Evaluation of dispersion type metal···π arene interaction in arylbismuth compounds – an experimental and theoretical study

Article abstract of DOI:10.3762/bjoc.14.187

The dispersion type Bi···π arene interaction is one of the important structural features in the assembly process of arylbismuth compounds. Several triarylbismuth compounds and polymorphs are discussed and compared based on the analysis of single crystal X-ray diffraction data and computational studies. First, the crystal structures of polymorphs of Ph₃Bi (1) are described emphasizing on the description of London dispersion type bismuth···π arene interactions and other van der Waals interactions in the solid state and the effect of it on polymorphism. For comparison we have chosen the substituted arylbismuth compounds (C₆H₄-CHCH₂-4)₃Bi (2), (C₆H₄-OMe-4)₃Bi (3), (C₆H₃-t-Bu₂-3,5)₃Bi (4) and (C₆H₃-t-Bu₂-3,5)₂BiCl (5). The structural analyses revealed that only two of them show London dispersion type bismuth···π arene interactions. One of them is the styryl derivative 2, for which two polymorphs were isolated. Polymorph 2a crystallizes in the orthorhombic space group P2₁2₁2₁, while polymorph 2b exhibits the monoclinic space group P2₁/c. The general structure of 2a is similar to the monoclinic C2/c modification of Ph₃Bi (1a), which leads to the formation of zig-zag Bi–arene_centroid ribbons formed as a result of bismuth···π arene interactions and π···π intermolecular contacts. In the crystal structures of the polymorph 2b as well as for 4 bismuth···π arene interactions are not observed, but both compounds revealed C–H_Ph···π intermolecular contacts, as likewise observed in all of the three described polymorphs of Ph₃Bi. For compound 3 intermolecular contacts as a result of coordination of the methoxy group to neighboring bismuth atoms are observed overruling Bi···π arene contacts. Compound 5 shows a combination of donor acceptor Bi···Cl and Bi···π arene interactions, resulting in an intermolecular pincer-type coordination at the bismuth atom. A detailed analysis of three polymorphs of Ph₃Bi (1), which were chosen as model systems, at the DFT-D level of theory supported by DLPNO-CCSD(T) calculations reveals how van der Waals interactions between different structural features balance in order to stabilize molecular arrangements present in the crystal structure. Furthermore, the computational results allow to group this class of compounds into the range of heavy main group element compounds which have been characterized as dispersion energy donors in previous work.

Full text of DOI:10.3762/bjoc.14.187

Evaluation of dispersion type metal···π arene interaction
in arylbismuth compounds – an experimental
and theoretical study
Ana-Maria Preda1, Małgorzata Krasowska2, Lydia Wrobel1, Philipp Kitschke1,
Phil C. Andrews3, Jonathan G. MacLellan3, Lutz Mertens1, Marcus Korb4, Tobias Rüffer4,
Heinrich Lang4, Alexander A. Auer*2 and Michael Mehring*1
Full Research Paper
Open Access
Address:
Beilstein J. Org. Chem. 2018, 14, 2125–2145.
1Technische Universität Chemnitz, Fakultät für Naturwissenschaften,
Institut für Chemie, Professur Koordinationschemie, 09107 Chemnitz,
Germany, 2Max-Planck-Institut für Kohlenforschung,
Kaiser-Wilhelm-Platz 1, 45470 Mülheim an der Ruhr, Germany,
3School of Chemistry, Monash University, Clayton, Melbourne, VIC
3800, Australia and 4Technische Universität Chemnitz, Fakultät für
Naturwissenschaften, Institut für Chemie, Professur Anorganische
Chemie, 09107 Chemnitz, Germany
doi:10.3762/bjoc.14.187
Received: 19 March 2018
Accepted: 12 July 2018
Published: 15 August 2018
This article is part of the Thematic Series "Dispersion interactions".
Guest Editor: P. Schreiner
Email:
Alexander A. Auer* - alexander.auer@kofo.mpg.de;
Michael Mehring* - michael.mehring@chemie.tu-chemnitz.de
© 2018 Preda et al.; licensee Beilstein-Institut.
License and terms: see end of document.
* Corresponding author
Keywords:
arylbismuth compounds; DFT-D; dispersion type Bi···π arene
interaction; DLPNO-CCSD(T); electronic structure calculations;
polymorphism; single crystal X-ray structure
Abstract
The dispersion type Bi···π arene interaction is one of the important structural features in the assembly process of arylbismuth com-
pounds. Several triarylbismuth compounds and polymorphs are discussed and compared based on the analysis of single crystal
X-ray diffraction data and computational studies. First, the crystal structures of polymorphs of Ph3Bi (1) are described emphasizing
on the description of London dispersion type bismuth···π arene interactions and other van der Waals interactions in the solid state
and the effect of it on polymorphism. For comparison we have chosen the substituted arylbismuth compounds
(C6H4-CH═CH2-4)3Bi (2), (C6H4-OMe-4)3Bi (3), (C6H3-t-Bu2-3,5)3Bi (4) and (C6H3-t-Bu2-3,5)2BiCl (5). The structural analyses
revealed that only two of them show London dispersion type bismuth···π arene interactions. One of them is the styryl derivative 2,
for which two polymorphs were isolated. Polymorph 2a crystallizes in the orthorhombic space group P212121, while polymorph 2b
exhibits the monoclinic space group P21/c. The general structure of 2a is similar to the monoclinic C2/c modification of Ph3Bi (1a),
which leads to the formation of zig-zag Bi–arenecentroid ribbons formed as a result of bismuth···π arene interactions and π···π inter-
molecular contacts. In the crystal structures of the polymorph 2b as well as for 4 bismuth···π arene interactions are not observed, but
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both compounds revealed C–HPh···π intermolecular contacts, as likewise observed in all of the three described polymorphs of
Ph3Bi. For compound 3 intermolecular contacts as a result of coordination of the methoxy group to neighboring bismuth atoms are
observed overruling Bi···π arene contacts. Compound 5 shows a combination of donor acceptor Bi···Cl and Bi···π arene interactions,
resulting in an intermolecular pincer-type coordination at the bismuth atom. A detailed analysis of three polymorphs of Ph3Bi (1),
which were chosen as model systems, at the DFT-D level of theory supported by DLPNO-CCSD(T) calculations reveals how van
der Waals interactions between different structural features balance in order to stabilize molecular arrangements present in the
crystal structure. Furthermore, the computational results allow to group this class of compounds into the range of heavy main group
element compounds which have been characterized as dispersion energy donors in previous work.
Introduction
Although known for more than a century, the interest on that is possible using computational methods allows to gain a
metal···π arene interaction of main group metals has increased deeper understanding of which interactions are dominating.
significantly, both experimentally and theoretically in the past This way, a given crystal structure can be rationalized, for ex-
decade [1-5]. Especially the development of novel computa- ample, as consisting of strongly interacting dimers which them-
tional tools demonstrated the importance of London dispersion selves interact weakly with their surroundings based on the
type interactions for structures and functions of molecules [6-8]. actual interaction energies. Elucidation of this is already
With regard to this the high relevance of London dispersion possible at the DFT-D level of theory, if functionals with estab-
type interactions in molecular organometallic chemistry was lished accuracy are used, or at the DLPNO-CCSD(T) level of
recently summarized by Liptrot and Power [9]. It should be theory, which yields near-quantitative accuracy from first prin-
noted that in this context and more generally organometallic ciples and can be applied to fairly large systems [32-38].
bismuth compounds are witnessing growing attention since ap-
plications in the field of supramolecular chemistry [10-12] and Herein, we report on intermolecular interactions with focus on
pharmacology are of interest [13-15].
bismuth···π arene interactions for the crystal structures of three
polymorphs of Ph3Bi (1). For comparison the crystal structures
Lately, several studies regarding the metal···π interactions in of substituted arylbismuth compounds of the type Ar3Bi
organometallic compounds of antimony and bismuth [16-19] [Ar = C6H4-CH═CH2-4 (2a, 2b), C6H4-OMe-4 (3)], Ar'3Bi (4)
have been reported including intramolecular [20-22] and inter- and Ar'2BiCl (5, Ar' = C6H3-t-Bu2-3,5) were analyzed with
molecular coordination [23,24]. Special attention was given to regard to their packing in the solid state. Electronic structure
bismuth···π arene interaction by us including the formation of calculations were carried out on Ph3Bi···C6H6 and selected
dimers and networks [1,25-28], and recently we reported a polymorphs of Ph3Bi (1). For this purpose, a series of elec-
study on the effect of intermolecular dispersion type interaction tronic structure methods are applied for a model compound in
on polymorphism and phase transition of compounds of the order to assess the performance of different methods and to
type Ar3Bi (Ar = C4H3NMe, C4H3O, C4H3S, C4H3Se) [28,29]. conceptually investigate and quantify the heavy main group ele-
ment···π interaction present in these type of compounds. In the
Other state of the art examples on the formation of supramolec- second part, DFT-D and DLPNO-CCSD(T) calculations are
ular assemblies via dispersion type metal···π arene intermolecu- carried out for a series of molecular structures, dimers, trimers
lar interactions [10,11] were summarized by Caracelli et al., and and tetramers that have been taken from the crystal structures of
recently Tiekink classified this type of interaction as one of the three selected polymorphs of compound 1. This allows to quan-
emerging intermolecular interactions that are of particular tify and to rationalize the balance of dispersion type interac-
interest to coordination chemists with regard to supramolecular tions between bismuth and aromatic ligands as well as between
chemistry [12]. However, most reports on main group metal···π the aromatic ligands itself.
interactions are based on the description of the single crystal
Results and Discussion
structures and lack a profound description of the theoretical
background so far. Rare examples on theoretical work about the Synthesis
pnictogen···π interaction were given by Frontera et al. [30,31]. So far, four polymorphs of Ph3Bi (1) have been reported in the
While analysis of structural parameters like interatomic dis- literature [39-45], but none of these reports contains an analysis
tances allows to assess the plausibility of certain interactions, of dispersion type interactions including bismuth···π interaction
this is exceedingly difficult and sometimes misleading for weak in the solid state. This prompted us to have a closer look at
intermolecular interactions. Here, the accurate quantification these simple organometallic compounds. Noteworthy, the first
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report on the synthesis of Ph3Bi dates back to 1887, which was 84% yield. The synthesis of 2 with very low yield is mentioned
based on the reaction of sodium alloy and bromobenzene in a patent from 1964 [49], but 2 was neither fully character-
[46,47]. A more convenient synthetic route makes use of the ized, nor was its crystal structure determined. We were able to
Grignard reagent phenylmagnesium bromide and its reaction crystallize two polymorphs of 2, an orthorhombic form 2a
with bismuth trichloride [48]. Following this approach with and a monoclinic form 2b, both were obtained from iPrOH
slight modifications provides Ph3Bi with a yield of more than solution.
80%. Crystallization from EtOH gave single crystals of the
monoclinic C2/c polymorph 1a, which was already subject of In order to develop a better understanding with regard to the
several studies including the description of its crystal structure effects of substituents, (C6H4-OMe-4)3Bi (3) [50,51] was pre-
[39-43]. Therefore, it is somewhat surprising that the pared starting from BiCl3 and the corresponding organolithium
bismuth···π interaction was not noted so far. We obtained poly- reagent following a general method as reported by Wang et al.
morph 1a upon crystallization from solution, but we isolated [52]. Compound 3 was obtained as colorless block-shaped crys-
another polymorph 1b by crystallization from the melt. Poly- tals in yields of 83%. While our work was in progress, a crystal
morph 1b was obtained starting from 1a in a temperature-de- structure of 3 was reported by Gagnon et al. The authors con-
pendent PXRD experiment (see Supporting Information File 1, firmed the formation of 3 from the corresponding Grignard
Figure S1). The polymorph 1b was obtained as a microcrys- reagent and BiCl3 upon crystallization at 20 °C by diffusion of
talline material, but Andrews and MacLellan did obtain single n-hexane into CH2Cl2 solution [53], but only gave a very brief
crystals on this orthorhombic form 1b prior to this study [45]. description of the molecular structure.
Noteworthy, a phase transition of 1a to 1b does not occur
before melting.
The Ar3Bi compound (C6H3-t-Bu2-3,5)3Bi (4) was prepared
with a yield of 73% following the Grignard route, with the
The latest report on a polymorph of Ph3Bi was made by intention to study the influence of very bulky substituents.
Stammler and Neumann, which submitted the crystallographic Finally its chloro derivative (C6H3-t-Bu2-3,5)2BiCl (5) was syn-
data of a monoclinic P21/c (1c) polymorph to the Cambridge thesized in 11% yield using the organolithium derivative
Crystallographic Data Base [44]. In addition a monoclinic poly- (C6H3-t-Bu2-3,5)Li and BiCl3.
morph 1d was mentioned in a brief report of Wetzel as early as
1942, but the atomic parameters were not given [39].
This series of compounds and polymorphs (Scheme 1) allows to
deduce some general trends regarding dispersion type interac-
Following the Grignard route we were able to develop a tions including bismuth···π, π···π and C–H···π interactions in
straightforward synthetic protocol for (C6H4-CH═CH2-4)3Bi organobismuth compounds and therefore the crystal structures
(2) starting from 4-bromostyrene and isolated compound 2 with are described and discussed in the following chapter. Please
Scheme 1: Triarylbismuth compounds, that serve as examples for the investigation of bismuth···π interactions in the solid state.
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note that the term C–H···π is used as a structure descriptor rather captions. Here, we focus mainly on the description of the
than to describe a special type of bonding. Thus we follow the supramolecular arrangements of these compounds in the solid
criticism given by Grimme [54] and Iverson et al. [55] on the state.
unreflected use of terms such as C–H···π, or π···π stacking previ-
ously. In most cases, these interactions rely on London disper- In the literature several reports exist on the monoclinic poly-
sion forces rather than special types of bonding due to the morph of Ph3Bi (1a), which crystallizes in the space group C2/c
π system.
[39-43]. The Bi···π arene interactions range from
3.727–3.856 Å, leading to the formation of 1D ribbons in the
solid state due to Bi···π arene interactions (see zig-zag
Crystal structures
In all of the presented compounds, the arrangement at the (Bi–arenecentroid)∞ chain in Figure 1a). These chains are further
bismuth atom is best described as a slightly distorted trigonal connected via C–HPh···π (arenecentroid) intermolecular contacts
pyramid, with the C–Bi–C angles significantly smaller than the with C33–H33Ph···π (arenecentroid) distances of 3.030 Å (blue
tetrahedral angle, indicating that the lone pair is of mainly dashed line), γ = 10.9°, (two parallelograms connected via one
6s character [41]. The Bi–C distances and C–Bi–C angles corre- edge in Figure 1b). Furthermore, two C–HPh···π (arenecentroid)
spond to bond lengths and angles as observed for the various intermolecular contacts are observed with C14–H14Ph···π
modifications of Ph3Bi [1,39,41-44] and other Ar3Bi (arenecentroid) distances of 3.042 Å (green dashed line,
compounds (Ar = Mes [56], p-Tolyl [57]). The molecular γ = 19.5°) and C15–H15Ph···π (arenecentroid) distances of
structures of 2a, 2b, 4 and 5 are illustrated in Figures S1–S4 2.760 Å (black dashed line, γ = 6.4°) to give a 2D network
(Supporting Information File 1), the selected bond (Figure 1c). Other additional C–HPh···π (arenecentroid) intermo-
lengths and angles are listed in the corresponding figure lecular contacts with C36–H36Ph···π (arenecentroid) distances of
Figure 1: Ball and stick model of a fragment of a) the zig-zag chain of a 1D arrangement of Ph3Bi (1a). Hydrogen atoms were omitted for clarity.
Selected distances [Å]: Bi1–arenecentroid 3.763 (violet dash line) [39-43]; b) formation of the two parallelograms connected via one edge, formed via
two C–HPh···π (arenecentroid) intermolecular contacts with C33–H33Ph···π (arenecentroid) 3.030 Å (blue dashed line, γ = 10.9°); c) wire and stick model
of 2D and 3D networks formed via C–HPh···π (arenecentroid) intermolecular contacts C14–H14Ph···π (arenecentroid) distances of 3.042 Å (green dashed
line, γ = 19.5°), C15–H15Ph···π (arenecentroid) distances of 2.760 Å (black dashed line, γ = 6.4°) and C36–H36Ph···π (arenecentroid) distances of 2.740
Å (red dashed line, γ = 11.2°), respectively (only hydrogen atoms involved in C–HPh···π (arenecentroid) contacts are shown). Symmetry transformation:
a = x, 1 + y, z; b = 1∕2 – x, 3∕2 – y, –z; c = 1∕2 – x, 5∕2 – y, –z.
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2.740 Å (red dashed line, γ = 11.2°) lead to the formation of a
3D network in the solid state (Figure 1c). The
C–HPh···arenecentroid contacts are shorter than 3.1 Å with an
angle γ between the normal to the arene ring and the line
defined by the H atom and the arenecentroid smaller than 30°
[58,59].
The polymorph 1b crystallizes in the orthorhombic space group
Pna21 [45]. The crystal structure of polymorph 1b shows two
different bismuth atoms in the unit cell, each of them being
involved in Bi···π arene intermolecular interactions, with
Bi2–arenecentroid 3.468 Å (grey dashed line in Figure 2) and
Bi1–arenecentroid 3.561 Å (blue dashed line in Figure 2), thus re-
sulting in zig-zag type 1D ribbons. In addition C–HPh···π
(arenecentroid) intermolecular contacts with C17–H17Ph···π
(arenecentroid) 3.083 Å (γ = 9.5°) and C29–H29Ph···π
(arenecentroid) 3.097 Å, (γ = 16.4°, green and purple dashed line
in Figure 2a, respectively) complement the structure. The
ribbons are connected via two additional C–HPh···π
(arenecentroid) intermolecular contacts with C15–H15Ph···π
(arenecentroid) 3.034 Å (black dashed line, γ = 8.4°) and
C28–H28Ph···π (arenecentroid) 2.890 Å (brown dashed line,
γ = 13.5°) and lead to the formation of a 2D network
(Figure 2b).
Figure 2: Ball and stick model of a fragment of the zig-zag type
arrangement of Ph3Bi (1b) [45], view along the b axis. Hydrogen atoms
were omitted for clarity. Selected distances [Å]: Bi1–arenecentroid 3.561
(blue dashed line), Bi2–arenecentroid 3.468 (grey dash line); a) the for-
mation of dimers via two C–HPh···π (arenecentroid) intermolecular
contacts with C17–H17Ph···π (arenecentroid) 3.083 Å (green dashed
line, γ = 9.5°) and C29–H29Ph···π (arenecentroid) 3.097 Å (γ = 16.4°);
b) wire and stick model of a 2D network build via additional C–HPh···π
(arenecentroid) intermolecular contacts with C15–H15Ph···π
Another polymorph of Ph3Bi (1c) was reported by Neumann
and co-workers in a CSD communication. The polymorph 1c
crystallizes in the monoclinic space group P21/c [1,44]. The
crystal structure of polymorph 1c reveals the formation of non-
centrosymmetric dimers in the solid state, which are formed via
two Bi···π arene intermolecular contacts (Figure 3a). These dis-
(arenecentroid) 3.034 Å (black dashed line), (γ = 8.4°) and
C28–H28Ph···π (arenecentroid) 2.890 Å (brown dashed line, γ = 13.5°),
(only hydrogen atoms involved in C–HPh···π (arenecentroid) contacts
are shown). Symmetry transformations: a = x, y, 1 + z.
tances amount to Bi1–arenecentroid 3.787 Å (green dashed line) (C6H4-CH═CH2-4)3Bi (2)
and Bi2–arenecentroid 3.939 Å (lime dashed line). A closer look Crystallization of (C6H4-CH═CH2-4)3Bi (2) from iPrOH solu-
at the crystal structure of polymorph 1c reveals that the dimeric tion gave pale yellow crystals, which either form needles or
units self-assemble via C–HPh···arenecentroid contacts, which rarely a more compact morphology. Both types of crystals of 2
leads to the formation of centrosymmetric units, based on were suitable for single crystal X-ray diffraction analysis and
C–HPh···π (arenecentroid) intermolecular contacts (four-mem- revealed the formation of two polymorphs 2a (colorless acic-
bered ring in Figure 3b), with C20–H20Ph···π (arenecentroid) ular crystals) and 2b (light yellow block-shaped crystals) in the
2.801 Å (dark red dashed line, γ = 12.3°) and C27–H27Ph···π solid state. Polymorph 2a crystallizes in the orthorhombic space
(arenecentroid) 2.763 Å (teal dashed line, γ = 12.6°), (1D layers group P212121 (Figure 4), while the crystal structure analysis of
in Figure 3b), respectively. Additionally, the 1D layers are polymorph 2b revealed the monoclinic space group P21/c
connected via two C–HPh···π (arenecentroid) intermolecular (Figure 5).
contacts, with C3–H3Ph···π (arenecentroid) 3.037 Å (blue dashed
line, γ = 7.9°) to give a 3D network in the solid state For 2a Bi···π arene interactions between the bismuth atom and
(Figure 3c).
the aryl ring of the neighboring molecule are deduced, which
leads to the formation of zig-zag Bi–arenecentroid chains along
It is worth to note that Wetzel has reported another crystal the crystallographic axis (1D ribbons in Figure 4a). The
structure of Ph3Bi (1d) in 1942, which crystallizes in the Bi–arenecentroid distance amounts at 3.835 Å (ΣvdW (Bi–C) =
triclinic space group
[39]. Unfortunately, the crystal struc- 3.77–4.31 Å), which corresponds to the distances of 3.47 to
ture of the latter could not be analyzed by us due to the lack of 3.96 Å, as reported for the polymorphs of Ph3Bi [1,39,41-44].
atomic parameters.
The overall crystal structure of 2a is very similar to the mono-
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Figure 3: Ball and stick model of Ph3Bi (1c) showing: a) non-centrosymmetric dimers formed via two Bi···π arene intermolecular contacts. Hydrogen
atoms were omitted for clarity. Selected distances [Å]: Bi1–arenecentroid 3.787 (green dashed line), Bi2–arenecentroid 3.939 (lime dash line) [1,44]; b)
the formation of a four-membered ring of a 1D layer build via two C–HPh···π (arenecentroid) intermolecular contacts with C20–H20Ph···π (arenecentroid)
2.801 Å (dark red dashed line, γ = 12.3°) and C27–H27Ph···π (arenecentroid) 2.763 Å (teal dashed line, γ = 12.6°); c) the formation of a 3D network
build via additional C–HPh···π (arenecentroid) intermolecular contacts with C3–H3Ph···π (arenecentroid) 3.037 Å (blue dashed line, γ = 7.9°), (only hydro-
gen atoms involved in C–HPh···π (arenecentroid) contacts are shown). Symmetry transformation: a = 2 – x, –y, 1 – z; b = 1 – x, –y, 1 – z.
Figure 4: Wire and stick representation of (C6H4-CH═CH2-4)3Bi (2a) showing: a) zig-zag chains of 1D ribbons formed via Bi···π arene intermolecular
contacts (Bi1–arenecentroid 3.835 Å), accompanied by πPh···πvinyl contacts of 3.798 Å and the formation of 2D network via C16B–H16Bvinyl···π
(arenecentroid) 2.980 Å (violet dashed line, γ = 14.5°); b) the formation of the 3D network via C5–H5···π (arenecentroid) 3.094 Å (black dashed line,
γ = 26.0°, only hydrogen atoms involved in C–HPh···π (arenecentroid) contacts are shown). Symmetry transformations: a = 1 + x, y, z; b = –1 + x, y, z.
clinic C2/c modification of Ph3Bi (1a) [41-43]. Additionally, arrangement between a bismuth atom, an aryl ligand, and the
short π···π distances were observed between one of the vinyl vinyl group with an angle of 171.8° is observed (Figure 4a).
groups and the aryl ligand, with a distance from the centroid of
the aromatic ring to the midpoint of the C═C double bond of In 2a each Bi···π arene contact is accompanied by a πPh···πvinyl
3.798 Å. The angle to the plane through the aryl ligand of the contact (orange dashed line in Figure 4a). The 1D chains are
neighboring molecule amounts at 13.1° and thus a nearly linear connected via C–Hvinyl···π (arenecentroid) intermolecular
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contacts with C16B–H16Bvinyl···π (arenecentroid) 2.980 Å (violet (C6H4-OMe-4)3Bi (3)
dashed line, γ = 14.5°) to form a 2D network (Figure 4a). Addi- (C6H4-OMe-4)3Bi (3) crystallized from CHCl3 in the form of
tional C–HPh···π (arenecentroid) intermolecular contacts with colorless cube-shaped or block-shaped crystals which were suit-
C5–H5···π (arenecentroid) of 3.094 Å (black dashed line, able for single crystal X-ray structure analysis. Compound 3
γ = 26.0°) lead to the formation of a 3D network in the solid crystallizes in the trigonal space group
(Figure 6). While
state (Figure 4b). By contrast, the crystal structure of 2b did not our work was in progress, Gagnon and co-workers reported the
show any Bi···π arene interaction, and it reveals only the pres- crystal structure of 3, which exhibits very similar lattice param-
ence of C–HPh···arenecentroid contacts. Two sorts of C–HPh···π eters [64]. However, the packing structure has not been dis-
(arenecentroid) intermolecular contacts, with C11–H11Ph···π cussed in detail and thus its description is given here.
(arenecentroid) 2.817 Å (cyan dashed line, γ = 8.5°) and
C18–H18Ph···π (arenecentroid) 2.940 Å (dark blue dashed line, A closer look at the bismuth environment reveals that for the
γ = 10.0°) are observed (Figure 5a). Furthermore, additional molecular structure of 3 the bismuth atom might be described as
C–Hvinyl···π (arenecentroid) intermolecular contacts with six-coordinated being surrounded by six 4-methoxyphenyl
C16Bb–H16Bbvinyl···π (arenecentroid) 2.960 Å (green dashed groups. Three of them are bonded covalently to bismuth with
line, γ = 25.0°) lead to the formation of a 2D network, while Bi–C of 2.248(3) Å and three units are bonded via weaker
other intermolecular contacts with C24Ac–H24Acvinyl···π Bi···O interactions, which have identical values (Bi···O
(arenecentroid) of 2.904 Å (brown dashed line, γ = 7.0°) result in 3.781 Å), finally leading to a [3 + 3] coordination (van der
the formation of a 3D network (Figure 5b). The Bi···Bi contacts Waals radii ΣvdW (Bi,O) = 3.57–4.09 Å) [60-62]. The
are considerably shorter than the sum of the van der Waals radii 4-methoxyphenyl moieties are pointing via the oxygen atoms to
of bismuth atoms (Bi···Bi contacts of 4.046 Å; ΣrvdW(Bi, Bi) the bismuth atom, which actually hinders the formation of
4.08–5.14 Å)) [60-62] and are in good agreement with the ones bismuth Bi···π arene interactions. A similar coordination envi-
r e p o r t e d r e c e n t l y i n
a t h e o r e t i c a l s t u d y b y ronment was observed in the case of the two polymorphs of
Jansen and co-workers who discussed dispersion type Bi···Bi (2-C4H3S)3Bi, where three thienyl molecules of the neigh-
interactions in the context of structure formation in R3Bi boring molecules interact with Ar3Bi [29]. The oxygen atoms of
compounds (Bi···Bi contacts vary between 4.015 and 4.059 Å) the methoxy groups each interact with the bismuth atom of a
[63].
neighboring molecule in a way that each bismuth atom inter-
Figure 5: Wire and stick model of (C6H4-CH═CH2-4)3Bi (2b) showing: a) the formation of 1D ribbons build via two C–HPh···π (arenecentroid) intermo-
lecular contacts with C11–H11Ph···π (arenecentroid) 2.817 Å (cyan dashed line, γ = 8.5°) and C18–H18Ph···π (arenecentroid) 2.940 Å (dark blue dashed
line, γ = 10.0°); b) 2D network formed via C16Bb–H16Bbvinyl···π (arenecentroid) 2.980 Å (γ = 25.0°) and a 3D network formed via C24Ac–H24Acvinyl···π
(arenecentroid) of 2.904 Å (γ = 7.0°), (only hydrogen atoms involved in C–HPh···π (arenecentroid) contacts are shown). Symmetry transformation: a = 1 –
x, 1 – y, 1 – z; b = 1 + x, y, 1 + z; Bi···Bi of 4.046 Å.
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Figure 6: Molecular structure of (C6H4-OMe-4)3Bi (3) showing: a) Thermal ellipsoids that are set at 50% probability level. Hydrogen atoms were
omitted for clarity. Symmetry transformations: a = –x + y + 2, –x + 1, z; b = – y + 1, x – y – 1, z; c = 7∕3 – x + y, 5∕3 – x, –1∕3 + z; d = 2∕3 + x, –1∕3 + y,
–1∕3 + z; e = 4∕3 + y, –4∕3 + x – y, –1∕3 + z. Selected bond lengths [Å]: Bi1–C1 2.248(3), Bi1–C1a 2.248(3), Bi1–C1b 2.248(3), Bi1–O1c 3.781, Bi1–O1d
3.781, Bi1–O1e 3.781. Selected bond angles [°]: C1–Bi1–C1a 93.7(11), C1–Bi1–C1b 93.7(11), C1a–Bi1–C1b 93.7(11), O1c–Bi1–O1d 69.6,
O1c–Bi1–O1e 69.6, O1d–Bi1–O1e 69.6; b) wire and stick representation of a 3D network built via Bi···O intermolecular interactions and via two
C–HPhyl···π (arenecentroid) intermolecular contacts C3–H3Ph···π (arenecentroid) 3.005 Å (blue dashed line, γ = 14.7°) and C5–H5Ph···π (arenecentroid)
2.845 Å (green dashed line, γ = 11.6°).
acts with three oxygen atoms of different neighbors. In the re- 2.884 Å (blue dashed line, γ = 7.8°), C37–H37Cat-Bu···π
sulting three-dimensional structure, one molecule of 3 interacts (arenecentroid) 3.012 Å (brown dashed line, γ = 11.5°) and
with six other molecules (Figure 6b). Similar Bi···O interac- C95–H95Bct-Bu···π (arenecentroid) 3.002 Å (green dashed line,
tions are also found in tris(2-methoxyphenyl)- and γ = 6.5°) in Figure 7, respectively. The presence of
tris(2,4-dimethoxyphenyl)bismuthine [65]. However, the bismuth···π arene interactions could not be observed
coordination sphere of the bismuth atoms in these most probably due to the bulky t-Bu groups attached to
compounds is complemented intramolecularly through the the aryl ligands, which hinder the interactions of the bismuth
methoxy groups in the ortho position (Bi···O of 3.05 Å and atom with the aryl ligands of the neighboring molecules
3.15 Å) [65].
(Figure 7).
The crystal structure of 3 did not show any Bi···π arene interac- The crystal structure analysis of 5 revealed intermolecular
tion, but reveals the presence of C–HPh···arenecentroid contacts. donor acceptor Bi···Cl interactions of Bi1–Cl1b 2.805(7) Å,
These intermolecular C–HPh···π (arenecentroid) contacts amount which are accompanied by Bi···π arene contacts of
to C3–H3Ph···π (arenecentroid) 3.005 Å (blue dashed line, Bi1–arenecentroid 3.725 Å. This arrangement results in a sort of
γ = 14.7°) and C5–H5Ph···π (arenecentroid) 2.845 Å (green intermolecular pincer-type coordination of the bismuth atom,
dashed line, γ = 11.6°, Figure 6b).
and thus in the formation of a 1D chain in the solid state
(Figure 8). Due to the Bi···π arene interactions, the local geome-
try of the bismuth atom becomes distorted square pyramidal
with one carbon atom of the (C6H3-t-Bu2-3,5) ligand in the
(C6H3-t-Bu2-3,5)3Bi (4) and
(C6H3-t-Bu2-3,5)2BiCl (5)
Colorless single crystals suitable for X-ray crystallography were axial positions and the two chlorine atoms, another carbon atom
isolated upon crystallization from a CH2Cl2 solution at ambient of the aryl ligand and the arenecentroid placed in the equatorial
temperature (for 4) and at −28 °C (for 5). Compounds 4 and positions, describing the basal plane. This is reflected
5·2CH2Cl2 crystallize in the hexagonal space group P63 and in the bond angles of C15–Bi1–arenecentroid 89.7°,
orthorhombic space group Pna21, respectively. The crystal C15–Bi1–Cl1 90.9(10)°, C15–Bi1–Cl1b 92.7(9)°, and
structure of compound 4 does not exhibit any Bi···π arene inter- C1–Bi1–C15 92.4(10)°. Besides these contacts, the crystal
actions, but shows four C–Ht-Bu···π (arenecentroid) intermolecu- structure of 5 revealed short C–Ht-Bu···π (arenecentroid) contacts
lar contacts, with C14–H14C1at-Bu···π (arenecentroid) 2.877 Å for C9–H9At-Bu···π (arenecentroid) 2.662 Å (brown dashed line,
(black dashed line, γ = 10.7°), C27–H27Cbt-Bu···π (arenecentroid) γ = 7.4°).
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Figure 7: Wire and stick model of (C6H3-t-Bu2-3,5)3Bi (4) showing a 3D network build via four C–Ht-Bu···π (arenecentroid) intermolecular contacts with
C14–H14Cat-Bu···π (arenecentroid) 2.877 Å (black dashed line, γ = 10.7°), C27–H27Cbt-Bu···π (arenecentroid) 2.884 Å (blue dashed line, γ = 7.8°),
C37–H37Cat-Bu···π (arenecentroid) 3.012 Å (brown dashed line, γ = 11.5°) and C95–H95Bct-Bu···π (arenecentroid) 3.002 Å (green dashed line, γ = 6.5°),
(only hydrogen atoms involved in C–Ht-Bu···π (arenecentroid) contacts are shown). Symmetry transformation: a = x, y, 1 + z; b = 1 – y, 1 + x – y, 1 + z; c
= 1 + x – y, 1 + x, 1∕2 + z; d = –1 + y, –x + y, 1∕2 + z.
Figure 8: Wire and stick model of (C6H3-t-Bu2-3,5)2BiCl (5) showing a fragment of the 1D arrangement, view along the b axis. Symmetry transforma-
tions: a = 2 – x, –y, 1∕2 + z; b = 2 – x, –y, –1∕2 + z. Selected bond lengths and distances [Å]: Bi1–Cl1 2.811(7), Bi1–Cl1b 2.805(7), Bi1a–Cl1 2.805(7),
Bi1–arenecentroid 3.725. Selected bond angles [°]: C15–Bi1–Cl1 90.9(10), C15–Bi1–Cl1b 92.7(9), C(15)–Bi(1)–arenecentroid 89.7, Cl1–Bi1–Cl1b
171.5(17), Bi1–Cl1–Bi1a 112.6(19). C–Ht-Bu···π (arenecentroid) intermolecular contacts, C9–H9At-Bu···π (arenecentroid) 2.662 Å (brown dashed line),
(γ = 7.4°).
As shown in this section, the crystal structures of 1–5 described donor (DED) only in some cases. In the absence of strong donor
above revealed the presence of London dispersion type interac- acceptor type interactions a competition between the different
tions in the solid state, with bismuth acting as dispersion energy types of dispersion interactions (Bi···π, π···π or C–H···π) is ob-
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served and thus leads to different structural features in the solid present in the polymorphs of compound 1 can be also found in
state (Table 1). Here the question arises how important and how polymorphs of compound 2.
large these interactions are and whether any type of interaction
is dominating. For this reason computational studies have been We will proceed as follows: First, an idealized model com-
performed with the focus on the crystal structures of three poly- pound is studied such that the basic Bi···π interaction can be
morphs of Ph3Bi (1), which revealed either the formation of classified in comparison to other systems previously studied.
non-centrosymmetric dimers as basic building block, or the for- Then, we will turn to the crystal structures of polymorph 1a, 1b,
mation of 1D ribbons (i.e., zig-zag type). Both are based on and 1c and investigate each polymorph in terms of intermolecu-
bismuth···π arene interactions: the formation of 2D networks is lar interactions to assess which influences are decisive for struc-
built up via C–HPh···π intermolecular contacts of T-shape. Note- ture formation. For this purpose, several tetrameric units have
worthy, polymorph 2a showed bismuth···π and π···π interac- been extracted from the crystal structure for each polymorph.
tions leading to 1D ribbons in the solid state, while 2b did not This way, all relevant intermolecular interactions in the solid
reveal Bi···π interactions. Thus, it is concluded that Bi···π, π···π state can be studied based on monomer distortion, intermolecu-
and C–H···π interactions must be of similar strength. Similar to lar interactions of representative dimers and the interaction of
the situation of 2b, compound 4 did not show any bismuth···π one molecule with several of its neighbors.
arene interactions, but also exhibits C–Ht-Bu···π intermolecular
Distance scan for the idealized
contacts. In compounds 3 and 5 intermolecular Bi···O and
Bi···Cl bonds are dominating.
BiPh3···benzene complex
In a previous study on the nature of Bi···π arene interactions in
various benzene complexes with BiR3 (with R = Me, OMe, and
Cl), we found that interaction energies for this type of com-
Electronic structure calculations on selected
polymorphs of Ph3Bi
In order to assess the role of dispersion interactions for the exis- pounds range from −10 kJ mol−1 to −40 kJ mol−1. The char-
tence of structural features in compounds including Bi···π inter- acter of the interaction varies from purely dispersive for BiMe3
actions, we focus our study on the wealth of structural informa- to dispersive with pronounced donor–acceptor character in case
tion for BiPh3 (compound 1). Note that various structural motifs of Bi(OMe)3 and BiCl3 complexes [66,67]. In order to assess
Table 1: Various intermolecular distances observed in the crystal structures of arylbismuth compounds.
Bi···π
intermolecular
distances
π···π
intermolecular
distances
C–H···π
intermolecular
distances
Bi···O/Cl
intermolecular
distances
structural
features
Ph3Bi (1)
polymorph 1a
3.763 Å
3.030 Å
3.042 Å
2.760 Å
2.740 Å
3D network
2D network
3D network
polymorph 1b
polymorph 1c
3.468 Å
3.561 Å
3.083 Å
3.097 Å
3.034 Å
2.890 Å
3.787 Å
3.939 Å
2.801 Å
2.763 Å
3.037 Å
(C6H4-CH═CH2-4)3Bi (2)
polymorph 2a
3.835 Å
3.798 Å
1D ribbons
1D ribbons
polymorph 2b
2.817 Å
2.940 Å
(C6H4-OMe-4)3Bi (3)
3.005 Å
2.845 Å
3.781 Å
3D network
3D network
(C6H3-t-Bu2-3,5)3Bi (4)
2.877 Å
2.884 Å
3.012 Å
3.002 Å
(C6H3-t-Bu2-3,5)2BiCl (5)
3.725 Å
2.662 Å
2.811 Å
2.805 Å
1D ribbons
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the nature of the interaction in the BiPh3···π complexes (com- a distance of 3.66 Å and to −17 kJ mol−1. Note that the Bi···π
pound 1), rigid potential energy surface scans for the idealized arene contact minimum distance is shorter than for 1a, 1c, and 2
BiPh3–benzene complex were performed at the PBE-D3 and but slightly longer than for 1b (see Table 1). The curve for the
DLPNO-CCSD(T) level of theory. The idealized structure was interaction energy without dispersion contribution (Figure 9,
constructed in order to disentangle pure Bi···π arene interaction E(int-disp)) is slightly attractive.
from the influence of substituents. The interaction potential
curve is shown in Figure 9. The distance scans obtained at the The interaction energy of the BiPh3 complex is higher than the
PBE-D3 level of theory are in good agreement with the interaction energy obtained for BiMe3 but smaller than for
DLPNO-CCSD(T) results which shows that using the PBE-D3 Bi(OMe)3 (see Figure 10a), however, the dispersion contribu-
functional is a cost efficient alternative to the DLPNO- tion to the interaction energy in the BiPh3 complex (see
CCSD(T) method. The minimum on the DLPNO-CCSD(T) Figure 10b) is comparable to the dispersion contributions in
potential energy curve estimated by interpolation corresponds to other BiR3–benzene complexes. This implies that the character
Figure 9: Computed interaction potentials of the distance scan for the idealized BiPh3–benzene complex. E(int) denotes the interaction energy ob-
tained at the particular level of theory, E(disp) denotes the dispersion energy, E(int-disp) – the interaction energy without the dispersion contribution.
Figure 10: a) The BiPh3 potential energy curve for idealized interaction structures compared to the interaction energy curves for the series of com-
pounds BiR3···C6H6 with R = Me, OMe, Cl obtained at the DLPNO-CCSD(T) level of theory. b) Dispersion energy contributions according to LED
(DLPNO-CCSD(T)) for the distance scans shown in Figure 9.
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of the interaction in the BiPh3–benzene complex is closer to that were then visualized as DED plots and are shown in Figures 12,
of BiMe3 rather than to Bi(OMe)3 and that the interaction is 14, and 16. The structures and interaction energies of all studied
dominated by dispersion with minor contribution of π-stacking dimers are given in Supporting Information File 1
donor–acceptor character.
(see Figures S12–S14 and Table S4 in Supporting Information
File 1). Please note that the positions of the hydrogen atoms in
the tetrameric and dimeric structures were optimized at the
PBE-D3/def2-TZVP level of theory. Hence, the intermolecular
Computational description of the polymorphs
of BiPh3
In this section we address the question which factors influence distances involving C–H groups may vary from the crystallo-
the structure in solid state for BiPh3 and what possible intermo- graphic data given in the previous sections.
lecular interactions within the polymorphs of compound 1 are.
As mentioned already earlier several tetrameric units of poly- Polymorph 1a
morphs of compound 1 were chosen in order to obtain a simpli- In case of polymorph 1a three different tetramers were chosen
fied description of the crystal structure. These tetramers contain that are shown in Figure 11. The simplest tetramer 1a-1 consists
the information on the different intermolecular interactions of linear chains of BiPh3 molecules belonging to one layer. It is
present in the solid state of BiPh3. The structures of the studied built from three equivalent Bi···phenyl dimers with an interac-
tetramers are shown in Figures 11, 13, and 15. Subsequently, tion energy of −46 kJ mol−1 (computed at the PBE-D3/def2-
tetramers were divided into dimeric units that represent specific TZVP level of theory, depicted in Figure 11 as Edim3_2).
intermonomer interactions, and can be considered as building Tetramers 1a-2 and 1a-3 are constructed from two Bi···π arene
blocks of the bulk. Monomer distortion energies (geometry dimers of two different layers of BiPh3 molecules. Within these
preparation; denoted as Eprep in Figures 11, 13, and 15) were two tetramers not only Bi···π arene interactions are present but
computed in order to gain knowledge on crystal packing effects. also π-stacking contacts of monomers between two layers. In
The distortion energy is obtained as the difference between the tetramer 1a-2 three C–HPh···π stacking interactions can be
energy of a single relaxed molecule and the energy of an unre- found. Two equal interactions between monomers 2 (green;
laxed molecule in the crystal structure geometry. Important numbering of the monomers is the same as the numbering of the
information on the intermolecular interaction strength within Bi atoms within a specific tetramer as depicted in Figure 11)
the tetramer is obtained when one monomer is removed from and 3 (red), and monomers 1 (grey) and 4 (blue). There is also a
the system. This energy (depicted as Eremove in Figures 11, 13, C–HPh···π type interaction between monomers 2 (green) and 4
and 15) contains the interactions with neighboring molecules (blue). All of these dimers have interaction energies of
and also possible long-range interactions within the tetramer. −29 kJ mol−1 (depicted in Figure 11 as Edim2_3 and Edim2_4) in-
This energy is determined as a difference between the interac- dicating that they are interacting fairly strongly. Similarly, in
tion energies of a tetramer and trimer formed after removing the tetramer 1a-3 three π-stacking interactions between monomers
appropriate monomer.
can be found. Two of them (monomers 1 and 4, and 2 and 3) are
equivalent and their interaction energy amounts to −42 kJ mol−1
The interaction energies of all tetramers and dimers were com- indicating strong interactions between the layers. The next
puted at the PBE-D3/def2-TZVP level of theory and are neighbor interaction between monomers 2 (green) and 4 (blue)
depicted in Figures 11, 13, and 15 as Etetramer and Edim, respec- in tetramer 1a-3 is much weaker and amounts to −15 kJ mol−1.
tively. A color code is introduced in Figures 11, 13, and 15 to
facilitate the understanding of the construction of tetramers and The distortion energies (Eprep) of the monomers in polymorph
dimers. A different color is ascribed to each monomer within 1a are quite large and amount to almost 17 kJ mol−1. This indi-
the tetramer. The interaction energies were computed with cates that, although the interactions between specific mono-
reference to the sum of the energies of all unrelaxed monomers mers to form dimeric structures by Bi···π arene are strong, the
(crystal structure geometry) included in the tetramer or dimer. crystal packing effects are significant in this case.
Interaction energies of tetrameric, trimeric, and dimeric struc-
tures can yield information about the additivity of intermolecu- Another factor that is useful in describing the energetics within
lar interactions. Additionally, interaction energies of all Bi···π the tetramers is the energy required to remove one of the mono-
arene type dimers and selected π-stacking dimers were com- mers from the corresponding tetramer. This quantity is depicted
puted at the DLPNO-CCSD(T)/cc-pVQZ (cc-pwCVQZ-PP for in Figure 11 as Eremove. By removing one of the molecules from
Bi) level of theory with TightPNO settings (see Figures 12, 14, the tetramer the interactions with this specific monomer are
and 16). Local energy decomposition analysis was performed in broken, which can involve contacts between neighboring mole-
order to obtain the dispersion energy contributions to the inter- cules or long-range interactions. In tetramer 1a-1 the energy
action energies. The dispersion energies of the specific dimers needed to remove one of the outer monomers (3 and 4) is
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Figure 11: Structures of studied BiPh3 tetramers extracted from the crystal structure of polymorph 1a. Etetramer indicates the interaction energy com-
puted for a given tetramer; Edim is the interaction energy computed for a specific dimer; Eprep is the distortion energy of a monomer in the crystal
structure; Eremove denotes the energy required to remove a monomer from the tetramer. All energies were computed at the PBE-D3/def2-TZVP and
are given in kJ mol−1. Numbering of monomers is the same as numbering of bismuth atoms within the specific tetramer. Hydrogen atoms in tetramers
were omitted for the clarity.
almost equal to the interaction energy of one Bi···π arene dimer. −191.3 kJ mol−1 which is very similar to the computed value
This indicates that only one dimer breaks. To remove one of the (−189.6 kJ mol−1). This shows that the interactions in the
inner monomers (2 or 1) an energy of 92 kJ mol−1 is required. crystal structure of polymorph 1a are pairwise neighbor interac-
This energy is very close to the sum of the interaction energies tions. Long-range interactions are probably mostly weak dipolar
of two dimers. For example, Eremove of monomer 2 in tetramer interactions that do not contribute significantly. The analysis of
1a-1 is roughly the sum of the interaction energies of two Bi···π specific dimeric interactions in tetramers 1a shows that not only
arene dimers (91.4 kJ mol−1). This simple example shows the Bi···π arene interactions are important structure building factors
additivity of the dimeric intermolecular interactions within the but also several C–HPh···π arene contacts play a crucial role in
tetramer. The situation is more complicated for tetramers 1a-2 structure formation. The strength of the π-stacking interactions
and 1a-3. In general, the energies to remove one of the mole- depends on the number of contacts and distances between inter-
cules from these tetramers are higher than for tetramer 1a-1 as acting molecules.
they contain interactions between the chains and each of the
monomers has more contacts on average within the tetramer. Figure 12 depicts structures of Bi···π arene dimers and one of
The energy needed to remove one of the monomers from the (strongest) C–HPh···π arene dimers in polymorph 1a. The
tetramer 1a-2 or 1a-3 is roughly the sum of the interaction ener- C–HPh···π arene dimer (depicted as 1a-3-1 in Figure 12) has two
gies involving this monomer (deviating by at most 5 kJ mol−1). very short (2.6 Å) contacts between a C–H group and a phenyl
Another important aspect is that the interaction energy com- ring. The interaction and dispersion energies given in Figure 12
puted for tetramers 1a-1–1a-3 can be also expressed as a sum of were obtained at the DLPNO-CCSD(T)/cc-pVQZ
energies of particular dimeric interactions present in the specif- (cc-pwCVQZ-PP for Bi and TightPNO settings) level of theory.
ic tetramer. For instance, the sum of the interaction energies of Note that PBE-D3 and DLPNO-CCSD(T) give very similar
specific dimers in tetramer 1a-2 amounts to −179 kJ mol−1 results. Inspection of dispersion energies obtained from the
which is higher by 4 kJ mol−1 than the interaction energy of the LED analysis reveals that both types of dimers (Bi···π arene and
whole tetramer (−175.1 kJ mol−1). For tetramer 1a-3 this sum is π-stacking) are exclusively dispersive. Figure 12 depicts two
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Figure 12: Detailed structures of selected dimers extracted from the crystal structure of polymorph 1a and dispersion energy plots. Eint denotes the
interaction energy of a given dimer and Edisp is the dispersion energy obtained from LED analysis computed at the DLPNO-CCSD(T)/cc-pVQZ
(cc-pwCVQZ-PP for Bi, TightPNO settings) level of theory. The distances are given in Å and energies are in kJ mol−1.
complementary graphical interpretations of the dispersion These 1D chains are bound strongly by the π-type interactions
energy density that can be plotted either as an isosurface (coral present between BiPh3 molecules belonging to different layers.
plots) or mapped on an isodensity surface (color gradient) of the The energies of such contacts range from −15 to −40 kJ mol−1.
electron density. Both plots display the regions with the highest The distortion energies of monomers (17 kJ mol−1) suggest that
contributions to the dispersion interaction present in the com- crystal packing effects are large in polymorph 1a.
plex.
Polymorph 1b
In summary, polymorph 1a is formed by one dimensional In case of polymorph 1b four tetrameric units were identified
chains consisting of strong Bi···π arene contacts with interac- and are depicted in Figure 13. Tetramers 1b-1 and 1b-2 consist
tion energies of −46 kJ mol−1 (see tetramer 1a-1 in Figure 11). of zig-zag chains formed by Bi···π arene interactions between
Figure 13: Structures of studied BiPh3 tetramers extracted from the crystal structure of polymorph 1b. See Figure 11 for details.
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one layer of BiPh3 molecules. The difference between these −112.2 kJ mol−1 which is roughly equal to the computed inter-
tetramers is that tetramer 1b-1 contains two Bi···π arene action energy of this tetramer (−111.3 kJ mol−1).
contacts with a distance of 3.47 Å between the Bi atom and the
phenyl ring centroid and one Bi···π arene contact with a dis- Figure 14 depicts Bi···π arene dimers and selected π-stacking
tance of 3.56 Å. In tetramer 1b-2 there are two 3.56 Å Bi···π dimers that are present in the structures of tetramers 1b-1–1b-4
arene contacts and one 3.47 Å contact. Both types of Bi···π and their dispersion energy density plots. It is concluded that
arene dimers have very similar interaction energies of the dispersion energies are a few kJ mol−1 higher for Bi···π
−28 kJ mol−1 (Edimer1_2 of tetramer 1b-1) and −31 kJ mol−1 arene dimers than for π-stacking dimers but in general all of
(Edimer2_3 of tetramer 1b-1). In tetramers 1b-1 and 1b-2 these interactions are purely dispersive. Note that typically the
π-stacking interactions are also present. We only discuss the dispersion contribution is larger than the overall interaction
interactions in tetramer 1b-1 as they are the same as in tetramer energy as it compensates the monomer preparation.
1b-2. For example, the C–HPh···π arene-type interactions be-
tween monomers 1 (red) and 3 (blue), and monomers 2 (green) Summarizing, polymorph 1b is built from zig-zag chains of
and 4 (grey) are as strong as the Bi···π arene interactions in BiPh3 molecules consisting of Bi···π arene contacts with inter-
polymorph 1b and amount to −28 kJ mol−1 and −29 kJ mol−1, action energies of about −30 kJ mol−1. The preparation energy
respectively. Tetramers 1b-3 and 1b-4 on the other hand, exhib- is notably smaller than in polymorph 1a. The contacts between
it interactions between neighboring zig-zag chains. In tetramer zig-zag chains are of π-stacking type and their interaction ener-
1b-3 two Bi···π arene interactions and three other stacking inter- gies amount also to about −30 kJ mol−1.
actions are present that vary in energy and contact area be-
tween the BiPh3 molecules. For example, the strongest Polymorph 1c
C–HPh···π arene dimer of tetramer 1b-3 with an interaction For polymorph 1c we identified three tetramers that are
energy of −30 kJ mol−1 is formed between monomers 1 (green) depicted in Figure 15. Each of them contains two Bi···π dimers
and 3 (grey). The other two stacking interactions between that consist of two Bi···π arene contacts. The interaction energy
monomers 1 (green) and 4 (blue), and monomers 2 (red) and 4 of these dimers is high and amounts to −47 kJ mol−1. Tetramer
(blue) are much weaker due to the smaller contact area between 1c-1 represents Bi···π arene dimers belonging to the same layer.
the molecules. Their interaction energies amount to There are two identical C–HPh···π arene dimers in tetramer 1c-1
−16 kJ mol−1 and −8 kJ mol−1, respectively. In tetramer 1b-4 with an interaction energy of −38 kJ mol−1. These π-stacking
only one additional π-stacking interaction between molecules 2 dimers are formed by monomers 2 (green) and 4 (grey), and
(green) and 4 (blue) is present but is quite strong monomers 1 (red) and 3 (blue). The detailed structure of this
(Edim2_4 = −28 kJ mol−1).
dimer is shown in Figure 16 (depicted as 1c-1-1). Monomers 2
(green) and 3 (blue) also interact to form a dimer that is based
The distortion energies of the monomers (Eprep) are much lower on CH···CH and CH···phenyl interactions (see Figure 16,
than that for polymorph 1a and range from 9 to 11 kJ mol−1. 1c-1-2). The interaction energy of this dimeric unit is moderate
This implies that crystal packing effects are less pronounced in and amounts to −20 kJ mol−1. Tetramers 1c-2 and 1c-3 include
this polymorph.
the Bi···π arene dimers from two different molecular layers. In
tetramer 1c-2 one very strongly bound π-stacking dimer is
Energies required to remove one of the monomers from the formed between monomers 1 (green) and 3 (blue). Its interac-
tetramer in case of polymorph 1b also depend on the number of tion energy amounts to −64 kJ mol−1 and is the highest among
interactions and the energy value is roughly the sum of the ener- all studied dimers, including Bi···π arene dimers. Its structure
gies of these interactions. For instance, one of the lowest ener- resembles the structure of a cube with multiple short C–HPh···π
gies needed to remove a molecule is found for monomer 2 (red) arene contacts (see Figure 16, dimer 1c-2-1). In case of tetramer
in tetramer 1b-3 that amounts to 38 kJ mol−1. This energy is 1c-3 the π-stacking interaction between the molecules are
simply the sum of the already discussed dimer energies (Edim1_2 weaker than in the other two tetramers. The interaction be-
and Edim2_4). Another example is when monomer 3 (blue) is re- tween monomers 1 (green) and 3 (blue) is of moderate strength
moved from tetramer 1b-1 which requires an energy of and the interaction energy is −20 kJ mol−1. The second
86 kJ mol−1. This energy is a sum of the dimer energies that are π-stacking interaction present in the tetramer involves mono-
formed including this monomer (Edim1_3, Edim2_3, and Edim3_4). mers 2 (red) and 3 (blue) and is a rather weak interaction with
This again demonstrates the additivity of intermolecular interac- −11 kJ mol−1.
tions and that the intermolecular interactions in the bulk can be
described as a sum of dimer interactions. Adding up energies of The distortion energies (Eprep) of the monomers of polymorph
all the dimeric units of tetramer 1b-3 results in an energy of 1c are very low and range from 5 to 7 kJ mol−1. This means that
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Figure 14: Detailed structures of selected dimers extracted from the crystal structure of polymorph 1b and dispersion energy plots. See Figure 12 for
details.
Figure 15: Structures of studied BiPh3 tetramers extracted from the crystal structure of polymorph 1c. See Figure 11 for details.
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Figure 16: Detailed structures of selected dimers extracted from the crystal structure of the polymorph 1c and dispersion energy plots. See Figure 12
for details.
in this case packing effects are not very strong compared to the dominated by Bi···π arene interaction, but rather consists of
other two polymorphs of BiPh3.
dimers connected by strong π···π interaction (Figure 16, 1c-2-1
with −64 kJ mol−1) which are connected by two weaker Bi···π
In case of polymorph 1c energies required to remove one mole- arene contacts (Figure 16, 1c-1-1, −47 kJ mol−1).
cule from the tetramer are significantly higher and are roughly
the sum of the interactions that involve a specific monomer. Figure 17 shows the comparison of the distortion and the inter-
Note that the sum of interaction energies of dimers in action energies of Bi···π arene and π stacking dimers. As for
tetramer 1c-2 amounts to −158.3 kJ mol−1 which is much BiPh3, Bi···π arene and π···π interactions are of comparable
smaller than the interaction energy of the tetramer magnitude and the existence of the different polymorphs can be
(Etetramer = −171.7 kJ mol−1). Most probably there are two explained by a balance of two competing interactions. While in
possible interactions between slightly remote monomers 1 case of polymorph 1a the Bi···π arene interaction dominates as a
(green) and 4 (grey), and 2 (red) and 3 (blue) each accounting structure building factor, for polymorph 1b Bi···π arene and
for about −7 kJ mol−1. In case of the other two tetramers of π···π interactions are in the same energy range. In case of poly-
polymorph 1c all interaction energies of dimers add up to morph 1c the π-stacking interaction dominates. Figure 17 also
roughly the interaction energy of the tetramer.
demonstrates the differences between distortion energies of
monomers (Eprep) as found for a specific polymorph and shows
Figure 16 depicts the most important dimers found in the struc- how packing effects decrease from polymorph 1a to 1c.
ture of polymorph 1c, for which the interaction and dispersion
energies are given. The dispersion energy plots show the spatial Conclusion
distribution of the dispersion interaction within each dimer. An Herein, we have shown that the dispersion type Bi···π arene
especially high dispersion energy contribution is observed for interactions provide an important contribution to the structure
dimer 1c-2-1 (−83 kJ mol−1). By looking at the distribution of formation of arylbismuth compounds. In the absence of stronger
the dispersion energy (dispersion energy density plots) for this donors such as -OR and -Cl, the dispersion type bismuth···π
dimer it is noticed that almost the entire monomers contribute to arene interaction is supplemented by other weak interactions
the overall dispersion from π···π interactions.
such as π···π or C–HPh···π. Each Bi···π arene contact with
bismuth as a strong dispersion energy donor (DED) provides a
In case of polymorph 1c the results of the quantification of the higher interaction energy than a single C–HPh···π contact, but
interaction energies reveal that this structure is actually not most often several of the latter compete with the single Bi···π
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Comparing the BiPh3–benzene complex with other BiR3-
benzene systems (with R = Me, OMe, Cl) exhibits that the
nature of this complex is mainly dispersive with small addition
of donor–acceptor character which brings it closer to the BiMe3
rather than to Bi(OMe)3 as a dispersion energy donor. The weak
donor–acceptor character of BiPh3 causes that the Bi···π arene
interactions compete with π···π and C–HPh···π interactions.
Inspection of the intermolecular interactions in polymorphs 1a,
1b, and 1c of BiPh3 (1) confirms that Bi···π arene interactions
are very important building blocks of the bulk. These are rather
strong with interaction energies in the range from −28 kJ mol−1
to −47 kJ mol−1 and are purely dispersive. These energies are
much higher than the interaction energy obtained for the model
BiPh3···benzene system. An analysis of selected tetramer units
reveals that also π-stacking interactions and contacts between
layers of BiPh3 molecules are crucial in the formation of the
crystal structures. The interaction energies of the π-stacking
dimers are as high as interaction energies of Bi···π arene com-
plexes or even larger (−64 kJ mol−1). The energy of such
dimers depends strongly on the distance and the contact area be-
tween two monomers. Both types of dimers are exclusively
dispersive as shown by LED analysis performed at the DLPNO-
CCSD(T) level of theory. Analysis of tetrameric units also
reveals that the interaction energy of tetramers is additive and
can be described as a sum of interaction energies of particular
dimers.
Figure 17: Distortion energies of monomers (Eprep, blue triangles) and
interaction energies of Bi···π and π-stacking dimers (grey squares and
red dots, accordingly) computed at the PBE-D3/def2-TZVP level of
theory for polymorphs 1a, 1b, and 1c of compound 1. Note that every
point denotes a distortion energy or dimer interaction energy obtained
for the given polymorph.
In the polymorphs of compound 1 the energetics of interactions
is balanced between Bi···π arene and π···π interactions that are
arene contact. In case of multiple C–HPh···π contacts these can of comparable strength. In case of polymorph 1a the Bi···π
become dominating. As a result, triorganobismuth compounds arene interaction dominates, in case of polymorph 1b the Bi···π
show a diversity of polymorphs.
arene and the π···π interactions are of similar magnitude. For
polymorph 1c, π···π interactions dominate the intermolecular
In compounds with bulky ligands the formation of Bi···π arene interactions.
contacts is hindered and multiple C–HPh···π contacts dominate.
In the presence of strong structure directing donor–acceptor Overall, the compounds and structures discussed in this work
bonds the role of bismuth as DED can usually be neglected. demonstrate that a broad range of intermolecular interaction
However, compounds of the type Ar2BiX (Ar = C6H3-t-Bu2- motifs are accessible by tuning the donor–acceptor properties of
3,5, X = halide) show some special features. In these com- bismuth as a dispersion energy donor. Using electronic struc-
pounds the formation of a one dimensional ribbon as a result of ture theory, these interactions can be quantified and studied in
Bi···X···Bi coordination is typical, which is supplemented by detail.
Bi···π arene interactions between two neighboring bismuth
Experimental
atoms in the chain. Thus, a sort of X, π-pincer system is ob-
tained. In order to strengthen the Bi···π arene interaction and to Crystallographic studies
induce directionality in structure formation it is important to Crystal data, data collection and refinement parameters for
introduce electron-withdrawing substituents. Otherwise, a Ph3Bi (polymorphs 1a, 1b, 1c, 1d), 1b, 2a, 2b and 3, 4,
subtle interplay between Bi···π arene and the dispersion type 5·2CH2Cl2 are given in Table S1, Table S2 and Table S3 (in
forces must be considered.
Supporting Information File 1), respectively. All data for the
new structures were collected with an Oxford Gemini S diffrac-
Analysis of the Bi···π arene interaction in the BiPh3–benzene tometer at 123 K (1b), 120 K (2a, 3), 115 K (4, 5·2CH2Cl2) and
complex shows that it is of moderate strength (−17 kJ mol−1). 100 K (2b) using Cu Kα radiation (λ = 1.54184 Å) for 2a and
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Beilstein J. Org. Chem. 2018, 14, 2125–2145.
Mo Kα radiation (λ = 0.71073 Å) for 1b, 2b, 3, 4, 5·2CH2Cl2. Eight Australia – Germany Joint Research Co-operation) for
The structures were solved by direct methods using SHELXS- financial support. P. K. gratefully acknowledges financial
2013 [68,69] and refined by full-matrix least-square procedures support from the Deutsche Akademie der Naturforscher
on F2 using SHELXL-2014 [68,70] and SHELXL-2016/6 [71]. Leopoldina–Nationale Akademie der Wissenschaften for a
All non-hydrogen atoms were refined anisotropically. All Leopoldina Postdoc Fellowship. M. Korb thanks the Fonds der
hydrogen atoms were geometrically placed and refined isotropi- Chemischen Industrie for a Ph.D. Chemiefonds fellowship.
cally in riding modes using default parameters. The drawings
ORCID® iDs
Ana-Maria Preda - https://orcid.org/0000-0003-0047-0152
were created with the Diamond program [72]. The identity of
Ph3Bi (polymorphs 1a, 1b), 2a, 2b, and 3 was confirmed by
Phil C. Andrews - https://orcid.org/0000-0002-3971-7311
PXRD analyses. The simulated diffraction patterns of
Marcus Korb - https://orcid.org/0000-0001-5453-4137
three polymorphs of Ph3Bi (1a, 1b, 1c) are illustrated in
Alexander A. Auer - https://orcid.org/0000-0001-6012-3027
Figure S6 (see Supporting Information File 1). The diffraction
Michael Mehring - https://orcid.org/0000-0001-6485-6156
patterns of the measured diffractograms are in good agreement
with those simulated from the single crystal X-ray crystallo-
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