorded IR spectra many bands connected with the presence of the organic
cations arise, therefore for their analysis it is helpful to compare them with the analogous IR
spectra of the corresponding phosphonium halides. The most characteristic band on these
spectra was assigned to the Re-Ot stretching mode (990.0 cm-1 for A, 995.1 cm-1 for B, at
993.2 cm-1 for C, at 1000.1 cm-1 for E, at 996.2 cm-1 for F). On the IR spectrum of F also two
broad bands at 882.0 and 926.1 cm-1 with a smaller band at 860.5 cm-1 could be clearly
-
distinguished. These bands can be assigned to the ReO4 unit vibrations and correspond well
to the experimentally detected two values of the Re-O bond lengths within this unit, resulting
in an approximate C3v symmetry. The band connected with the Re-Oµ-Re stretching mode is
observed in a less straightforward manner due to the presence of phosphonium cations at
724.2 cm-1. On the IR spectrum recorded for the sake of comparison for
ethyltriphenylphosphonium rhenate(VII) a single band at 902.3 cm-1 could be assigned to the
Re-O stretching mode. Further, the recorded data could also be compared with the available
literature, e.g. Göldner et al. [22] provide a detailed analysis of the spectroscopic properties of
-
the ReV-phtalocyaninate compound with a coordinated ReO4 unit. The vibrations of the
-
ReO4 unit are attributable to the IR bands at 937, 832 and 807 cm-1, respectively.
4. Conclusions
Secondary reactions occurring when the mixture obtained in a reaction of
rhenates(VII) with hydrogen chloride is exposed to air, have been shown to be a rich source of
Re(VII), Re(V), Re(IV) complexes. It is essential to be aware of these possibilities when this
reaction mixture is used as a reagent in a multi-stage synthesis. The structure aspects of the
salts containing [ReOCl4(ROH)]-, [ReOCl4(H2O)]- and [ReOCl4ReO4]2- anions, have been
discussed and brought new insights into the crystalochemistry of rhenium compounds at
higher oxidation states. Moreover, IR spectra and thermal decomposition patterns for these
salts have been described.
Acknowledgments
13

Partial financial support from Ministry of Science and Higher Education (project
number N204 130 32/3318).
Supporting Information
Electronic Supplementary Information (ESI) available: additional tables/figures for
crystal structures. X-ray crystallographic data in CIF format: CCDC 985323-985328 contains
the supplementary crystallographic data for this paper. Copies of this information can be
obtained free of charge upon application to CCDC, 12 Union Road, Cambridge CB21EZ,
U.K. (fax. 44-1223/336- 033; e-mail deposit@ccdc.cam.ac.uk).
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15

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16

Figures and schemes
Scheme 1 A general scheme showing the products formed in decomposition of
pentachloridooxidorhenates(VI).
(a)
(b)
17

(c)
(d)
(e)
18

(f)
Fig. 1. Structure of the complex anions in A-F (a-f) with atom labeling scheme. Thermal
ellipsoids are drawn at 30% probability level. Intramolecular hydrogen bonds are denoted
with dashed lines.
19

Tables
Table 1 Basic X-ray diffraction experimental data for A-F.
A
B
C
D
E
F
Formula
[PPh3CH2CH3]
[ReOCl4(H2O)]
[PPh3CH2CH2PPh3]
[PPh3CH2CH3]
2([PPh3CH2C6H4CH3]
[PPh3CH2C6H4CH3]
[PPh3CH2CH3]2
[ReOCl4ReO4]
[ReOCl4(CH3OH)]2 [ReOCl4(C2H5OH)]· [ReOCl4(nPrOH)])·nPrOH [ReOCl4(iPrOH)]
C2H5OH
Formula weight
Temperature [K]
λ [Å]
Crystal system
Space group
a [Å]
b [Å]
c [Å]
α [°]
β [°]
653.35
100(2)
0.71073
triclinic
1304.68
100(2)
0.71073
triclinic
727.47
85(2)
0.71073
monoclinic
P21/n
12.362(3)
14.122(4)
16.726(4)
1603.13
100(2)
0.71073
triclinic
771.52
100(2)
0.71073
triclinic
1176.86
120(2)
0.71073
monoclinic
P21/c
18.058(4)
13.836(3)
19.430(4)
Pī
Pī
Pī
Pī
10.478(3)
13.057(4)
18.735(4)
100.51(3)
94.19(3)
111.45(3)
2318(2)
10.116(6)
11.856(7)
19.663(7)
96.46(5)
101.01(5)
97.61(5)
2271(2)
2, 1.908
5.91
10.846(6)
14.930(6)
21.953(9)
96.66(3)
102.10(4)
110.46(4)
3186(3)
10.314(3)
13.327(4)
22.598(5)
91.89(3)
101.30(3)
101.05(3)
2982(2)
104.88(3)
120.81(3)
γ [°]
V [Å3]
2822(2)
4, 1.712
4.76
4170(2)
4, 1.875
6.18
Z, ρcalc [g cm-3]
µ [mm-1]
4, 1.872
5.79
2, 1.671
4.23
4, 1.719
4.51
F(000)
1264
1260
1432
1588
1520
2272
Crystal size [mm]
θ range[º]
rflns: total/unique
R(int)
0.23x0.12x0.07
2.8-35.0
49106/18738
0.046
0.38x0.33x0.16
2.9-28.5
16971/9804
0.069
0.30x0.28x0.25
4.7-32.5
46974/12215
0.026
0.26x0.14x0.08
3.0-32.5
53261/21548
0.063
0.20x0.14x0.10
2.8-32.5
49972/19532
0.055
0.20x0.15x0.11
4.4-35.0
77211/18320
0.048
Abs. corr.
analytical
0.285, 0.661
analytical
0.204, 0.723
analytical
0.292, 0.428
analytical
0.635, 0.843
analytical
0.415, 0.727
analytical
0.328, 0.574
Min., max.
transmission factors
Data/restraints/params
GOF on F2
R1 [I > 2σ(I)]
wR2 (all data)
Max., min. ∆ρelect [e Å-3]
18738/0/505
1.02
0.037
0.061
3.31, -1.91
9804/2/511
1.00
0.056
0.174
3.66, -2.21
12215/0/298
1.01
0.019
0.029
0.84, -0.78
21548/2/722
1.03
0.052
0.098
1.67, -1.49
19532/0/673
1.00
0.046
0.069
1.81, -1.83
18320/0/480
0.86
0.031
0.039
3.25, -2.16
20

Table 2 Selected geometric data for the complex anions for A-F [Å, °].
A
Re1—O11
Re1—O1W
1.664(2)
2.265(2)
Re2—O12
Re2—O2W
1.665(2)
2.261(2)
Re1—Cl11
Re1—Cl21
Re1—Cl41
Re1—Cl31
2.3549(12)
2.3563(11)
2.3611(11)
2.3956(11)
176.39(10)
98.51(9)
85.09(6)
100.76(8)
79.06(6)
88.34(5)
100.03(8)
80.20(6)
88.35(5)
159.21(3)
95.28(9)
Re2—Cl12
Re2—Cl42
Re2—Cl22
Re2—Cl32
2.3563(12)
2.3599(11)
2.3627(10)
2.3791(11)
177.73(10)
98.41(11)
83.69(6)
99.14(10)
80.04(7)
88.28(4)
100.51(10)
80.34(7)
88.50(4)
160.35(3)
96.47(11)
81.44(6)
165.12(3)
89.80(4)
O11—Re1—O1W
O11—Re1—Cl11
O1W—Re1—Cl11
O11—Re1—Cl21
O1W—Re1—Cl21
Cl11—Re1—Cl21
O11—Re1—Cl41
O1W—Re1—Cl41
Cl11—Re1—Cl41
Cl21—Re1—Cl41
O11—Re1—Cl31
O1W—Re1—Cl31
Cl11—Re1—Cl31
Cl21—Re1—Cl31
Cl41—Re1—Cl31
B
O12—Re2—O2W
O12—Re2—Cl12
O2W—Re2—Cl12
O12—Re2—Cl42
O2W—Re2—Cl42
Cl12—Re2—Cl42
O12—Re2—Cl22
O2W—Re2—Cl22
Cl12—Re2—Cl22
Cl42—Re2—Cl22
O12—Re2—Cl32
O2W—Re2—Cl32
Cl12—Re2—Cl32
Cl42—Re2—Cl32
Cl22—Re2—Cl32
81.11(6)
166.20(3)
88.70(5)
89.65(4)
88.36(4)
Re1—O11
Re1—O1M
Re1—Cl21
Re1—Cl11
Re1—Cl41
Re1—Cl31
1.649(7)
2.259(7)
2.350(3)
2.353(3)
2.361(3)
2.380(3)
177.2(3)
99.6(2)
83.0(2)
97.5(3)
83.4(2)
87.57(10)
97.7(2)
Re2—O12
Re2—O2M
Re2—Cl22
Re2—Cl42
Re2—Cl12
Re2—Cl32
1.669(7)
2.254(8)
2.338(3)
2.343(3)
2.349(3)
2.371(3)
174.6(3)
99.7(3)
82.7(2)
98.5(3)
79.0(2)
161.70(12)
100.9(3)
83.9(2)
88.37(14)
89.71(15)
95.3(3)
O11—Re1—O1M
O11—Re1—Cl21
O1M—Re1—Cl21
O11—Re1—Cl11
O1M—Re1—Cl11
Cl21—Re1—Cl11
O11—Re1—Cl41
O1M—Re1—Cl41
Cl21—Re1—Cl41
Cl11—Re1—Cl41
O11—Re1—Cl31
O1M—Re1—Cl31
Cl21—Re1—Cl31
Cl11—Re1—Cl31
Cl41—Re1—Cl31
C
O12—Re2—O2M
O12—Re2—Cl22
O2M—Re2—Cl22
O12—Re2—Cl42
O2M—Re2—Cl42
Cl22—Re2—Cl42
O12—Re2—Cl12
O2M—Re2—Cl12
Cl22—Re2—Cl12
Cl42—Re2—Cl12
O12—Re2—Cl32
O2M—Re2—Cl32
Cl22—Re2—Cl32
Cl42—Re2—Cl32
Cl12—Re2—Cl32
79.6(2)
162.63(9)
91.28(10)
97.3(3)
81.8(2)
79.9(2)
89.53(10)
165.16(10)
87.17(11)
89.16(13)
87.61(14)
163.77(10)
Re1—O1
Re1—O1E
Re1—Cl2
1.6646(10)
2.2053(10)
2.3634(6)
178.62(4)
98.14(4)
83.24(3)
98.19(4)
80.43(3)
163.66(2)
96.35(4)
83.69(3)
Re1—Cl4
Re1—Cl1
Re1—Cl3
Cl2—Re1—Cl1
Cl4—Re1—Cl1
O1—Re1—Cl3
O1E—Re1—Cl3
Cl2—Re1—Cl3
Cl4—Re1—Cl3
Cl1—Re1—Cl3
2.3659(6)
2.3668(7)
2.3719(7)
87.59(3)
90.25(3)
96.68(4)
83.30(3)
89.85(3)
88.61(3)
166.95(2)
O1—Re1—O1E
O1—Re1—Cl2
O1E—Re1—Cl2
O1—Re1—Cl4
O1E—Re1—Cl4
Cl2—Re1—Cl4
O1—Re1—Cl1
O1E—Re1—Cl1
21

D
Re1—O11
Re1—O1P
1.640(4)
2.222(4)
Re2—O12
Re2—O2P
1.657(3)
2.211(3)
Re1—Cl41
Re1—Cl31
Re1—Cl21
Re1—Cl11
2.3521(18)
2.3618(19)
2.362(2)
Re2—Cl42
Re2—Cl12
Re2—Cl22
Re2—Cl32
2.3574(14)
2.3599(15)
2.3786(14)
2.3808(15)
177.35(14)
97.07(12)
82.58(9)
100.01(12)
82.61(10)
89.36(5)
97.30(13)
83.03(9)
165.62(4)
88.80(5)
94.55(12)
82.84(10)
90.41(5)
165.36(4)
87.80(5)
2.383(3)
O11—Re1—O1P
O11—Re1—Cl41
O1P—Re1—Cl41
O11—Re1—Cl31
O1P—Re1—Cl31
Cl41—Re1—Cl31
O11—Re1—Cl21
O1P—Re1—Cl21
Cl41—Re1—Cl21
Cl31—Re1—Cl21
O11—Re1—Cl11
O1P—Re1—Cl11
Cl41—Re1—Cl11
Cl31—Re1—Cl11
Cl21—Re1—Cl11
E
176.21(18)
98.75(15)
78.12(12)
98.15(13)
84.01(11)
89.06(7)
101.10(16)
82.08(14)
160.12(12)
87.17(8)
O12—Re2—O2P
O12—Re2—Cl42
O2P—Re2—Cl42
O12—Re2—Cl12
O2P—Re2—Cl12
Cl42—Re2—Cl12
O12—Re2—Cl22
O2P—Re2—Cl22
Cl42—Re2—Cl22
Cl12—Re2—Cl22
O12—Re2—Cl32
O2P—Re2—Cl32
Cl42—Re2—Cl32
Cl12—Re2—Cl32
Cl22—Re2—Cl32
97.5(2)
80.38(19)
89.26(15)
164.31(18)
89.13(16)
Re1—O11
Re1—O1I
Re1—Cl11
Re1—Cl21
Re1—Cl31
Re1—Cl41
1.663(2)
2.222(2)
2.3632(11)
2.3642(12)
2.3718(11)
2.3749(12)
177.25(10)
99.32(9)
82.61(7)
97.66(9)
84.32(7)
88.48(4)
96.33(9)
81.73(7)
164.33(3)
90.23(4)
96.24(9)
81.79(7)
88.97(4)
166.09(3)
88.54(4)
Re2—O12
Re2—O2I
Re2—Cl12
Re2—Cl22
Re2—Cl42
Re2—Cl32
1.663(3)
2.212(2)
2.3469(12)
2.3530(12)
2.3698(11)
2.3921(12)
174.50(10)
99.80(10)
83.97(7)
99.79(10)
84.31(7)
87.54(4)
96.14(10)
79.83(7)
89.15(4)
164.06(3)
95.57(10)
80.75(7)
164.62(4)
89.27(4)
O11—Re1—O1I
O11—Re1—Cl11
O1I—Re1—Cl11
O11—Re1—Cl21
O1I—Re1—Cl21
Cl11—Re1—Cl21
O11—Re1—Cl31
O1I—Re1—Cl31
Cl11—Re1—Cl31
Cl21—Re1—Cl31
O11—Re1—Cl41
O1I—Re1—Cl41
Cl11—Re1—Cl41
Cl21—Re1—Cl41
Cl31—Re1—Cl41
F
O12—Re2—O2I
O12—Re2—Cl12
O2I—Re2—Cl12
O12—Re2—Cl22
O2I—Re2—Cl22
Cl12—Re2—Cl22
O12—Re2—Cl42
O2I—Re2—Cl42
Cl12—Re2—Cl42
Cl22—Re2—Cl42
O12—Re2—Cl32
O2I—Re2—Cl32
Cl12—Re2—Cl32
Cl22—Re2—Cl32
Cl42—Re2—Cl32
89.80(4)
Re1—O1
Re1—O12
Re1—Cl1
Re1—Cl4
1.6679(15)
2.1588(15)
2.3637(8)
2.3665(8)
2.3752(9)
177.82(7)
98.29(6)
83.55(5)
96.78(5)
84.40(5)
89.19(4)
97.55(6)
80.62(5)
Re1—Cl2
Re2—O32
Re2—O42
Re2—O22
2.3823(9)
1.692(2)
1.696(2)
1.7048(17)
1.7391(15)
82.41(4)
88.96(4)
166.80(2)
89.88(4)
109.48(12)
108.56(9)
107.37(10)
111.68(9)
Re1—Cl3
Re2—O12
O1—Re1—O12
O1—Re1—Cl1
O12—Re1—Cl1
O1—Re1—Cl4
O12—Re1—Cl4
Cl1—Re1—Cl4
O1—Re1—Cl3
O12—Re1—Cl3
O12—Re1—Cl2
Cl1—Re1—Cl2
Cl4—Re1—Cl2
Cl3—Re1—Cl2
O32—Re2—O42
O32—Re2—O22
O42—Re2—O22
O32—Re2—O12
22

Cl1—Re1—Cl3
Cl4—Re1—Cl3
O1—Re1—Cl2
164.14(2)
88.33(4)
96.42(5)
O42—Re2—O12
O22—Re2—O12
Re2—O12—Re1
109.86(9)
109.78(8)
160.67(9)
23

Supplementary material
1. Structure of the phosphonium cations
The ethyltriphenylphosphonium ion present in A is also the counterion of C and F
(Fig. S3a). Based on studies on the structure of ethyltriphenylphosphonium rhenate(VII) [S1]
it was concluded, that the ethyltriphenylphosphonium cation may adopt different forms
depending on the degree of a shift of the ethyl group from the plane of the phenyl ring in
trans position. In the case of both symmetry-independent cations in A this shift is not
considerable (for the cation with P1 the shift of the methyl C11 atom is of -0.030(8) Å, the
shift of the methylene C21 atom is of 0.130(6) Å; for the cation with P2 the shift of the
methyl C12 atom is of 0.031(9) Å, the shift of the methylene C22 atom is of 0.164(7) Å; it is
interesting to note, that the shift is greater for the methylene moiety than for the methyl
group). For the cation with P1 the maximum shift of the P1 atom from the phenyl rings planes
is at 0.078(5) Å (from the phenyl ring with the C111 atom). The interplanar angles for the
phenyl rings within the -PPh3 moiety are of 69.1(1), 72.6(1) and 53.0(1)°, respectively. For
the cation with P2 the maximum shift of the P2 atom from the phenyl rings planes is at
0.082(5) Å (from the phenyl ring with the C132 atom); the interplanar angles for the phenyl
rings within the -PPh3 moiety are of 70.4(2), 73.0(2) and 62.0(1)°. In the case of the cation
from C the ethyl group is considerably shifted from the plane of the phenyl ring in trans
position (the shift of the methyl C1 atom is of 0.627(4) Å, the shift of the methylene C2 atom
is of 0.442(3) Å). The maximum shift of the P1 atom from the phenyl rings planes is of only
0.050(2) Å (from the phenyl ring with the C11 atom); the interplanar angles for the phenyl
rings within the -PPh3 moiety are of 65.3(1), 66.9(1) and 53.9(1)°. The two symmetry-
independent cations in F represent two different cases: of not considerable (the shift of the
methyl C11 atom is of -0.002(6) Å, the shift of the methylene C21 atom is of -0.033(5) Å)
and considerable (the shift of the methyl C12 atom is of 0.434(6) Å, the shift of the methylene
C22 atom is of -0.372(5) Å) shift of the ethyl group from the plane of the phenyl ring in trans
position. For the cation with the P1 the maximum shift of P1 atom from the phenyl rings
planes is of -0.159(3) Å (from the phenyl ring with the C111 atom). The interplanar angles for
the phenyl rings within the -PPh3 moiety are of 77.5(1), 67.8(1) and 66.5(1)°. For the cation
with P2 the maximum shift of the P2 atom from the phenyl rings planes is of -0.114(4) Å
(from the phenyl ring with the C122 atom). The interplanar angles for the phenyl rings within
the -PPh3 moiety are of 67.5(1), 75.0(1) and 53.7(1)°.
24

The phosphonium cation in B (Fig. S3b) lies in general position, contrary to the cation
in the analogous rhenate(VII) salt [S2], which is centrosymmetric. The P1-C1-C2-P2 torsion
angle is of 146.7(6)°. For the -PPh3 moiety with P1 the maximum shift of the P1 atom from
the phenyl rings planes is of -0.13(2) Å (from the phenyl ring with the C111 atom). The
interplanar angles for the phenyl rings within this moiety are of 75.6(3), 61.8(4) and 89.9(3)°.
For the -PPh3 moiety with P2 the maximum shift of the P2 atom from the phenyl rings planes
is of -0.20(2) Å (from the phenyl ring with the C112 atom). The interplanar angles for the
phenyl rings within this moiety are of 80.7(3), 86.4(4) and 58.5(4)°.
The (4-methylphenyl)triphenylphosphonium cation, present as a counterion in D and
in E (Fig. S3c) has appeared in only one crystal structure report so far, namely for the
[ZnCl2(NA)] compound (NA = nicotinic acid) [S3]. It seems, that this cation is capable of
adopting different conformations. In D there are two symmetry-independent cations with the
corresponding torsion angles: C131-P1-C11-C111 of -160.0(4)° and C132-P2-C12-C112 of -
178.4(4)°. For the cation with P1 the maximum shift of the P1 atom from the phenyl rings
planes is of 0.282(6) Å (from the phenyl ring with the C131 atom). The interplanar angles for
the phenyl rings within the -PPh3 moiety are 72.6(2), 73.3(2) and 69.8(2)°. For the cation with
the P2 the maximum shift of P2 atom from the phenyl rings planes is of 0.074(6) Å (from the
phenyl ring with the C142 atom); the interplanar angles for the phenyl rings within the -PPh3
moiety are of 89.0(2), 83.3(2) and 68.8(2)°. On the other hand, in E the two symmetry-
independent cations adopt similar conformations (the C131-P1-C11-C111 torsion angle of -
166.3(4)°; the C132-P2-C12-C112 torsion angle of 166.5(3)°). For the cation with P1 the
maximum shift of the P1 atom from the phenyl rings planes is of 0.145(5) Å (from the phenyl
ring with the C121 atom). The interplanar angles for the phenyl rings within the -PPh3 moiety
are of 88.1(1), 82.4(1) and 56.5(2)°. For the cation with P2 the maximum shift of the P2 atom
from the phenyl rings planes is of 0.233(5) Å (from the phenyl ring with the C122 atom). The
interplanar angles for the phenyl rings within the -PPh3 moiety are of 89.2(2), 70.9(1) and
67.4(2)°.
25

2. Figures
(a)
26

(b)
O2E
Cl2vi
vi
(c)
27

(d)
28

(e)
Fig. S1. Anion hydrogen-bonded motifs in A-E. Hydrogen bonds are denoted with dashed
lines. Symmetry codes: (i) -x+2, -y+1, -z+1; (ii) -x+2, -y+2, -z+2, (iii) -x+2, -y+1, -z+2, (iv)
x+1/2, -y+1/2, z+1/2; (v) -x+1, -y, -z+1, (vi) 1.5-x, 0.5+y, 1.5-z.
29