Pyridine adducts of arylbismuth(III) halides

Article abstract of DOI:10.1039/a900823c

A range of bismuth trihalide and arylbismuth(III) halide complexes with pyridine ligands has been prepared and structurally characterised. The complex [BiI₃(py)₃] (py = pyridine) is octahedral with the iodide and pyridine ligands arranced in a mer configuration. A seven-co-ordinate complex [BiCl₃(py)₄] is also described. The compounds [BiCl₂Ph(4-Mepy)₂] (4-Mepy = 4-methylpyridine), [BiBr₂Ph(4-Mepy)₂], [BiBr₂Ph(4-Bu^tpy)₂] (4-Bu^tpy = 4-tert-butylpyridine) and [BiI₂Ph(4-Bu^tpy)₂] all have a five-co-ordinate, square-based pyramidal bismuth centre in which the phenyl group occupies the apical position with two trans halides and two trans pyridine ligands residing in the basal plane. In the solid state these moieties are dimerised through a pair of weak asymmetric halide bridging interactions. The complexes [BiBr₂Ph(py)₂] and [BiI₂Ph(4-Mepy)₂] have similar monomeric units but in the former case these are weakly associated into polymeric chains rather than dimers whereas, for the latter, dimers are formed through a single bridging iodide. In the structure of the ionic compound [4-Bu^tpyH][BiCl₃Ph(4-Bu^tpy)] the [BiCl₃Ph(4-Bu^tpy)]^- amon is monomeric with a square-based pyramidal structure in which the phenyl group is in an apical site whilst the three chlorides and 4-Bu^tpy ligand occupy the basal positions. An example of a diphenylbismuth halide complex is seen in the structure of [BiIPh₂(4-Mepy)], the monomeric unit of which contains a four-co-ordinate bismuth centre with a ceometry based on an equatorially vacant trigonal bipyramid in which the two phenyl groups are equatorial and the iodide and 4-methylpyridine ligand are axial. A weak association into polymeric chains occurs through long Bi...I interactions approximately trans to one phenyl group. All compounds are discussed in terms of their structure and bonding and compared with related materials previously characterised.

Full text of DOI:10.1039/a900823c

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Pyridine adducts of arylbismuth(III) halides
Siân C. James, Nicholas C. Norman* and A. Guy Orpen
The University of Bristol, School of Chemistry, Cantock’s Close, Bristol, UK BS8 1TS.
E-mail: N.C.Norman@Bristol.ac.uk
Received 1st February 1999, Accepted 4th June 1999
A range of bismuth trihalide and arylbismuth() halide complexes with pyridine ligands has been prepared and
structurally characterised. The complex [BiI3(py)3] (py = pyridine) is octahedral with the iodide and pyridine ligands
arranged in a mer configuration. A seven-co-ordinate complex [BiCl3(py)4] is also described. The compounds
[BiCl2Ph(4-Mepy)2] (4-Mepy = 4-methylpyridine), [BiBr2Ph(4-Mepy)2], [BiBr2Ph(4-Butpy)2] (4-Butpy = 4-tert-butyl-
pyridine) and [BiI2Ph(4-Butpy)2] all have a five-co-ordinate, square-based pyramidal bismuth centre in which the
phenyl group occupies the apical position with two trans halides and two trans pyridine ligands residing in the basal
plane. In the solid state these moieties are dimerised through a pair of weak asymmetric halide bridging interactions.
The complexes [BiBr2Ph(py)2] and [BiI2Ph(4-Mepy)2] have similar monomeric units but in the former case these are
weakly associated into polymeric chains rather than dimers whereas, for the latter, dimers are formed through a single
bridging iodide. In the structure of the ionic compound [4-ButpyH][BiCl3Ph(4-Butpy)] the [BiCl3Ph(4-Butpy)]– anion
is monomeric with a square-based pyramidal structure in which the phenyl group is in an apical site whilst the three
chlorides and 4-Butpy ligand occupy the basal positions. An example of a diphenylbismuth halide complex is seen in
the structure of [BiIPh2(4-Mepy)], the monomeric unit of which contains a four-co-ordinate bismuth centre with a
geometry based on an equatorially vacant trigonal bipyramid in which the two phenyl groups are equatorial and
the iodide and 4-methylpyridine ligand are axial. A weak association into polymeric chains occurs through long
Bi ؒ ؒ ؒ I interactions approximately trans to one phenyl group. All compounds are discussed in terms of their
structure and bonding and compared with related materials previously characterised.
The Lewis acidity of bismuth() halides and their co-
ordination chemistry with two-electron donor ligands is now
well established although there are as yet no comprehensive
reviews of this field. Reviews dealing with some aspects of
this topic are given in ref. 1 whereas those listed in ref. 2 deal
with more theoretical features such as the concept of secondary
bonding interactions arising from the Lewis acidity, co-
ordination geometry, lone pair stereochemical activity and the
nature of acceptor orbitals. In this paper we describe a range of
co-ordination compounds where the ligands are pyridine (or
derivatives thereof), many of which exhibit structures of types
not previously seen. In order to place the present work in con-
text, therefore, the main structural types characterised in earlier
studies are briefly described below.
The range of adducts formed by the bismuth trihalides BiX3
(X = Cl, Br or I) has been discussed in some detail in ref. 3 and
will not be reproduced here. In the present context, however,
we note that six-co-ordinate complexes of the general form
[BiX3(L)3], where L is a two-electron donor ligand, adopt
octahedral geometries and are known with both fac and mer
configurations: e.g. fac-[BiCl3(tu)3] (tu = thiourea),4 fac-[BiCl3-
(dmso)3] (dmso = dimethyl sulfoxide),5 fac-[BiCl3(thf)3]
(thf = tetrahydrofuran),6 fac-[BiBr3(thf)3],3c mer-[trichlorotris-
{1-phenyl-3-(2-pyridyl)thiourea-S}bismuth]7 and mer-[tri-
chlorotris(imidazolidine-2-thione-S)bismuth].8 In none of these
examples is there much evidence for any stereochemical activity
associated with the bismuth() lone pair.
has a five-co-ordinate, square-based pyramidal geometry with
the aryl group in the apical position. Examples include poly-
meric BiBr2Ph, a small unit of which is shown in A,9 ‡ [BiX2Ph-
(thf)] (X = Cl, Br or I) for which a one-dimensional structure
is found (two monomers are shown in B),12 [BiBr2Ph(OPPh3)]
which is dimeric (C)13 and [BiBr2Ph(dmpu)2] (dmpu = N,NЈ-
dimethylpropyleneurea) where a monomeric structure D is
observed.13 In situations where the ligand L in the mono
adducts [BiX2Ar(L)] is a halide anion, dimeric species of
the general formula [Bi2X6Ph2]2– are observed for which the
structures [NBun ] [Bi2Br6Ph2] E12b and [NEt4]2[Bi2I6Ph2] F12a
4 2
are typical.
The diaryl monohalides, BiXAr2, and the monoligand
complexes derived from them, [BiXAr2(L)],† generally adopt
structures in which the bismuth centre is four-co-ordinate
(disphenoidal). Thus in [BiBr(2,4,6-Me3C6H2)2]14 a polymeric
one-dimensional arrangement with single bromide bridges
between bismuth centres is found, although the structure of
[BiCl{2,4,6-(CF3)3C6H2}2]15 with bulky aryl groups is mono-
meric, whilst the ligand complex [BiBr(2,4,6-Me3C6H2)2(hmpa)]
(hmpa = hexamethylphosphoramide)13 G and the anions [BiX2-
Ph2]Ϫ H12 are monomeric.
The structure and bonding in the compounds mentioned
above has been discussed in more detail in refs. 2(b),(c), aspects
of which will be further explored below. In most cases, related
antimony compounds are also known, references to which are
given in ref. 13.
The monoaryl dihalides, BiX2Ar, and the mono- and bis-
ligand complexes derived from them, [BiX2Ar(L)] and [BiX2-
Ar(L)2],† tend to adopt structures in which the bismuth centre
‡ Two exceptions to this structure type are found in BiBr2(2,4,6-
Me3C6H2)10 and BiCl2(2,4,6-Ph3C6H2);11 in the former, adjacent pairs
of bismuth atoms are bridged by one bromine and one aryl–bismuth
π interaction whilst in the latter a weakly bound dimeric structure
is observed presumably due to the bulkiness of the aryl group in this
case.
† In general, the number of ligands (L) which bind to the bismuth
centre is equal to the number of electronegative X groups as described
in the discussion section.2b,3c
J. Chem. Soc., Dalton Trans., 1999, 2837–2843
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bismuth–pyridine complexes to compare with 1 but we note
four in particular. The anion in the compound [BiI2(py)3(dp-
pom)][BiI4(py)2]16 (dppom = bis(diphenylphosphino)methane
dioxide) is octahedral with the pyridines in a cis configuration,
i.e. cis-[BiI4(py)2]Ϫ, with Bi–N distances 2.70(2) and 2.75(3) Å.
17
In the complex [Mg(py)2(H2O)4][BiBr4(py)2]2 an analogous
bromo anion is present although in this case the geometry is
trans, i.e. trans-[BiBr4(py)2]Ϫ. Also relevant is the structure of
the octahedral anion [BiCl5(py)]2Ϫ present in the complexes
[Hpy]2[BiCl5(py)] (Bi–N 2.535(7) Å)17 and [C5H5NCSNEt2]-
[BiCl5(py)] (Bi–N 2.615(8) Å).18
Results
Crystals of a complex of BiCl3 and pyridine were obtained
by similar procedures, a partial structure determination for
which revealed the presence of four co-ordinated pyridines, i.e.
[BiCl3(py)4] 2. The structure determination was not of sufficient
quality to be fully reported here due to pyridine disorder
problems (unit cell dimensions are given in the Experimental
section) but was sufficient to establish the molecular struc-
ture, a representation of which is shown in the diagram
which illustrates a seven-co-ordinate bismuth centre having
a pentagonal bipyramidal geometry in which the pyridine
ligands are all in the equatorial plane. This structure is not
unlike that observed for the [BiI2(py)3(dppom)]ϩ cation
described in ref. 16.
Solutions of BiI3 and an excess of pyridine afforded crystals
of the complex mer-[BiI3(py)3] 1 (py = pyridine) as a pyridine
solvate (Fig. 1). Crystallographic data for this and all other
structures are given in Table 1. All angles around the bismuth
centre in 1 are close to 90 or 180Њ such that there is little
evidence for any stereochemical activity associated with the
bismuth() lone pair consistent with previous examples of
octahedral [BiX3(L)3] structures (mer or fac, see above). The
Bi–N bond lengths range from 2.533(4) to 2.625(4) Å but the
bond to N(3) trans to I(2) is longer than the other two Bi–N
bonds. Similarly, the Bi–I bond trans to the pyridine is shorter
than the two mutually trans Bi–I bonds (all lengths are given in
the caption to Fig. 1) indicating that iodine has a higher trans
influence than pyridine. There are few examples of similar
Treatment of solutions of BiX2Ph (X = Cl, Br or I) with pyri-
dine, or derivatives thereof, afforded complexes with the basic
formula [BiX2Ph(L)2] in reasonable isolated yields (in many
cases the same compounds were isolated when the diphenyl
compounds BiXPh2 were used although this is not unexpected
in view of the facile group exchange reactions previously en-
countered for these types of compound9,12,13). The compounds
[BiCl2Ph(4-Mepy)2] 3 (4-Mepy = 4-methylpyridine) (Fig. 2),
[BiBr2Ph(4-Mepy)2]
4 5 (4-
(Fig. 3), [BiBr2Ph(4-Butpy)2]
Butpy = 4-tert-butylpyridine) (Fig. 4) and [BiI2Ph(4-Butpy)2]
6 are all similar and have as their basic structural unit a five-
co-ordinate, square-based pyramidal bismuth centre in which
the phenyl group occupies the apical position with two trans
halides and two trans pyridine ligands residing in the basal
plane. All interbond angles are close to 90 or 180Њ although the
N–Bi–N angles are somewhat less than the X–Bi–X angles
possibly for steric reasons (see Figure captions). As is clear
Fig. 1 A view of the molecular structure of complex 1. Atoms are
drawn as ellipsoids of 30% probability. Hydrogen atoms are omitted.
Bond lengths include Bi(1)–N(1) 2.533(4), Bi(1)–N(2) 2.563(4), Bi(1)–
N(3) 2.625(4), Bi(1)–I(1) 3.0367(7), Bi(1)–I(2) 2.9609(7) and Bi(1)–I(3)
3.0309(7) Å.
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Fig. 4 A view of the molecular structure of complex 5 showing the
Fig. 2 A view of the molecular structure of complex 3 showing the
weakly bonded dimers. Details as in Fig. 1. Bond lengths and angles
include Bi(1)–C(1) 2.275(9), Bi(1)–N(1) 2.504(8), Bi(1)–N(2) 2.547(8),
Bi(1)–Cl(1) 2.678(2), Bi(1)–Cl(2) 2.701(2) and Bi(1)–Cl(2a) 3.657(3) Å;
C(1)–Bi(1)–Cl(2a) 151.2(2), Bi(1)–Cl(2)–Bi(1a) 90.02(7), N(1)–Bi(1)–
N(2) 167.8(2) and Cl(1)–Bi(1)–Cl(2) 178.01(7)Њ.
weakly bonded dimers. Details as in Fig. 1. Bond lengths and angles
include Bi(1)–C(1) 2.265(5), Bi(1)–N(1) 2.542(4), Bi(1)–N(2) 2.527(4),
Bi(1)–Br(1) 2.885(1), Bi(1)–Br(2) 2.805(1) and Bi(1)–Br(2a) 3.691(2) Å;
C(1)–Bi(1)–Br(2a) 158.36(12), Bi(1)–Br(2)–Bi(1a) 105.80(4), N(1)–
Bi(1)–N(2) 169.46(14) and Br(1)–Bi(1)–Br(2) 177.40(2)Њ.
Fig. 5 A view of the molecular structure of complex 7 showing four
monomers as part of the polymeric chain. Each monomer resides
on a crystallographic C2 axis and the polymeric chain lies along the
crystallographic c axis. Other details as in Fig. 1. Bond lengths and
angles include Bi(1)–C(1) 2.282(8), Bi(1)–N(1) 2.547(5), Bi(1)–Br(1)
2.8445(6) and Bi(1)–Br(1a) 3.9861(7) Å; C(1)–Bi(1)–Br(1b) 145.30(1),
Bi(1)–Br(1)–Bi(1a) 90.51(12), N(1)–Bi(1)–N(1a) 167.6(2) and Br(1)–
Bi(1)–Br(1a) 177.32(3)Њ.
Fig. 3 A view of the molecular structure of complex 4 showing the
weakly bonded dimers. Details as in Fig. 1. Bond lengths and angles
include Bi(1)–C(1) 2.263(12), Bi(1)–N(1) 2.519(9), Bi(1)–N(2) 2.564(9),
Bi(1)–Br(1) 2.840(2), Bi(1)–Br(2) 2.845(2) and Bi(1)–Br(2a) 3.772(2) Å;
C(1)–Bi(1)–Br(2a) 151.7(3), Bi(1)–Br(2)–Bi(1a) 91.03(4), N(1)–Bi(1)–
N(2) 169.9(3) and Br(1)–Bi(1)–Br(2) 175.29(4)Њ.
from the diagram and Figs. 2–4, pairs of these monomeric units
form weakly bonded dimers through very asymmetric halide
bridging interactions, the longer secondary Bi ؒ ؒ ؒ X bond being
approximately trans to the phenyl group. For 3, 4 and 5 the
primary and secondary Bi–X distances are, respectively Bi–Cl
2.701(2), 3.657(3); Bi–Br 2.845(2), 3.772(2); Bi–Br 2.805(1),
3.691(2) Å and the trans C–Bi ؒ ؒ ؒ X angles are 151.2(2),
151.7(3) and 158.36(12)Њ. Crystallographic details for 3–5 are
given in Table 1 and further bond length and angle data are
presented in the Figure captions. The quality of the data set
for 6 was poor and its analysis is therefore not reported here
although unit cell dimensions are given in the Experimental
section.
mutually trans halides and trans pyridines in the square-basal
plane. However, unlike 3–6, the monomers in 7 are weakly
associated into polymeric chains, as shown for four such units
in Fig. 5, rather than dimers. In the case of 7 the intermolecular
interactions also comprise asymmetric halide bridges although
As observed for the structures of complexes 3–6, the struc-
ture of [BiBr2Ph(py)2] 7 (Fig. 5) has a monomeric unit with
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now there are two such interactions per bismuth rather than
one. As a result the bridges are even more asymmetric;
Bi–Br 2.8445(6), 3.9861(7) Å. Since both halides are involved in
bridging, two long Bi ؒ ؒ ؒ Br contacts occur approximately trans
to the phenyl group; C–Bi ؒ ؒ ؒ Br 145.30(1)Њ. Each monomer
resides on a crystallographic C2 axis and is related to other
monomers in the polymer chain by the crystallographic c glide.
In the structure of [BiI2Ph(4-Mepy)2] 8, monomeric units
structurally similar to those found in complexes 3–7 are also
present although these are linked into dimers through a single
bridging iodine and a weak 4-methylpyridine to bismuth π
interaction as shown in the diagram. Owing to the poor quality
of the data set obtained for 8, however, the structure will not be
discussed further. Unit cell data are given in the Experimental
section.
from Fig. 7 however, a weak association into polymeric chains
occurs through long Bi ؒ ؒ ؒ I interactions approximately trans
to one phenyl group [C(1)–Bi ؒ ؒ ؒ I 161.1(2)Њ] although the
bridging Bi ؒ ؒ ؒ I distance [4.3099(9) Å] is considerably longer
than the primary Bi–I distance [Bi–I 3.0229(8) Å].
As a final structure in this sub-section on monoaryl com-
pounds an ionic species, possibly formed by hydrolysis of a
precursor complex [BiCl2Ph(4-Butpy)2], was identified as [4-
ButpyH][BiCl3Ph(4-Butpy)] 9 (Fig. 6) by X-ray crystallography.
The [BiCl3Ph(4-Butpy)]Ϫ anion is monomeric with a square-
based pyramidal structure in which the phenyl group is in the
apical site whilst the three chlorines and 4-Butpy ligand occupy
the basal positions. All interbond angles are close to either 90
or 180Њ and the distances are unexceptional. In the crystal
structure the cation [4-ButpyH]ϩ is hydrogen bonded to the
anion, as shown in the diagram and Fig. 6, in a manner where
two chlorines act as a chelate to the N–H hydrogen bond donor.
Hydrogen bonding interactions of this type where a metal
dichloride chelates to a N–H or O–H group have recently been
discussed.19
Fig. 7 A view of the molecular structure of complex 10 showing four
monomers as part of the polymeric chain. Details as in Fig. 1. Bond
lengths and angles include Bi(1)–C(1) 2.267(8), Bi(1)–C(7) 2.246(8),
Bi(1)–N(1) 2.604(7), Bi(1)–I(1) 3.0229(8) and Bi(1)–I(1a) 4.3099(9) Å;
N(1)–Bi(1)–I(1) 174.2(2), C(1)–Bi(1)–C(7) 96.2(3) and C(1)–Bi(1)–I(1a)
161.1(2)Њ.
The structure of a complex with the empirical formula
[BiIPh2(dmap)] 11 (dmap = 4-dimethylaminopyridine) was
also determined. Whilst the data were not of a sufficient
quality to discuss in detail, an unusual structure was clearly
present involving linked pairs of [BiPh2(dmap)2]ϩ cations and
[BiI2Ph2]Ϫ anions as shown in the diagram. Similar cationic
and anionic units have been previously observed as described
in refs. 12 and 16. Unit cell data are given in the Experimental
section.
As an example of a diphenylbismuth halide complex the
structure of [BiIPh2(4-Mepy)] 10 is shown in Fig. 7. The
monomeric unit of 10 contains a four-co-ordinate bismuth
centre, the geometry of which is equatorially vacant trigonal
bipyramidal (disphenoidal) with two phenyl groups equatorial
and the iodine and 4-methylpyridine ligand axial. As is clear
Fig. 6 A view of the molecular structure of the anion in complex 9.
Atoms are drawn as ellipsoids of 30% probability. Hydrogen atoms
are omitted except for the one bonded to N(2). Bond lengths include
Bi(1)–C(1) 2.241(6), Bi(1)–N(1) 2.676(5), Bi(1)–Cl(1) 2.630(2), Bi(1)–
Cl(2) 2.604(2), Bi(1)–Cl(3) 2.788(2), Cl(2) ؒ ؒ ؒ H(2A) 3.144(6) and
Cl(3) ؒ ؒ ؒ H(2A) 2.357(6) Å.
Discussion
Many of the structures described in the previous section are
of new types but a number of structural trends are never-
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theless apparent. In general, the Lewis acidity of arylbismuth
halides results in the formation of complexes of general
formula [BiXnAr3Ϫn(L)n] with a co-ordination number around
the bismuth centre equal to (3 ϩ n) (some of these ideas have
been discussed previously in refs. 2(b), 3(c), 13 and 20). Thus,
as detailed in the Introduction, for the trihalides with three
monomeric ligands L, this rule results in six-co-ordinate com-
pounds of the general formula [BiX3(L)3], as seen in 1, although
as is evident from the structure of 2, higher co-ordination
numbers are possible albeit rare. In all cases including 1, the
co-ordination geometry of the [BiX3(L)3] species is close to
regular octahedral with little evidence of a stereochemically
active bismuth() lone pair (in terms of bond length or angular
distortions).2c Both fac and mer configurations are known
although we note that complexes with oxygen donors are fac
whereas those with sulfur donors tend to be mer. In the case of
nitrogen donor ligands, with only one example, i.e. 1, it is not
very sensible to make any general comments although the mer
structure of 1 is certainly consistent with what is found for some
of the other complexes examined in this study as will become
apparent.
action and that in the structure J the X–Bi–X and N→Bi←N
units are also of the three-centre, four-electron type albeit
symmetrical and not amenable to a donor–acceptor definition.
The distinction between the bonding in I and J and between
mer- and fac-[BiX3(L)3] (and cis- and trans-[BiX3(L)2]) is,
therefore, more one of degree than of kind and the stabilities
of both are likely to be similar making rationalisation of any
particular isomer rather difficult. A further insight into these
systems, though again with little predictive power, is that
whereas fac-[BiX3(L)3] and I can be viewed as ligand com-
plexes of the pyramidal BiX3 or BiX2Ar species (the expected
ground state structure), mer-[BiX3(L)3] and J can be thought
of as ligand complexes of T-shaped BiX3 or BiX2Ar moieties.
Although the T-shaped form is never the ground state structure,
its energy is not prohibitively high compared with that of the
pyramidal form. T-Shaped geometries in trivalent Group 15
compounds have been discussed extensively by Arduengo and
co-workers.22
As a final point regarding the structures 3–8 we note that in
all cases weak intermolecular interactions lead to dimers or
polymers and that, specifically, these interactions involve a close
contact between a halide and the bismuth centre approximately
trans to the apical phenyl group. Although these interactions
are weak, as evidenced by the long Bi ؒ ؒ ؒ X distances, they are
much more commonly encountered in these pyridine complexes
than in other systems previously studied, i.e. neutral O- and S-
donor complexes and halogeno anions; similar interactions are,
however, seen in [NEt4][BiI2Ph2],12b [BiBr(2,4,6-Me3C6H2)2-
(Ph2SO)]13 and in cationic complexes of the form [BiAr2(L)2]ϩ 16
(see also ref. 23). No obvious explanation presents itself but a
similar interaction is also found in 10 resulting in the polymeric
structure obseved. In the complex [BiBr(2,4,6-Me3C6H2)2-
(Ph2SO)]13 the weak interactions are such that a dimer is
present in the solid state.
In cases where one of the ligands L is formally XϪ, complexes
with the general formulae [BiX4(L)2]Ϫ (cis and trans),
[BiX5(L)]2Ϫ and [BiX6]3Ϫ result, examples of all of which have
been characterised; the former two types are discussed above
and examples of [BiX6]3Ϫ anions are described in ref. 21. With
reference to the discussion which follows, it is also worth noting
the structures of bis-ligand complexes of the form [BiX3(L)2]
which are either dimeric or polymeric due to the presence of
bridging halides (here a bridging halide X acts like the third
ligand L in [BiX3(L)3]). Their structures have been described in
refs. 3(b) and 3(c) and will not be discussed in detail here except
to note that in almost all cases the two ligands on each bismuth
centre (usually O and P donors) are cis3b,c the only exception
being in the polymeric complex [BiCl3(dmso)2] where the dmso
ligands are trans.3d
For the monoarylbismuth dihalides the basic unit relevant
to this study is the five-co-ordinate bis-ligand species [BiX2-
Ar(L)2]. In this case the co-ordination geometry is square-based
pyramidal with the aryl group in the apical site and the halide
atoms and ligands in the basal plane. Two isomers are possible
depending on whether the halide atoms and ligands are
mutually cis (I) or trans (J).
Further work is in progress more fully to understand the
bonding in halogenobismuth() complexes (and secondary
bonding in general2a) and also to utilise the directional nature
of this type of bonding to design and prepare solid state net-
work structures.
Experimental
General considerations
All reactions were carried out under an atmosphere of dry
dinitrogen or argon using standard Schlenk or dry-box tech-
niques and oven-dried glassware. All solvents used were dis-
tilled under nitrogen and dried over appropriate drying
agents (CaH2 for CH2Cl2, Na for hexanes and sodium–
benzophenone for thf and Et2O). The compound BiCl3
(99.99%) was procured from Aldrich and generally used
without further purification (filtration to remove insoluble
BiOX was occasionally necessary). Substituted pyridines were
also from Aldrich and dried over molecular sieves. Pyridine,
from BDH, was handled in a similar manner. Arylbismuth
halides were prepared according to literature routes.9,12,13
Most of the arylbismuth halide complexes described here
were produced by micro-scale procedures designed to afford
crystals suitable for structural studies. The small quantities
produced make any numerical values for yields rather uncertain
but in all cases they were good and the purity of the materials
was established by elemental analysis in most cases. For the
monoaryl complexes 3–9 the starting materials used were of the
form BiX2Ph although as mentioned in the text these complexes
were also obtained in many cases when the starting compound
was the diaryl species BiXPh2.
For the complexes 3–8 the observed geometry is trans (J)
but for the complex [BiBr2Ph(dmpu)2]13 a cis structure (I) is
found. These results, together with the observations made con-
cerning fac and mer preferences for the [BiX3(L)3] complexes
(and the cis and trans preferences for the [BiX3(L)2] complexes),
indicate that oxygen donor ligands tend to prefer mutually
cis co-ordination whereas pyridine donors, albeit with only
one example, prefer to be mutually trans. There is no obvious
explanation for this feature and it is possible that the two iso-
mers have similar stabilities in any case so we must beware of
overinterpretation. Nevertheless, the point has been made2b,3c,13
that fac-[BiX3(L)3] and geometries such as I (and G) can be
understood if the acceptor orbitals through which the ligands
bind are the Bi–X σ* orbitals. This leads directly to structures
in which the ligands L are trans to X. Clearly this is not the case
in complexes such as 1 and 3–8. Some insight can be had from
the fact that bonding of this sort in L→Bi–X moieties is no
more than an asymmetric three-centre, four-electron inter-
Preparations
[BiI3(py)3]ؒpy 1. A solution of BiI3 (0.05 g, 0.08 mmol) in
pyridine (1 cm3) was cooled at Ϫ20 ЊC over three months during
J. Chem. Soc., Dalton Trans., 1999, 2837–2843
2841

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Table 1 Selected crystallographic details for the complexes 1, 3–5, 7, 9 and 10a
1
3
4
5
7
9
10
Empirical formula
Formula weight, M
C20H20BiI3N4
453.04
C18H19BiCl2N2 C18H19BiBr2N2 C24H31BiBr2N2 C16H15BiBr2N2 C24H32BiCl3N2 C18H17BiIN
543.23
632.15
716.31
604.10
663.85
583.21
Crystal system
Space group
Triclinic
P1
Monoclinic
P21/c
Monoclinic
P21/c
Triclinic
P1
Monoclinic
C2/c
Monoclinic
P21/c
Orthorhombic
Pca21
¯
¯
a/Å
b/Å
c/Å
α/Њ
9.129(2)
11.301(2)
13.191(2)
81.626(14)
99.90(3)
68.692(13)
1253.0(4)
2
9.6039(7)
13.2094(9)
15.6045(11)
9.812(3)
13.392(5)
15.845(6)
9.828(2)
11.673(2)
12.475(3)
101.65(3)
101.75(3)
108.01(3)
1277.5(4)
2
13.520(3)
14.687(2)
8.699(2)
16.891(3)
8.996(2)
17.280(5)
10.786(2)
9.463(2)
17.611(4)
β/Њ
99.777(1)
102.15(3)
99.60(1)
98.59(2)
γ/Њ
V/Å3
1950.9(2)
4
9.312
0.00040(7)
10152
3433
2035.4(12)
4
12.589
0.00042(7)
12854
1703.15(8)
4
15.039
0.00038(9)
8717
2596.3(11)
4
7.113
0.00086(6)
15965
5926
1797.5(6)
4
11.520
0.00053(4)
10964
3981
Z
µ/mmϪ1
10.744
N/A
9327
10.041
N/A
13086
Extinction coefficient
Reflections measured
Independent reflections 5681
4636
5769
1949
Rint
0.0305
0.0258
0.0790
0.0418
0.0999
0.0646
0.0331
0.0371
0.0582
0.0340
0.0726
0.0419
0.0596
0.0303
Final R [I > 2σ(I)]
a Data collected at 173(2) K.
which time small red crystals of complex 1 were formed.
C20H20BiI3N4 (i.e. 1ؒpy as found in the structure) requires C,
26.50; H, 2.20; N, 6.20. C15H15BiI3N3 (i.e. 1) requires C, 21.80;
H, 1.85; N, 5.10. Found: C, 19.40; H, 1.65; N, 4.50% indicating
some further loss of pyridine from the crystals.
[BiIPh2(4-Mepy)] 10. Crystals of complex 10 were obtained
as a minor product in the crystallisation of 8 and were also
yellow block-like crystals.
X-Ray crystallography
[BiCl3(py)4] 2. A solution of BiCl3 in pyridine was layered
with hexane and cooled at Ϫ20 ЊC over several days yielding
colourless crystals of complex 2. Satisfactory elemental analysis
was not obtained due to facile loss of pyridine.
All crystals were mounted in air onto glass fibres. Crystals for
low temperature data collection were mounted using grease,
whilst samples for room temperature analysis were fixed to the
glass fibre using glue. Data collections were performed on a
Siemens (Bruker) SMART area detector diffractometer using
graphite monochromated Mo-Kα radiation, at Ϫ100 ЊC, except
for complexes 6 and 8 for which data were collected on a
Siemens (Bruker) P4 four circle diffractometer at room
temperature.
For the structures of complexes 1, 5 and 7 a full sphere
of reciprocal space was scanned by 0.3Њ ω steps. For other
compounds studied using the area detector diffractometer
a full hemisphere of reciprocal space was scanned by 0.3Њ ω
steps. Structures were solved and refined by standard methods.
The crystal of 4 was a non-merohedral twin with twin law
(1 0 0, 0 Ϫ1 0, 0 0 1/3).24
[BiCl2Ph(4-Mepy)2] 3. Several drops of 4-Mepy were added
to a small spatula of BiCl2Ph in a thin-walled glass tube. This
was layered with hexane and clear block-like crystals of com-
plex 3 were obtained over two days at Ϫ20 ЊC. C18H19BiCl2N2
requires C, 39.80; H, 3.55; Cl, 13.05; N, 5.15. Found: C, 39.65;
H, 3.15; Cl, 13.50; N, 5.10%.
[BiBr2Ph(4-Mepy)2] 4. This compound was prepared in a
similar manner to 3 using BiBr2Ph. C18H19BiBr2N2 requires C,
34.20; H, 3.05; Br, 25.30; N, 4.45. Found: C, 32.10; H, 2.90; Br,
25.90; N, 4.30%.
As noted in the text, the structure determinations for com-
plexes 2, 6, 8 and 11 were of poor quality and various problems
were encountered during refinement. Specifically, these were
associated with pyridine disorder (2), high thermal motion in
some of the ligand carbon atoms (6 and 8), weak data (6 and 8),
the possibility of the presence of a satellite crystal (8) and high
residual electron density and absorption problems (2, 6 and 11)
leading to poor R indices. Although little doubt remains con-
cerning the gross molecular structures (which are discussed in
the text), full crystallographic details are not reported. Unit cell
data, however, are as follows: 2, orthorhombic, space group
Pnma, a = 16.007(3), b = 15.322(3), c = 9.083(2) Å; 6, triclinic,
[BiBr2Ph(4-Butpy)2] 5. This compound was prepared in a
similar manner to 3 using BiBr2Ph and a few drops of 4-Butpy.
C24H31BiBr2N2 requires C, 40.25; H, 4.35; N, 3.90. Found: C,
41.20; H, 4.40; N, 3.85%.
[BiI2Ph(4-Butpy)2] 6. This compound was prepared in a
similar manner to 3 using BiI2Ph and a few drops of 4-Butpy.
C24H31BiI2N2 requires C, 35.60; H, 3.85; I, 31.30; N, 3.45.
Found: C, 35.55; H, 3.40; I, 31.00; N, 3.40%.
[BiBr2Ph(py)2] 7. This compound was prepared in a similar
manner to 3 using BiBr2Ph and a few drops of py. Satisfactory
elemental analyses could not be obtained due to ready loss of
pyridine.
¯
space group P1, a = 10.104(2), b = 11.893(3), c = 13.120(2) Å,
α = 102.33(5), β = 102.42(3), γ = 110.02(2)Њ; 8, monoclinic,
space group P21/c, a = 17.646(4), b = 10.453(2), c = 23.588(9) Å,
¯
β = 103.50(3)Њ; 11, triclinic, space group P1, a = 10.564(2),
[BiI2Ph(4-Mepy)2] 8. This compound was prepared in a
similar manner to 3 using BiI2Ph and a few drops of 4-Mepy.
C18H19BiI2N2 requires C, 29.75; H, 2.65; I, 34.95; N, 3.85.
Found: C, 29.30; H, 2.00; I, 34.50; N, 3.70%.
b = 13.657(3), c = 13.718(3) Å, α = 96.22(3), β = 91.54(3), γ =
103.65(3)Њ.
Crystallographic data for the compounds [(2,6-Me2py)2H]2-
[Bi2Br6Ph2] 12 and [(4-Butpy)2H][4-ButpyH][SbBr4Ph] 13, which
were also characterised as part of this study, have also been
deposited. The dianion in the former is closely similar to that
[4-ButpyH][BiCl3Ph(4-Butpy)] 9. This compound was pre-
pared in a similar manner to 3 using BiCl2Ph and a few
drops of 4-Butpy. Elemental analyses indicated a mixture of
products.
found in [NBun ] [Bi2Br6Ph2]12b although in the example seen
4 2
here a weak π to bismuth interaction is present between one
of the pyridine rings in each of the [(2,6-Me2py)2H]ϩ cations;
2842
J. Chem. Soc., Dalton Trans., 1999, 2837–2843

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7 L. P. Battaglia and A. Bonamartini Corradi, J. Chem. Soc., Dalton
Trans., 1983, 2425.
8 L. P. Battaglia, A. Bonamartini Corradi and G. Pelosi, J. Crys-
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9 W. Clegg, M. R. J. Elsegood, R. J. Errington, G. A. Fisher and
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11 E. V. Avtomonov, X.-W. Li and J. Lorberth, J. Organomet. Chem.,
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12 (a) W. Clegg, R. J. Errington, G. A. Fisher, D. C. R. Hockless,
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aryl π to Bi interactions have been noted in complexes such as
[BiX2Ph(thf)] (X = Cl, Br or I) (B) and arene π to Bi inter-
actions are described in ref. 25. The anion in [(4-Butpy)2H][4-
ButpyH][SbBr4Ph] is analogous to that in [C5H5NH]2[SbCl4Ph]
and contains a hydrogen bonding interaction similar to that
found in 9.26
CCDC reference number 186/1497.
See http://www.rsc.org/suppdata/dt/1999/2837/ for crystallo-
graphic files in .cif format.
Acknowledgements
We thank the EPSRC and Laporte plc for research support
and also R. Herbst-Irmer for useful discussions regarding the
twinning of complex 4.
14 K. H. Ebet, R. E. Schulz, H. J. Breunig, C. Silvestru and I. Haiduc,
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16 C. J. Carmalt, L. J. Farrugia and N. C. Norman, J. Chem. Soc.,
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17 Preliminary observations, S. C. James, Ph.D. Thesis, University of
Bristol, 1999.
18 C. L. Raston, G. L. Rowbottom and A. H. White, J. Chem. Soc.,
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