Formation of M4Se4 cuboids (M = As, Sb, Bi) via secondary pnictogen-chalcogen interactions in the co-crystals MX 3·SeP(p-FC6H4)3 (M = As, X = Br; M = Sb, X = Cl; M = Bi, X = Cl, Br)

Article abstract of DOI:10.1039/c2dt31010d

The reactions of the group 15 trihalides, MX₃ (M = As, Sb, Bi; X = Cl, Br), with the phosphine selenide SeP(p-FC₆H₄) ₃ result in the formation of co-crystals of formula MX ₃·SeP(p-FC₆H₄)₃. No reaction was observed with MI₃ (M = As, Sb, Bi). The structures of MX ₃·SeP(p-FC₆H₄)₃ (M = As, X = Br 2; M = Sb, X = Cl 3; M = Bi, X = Cl 5; M = Bi, X = Br 6) have been established, and are isomorphous, crystallising in the cubic I23 space group. All the structures feature a primary MX₃ unit, which has three weak secondary M...Se interactions to SeP(p-FC₆H₄) ₃ molecules. However, each of these SeP(p-FC₆H ₄)₃ molecules bridges three MX₃ molecules, resulting in the generation of an M₄Se₄ (M = As, Sb, Bi) distorted cuboid linked by the pnictogen-chalcogen interactions. Four opposing corners of the cuboid are occupied by the M atom (M = As, Sb, Bi) of an MX ₃ pyramid, and the other four by the selenium atom of the phosphine selenide.

Full text of DOI:10.1039/c2dt31010d

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PAPER
Formation of M4Se4 cuboids (M = As, Sb, Bi) via secondary
pnictogen–chalcogen interactions in the co-crystals MX3·SevP(p-FC6H4)3
(M = As, X = Br; M = Sb, X = Cl; M = Bi, X = Cl, Br)†
Fatma B. Alhanash, Nicholas A. Barnes,* Alan K. Brisdon, Stephen M. Godfrey and Robin G. Pritchard
Received 9th May 2012, Accepted 22nd June 2012
DOI: 10.1039/c2dt31010d
The reactions of the group 15 trihalides, MX3 (M = As, Sb, Bi; X = Cl, Br), with the phosphine selenide
SeP(p-FC6H4)3 result in the formation of co-crystals of formula MX3·SeP(p-FC6H4)3. No reaction was
observed with MI3 (M = As, Sb, Bi). The structures of MX3·SeP(p-FC6H4)3 (M = As, X = Br 2; M = Sb,
X = Cl 3; M = Bi, X = Cl 5; M = Bi, X = Br 6) have been established, and are isomorphous, crystallising
in the cubic I23 space group. All the structures feature a primary MX3 unit, which has three weak
secondary M⋯Se interactions to SeP(p-FC6H4)3 molecules. However, each of these SeP(p-FC6H4)3
molecules bridges three MX3 molecules, resulting in the generation of an M4Se4 (M = As, Sb, Bi)
distorted cuboid linked by the pnictogen–chalcogen interactions. Four opposing corners of the cuboid are
occupied by the M atom (M = As, Sb, Bi) of an MX3 pyramid, and the other four by the selenium atom
of the phosphine selenide.
and [Bi2I6(OPPh3)4],10 have been crystallographically character-
ised. Recent reports have shown that AsF3 and SbF3 form hydro-
Introduction
The coordination chemistry of the main group elements is much
less well established than that of the transition metals, and com-
plexes of the group 15 trihalides (arsenic, antimony and
bismuth) have received relatively little attention.1–4 Studies of
their complexes are often complicated, due to the labile nature of
the ligands in solution, and the prevalence of significant second-
ary bonding interactions in the solid-state. These secondary inter-
actions occur as the M–X (M = As, Sb, Bi) σ* anti-bonding
orbital has the potential to act as an acceptor orbital towards
another donor atom.5 The presence of primary and secondary
“coordination spheres” often results in unpredictable structural
variations, which may be further complicated by the presence of
stereochemically active (or non-active) lone pairs.
Much of the coordination chemistry of group 15 halides with
chalcogen donors has focused on thioether and selenoether com-
plexes.3,4 The structures of these complexes are usually poly-
meric, and frequently feature primary MX3 units, with weaker,
secondary interactions to the chalcogen donor atoms. This
usually results in the retention of a pyramidal MX3 unit. By con-
trast, far fewer reports have appeared with phosphine chalcogen-
ide ligands. A number of phosphine oxide complexes of arsenic
(III), antimony(III) and bismuth(III) halides (X = Cl, Br, I) have
been reported,6,7 of which [SbCl3(OPPh3)2],8 [SbCl3(dppmO2)],9
lytically unstable complexes with phosphine oxides, but BiF3
does not.11 No reaction is observed between the trifluorides and
sulfur donors, whilst in contrast, SbCl5 forms complexes with
phosphine oxide and sulfide donors, but not with phosphine
selenides.12 The only reported group 15 complexes with the
softer phosphine chalcogenides (S and Se donors) are the tetra-
meric [Sb4Br12(SPMe2Ph)4], and the dimeric [Sb2Br6(SPPh3)2]
and [Sb2I6(SePPh3)2].13,14 The former contains antimony in a
distorted octahedral environment, with bridging SPMe2Ph
ligands, whilst the two dimeric structures consist of two
[SbX3(EPR3)] units of see-saw geometry, which are linked into a
dimer via two halide bridges. The overall geometry at antimony
is square pyramidal with the aryl ring orientated over the vacant
sixth coordination site. The only reported reaction between
bismuth(III) trihalides and phosphine selenides is that of BiCl3
with (Me2N)3PSe, which does not result in a bismuth phosphine
selenide complex. Instead, an unusual Se–Se bridged ionic
complex, [(Me2N)3PSe–SeP(NMe2)3][BiCl4]2, is formed which
contains polymeric [BiCl4]− anions.15
In view of the paucity of reports concerning group 15 halide
complexes with tertiary phosphine chalcogenide ligands, and
phosphine selenides in particular, we now report the results of
the reactions between the group 15 trihalides, MX3 (M = As, Sb,
Bi; X = Cl, Br, I) with SeP(p-FC6H4)3.
School of Chemistry, University of Manchester, Oxford Road,
Manchester M13 9PL, UK. E-mail: nick_barnes28@hotmail.com
†Electronic supplementary information (ESI) available: Table S1: Short
F⋯F and F⋯H contacts in the structures of 2, 3, 5 and 6. CCDC
881801–881804. For ESI and crystallographic data in CIF or other elec-
tronic format see DOI: 10.1039/c2dt31010d
Results and discussion
The reactions of SeP(p-FC6H4)3 with the series of group 15 tri-
halides MX3 (M = As, Sb, Bi; X = Cl, Br, I) have been
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Scheme 1 Formation of co-crystals from the reaction of MX3
(M = As, Sb, Bi; X = Cl, Br) with SeP(p-FC6H4)3.
undertaken, as outlined in Scheme 1. The reactions were per-
formed in diethyl ether at room temperature, and solids were
generally isolated via concentration of the solvent and precipi-
tation upon the addition of anhydrous pentane. The exception
was compound 4, which precipitated from diethyl ether and was
directly filtered from solution. The reactions of the group 15
iodides MI3 (M = As, Sb, Bi) with SeP(p-FC6H4)3 resulted in
the isolation of highly insoluble powders (orange for As and Sb,
and dark grey for Bi). Microanalysis of these solids revealed
them to be the starting tri-iodides in all three cases. Evaporation
of the filtrate from these reactions produced a white solid, which
was shown by 31P{1H} NMR spectroscopy to be unreacted SeP-
(p-FC6H4)3.
Fig. 1 ORTEP representation of the monomeric unit of AsBr3·SeP-
(p-FC6H4)3, 2. Thermal ellipsoids are shown at the 30% probability
level. The structures of SbCl3·SeP(p-FC6H4)3, 3, BiCl3·SeP(p-FC6H4)3,
5 and BiBr3·SeP(p-FC6H4)3, 6 are isomorphous with that of 2.
Symmetry operations used to generate equivalent atoms in 2: (i): 1 + z,
−1 + x, y, (ii): 1 − y, z, 1 − x, (iii): 1 + y, z, −1 + x, (iv): 1 − z, 1 − x, y.
Crystals of 2 were grown by layering of a concentrated
dichloromethane solution of the product with pentane, whilst
crystals of 3, 5 and 6 were formed by layering of dichloro-
methane solutions with diethyl ether. The structures of the four
compounds are isomorphous, all crystallising in the cubic space
group I23. The asymmetric unit of each of the four structures
consists of a trigonal pyramidal MX3 molecule (with crystallo-
graphically imposed C3v symmetry), which weakly interacts
with a SeP(p-FC6H4)3 molecule (which has crystallographically
imposed C3 symmetry). An ORTEP representation of the mol-
ecular structure of 2 is shown in Fig. 1, and selected bond
lengths and angles for 2, 3, 5 and 6 are shown in Table 1.
In all of the structures the interaction between the group
15 metal atom and the selenium donor atom of the SeP(p-
FC6H4)3 molecule is too long to be considered a bond, and all
the structures are better represented as 1 : 1 co-crystals of MX3
and SeP(p-FC6H4)3, which are linked by weak pnictogen⋯chal-
cogen interactions. The As⋯Se interaction in 2 is 3.372(2) Å,
the Sb⋯Se interaction in 3 is 3.3640(15) Å, and the Bi⋯Se
interactions in 5 and 6 are 3.3464(12) and 3.3691(13) Å respect-
ively. All of these are significantly longer than the sum of the
relevant covalent radii, (As & Se: 2.37–2.39 Å, Sb & Se:
2.56–2.59 Å, Bi & Se: 2.67–2.68 Å), which have recently been
re-determined by Alvarez and co-workers,16 and Pyykkö and co-
workers.17 A comparison of the Sb⋯Se interaction in 3 can be
made with the only other reported antimony(III) phosphine sele-
nide complex [Sb2I6(SePPh3)2], where the Sb–Se bond is con-
siderably shorter at 2.861(2) Å.13,14
secondary As⋯Se interactions of 3.289(2) and 3.423(2) Å,21
which are of comparable distance to the As⋯Se interaction in 2.
Similarly, the Bi⋯Se interactions in 5 and 6 [3.3464(12) and
3.3691(13) Å] are significantly longer than the Bi–Se bonds
observed in selenoether complexes, which range between
2.952(2) and 3.156(4) Å.21–23 Despite the M⋯Se interactions
being significantly longer in all cases than the sum of the rel-
evant covalent radii, they are still considerably shorter (by 0.4 to
0.6 Å) than the sum of the relevant van der Waals radii (3.75 Å
for As and Se, 3.96 Å for Sb and Se, 3.97 Å for Bi and Se).24
There appears to be no direct correlation between the magnitude
of the M⋯Se interaction and the size of the group 15 atom, re-
inforcing the interpretation of these complexes as co-crystals. A
comparison of the two bismuth structures 5 and 6 shows an
increase in the length of the Bi⋯Se interaction with an increase
in the size of the halide, from 3.3464(12) Å in the BiCl3 struc-
ture 5, to 3.3691(13) Å in the BiBr3 structure 6.
The P–Se bonds of 2.182(3) Å and 2.189(3) Å observed for
the two bismuth compounds 5 and 6 are somewhat longer than
those in the structures of 2 and 3, which are 2.155(5) and 2.152(3)
Å respectively. However, these are all lengthened when com-
pared with the PvSe bonds of 2.1100(13) Å and 2.1115(12) Å
in the structure of SeP(p-FC6H4)3 (which contains two indepen-
dent molecules).25 The P–Se bonds in 2, 3, 5 and 6 still have
considerable double bond character, (sum of the single bond
covalent radii of P and Se is 2.27 Å, compared to the sum of the
double bond covalent radii, which is 2.09 Å),17 and are shorter
than typical single P–Se bonds observed for phenyl–seleno
phosphonium cations [2.2189(15) to 2.2686(18) Å],26–29 or
in phosphine adducts of selenium substituted N-heterocycles
[2.284(1) to 2.327(1) Å].30 However, it should be noted that the
P–Se bonds in 2, 3, 5 and 6 are similar in magnitude to those of
2.1659(18) to 2.1673(18) Å observed for the two independent
No phosphine selenide complexes of arsenic(III) or bismuth(III)
are known for comparison with the structures of 2, 5 and 6.
However, a comparison can be made with related selenoether
complexes. The As⋯Se interaction of 3.372(2) Å in 2 is signifi-
cantly longer than has been generally observed for the As–Se
bonds in macrocyclic selenoether complexes, which range
between 2.7840(7) and 3.1633(19) Å.18–20 However, the
complex [(AsCl3)2{1,2,4,5-C6H2(CH2SeMe)4}] shows long
10212 | Dalton Trans., 2012, 41, 10211–10218
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Table 1 Selected bond lengths [Å] and angles [°] for the structures of 2, 3, 5 and 6
Compound
M–X (Å)
P–Se (Å)
M⋯Se (Å)
X–M–X (°)
X–M⋯Se (°)
P–Se⋯M (°)
AsBr3·SeP(p-FC6H4)3, 2
SbCl3·SeP(p-FC6H4)3, 3
BiCl3·SeP(p-FC6H4)3, 5
BiBr3·SeP(p-FC6H4)3, 6
2.379(3)
2.388(3)
2.495(3)
2.6401(14)
2.155(5)
2.152(3)
2.182(3)
2.189(3)
3.372(2)
96.54(9)
94.19(11)
94.38(11)
94.40(4)
84.72(7)/106.13(8)/157.02(9)
85.61(8)/105.47(8)/160.31(9)
86.68(8)/106.73(8)/158.75(8)
85.92(4)/106.50(4)/159.03(4)
113.90(15)
115.54(10)
113.75(9)
114.52(9)
3.3640(15)
3.3464(12)
3.3691(13)
molecules in the structure of (p-FC6H4)3PSeI2.25 A similar small
elongation of the PvSe bond upon complexation was observed
for [Sb2I6(SePPh3)2], where the PvSe is 2.162(2) Å,13,14 com-
pared to the PvSe bond lengths reported for the polymorphs of
Ph3PSe [2.105(1) to 2.114(4) Å].31,32
The NMR spectroscopic data of 1 to 6 reflect the lack of sig-
nificant change in the PvSe bond. δP are observed between 29.9
and 32.3 ppm for the six co-crystals, which are close to the shift
of 33.6 ppm for SeP(p-FC6H4)3.25,33 Due to the limited solubi-
lity of most of these compounds we were only able to obtain
77Se{1H} NMR spectra and 1J(SeP) coupling constants for 1
1
and 2. The J(SeP) coupling of 740 Hz, and the 77Se{1H} NMR
shifts (δSe: −248.3 ppm for 1 and −249.4 ppm for 2), are very
similar to those of the free phosphine selenide (δSe: −246.1 ppm
1
with a J(SeP) coupling of 741 Hz).25 The Raman spectra of 1
to 6 all show peaks around 530 to 538 cm−1, which are similar
to the ν(P–Se) band of 532 cm−1 observed for (p-
FC6H4)3PSeI2,25 and reflect the partial double bond character of
the P–Se bond in 1 to 6, as the bands are shifted to lower fre-
quency compared with the ν(P–Se) band observed at 552 cm−1
for SeP(p-FC6H4)3.25
The pyramidal MX3 units in each of the four structures all
have three primary M–X bonds of equal length, and each MX3
unit further interacts with three SeP(p-FC6H4)3 groups resulting
in an overall distorted [3 + 3] octahedral arrangement around M,
as shown for 2 in Fig. 2. However, each of the SeP(p-FC6H4)3
groups also bridges three MX3 units, resulting in the generation
of a distorted M4Se4 (M = As, Sb, Bi) cuboid, as shown for 2 in
Fig. 3, where four opposing corners of the cuboid are occupied
by the M atom of an MX3 pyramid, and the other four by the
selenium atom of the phosphine selenide.
This arrangement of primary and secondary bonds around M
is similar to the structures of the parent trihalides, where pyrami-
dal MX3 molecules extend their coordination sphere via
additional secondary interactions to halide atoms from neigh-
bouring MX3 molecules.34 In the case of the structures of MCl3
or MBr3 (M = As, Sb, Bi) there are commonly either five or six
secondary M⋯X interactions, resulting in overall coordination
numbers of [5 + 3] (bicapped trigonal prismatic geometry) as
seen for SbCl3,35 β-SbBr3,36 BiCl3,37 and α-BiBr3,38 or [5 + 4]
(tricapped trigonal prismatic geometry) as seen for AsCl3,39
AsBr3,40 and α-SbBr3.41 The exception is the polymeric β-BiBr3
form (which has an AlCl3-type structure), with six long Bi–Br
bonds of intermediate distance between primary and secondary
bonds.38
Fig. 2 Octahedral [3 + 3] coordination environment around the arsenic
atom in the structure of AsBr3·SeP(p-FC6H4)3, 2, showing the primary
AsBr3 fragment interacting with three SeP(p-FC6H4)3 molecules. The
same [3 + 3] arrangement is also observed in the structures of 3, 5
and 6.
selone), where there are three primary Sb–Cl bonds, and three
secondary Sb⋯Se interactions.42 Table 2 summarises the geo-
metrical parameters of the MX3 fragments in 2, 3, 5 and 6, along
with those of the parent trihalides, and the related [SbCl3(mbts)-
(μ-mbts)2SbCl3(mbts)].
The MX3 fragments in 2, 3, 5 and 6 have crystallographically
imposed C3v symmetry, which results in equal lengths for the
primary M–X bonds. In contrast, most of the structures of the
parent trihalides have three slightly unequal bonds lengths,
except for SbCl3 (Cs symmetry with two equal Sb–Cl bonds),35
and the polymeric β-BiBr3 (where there are six bonds of inter-
mediate distance rather than primary and secondary bonds).38 In
the case of 2 and 3 the geometrical parameters are broadly
similar to the parent trihalide, with only small differences in the
M–X bonds and X–M–X angles. However, both structures
exhibit considerably shorter secondary M⋯Se interactions than
the secondary M⋯X interactions in the structures of the parent
trihalides. In the case of 5 the Bi–Cl bonds are intermediate in
length between the rather large spread of the three different
Bi–Cl bonds in BiCl3, whilst in 6 the Bi–Br bonds are similar to
The structures of 2, 3, 5 and 6 have three M⋯Se interactions
(in place of five or six M⋯X interactions) to give a distorted
octahedral geometry. This is similar to the arrangement observed
in the structure of the antimony selone complex [SbCl3(mbts)
(μ-mbts)2SbCl3(mbts)] (mbts
=
N-methylbenzothiazole-2-
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In contrast, the ν(Bi–X) bands of the bismuth complexes 5
and 6 are shifted slightly to higher wavenumbers, viz. ν(Bi–Cl)
of 298 and 274 cm−1 in 5 compared with ν(Bi–Cl) of 282 and
263–252 cm−1 in BiCl3.43 The Raman spectrum of 6 shows two
intense bands at 199 and 187 cm−1 which are assigned as ν(Bi–
Br), which are again slightly shifted to higher wavenumbers than
the ν1 and ν3 bands of 189 and 180 cm−1 observed for BiBr3.48
Whilst the spectra of the bromide co-crystals 2, 4 and 6 are
dominated by intense ν(M–Br) bands, other bands are observed
at low wavenumbers for the chloride analogues 1, 3 and 5 which
may be features due to ν(M–Se). The observed changes in the
Raman spectra on formation of the co-crystals are likely to be
due to the MX3 fragments in 1 to 6 having crystallographically
imposed C3v symmetry, whilst in the solid state the majority of
the parent trihalides usually have all three bond lengths different
(C1 symmetry) or two equal bonds (Cs symmetry).
Whilst the presence of secondary bonding interactions to
group 15 MX3 fragments is not at all unusual, the generation of
M4E4 (M = As, Sb or Bi; E = Se) cuboid motifs via this type of
interaction is, to the best of our knowledge, unprecedented. A
cuboid-like motif has been observed for the bismuth thioether
complex [Bi4Cl12(MeSCH2CH2CH2SMe)4]n·nH2O,49 but here a
Bi4Cl4 pseudo-cuboid was formed, with an open-cradle arrange-
ment and very unequal Bi–Cl bonds. The formation of a Bi4Cl4
cuboid is similar to the aggregation of [MnXn]− (M = As, Sb, Bi;
X = Cl, Br, I) anions into larger networks, which is well docu-
mented for these systems,50 and a few examples involving
Sb4Cl4 cuboids are known, in [CpFe(CO)2Cl]4[SbCl3]4,51 and in
the anion of [Et4N]4[Sb4Cl16].52 However, the formation of an
M4E4 cuboid via weak pnictogen⋯chalcogen interactions has
not previously been observed.
These cuboids can be thought of as being generated from a
square made up of M atoms (M = As, Sb or Bi) with a smaller
square made up of Se atoms sat inside it, which results in a sig-
nificant distortion of both the M–Se–M and Se–M–Se from the
90° expected for a regular cube. This results in a lowering of the
overall symmetry from Td to T. Two different views of the frame-
work of the cuboid are shown for AsBr3·SeP(p-FC6H4)3, 2 in
Fig. 4. The M⋯Se distances and inter-cuboidal angles vary only
slightly between the four structures, and are shown in Table 3.
The M–Se–M angles range between 102.78(4)° for 3 to
104.87(3)° for 5, whilst the Se–M–Se vary between 72.75(3)°
for 5 to 75.53(4)° for 3.
An examination of the crystal packing shows that the for-
mation of the cuboid also results in F⋯F and F⋯H contacts
being set up between the para-fluorophenyl rings, as shown for
2 in Fig. 5. In all cases the F⋯F and F⋯H contacts are very
weak, and are around (or in some cases longer than) the sum of
the van der Waals radii, see Table S1 in the ESI.† The F⋯F
interactions vary between 2.897(14) Å for 3 and 2.972(11) Å for
6 (compared to 2.94 Å for twice the van der Waals radii of
fluorine)24 whilst the F⋯H interactions vary between 2.53 Å for
5 and 2.60 Å for 3 (compared to 2.57 Å for the sum of van der
Waals radii of hydrogen and fluorine).24 These F⋯F and F⋯H
contacts result in aggregation of the fluorous portions of the mo-
lecules, and are present in conjunction with the M⋯Se inter-
actions in all four structures, and although weak in terms of
magnitude appear to assist in the formation of the M4Se4 cuboid
arrangement, as shown in Fig. 5.
Fig. 3 Generation of the As4Se4 cuboid motif in the structure of
AsBr3·SeP(p-FC6H4)3, 2, via As⋯Se interactions. The cuboid motif in
3, 5 and 6 is generated in the same way.
those observed for the α-form of BiBr3, and significantly shorter
than those in the polymeric β-BiBr3. In both bismuth structures
5 and 6 the secondary Bi⋯Se interactions are of comparable
magnitude to the secondary Bi⋯X interactions in the structures
of BiCl3 and α-BiBr3.
Although only small changes were generally observed in the
geometrical parameters of the MX3 fragments in 2, 3, 5 and 6
compared to the parent trihalide, an examination of the Raman
spectra of 1 to 6 show that the ν(M–X) bands often exhibit a
marked shift from those of the parent trihalides. The most
intense bands in the Raman spectra of MX3 are the ν1 symmetric
M–X stretch and the ν3 degenerate M–X stretch.43 These bands
also appear to be the most intense in the Raman spectra of 1 to
6, and can be compared with Raman data for the parent tri-
halides. The spectra of 1 and 2 show that the ν(As–X) bands are
shifted to lower wavenumbers than in AsX3, viz. ν(As–Cl) of
364 and 337 cm−1 in 1 compared with ν(As–Cl) of 416 and
393 cm−1 in AsCl3.44 The Raman spectrum of 2 showed only
one intense feature at 253 cm−1, which was assigned as ν(As–
Br), although the Raman spectrum of AsBr3 does display both
ν1 and ν3 bands close to each other at 281 and 277–254 cm−1 43
,
so it may be that the peak in 2 is due to overlapping ν1 and ν3
bands. The antimony co-crystals show a similar trend, with
ν(Sb–Cl) of 327 and 307 cm−1 in 3 compared with ν(Sb–Cl) of
340 and 318–312 cm−1 in SbCl3,45 and ν(Sb–Br) of 222 and
214 cm−1 in
3 compared with ν(Sb–Br) of 243 and
238–230 cm−1 in SbBr3.46 It should be noted that weak “com-
plexes” of SbCl3 with aromatic hydrocarbons (such as benzene
or phenanthrene) also show a shift of the ν1(Sb–Cl) band to
lower wavenumbers (360 to 337 cm−1), and splitting of the ν3
band to give two bands between 340 and 302 cm−1 47
.
10214 | Dalton Trans., 2012, 41, 10211–10218
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Table 2 Geometric parameters of the MX3 fragment in the structures of 2, 3, 5 and 6, and a comparison with the MX3 parent trihalide, and related
complexes with selenium donors
X–M–X angles of
pyramidal MX3 (°)
Secondary M⋯X or M⋯Se
Compound
M–X primary bonds (Å)
interactions (Å)
Ref.
40
AsBr3
CN: 9 [3 + 6]
2.354(15), 2.354(15), 2.384(15)
97.3(5), 97.5(5), 98.2(5)
3.783, 3.863, 3.869, 3.947,
4.170, 4.210
(tricapped trigonal prism)
AsBr3·SeP(p-FC6H4)3, 2
CN: 6 [3 + 3] (distorted
octahedral)
2.379(3) × 3
96.54(9) × 3
3.372(2) × 3
This work
35
SbCl3
2.368(1) × 2, 2.340(2)
2.388(3) × 3
95.70(5) × 2, 90.98(5)
94.19(11) × 3
3.457(1) × 2, 3.609(2),
3.736(1) × 2
CN: 8 [3 + 5] (bicapped
trigonal prism)
SbCl3·SeP(p-FC6H4)3, 3
CN: 6 [3 + 3] (distorted
octahedral)
3.3640(15) × 3
This work
42
[SbCl3(mbts)
Mol 1: 2.4593(16), 2.447(2),
2.4068(18)
Mol 2: 2.4557(15), 2.4322(18),
2.4279(17)
Mol 1: 91.39(6),
92.64(6), 91.84(6)
Mol 2: 89.25(6),
89.45(5), 93.02(6)
Mol 1: 3.1812(8), 3.2208(8),
3.1395(8)
Mol 2: 3.1366(8), 3.2226(8),
3.3145(8)
(μ-mbts)2SbCl3(mbts)]
CN: 6 [3 + 3] (distorted
octahedral)
BiCl3
2.468(4), 2.513(7), 2.518(7)
84.45(14), 94.9(3),
93.2(3)
3.216(9), 3.224(3), 3.256(9),
3.398(8), 3.450(9)
37
CN: 8 [3 + 5] (bicapped
trigonal prism)
BiCl3·SeP(p-FC6H4)3, 5
CN: 6 [3 + 3] (distorted
octahedral)
2.495(3) × 3
94.38(11) × 3
3.3464(12)
This work
38
α-BiBr3
CN: 8 [3 + 5] (bicapped
trigonal prism)
2.636(4), 2.660(3), 2.692(3)
88.19(10), 90.08(11),
96.29(11)
3.246(4), 3.306(4), 3.397(3),
3.699(4), 4.106(3)
β-BiBr3
CN: 6 long bonds
(distorted octahedral)
2.79(8) × 2, 2.80(8) × 2, 2.84(8) × 2
(AlCl3 type structure)
N/A as not pyramidal
94.40(4) × 3
N/A as all six bonds are
intermediate in length
38
BiBr3·SeP(p-FC6H4)3, 6
CN: 6 [3 + 3] (distorted
octahedral)
2.6401(14) × 3
3.3691(13) × 3
This work
M = As, Sb or Bi, X = Cl or Br, mbts = N-methylbenzothiazole-2-selone.
Conclusions
Experimental
The reactions of MCl3 or MBr3 (M = As, Sb, Bi) with Sev
P(p-FC6H4)3 result in the formation of 1 : 1 co-crystals, of
which four examples have been structurally characterised.
All four structures are isomorphous, and crystallise in the
cubic space group I23. Unusually, these co-crystals aggregate as
tetramers via secondary pnictogen–chalcogen interactions
between the group 15 atom and the selenium donor atom of
the phosphine selenide. Each of the structures consists of a
pyramidal MX3 unit of C3v symmetry, which participates in
three secondary interactions to the selenium atoms of three
μ3-bridging SevP(p-FC6H4)3 ligands. In this way a highly
unusual distorted cuboid motif of T symmetry is formed for all
of the four structures reported. The crystal packing of these four
structures show that weak F⋯F and F⋯H contacts are also
present which may also assist in directing the formation of the
cuboid motif.
Reagents and physical measurements
Many of the reagents and compounds synthesised herein are
somewhat moisture sensitive, therefore anhydrous and anaerobic
conditions were used throughout their synthesis. Diethyl ether
and pentane were purchased commercially (Fisher) and freshly
distilled from sodium/benzophenone ketyl before their use.
AsCl3 (Aldrich), AsBr3 (Acros), SbCl3, SbBr3, BiCl3 and BiBr3
(all Alfa Aesar) were purchased commercially, and used without
further purification. (p-FC6H4)3PSe was synthesised according
to the literature method.25 Elemental analyses were performed by
the departmental microanalytical service. FT-Raman spectra
were recorded as solid samples on a Nicolet-Nexus combined
FT-IR/FT-Raman spectrometer using the OMNIC E.S.P. 5.1
software package. Spectra were recorded to the low frequency
cut off point of 100 cm−1
.
31P{1H} and 77Se{1H} NMR spectra
This journal is © The Royal Society of Chemistry 2012
Dalton Trans., 2012, 41, 10211–10218 | 10215

View Article Online
Fig. 4 Two different views of the As4Se4 cuboid in AsBr3·SeP(p-FC6H4)3, 2.
radiation (λ = 0.71073 Å). All data were collected at 100(2)
K. Structural data were solved by direct methods, with full-
matrix least squares refinement on F2 using the SHELX-97
program.53 Absorption corrections were applied by the multiscan
method, using the SORTAV program.54 Non-hydrogen atoms
were refined with anisotropic thermal parameters, whilst all
hydrogen atoms were modelled in ideal positions. Flack para-
meters are 0.03(7), 0.40(6), 0.002(19) and 0.057(19) for 2, 3, 5
and 6 respectively. All thermal ellipsoid plots were generated
using ORTEP-3 for Windows,55 whilst all other pictures were
generated using the MERCURY program.56
Table 3 Geometric parameters of the M4Se4 cuboid (M = As, Sb or
Bi) in the structures of 2, 3, 5 and 6
Compound
M⋯Se (Å) M⋯Se⋯M (°) Se⋯M⋯Se (°)
AsBr3·SeP(p-FC6H4)3, 2 3.372(2)
104.71(6)
72.98(5)
75.53(4)
72.75(3)
73.95(3)
SbCl3·SeP(p-FC6H4)3, 3 3.3640(15) 102.78(4)
BiCl3·SeP(p-FC6H4)3, 5 3.3464(12) 104.87(3)
BiBr3·SeP(p-FC6H4)3, 6 3.3691(13) 103.99(3)
Synthetic details
Synthesis of MX3·SeP(p-FC6H4)3 co-crystals (M = As, Sb. Bi;
X = Cl, Br). The co-crystals formed in the reaction of (p-
FC6H4)3PSe with MX3 (M = As, Sb, Bi; X = Cl, Br) were syn-
thesised by mixing the two reagents together in diethyl ether at
room temperature, the synthesis of AsCl3·SeP(p-FC6H4)3, 1
being typical: 0.500 g (1.26 mmoles) of (p-FC6H4)3PSe was
added to a pre-dried rotaflo tube containing 50 mL of anhydrous
diethyl ether, against a stream of dry nitrogen. 0.216 g (0.10 mL,
1.26 mmoles) of arsenic(III) chloride was added to the solution
which was stirred for approx. 48 hours. After this time the sol-
ution was reduced in volume to 5 mL, followed by addition of
15 mL of anhydrous pentane which resulted in the precipitation
of a white solid. This solid was isolated using standard Schlenk
techniques, and dried in vacuo for two hours.
Fig. 5 MERCURY representation of the crystal packing of AsBr3·SeP-
(p-FC6H4)3, 2, showing the As⋯Se, F⋯F and F⋯H interactions present
in the extended structure of the co-crystal. Hydrogen atoms are omitted
for clarity.
AsCl3·SeP(p-FC6H4)3, 1. Yield = 37%. White solid. Calcu-
lated for C18H12F3Cl3PSeAs: C, 37.5; H, 2.1; Cl, 18.5; Found:
were recorded on a Bruker AVANCE III 400 spectrometer operat-
ing at 162.0 (31P) and 76.3 (77Se) MHz, respectively. Peak pos-
itions are quoted relative to 85% H3PO4 (31P) or Me2Se (77Se),
using the high frequency positive convention throughout.
1
C, 38.0; H, 1.9; Cl, 18.1. 31P{1H} NMR (CDCl3): 32.3 [s, J
(SeP) = 740 Hz]. 77Se{1H} NMR (CDCl3): −248.3 [d, 1J(SeP) =
740 Hz]. Raman (cm−1): 3076, 1591, 1302, 1228, 1167, 1093,
827, 638, 538 ν(P–Se), 499, 364 ν(As–Cl), 337 ν(As–Cl), 241,
218, 187, 156.
Crystallographic details
AsBr3·SeP(p-FC6H4)3, 2. Was synthesised via the method
used for 1 above, except using 0.400 g (1.26 mmoles) of arsenic(III)
bromide and 0.500 g (1.26 mmoles) of (p-FC6H4)3PSe.
Yield = 39%. White solid. Calculated for C18H12F3Br3PSeAs: C,
Details of the structural analysis for 2, 3, 5 and 6 are summarised
in Table 4. Diffraction data were recorded on a Nonius κ-CCD
four-circle diffractometer using graphite-monochromated Mo-Kα
10216 | Dalton Trans., 2012, 41, 10211–10218
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Table 4 Crystallographic parameters for compounds 2, 3, 5 and 6
AsBr3·SeP(p-FC6H4)3, 2 SbCl3·SeP(p-FC6H4)3, 3
18H12Br3F3PSeAs
BiCl3·SeP(p-FC6H4)3, 5
BiBr3·SeP(p-FC6H4)3, 6
Empirical formula
Fw
C
C18H12Cl3F3PSeSb
623.31
C18H12Cl3F3PSeBi
710.54
C18H12Br3F3PSeBi
843.89
709.83
Colour, habit
Crystal system
Space group
Crystal size
Colourless, block
Cubic
Colourless, block
Cubic
Colourless, block
Cubic
Yellow, block
Cubic
I23 (no. 197)
0.07 × 0.07 × 0.05 mm3
a = 16.2032(18) Å, α = 90°
b = 16.2032(18) Å, β = 90°
c = 16.2032(18) Å, γ = 90°
4254.0(8) Å3
100(2) K
I23 (no. 197)
0.08 × 0.08 × 0.08 mm3
a = 16.1817(5) Å, α = 90°
b = 16.1817(5) Å, β = 90°
c = 16.1817(5) Å, γ = 90°
4237.1(2) Å3
100(2) K
I23 (no. 197)
0.07 × 0.07 × 0.07 mm3
a = 16.1403(9) Å, α = 90°
b = 16.1403(9) Å, β = 90°
c = 16.1403(9) Å, γ = 90°
4204.7(4) Å3
100(2) K
I23 (no. 197)
0.12 × 0.12 × 0.10 mm3
a = 16.3328(8) Å, α = 90°
b = 16.3328(8) Å, β = 90°
c = 16.3328(8) Å, γ = 90°
4356.9(4) Å3
100(2) K
Unit cell dimensions
Volume
T
Z
8
8
8
8
Dcalcd
λ
μ (Mo-Kα)
F(000)
2.217 mg m−3
0.71073 Å
1.954 mg m−3
0.71073 Å
2.245 mg m−3
0.71073 Å
2.573 mg m−3
0.71073 Å
9.047 mm−1
2672
3.501 mm−1
2384
10.602 mm−1
2640
15.367 mm−1
3072
θ range
No. of reflections
Rint
3.56 to 26.36°
1670 (1011 unique)
0.105
3.56 to 25.98°
1401 (777 unique)
0.055
3.09 to 25.99°
2214 (1379 unique)
0.078
3.06 to 27.49°
2034 (1491 unique)
0.082
R1/wR2
0.0631/0.1376
0.0907/0.1600
0.744 and −0.673 e Å−3
1.077
0.0587/0.1551
0.0711/0.1669
2.555 and −1.222 e Å−3
1.107
0.0469/0.1005
0.0632/0.1092
1.378 and −1.391 e Å−3
1.116
0.0454/0.0978
0.0571/0.1062
1.697 and −1.158 e Å−3
1.061
R1/wR2 (all data)
Largest diff. peak and hole
GOF
Flack parameter
0.03(7)
0.40(6)
0.002(19)
0.057(19)
BiBr3·SeP(p-FC6H4)3, 6. Was synthesised via the method
used for 1 above, except using 0.560 g (1.26 mmoles) of
30.4; H, 1.7; Br, 33.8; P, 4.8; Found: C, 29.7; H, 1.1; Br, 33.5;
1
4.8. 31P{1H} NMR (CDCl3): 32.3 [s, J(SeP) = 740 Hz]. 77Se
{1H} NMR (CDCl3): −249.4 [d, 1J(SeP) = 740 Hz]. Raman
(cm−1): 3072, 1591, 1302, 1228, 1167, 1093, 827, 638, 619,
534 ν(P–Se), 496, 341, 253 ν(As–Br), 218.
bismuth(III) bromide and 0.500
g
(1.26 mmoles) of
(p-FC6H4)3PSe. Yield = 32%. Yellow solid. Calculated for
C18H12F3Br3PSeBi: C, 25.6; H, 1.4; Br, 28.4; P, 3.7; Found:
C, 25.8; H, 1.0; Br, 28.7; P, 3.7. 31P{1H} NMR (CDCl3): 29.9
[s]. Raman (cm−1): 3076, 1591, 1495, 1394, 1298, 1232, 1163,
1093, 827, 634, 615, 530 ν(P–Se), 488, 415, 337, 237, 199
ν(Bi–Br), 187 ν(Bi–Br).
SbCl3·SeP(p-FC6H4)3, 3. Was synthesised via the method
used for 1 above, except using 0.250 g (1.13 mmoles) of anti-
mony(III) chloride and 0.450
g (1.13 mmoles) of (p-
FC6H4)3PSe. Yield 80%. White solid. Calculated for
=
C18H12F3Cl3PSeSb: C, 34.7; H, 1.9; Cl, 17.1; Found: C, 35.2;
H, 1.6; Cl, 17.3. 31P{1H} NMR (CDCl3): 30.8 [s]. Raman
(cm−1): 3074, 1591, 1490, 1299, 1237, 1167, 1097, 828, 641,
536 ν(P–Se), 497, 327 ν(Sb–Cl), 307 ν(Sb–Cl), 242, 217, 152,
127.
Acknowledgements
We are grateful to EPSRC for providing funding for the
IR-Raman facility (Grant No. GR/M30135), NMR facility
(Grant No. GR/L52246), and X-ray facility (Research Initiative
Grant). One of us (FBA) thanks the Libyan General People’s
Committee for Higher Education for funding.
SbBr3·SeP(p-FC6H4)3, 4. Was synthesised via the method
used for 1 above using 0.450 g (1.26 mmoles) of antimony(III)
bromide and 0.500 g (1.26 mmoles) of (p-FC6H4)3PSe. The
product was filtered off after 48 hours stirring and dried in vacuo
for two hours. Yield = 34%. Yellow solid. Calculated for
C18H12F3Br3PSeSb: C, 28.6; H, 1.6; Br, 31.7; Found: C, 29.4;
H, 1.4; Br, 31.5. 31P{1H} NMR (CDCl3): 32.3 [s]. Raman
(cm−1): 3072, 1591, 1298, 1232, 1163, 1093, 827, 634, 615,
530 ν(P–Se), 492, 411, 337, 222 ν(Sb–Br), 214 ν(Sb–Br), 168.
References
1 S. M. Godfrey, C. A. McAuliffe, A. G. Mackie and R. G. Pritchard, in
Chemistry of Arsenic, Antimony and Bismuth, ed. N. C. Norman, Blackie,
London, 1998, ch. 4.
2 W. Levason and G. Reid, in Comprehensive Coordination Chemistry II,
ed. J. A. McCleverty and T. J. Meyer, Elsevier, Oxford, 2004, vol. 3,
p. 465.
3 W. Levason and G. Reid, J. Chem. Soc., Dalton Trans., 2001, 2953.
4 W. Levason, G. Reid and W. Zhang, Dalton Trans., 2011, 40, 8491.
5 C. J. Carmalt and N. C. Norman, in Chemistry of Arsenic, Antimony and
Bismuth, ed. N. C. Norman, Blackie, London, 1998, ch. 1.
6 M. Zackrisson and K. I. Alden, Acta Chem. Scand., 1960, 14, 994;
D. J. Phillips and S. Y. Tyree Jr., J. Am. Chem. Soc., 1961, 83, 1806;
M. J. Frazer, W. Gerrard and R. Twaits, J. Inorg. Nucl. Chem., 1963, 25,
637.
7 S. Milićev and D. Hadži, Inorg. Nucl. Chem. Lett., 1971, 7, 745;
S. Milićev and D. Hadži, Inorg. Chim. Acta, 1977, 21, 201.
8 L. Golič and S. Milićev, Acta Crystallogr., Sect. B: Struct. Crystallogr.
Cryst. Chem., 1978, 34, 3379.
BiCl3·SeP(p-FC6H4)3, 5. Was synthesised via the method used
for 1 above, except using 0.360 g (1.13 mmoles) of bismuth(III)
chloride and 0.450 g (1.13 mmoles) of (p-FC6H4)3PSe. Yield =
41%. Pale yellow solid. Calculated for C18H12F3Cl3PSeBi:
C, 30.4; H, 1.7; Cl, 15.0; P, 4.4; Found: C, 30.4; H, 1.1; Cl,
15.0; P, 4.2. 31P{1H} NMR (CDCl3): 30.8 [s]. Raman (cm−1):
3078, 1595, 1502, 1394, 1300, 1234, 1167, 1092, 828, 636, 531
ν(P–Se), 494, 413, 337, 298 ν(Bi–Cl), 274 ν(Bi–Cl), 238, 219.
This journal is © The Royal Society of Chemistry 2012
Dalton Trans., 2012, 41, 10211–10218 | 10217

View Article Online
9 I. Abdul Razak, H.-K. Fun, B. M. Yamin, K. Chinnakali, H. Zakaria and
N. Binti Ismail, Acta Crystallogr., Sect. C: Cryst. Struct. Commun., 1999,
55, 172.
32 P. G. Jones, C. Kienitz and C. Thöne, Z. Kristallogr., 1994, 209,
80.
33 R. F. de Ketelaere and G. P. van der Kelen, J. Mol. Struct., 1975, 27, 363;
J. Malito and E. C. Alyea, Phosphorus, Sulfur Silicon Relat. Elem., 1990,
54, 95; J. A. S. Howell, N. Fey, J. D. Lovatt, P. C. Yates, P. McArdle,
D. Cunningham, E. Sadeh, H. E. Gottlieb, Z. Goldschmidt,
M. B. Hursthouse and M. E. Light, J. Chem. Soc., Dalton Trans., 1999,
3015.
34 J. Galy and R. Enjalbert, J. Solid State Chem., 1982, 44, 1.
35 A. Lipka, Acta Crystallogr., Sect. B: Struct. Crystallogr. Cryst. Chem.,
1979, 35, 3020.
36 D. W. Cushen and R. Hulme, J. Chem. Soc., 1962, 2218.
37 S. C. Nyburg, G. A. Ozin and J. T. Szymański, Acta Crystallogr., Sect. B:
Struct. Crystallogr. Cryst. Chem., 1971, 27, 2298.
38 H. von Benda, Z. Kristallogr., 1980, 151, 271.
39 J. Galy, R. Enjalbert, P. Lecante and A. Burian, Inorg. Chem., 2002, 41,
693.
10 F. Lazarini and S. Milićev, Acta Crystallogr., Sect. B: Struct. Crystallogr.
Cryst. Chem., 1976, 32, 2873.
11 W. Levason, M. E. Light, S. Maheshwari, G. Reid and W. Zhang, Dalton
Trans., 2011, 40, 5291.
12 S. Corcoran, W. Levason, R. Patel and G. Reid, Inorg. Chim. Acta, 2005,
358, 1263.
13 D. Haase, R. Lotz and S. Pohl, Z. Kryst., 1989, 186, 111.
14 S. Pohl, W. Saak, R. Lotz and D. Haase, Z. Naturforsch., Teil B, 1990,
45, 1355.
15 G. R. Willey, J. R. Barras, M. D. Rudd and M. G. B. Drew, J. Chem.
Soc., Dalton Trans., 1994, 3025.
16 B. Cordero, V. Gómez, A. E. Platero-Prats, M. Revés, J. Echeverría,
E. Cremades, F. Barragán and S. Alvarez, Dalton Trans., 2008, 2832.
17 P. Pyykkö and M. Atsumi, Chem.–Eur. J., 2009, 15, 186; P. Pyykkö and
M. Atsumi, Chem.–Eur. J., 2009, 15, 12770.
40 J. Trotter, Z. Kristallogr., 1965, 122, 230.
18 A. J. Barton, N. J. Hill, W. Levason and G. Reid, J. Am. Chem. Soc.,
2001, 123, 11801.
19 N. J. Hill, W. Levason and G. Reid, Inorg. Chem., 2002, 41, 2070.
20 N. J. Hill, W. Levason, R. Patel, G. Reid and M. Webster, Dalton Trans.,
2004, 980.
41 D. W. Cushen and R. Hulme, J. Chem. Soc., 1964, 4162.
42 N. A. Barnes, S. M. Godfrey, R. G. Pritchard and S. Ratcliffe, Poly-
hedron, 2010, 29, 1822.
43 A. Kondyurin, N. Byelousova, S. Byelousova and A. Kozulin, J. Raman
Spectrosc., 1993, 24, 825.
21 W. Levason, S. Maheshwari, R. Ratnani, G. Reid, M. Webster and
W. Zhang, Inorg. Chem., 2010, 49, 9036.
22 A. J. Barton, A. R. J. Genge, W. Levason and G. Reid, J. Chem. Soc.,
Dalton Trans., 2000, 859.
23 A. J. Barton, A. R. J. Genge, W. Levason and G. Reid, J. Chem. Soc.,
Dalton Trans., 2000, 2163.
24 M. Mantina, A. C. Chamberlin, R. Valero, C. J. Cramer and
D. G. Truhlar, J. Phys. Chem. A, 2009, 113, 5806.
44 T. M. Klapötke, Main Group Met. Chem., 1997, 2, 81.
45 K. W. Fung, G. M. Begun and G. Mamantov, Inorg. Chem., 1973, 12, 53.
46 J. C. Evans, J. Mol. Spectrosc., 1960, 4, 435.
47 A. V. Kondyurin, S. N. Mikov and A. T. Kozulin, J. Raman Spectrosc.,
1991, 22, 249.
48 K. Ichikawa and K. Fukushi, J. Raman Spectrosc., 1986, 17, 139.
49 A. R. J. Genge, W. Levason and G. Reid, Chem. Commun., 1998,
2159.
25 N. A. Barnes, S. M. Godfrey, R. T. A. Halton, R. Z. Khan, S. L. Jackson
and R. G. Pritchard, Polyhedron, 2007, 26, 4294.
26 S. M. Godfrey, R. T. A. Ollerenshaw, C. L. Richards and R. G. Pritchard,
J. Chem. Soc., Dalton Trans., 2001, 508.
27 N. A. Barnes, S. M. Godfrey, R. T. A. Halton, I. Mushtaq,
R. G. Pritchard and S. Sarwar, Dalton Trans., 2006, 1517.
28 N. A. Barnes, S. M. Godfrey, R. T. A. Halton, I. Mushtaq and
R. G. Pritchard, Dalton Trans., 2006, 4795.
50 G. A. Fisher and N. C. Norman, Adv. Inorg. Chem., 1994, 41, 233.
51 Trinh-Toan and L. F. Dahl, Inorg. Chem., 1976, 15, 2953.
52 U. Ensinger, W. Schwarz and A. Schmidt, Z. Naturforsch. Teil B, 1982,
37, 1584; J. Zaleki, Ferroelectrics, 1997, 192, 71.
53 G. M. Sheldrick, SHELX-97, University of Göttingen, Göttingen,
Germany, 1998.
54 R. H. Blessing, Acta Crystallogr., Sect. A: Found. Crystallogr., 1995, 51,
33.
29 N. A. Barnes, S. M. Godfrey, R. T. A. Halton, I. Mushtaq and
R. G. Pritchard, Dalton Trans., 2008, 1346.
55 ORTEP 3 for Windows: L. J. Farugia, J. Appl. Crystallogr., 1997, 30,
565.
30 J. L. Dutton and P. J. Ragogna, Inorg. Chem., 2009, 48, 1722.
31 P. W. Codding and K. A. Kerr, Acta Crystallogr., Sect. B: Struct.
Crystallogr. Cryst. Chem., 1979, 35, 1261.
56 MERCURY: C. F. Macrae, P. R. Edgington, P. McCabe, E. Pidcock,
G. P. Shields, R. Taylor, M. Towler and J. van de Streek, J. Appl.
Crystallogr., 2006, 39, 453.
10218 | Dalton Trans., 2012, 41, 10211–10218
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