Synthesis and Molecular Structure of Pseudo-Hexacoordinated Pnictines Bearing 2-Phenylpyridine Ligands

Article abstract of DOI:10.1002/ejic.202000795

The pseudo-hexacoordinated organo-pnictogen(III) compounds tris[2-(2-pyridyl)phenyl]stibine [(ppy)₃Sb, 1] and tris[2-(2-pyridyl)phenyl]bismuthine [(ppy)₃Bi, 2], which bear three 2-phenylpyridine (ppy) ligands, were prepared and isola

Full text of DOI:10.1002/ejic.202000795

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Hexacoordinated Pnictines
Synthesis and Molecular Structure of Pseudo-Hexacoordinated
Pnictines Bearing 2-Phenylpyridine Ligands
Masato Sakabe,[a] Akihisa Ooizumi,[a] Wataru Fujita,[b] Shinobu Aoyagi,[c] and Soichi Sato*[a]
Abstract: The pseudo-hexacoordinated organo-pnictogen(III) distorted facial octahedral bonding geometries around the cen-
compounds tris[2-(2-pyridyl)phenyl]stibine [(ppy)3Sb, 1] and tral pnictogen atoms, wherein the three pyridyl groups coordi-
tris[2-(2-pyridyl)phenyl]bismuthine [(ppy)3Bi, 2], which bear nate to the pnictogen atoms via three weak LP(N)→σ*(Pn–C)
three 2-phenylpyridine (ppy) ligands, were prepared and iso- donor–acceptor interactions. Natural bond orbital (NBO) and
lated from the reaction of 2-(2-lithiophenyl)pyridine with the atoms in molecules (AIM) analyses were used to characterize
corresponding pnictogen(III) chloride (PnCl3; Pn = Sb, Bi). Com- the weak ionic interactions between the nitrogen and pnicto-
pounds 1 and 2 were characterized using NMR spectroscopy, gen atoms. The HOMOs of 1 and 2 correspond to the lone pairs
mass spectrometry, and elemental analysis. Their solid-state of electrons on the central pnictogen atom, which indicates
structures were determined using single-crystal X-ray diffrac- that these compounds can be classified as 14–Pn–6 chemical
tion analysis, which revealed similar pseudo-hexacoordinated, species.
Introduction
(phosphines and arsines). Furthermore, the σ*(Pn–C) orbitals in
heavy pnictines behave as Lewis acceptors and interact easily
with the LPs of nucleophiles.[5] The resulting compounds be-
come hypervalent species that bear three-center four-electron
(3c–4e) bonds. The introduction of a bidentate ligand with an
intramolecular donor moiety (pendant-arm ligands) to a heavy
pnictogen element is a commonly used method to generate
relatively stable hypercoordinated pnictines that have valence
electrons beyond the octet rule.[32,33] However, due to the steric
hindrance between ligands, there are not many reports of hexa-
or higher coordinated compounds. Hitherto reported neutral
(pseudo-)hexacoordinated stibines (R3Sb) and bismuthines
(R3Bi) contain either amino (A),[34–38] formyl (B),[39] imino (C),[40]
In recent years, the chemistry of organoantimony and organo-
bismuth compounds has seen significant progress[1–6] espe-
cially toward their use as Lewis-acid catalysts,[7–17] as anion-
sensing molecules,[18–24] and as non-innocent ligands for transi-
tion-metal complexes.[25–30] Heavy triorganopnictines of the
type R3Pn (Pn = Sb and Bi) are well-known organopnictogen(III)
compounds that obey the octet rule and that can be classified
as 8–Pn–3 chemical species.[31] In general, heavy pnictines
adopt a trigonal pyramidal coordination geometry with three
covalent bonds and a lone pair (LP) of electrons on the central
atom.[2,4] Due to the diminished propensity toward hybridiza-
tion of heavy atoms, the three covalent bonds and the LP con-
sist predominantly of contributions from the p- and s-orbitals
of the bonding atoms. In addition, the Allred-Rochow electro-
negativity values (ꢀ) of antimony and bismuth (ꢀSb = 1.82; ꢀBi
=
1.67) are much smaller than that of carbon (ꢀC = 2.50), which
renders the central atom of the heavy pnictines cationic and
means that the heavy pnictines form polarized Pnδ+–Cδ– bonds.
Therefore, the LPs of heavier pnictines are more weakly coordi-
nating than those of their corresponding lighter analogues
[a] M. Sakabe, A. Ooizumi, Prof. Dr. S. Sato
Department of Chemistry, Graduate School of Science, Tokyo Metropolitan
University,
1-1 Minami-osawa, Hachioji, Tokyo 192-0397, Japan
E-mail: ssato@tmu.ac.jp
[b] Prof. Dr. W. Fujita
Faculty of Science and Technology, Seikei University,
3-3-1 Kichijoji-kitamachi, Musashino, Tokyo 180-8633, Japan
[c] Prof. Dr. S. Aoyagi
Department of Information and Basic Science, Nagoya City University,
Nagoya 467-8501, Japan
Supporting information and ORCID(s) from the author(s) for this article are
available on the WWW under https://doi.org/10.1002/ejic.202000795.
Figure 1. (a) Previously reported examples of (pseudo-)hexacoordinated
heavy pnictines (Pn = Sb, Bi). (b) Previously reported example of monomeric
hexacoordinated telluronium cation. (c) (Pseudo-)hexacoordinated pnictines
reported in this work.
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or phosphino (D)[27,41] groups as the intramolecular donor (Fig- ecules. In 1B and 2B, one of the three ppy groups (that carrying
ure 1a). Although these (pseudo-)hexacoordinated pnictines the N2′ and C12′ atoms) is disordered over two positions with
can be classified as rare 14–Pn–6-type chemical species, de- relative occupancies of 0.695(7)/0.305(7) (1B) or 0.652(7)/
tailed investigations into the bonding character and reactivity 0.348(7) (2B). The structures are shown in Figure 2 with the
of these hypervalent species remain scarce.
type A structures presented on top and the type B structures
presented below. The packing structures are shown in Figure
S5 and selected structural parameters obtained from around
the central pnictogen atoms are summarized in Table 1. Al-
Recently, Singh and co-workers have synthesized the asym-
metrical telluronium salt [(ppy)3Te][Br], which contains three
2-phenylpyridine (ppy) ligands (Figure 1b).[42] This cationic
hexacoordinated chalcogen species (14–Te–6) resembles the
(valence-)isoelectronic molecules of the neutral hexacoordi-
nated pnictines (14–Pn–6, Pn = Sb or Bi). Similar to the 14–
Te–6-type species, the novel hexacoordinated heavy pnictines,
which bear various bidentate ligands, are of great interest due
to their unique structure, bonding character, and electrochemi-
cal properties.
Herein, we report the synthesis and molecular structures of
stibine [(ppy)3Sb] (1) and bismuthine [(ppy)3Bi] (2), which con-
tain three ppy ligands (Figure 1c), together with detailed calcu-
lations on the electronic properties of these 14–Pn–6 chemical
species.
Results and Discussion
2-(2-Lithiophenyl)pyridine (ppy-Li) was prepared via a halogen–
lithium exchange reaction of 2-(2-iodophenyl)pyridine with
n-butyllithium in Et2O at low temperature to give a yellow sus-
pension. As shown in Scheme 1, the ppy-Li suspension was
added to a solution of 0.3 equivalents of pnictogen(III) chloride
(PnCl3; Pn = Sb, Bi) in Et2O to give 1 and 2 as moderately air-
stable solids in reasonable yield [1: pale yellow, 59 %, 2: beige,
52 %]. Products 1 and 2 were easily isolated by elution from
the respective residues with dry toluene. Compounds 1 and 2
exhibit decomposition points of 208 °C and 188–190 °C, respec-
Figure 2. Molecular structure of 1 (left) and 2 (right) in the solid state [type
A molecules (top) and type B molecules (bottom)]. Thermal ellipsoids are
shown at 50 % probability. Hydrogen atoms are omitted for clarity and in the
disordered part, only the positions with higher occupancy are shown.
1
tively. The H and 13C NMR spectra of 1 and 2 show that the
three ppy ligands on the pnictogen atoms are magnetically
equivalent at room temperature. Equivalency of these resonan-
ces is also encountered for most other reported hexacoordi-
nated pnictines (Figure 1a) and (valence-)isoelectronic
[(ppy)3Te]+ molecules.[42] The exception to this rule are gemi-
nally substituted tris(acenaphthyl)pnictines (Figure 1a; D, R =
iPr).[41] The identification of 1 and 2 was completed via the use
of atmospheric pressure chemical ionization-mass spectrometry
(APCI-MS) and elemental analyses.
Table 1. Selected bond lengths [Å] and bond angles [°] of 1 and 2 (values in
brackets correspond to the positions with lower occupancy in the disordered
part).
1 (Pn = Sb)
1A 1B
2 (Pn = Bi)
2A
Parameters
1calcd
2B
2calcd
Pn–C1
Pn–C12
2.191(3) 2.191(3) 2.203
2.169(3) 2.238(7)
[2.07(2)]
2.299(5) 2.294(6) 2.312
2.262(5) 2.36(1)
[2.17(2)]
Pn–C23
Pn···N1
Pn···N2
2.212(4) 2.206(4)
2.779(3) 2.815(3) 2.871
2.808(3) 2.834(7)
[2.76(1)]
2.301(5) 2.306(5)
2.853(5) 2.880(5) 2.906
2.840(5) 2.878(8)
[2.84(2)]
Pn···N3
3.044(3) 3.002(3)
3.031(5) 3.018(5)
C1–Pn–C12 97.6(1)
C12–Pn–C23 91.1(1)
C23–Pn–C1 92.8(1)
N1···Pn···N2 112.33(9) 117.3(1) 113.7
[122.0(3)]
N2···Pn···N3 91.02(9) 115.4(1)
[106.3(3)]
93.2(2)
[100.4(5)]
92.6(2)
[91.9(5)]
96.4(1)
94.8
96.2(2)
90.4(2)
92.3(2)
91.2(3)
[98.9(6)]
91.5(3)
[90.2(6)]
96.0(2)
93.2
Scheme 1. Synthesis of 1 and 2.
Single crystals of 1 and 2 suitable for X-ray crystallographic
analysis were prepared by slow evaporation of solvent from an
ethanol/chloroform solution of 1 or from a toluene solution of
2 at room temperature. The crystal data are summarized in
Table S1. The crystal structures of 1 and 2 are very similar and
show two independent molecules per asymmetric unit. These
independent molecules can be classified as type A and B mol-
112.7(1) 119.0(2) 114.7
[123.1(3)]
90.5(1)
117.9(2)
[108.2(3)]
N3···Pn···N1 137.01(9) 114.00(9)
139.6(1) 114.0(1)
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though it seems that intramolecular repulsion exists between
the LPs of the central pnictogen atom and the donor nitrogen
atoms, all nitrogen atoms are directed toward the pnictogen
atom, commensurate with a facial configuration. The Pn–C
bond lengths observed in 1 [2.169(3)–2.212(4) Å] and 2
[2.262(5)–2.36(1) Å] are slightly longer than the average Pn–C
bond length of the analogous molecules Ph3Sb (av. 2.155 Å)[43]
and Ph3Bi (av. 2.237 Å).[44] Although the values found for the
C–Pn–C angles in 1 [91.1(1)–97.6(1)°] and 2 [90.4(2)–96.2(2)°]
vary widely due to their asymmetric structures, the averages of
these angles are slightly smaller than those of Ph3Sb [95.1(3)–
98.0(3)] and Ph3Bi [92(1)–96(1)°].
In addition, the Pn···N3 bond, depicted with dotted lines in
Figure 2, is ca. 0.2 Å longer than the other Pn···N bonds. Thus,
1 and 2 can be described as having a pseudo-hexacoordinated
and distorted octahedral bonding geometry. However, the
Sb···N bond lengths of 1 [2.76(1)–3.044(3) Å] and the Bi···N
bond lengths of 2 [2.84(2)–3.031(5) Å] are significantly shorter
than the sum of the van der Waals radii [ΣrvdW(Sb,N) = 3.61 Å;
Figure 3. Space-filling models of 1B (left) and 2B (right).
ΣrvdW(Bi,N)
=
3.62 Å],[45,46] supporting the presence of
ing crystal structures, and slightly longer than those of Ph3Sb
(2.160 Å) and Ph3Bi (2.258 Å) when calculated at the same level
of theory. The optimized Pn···N bonds (1calcd: 2.871 Å; 2calcd
LP(N)→σ*(Pn–C) intramolecular donor–acceptor interactions.
The Sb···N bond lengths of 1 are shorter than those of other
known (pseudo-)hexacoordinated stibines that possess three
Sb···N interactions.[27,34,35,37,38,40,41] Similarly, the Bi···N bond
lengths of 2 are shorter than those of other known (pseudo-
)hexacoordinated bismuthines such as (Et2NCH2C6H4)3Bi
[3.214(7) Å].[36] These results are interesting because the basicity
of the pyridyl group is much lower than that of the amino or
imino group. These short Pn···N bond lengths in 1 and 2 are
due to the lower steric hindrance between the ppy ligands rela-
tive to that of pendant-arm ligands that contain amino or imino
groups. As supported by theoretical calculations (vide infra), 1
and 2 contain relatively short Pn···N bonds and three sets of
weak three-center four-electron (3c–4e) bonds formed by three
LP(N)→σ*(Pn–C) donor–acceptor interactions.
:
2.906 Å) fall in the middle of the range of Pn···N bond lengths
found in the crystal structure [1: 2.76(1)–3.044(3) Å; 2: 2.84(5)–
3.031(5) Å]. The crystal structures of the type B molecules are
closer to the optimized structures than those of the type A
molecules. The differences between the optimized structures
and the X-ray crystal structures probably originate from crystal-
packing effects. The small deferent energy gap (< 3 kcal/mol)
between these structures is supported by theoretical calcula-
tions (Tables S4 and S5).
Furthermore, the Pn···N bonds in (R2NCH2C6H4)3Pn (Pn = Sb
or Bi; R = Me or Et) optimized at the same level of theory are
significantly longer than 1calcd or 2calcd (Table S6). These results
are consistent with the results of the X-ray diffraction analyses,
supporting that the shorter Pn···N bonds in 1calcd or 2calcd rela-
tive to those of other known (pseudo-)hexacoordinated pnict-
ines are due to the small steric hindrance between the ppy
ligands.
An analysis of the molecular orbitals of the optimized struc-
tures of 1calcd and 2calcd showed that the HOMOs correspond
to the LP on the NNN-face side of each central pnictogen atom
(Figure 4), and this result agrees with the space-filling models
(Figure 3). The LPs occupy orbitals that have high s-character
(1calcd: Sb 5s orbital, 74.03 %; 2calcd: Bi 6s orbital, 84.07 %) due
to the non-hybridization effect of the heavier pnictogen atoms.
A natural bond orbital (NBO) analysis[47] of 1calcd and 2calcd re-
vealed that the Pn···N interactions result from LP(N)→σ*(Pn–C)
donor–acceptor interactions with weak second order perturba-
tion energies [1calcd: E(2) = 7.84 kcal/mol; 2calcd: 9.05 kcal/mol].
Compounds 1 and 2 crystallize exclusively in facial configura-
tions and a racemic mixture of Δ and Λ isomers. The most
significant difference between the structures of the two inde-
pendent molecules (type A and B) is the set of three N···Pn···N
angles in each molecule (Table 1). In the more distorted A mol-
ecules, these angles are approximately 90°, 110°, and 140°,
whereas in the B molecules, all three angles are ca. 115°.
Space-filling models of the type B molecules (1B and 2B) are
shown in Figure 3. There is no significant difference between
the type A and type B space-filling models and thus only the
type B illustrations are depicted in Figure 3. This figure shows
that both 1 and 2 contain a larger space on the NNN-face side
than on the CCC-face side. These results indicate that the LP on
the central pnictogen atom in 1 and 2 should be located on
the NNN-face side.
The structure and the electronic states of 1 and 2 were inves- The Wiberg bond indexes (WBIs) for the Pn···N interactions
tigated by density functional theory (DFT) calculations at the [1calcd: 0.0849; 2calcd: 0.0853] confirm that these interactions can
B3PW91/aug-cc-pVTZ-PP [Sb, Bi]/6-31G(d) [C, H, N] level of be expected to be very weak. Each central pnictogen atom ex-
theory. The optimized structures of 1calcd and 2calcd show C3 hibits a higher positive charge [1calcd: +1.21; 2calcd: +1.23] than
symmetry, which differs from their respective crystal structures the central atom in the corresponding triphenylpnictine [Ph3Sb:
(Table 1). The optimized Pn–C bonds (1calcd: 2.203 Å; 2calcd
:
+1.08; Ph3Bi: +1.07]. When the X-ray structures were optimized
2.312 Å) are in good agreement with those in the correspond- with fixed Pn···N geometries (Table S5), slightly different second
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order perturbation energies and WBIs were obtained at the revealed irreversible oxidation potentials at 0.07 V (1) and
same level of theory.
0.40 V (2) (vs. the ferrocene/ferrocenium couple) (Figure 5). In-
terestingly, the oxidation value of 1 is much lower than the
corresponding value found for Ph3Sb [1.22 V vs. SCE (j 1.06 V
vs. Fc/Fc+)],[49,50] which indicates that the LP on the central anti-
mony atom of 1 is electrochemically more easily oxidized than
that in Ph3Sb. This is probably due to the presence of three
intramolecular donor–acceptor interactions. In fact, the calcu-
lated HOMO level of 1 (–5.09 eV) is higher than that of Ph3Sb
(–6.13 eV), which is in agreement with the experimentally ob-
served oxidation behavior of 1. As far as we know, there have
so far been no reports on the electrochemical behavior of Ph3Bi,
but the results of the DFT calculations suggest a similar tend-
ency for the HOMO levels of the bismuth analogues (2:
–5.42 eV; Ph3Bi: –6.28 eV). The observed irreversible waves likely
occur because the corresponding radical cations ([1]·+ or [2]·+),
generated by the one-electron oxidation, are unstable. Due to
the lanthanide contraction and the relativistic effects,[51] 2 ex-
hibits a higher oxidation potential than 1. Indeed, DFT calcula-
tions show that the HOMO energy level of 2 (–5.42 eV) is lower
than that of 1 (–5.09 eV).
Figure 4. (a) HOMOs calculated for 1calcd (left) and 2calcd (right). (b) AIM plots
of 1calcd (left) and 2calcd (right).
In order to better understand the bonding situation around
the central atoms in 1 and 2, these compounds were analyzed
using the atoms-in-molecules (AIM) method[48] based on a
C3-symmetric optimized structure (1calcd and 2calcd). Six bond
critical points (BCPs) were found around the central pnictogen
atom of 1calcd and 2calcd. The electron density (ρbcp), Laplacian
of the electron density (∇2ρbcp), and total energy (H) of each
BCP are summarized in Table 2. At the same level of theory, the
calculated Pn–C bond parameters do not show any substantial
differences between (ppy)3Pn (1calcd and 2calcd) and Ph3Pn
(Pn = Sb, Bi). The small positive ∇2ρbcp values observed for the
Pn···N bonds are indicative of weak associative ionic interac-
tions. Given the results of the DFT calculations and the AIM
analyses, 1calcd and 2calcd can be classified as 14–Pn–6 (Pn = Sb,
Bi) chemical species.
Figure 5. Cyclic voltammograms of 1 (red) and 2 (green), recorded in CH2Cl2
with 0.10
M [nBu4N][PF6] at room temperature.
Conclusions
We have described the new stibine 1 and the new bismuthine
2, which bear three 2-phenylpyridine (ppy) pendant-arm li-
gands. The three ppy ligands of 1 and 2 are magnetically equiv-
alent in solution, as evident by NMR spectroscopy. However, in
the crystalline state, the structures of 1 and 2 are distorted,
probably due to packing forces. Each crystal contains two inde-
pendent molecules (A and B), both of which adopt a pseudo-
hexacoordinated facial octahedral coordination geometry. DFT
calculations revealed three relatively weak intramolecular do-
nor–acceptor interactions [LP(N)→σ*(Pn–C)] and an LP on the
central pnictogen atom, indicating that 1 and 2 can be classi-
fied as 14–Pn–6 (Pn = Sb, Bi) chemical species. Cyclic voltamme-
try measurements revealed that the first oxidation potentials of
1 and 2 are relatively low, suggesting that these LPs are easily
oxidized. While several (pseudo-)hexacoordinated pnictines that
bear three pendant-arm ligands have previously been reported,
Table 2. Selected AIM parameters for the optimized structures of 1calcd and
2calcd
.
Parameters
Pn–C
1calcd
3
ρbcp (e/a0
)
0.1022
0.0639
–0.0453
0.0232
0.0530
–0.0003
0.0913
0.0846
–0.0330
0.0231
0.0599
+0.0003
∇2ρbcp (e/a0
)
)
5
5
Hbcp (au)
ρbcp (e/a0
3
Pn···N
)
∇2ρbcp (e/a0
Hbcp (au)
To investigate the oxidative behavior of 1 and 2, the electro- their reactivity has not been studied systematically. The low
chemical oxidation potentials of these pnictines were measured oxidation potentials of 1 and 2 suggest promising potential to
using cyclic voltammetry in CH2Cl2/0.1
M
[nBu4N][PF6], which be converted into new cationic chemical species. Investigations
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(dt, J = 7.4, 1.1 Hz, 1H, Ph), 7.53 (dd, J = 7.4, 1.1 Hz, 1H, Ph), 7.59
(dt, J = 7.4, 1.8 Hz, 1H, py), 7.65 (d, J = 8.0 Hz, 1H, py), 7.78 (d, J =
7.7 Hz, 1H, Ph), 8.26 (d, J = 4.8 Hz, 1H, py); 13C NMR (126 MHz,
CDCl3, 25 °C) δ = 121.7 (s, py), 121.7 (s, py), 127.3 (s, Ph), 127.5 (s,
Ph), 128.6 (s, Ph), 136.3 (s, py), 138.6 (s, Ph), 144.5 (s, Ph), 147.8 (s,
py), 148.4 (s, Ph), 159.1 (s, py); MS (APCI, pos) m/z 582 ([M – 1]+),
429 {[M – (ppy)]+}, 275 {[M – 2(ppy)]+}; elemental analysis calcd. (%)
for C33H24N3Sb: C, 67.83; H, 4.14; N, 7.19; found C, 67.64; H, 4.10;
N, 7.17.
into oxidation reactions of these 14–Pn–6 chemical species are
currently in progress in our laboratory.
Experimental Section
General: All reactions were performed under an atmosphere of dry
argon. Unless otherwise stated, reagents were purchased from com-
mercial suppliers and used as supplied. 2-Phenylpyridine (ppy-H)
was dried with CaH2, distilled under reduced pressure and kept
under argon. Dry diethyl ether and dichloromethane were pur-
chased from Kanto chemical (dehydrated). Toluene was dried with
CaH2 and distilled prior to use. Nuclear magnetic resonance (NMR)
spectra were recorded on a Bruker Avance III 500 (1H: 500 MHz; 13C:
126 MHz) spectrometer. Chemical shifts (δ) are reported in ppm.
Synthesis of Tris[2-(2-pyridyl)phenyl]bismuthine, (ppy)3Bi (2): A
yellow suspension of ppy-Li was prepared by treatment of ppy-I
(2.17 g, 7.7 mmol) with n-butyllithium (5.4 mL, 8.6 mmol, 1.60
M in
n-hexane) in dry diethyl ether (20 mL) at –70 °C under an atmos-
phere of dry argon. After stirring for 2 h at –70 °C, the yellow sus-
pension of ppy-Li was added via cannula to a solution of BiCl3
(0.650 g, 2.06 mmol) in dry diethyl ether (30 mL) at –70 °C, where
stirring was continued for 2 h. Then, the reaction mixture was al-
lowed to slowly warm to room temperature, where stirring was
continued overnight. The resulting mixture was filtered and the
dark solid was washed with diethyl ether under an atmosphere of
dry argon. The thus obtained brown residue was eluted with tolu-
ene, filtered, and the filtrate was concentrated under reduced pres-
sure to afford 2 (0.715 g, 52 %) as a brown solid. The signal of the
ipso carbon atoms bound to the Bi atom (172.8 ppm) were not
observed at room temperature. Therefore, the corresponding
13C{1H} NMR spectrum was measured at –20 °C. M.p. 188–190 °C.
1H NMR (500 MHz, CDCl3, 25 °C) δ = 7.00–7.03 (m, 1H, py), 7.10 (dt,
J = 7.3, 1.3 Hz, 1H, Ph), 7.33 (dt, J = 7.3, 1.3 Hz, 1H, Ph), 7.60–7.65
(m, 2H, py), 7.85 (dd, J = 7.4, 1.3 Hz, 1H, Ph), 8.04 (dd, J = 7.4, 1.3 Hz,
1H, Ph), 8.27 (md, J = 4.8 Hz, 1H, py); 13C NMR (126 MHz, CDCl3,
–20 °C) δ = 121.4 (s, py), 121.5 (s, py), 126.6 (s, Ph), 127.9 (s, Ph),
130.7 (s, Ph), 136.4 (s, py), 141.4 (s, Ph), 145.0 (s, Ph), 148.2 (s, py),
160.8 (s, py), 172.8 (s, Ph); MS (APCI, pos) m/z 670 ([M – 1]+), 517
{[M – (ppy)]+}, 363 {[M – 2(ppy)]+}; elemental analysis calcd. (%) for
C33H24N3Bi: C, 59.02; H, 3.60; N, 6.26; found C, 58.72; H, 3.55; N, 6.13.
1
The chemical shifts of the H and 13C{1H} NMR spectra in CDCl3 are
reported relative to the internal standard Me4Si (0 ppm). The abso-
lute values of the coupling constants (J) are giving in Hertz (Hz).
Multiplicities are abbreviated to singlet (s), doublet (d), triplet (t),
and multiplet (m). The assignment of the 1H and 13C{1H} resonance
signals was based on the corresponding COSY and HSQC spectra.
Atmospheric pressure chemical ionization-mass spectrometry
(APCI-MS) measurements were collected on a Bruker micrOTOF II
mass spectrometer for a minute and averaged. Melting points were
determined on a Yanako MP-J3 apparatus and are uncorrected. Ele-
mental analyses were carried out in the Elemental analysis room at
Tokyo Metropolitan University.
Synthesis of (2-Iodophenyl)pyridine (ppy-I): 2-(2-Iodophenyl)pyr-
idine (ppy-I) was prepared on a large scale using a modified litera-
ture procedure.[52] In a 100 mL flask, distilled 2-phenylpyridine
(5.76 g, 37 mmol), Copper(II) acetate monohydrate (7.39 g,
37 mmol), and I2 (9.39 g, 37 mmol) were dissolved in 1,2-dichloro-
ethane (40 mL) under atmospheric air. The mixture was then heated
to reflux (100 °C) and stirred overnight. Subsequently, the reaction
mixture was filtered, and the filtrate was washed consecutively with
saturated aqueous Na2S2O3 (40 mL), saturated aqueous Na2S
(40 mL), and brine (40 mL). The organic layer was filtered, dried
with Na2SO4, and concentrated under reduced pressure. The result-
ing brown oil was purified by column chromatography on silica gel
using hexane/ethyl acetate (2:1, v/v) as the eluent to afford ppy-I
as a pale-yellow oil (3.72 g, 35 %). Unfortunately, ppy-I contains a
small amount of inseparable 2-(2-chlorophenyl)pyridine (ppy-Cl) as
a by-product. 1H NMR (500 MHz, CDCl3, 25 °C) δ = 7.09 (ddd, J =
8.0, 6.9, 2.2, 1H), 7.30 (ddd, J = 7.5, 4.8, 1.1 Hz, 1H), 7.43 (dt, J = 7.4,
1.2 Hz, 1H), 7.46 (dd, J = 7.8, 2.2 Hz, 1H), 7.51 (d, J = 7.8 Hz, 1H),
7.77 (dt, J = 7.8, 1.8 Hz, 1H), 7.97 (dd, J = 8.0, 0.8 Hz, 1H), 8.71 (d,
J = 4.8 Hz, 1H). These spectroscopic data are consistent with litera-
ture values.
Electrochemical Measurements: Cyclic voltammograms (CV) were
recorded at room temperature on a BAS-ALS620B apparatus under
atmospheric air. Dry dichloromethane and [nBu4N][PF6] were used
as the solvent and the supporting electrolyte, respectively, under
the following conditions. Working electrode: glassy carbon; refer-
ence electrode: Ag/AgCl; counter electrode: platinum wire; concen-
tration of the analyte: 1 mM; concentration of the supporting elec-
trolyte: 0.1 ; scan rate: 100 mV/s. Ferrocene was used as an internal
M
standard, and all potentials are referenced with respect to the E1/2
of the Fc/Fc+ redox couple.
X-ray Crystallographic Analyses: Single crystals of 1 and 2 were
prepared by slow evaporation of solvent from an ethanol/chloro-
form solution of 1 or from a toluene solution of 2 at room tempera-
ture. These crystals were coated with mineral oil and put on a
MacroMountTM (MiTeGen, LLC), before they were mounted on
a Rigaku Mercury CCD detector, where data were collected using
Mo-Kα radiation (λ = 0.71073 Å). Structures were solved by a dual
space method using the SHELXT program[53] and refined by a least-
squares method using SHELXL vers. 2018/1.[54] All hydrogen atoms
were put at calculated positions, while all other atoms were refined
anisotropically.
Synthesis of Tris[2-(2-pyridyl)phenyl]stibine, (ppy)3Sb (1):
n-Butyllithium (5.4 mL, 8.64 mmol, 1.60
M in n-Hexane) was added
dropwise to a solution of ppy-I (2.16 g, 7.68 mmol) in dry diethyl
ether (25 mL) under a dry argon atmosphere at –70 °C, and stirring
was continued for 2 h at this temperature. The resulting yellow
suspension was added via cannula to a solution of SbCl3 (0.540 g,
2.37 mmol) in dry diethyl ether (40 mL) at –70 °C, where stirring
was continued for 2 h. Then, the reaction mixture was allowed to
slowly warm to room temperature, where stirring was continued
overnight. The resulting mixture was filtered and the dark solid was
washed with diethyl ether. The thus obtained brown residue was
eluted with toluene, filtered, and the filtrate was concentrated un-
der reduced pressure to afford 1 (0.82 g, 59 %) as a pale-brown
Deposition Numbers 1997509 (for 1) and 1997510 (for 2) contain
the supplementary crystallographic data for this paper. These data
are provided free of charge by the joint Cambridge Crystallographic
Data Centre and Fachinformationszentrum Karlsruhe Access Struc-
tures service www.ccdc.cam.ac.uk/structures.
1
solid. M.p. 208 °C. H NMR (500 MHz, CDCl3, 25 °C) δ = 7.01 (ddd,
J = 7.4, 4.8, 1.1 Hz, 1H, py), 7.11 (dt, J = 7.4, 1.1 Hz, 1H, Ph), 7.34
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[27]
[28]
[29]
[30]
[31]
[32]
S. Furan, E. Hupf, J. Boidol, J. Brünig, E. Lork, S. Mebs, J. Beckmann, Dalton
Trans. 2019, 48, 4504–4513.
T. P. Lin, I.-S. Ke, F. P. Gabbaï, Angew. Chem. Int. Ed. 2012, 51, 4985–4988;
Angew. Chem. 2012, 124, 5069.
C. R. Wade, I.-S. Ke, F. P. Gabbaï, Angew. Chem. Int. Ed. 2012, 51, 478–481;
Angew. Chem. 2012, 124, 493.
D. You, J. E. Smith, S. Sen, F. P. Gabbaï. Organometallics 2020, DOI: https://
doi.org/10.1021/acs.organomet.0c00193.
C. W. Perkins, J. C. Martin, A. J. Arduengo, W. Lau, A. Alegria, J. K. Kochi,
J. Am. Chem. Soc. 1980, 102, 7753–7759.
N. Tan, Y. Chen, S. Yin, R. Qiu, Y. Zhou, C. T. Au, Curr. Org. Chem. 2012,
16, 2462–2481.
Theoretical Calculations: Geometry optimization and frequency
calculations on 1 and 2 were carried out using the Gaussian 09
(Revision D.01) program package.[55] These calculations were per-
formed at the B3PW91[56,57] /aug-cc-pVTZ-PP [Sb, Bi],[58,59] 6-31G(d)
[C, H, N][60] level of theory.[61–63] Second order perturbation ener-
gies, Wiberg bond indexes (WBI), and natural population charges
were calculated using the natural bond orbital (NBO) method via
the NBO 3.1 program implemented in Gaussian 09.[47,64] The QTAIM
analysis was carried out using the AIMAll program package[65] with
a wavefunction file based on the optimized structure generated by
Gaussian 09.
[33]
[34]
C. I. Raţ, C. Silvestru, H. J. Breunig, Coord. Chem. Rev. 2013, 257, 818–879.
S. Kamepalli, C. J. Carmalt, R. D. Culp, A. H. Cowley, R. A. Jones, N. C.
Norman, Inorg. Chem. 1996, 35, 6179–6183.
P. Sharma, D. Castillo, N. Rosas, A. Cabrera, E. Gomez, A. Toscano, F. Lara,
S. Hernández, G. Espinosa, J. Organomet. Chem. 2004, 689, 2593–2600.
A. Soran, H. J. Breunig, V. Lippolis, M. Arca, C. Silvestru, J. Organomet.
Chem. 2010, 695, 850–862.
D. Copolovici, C. Silvestru, R. A. Varga, Acta Crystallogr., Sect. C 2008, 64,
m37–m39.
H. J. Breunig, M. G. Nema, C. Silvestru, A. Soran, R. A. Varga, Z. Anorg.
Allg. Chem. 2010, 636, 2378–2386.
P. Sharma, D. Pérez, N. Rosas, A. Cabrera, A. Toscano, J. Organomet. Chem.
2006, 691, 579–584.
P. Sharma, D. Pérez, J. Vázquez, A. Toscano, R. Gutiérrez, Inorg. Chem.
Commun. 2007, 10, 389–392.
B. A. Chalmers, C. B. E. Meigh, P. S. Nejman, M. Bühl, T. Lébl, J. D. Woollins,
A. M. Z. Slawin, P. Kilian, Inorg. Chem. 2016, 55, 7117–7125.
R. Deka, A. Sarkar, R. J. Butcher, P. C. Junk, D. R. Turner, G. B. Deacon,
H. B. Singh, Organometallics 2020, 39, 334–343.
E. A. Adams, J. W. Kolis, W. T. Pennington, Acta Crystallogr., Sect. C 1990,
46, 917–919.
D. M. Hawley, G. Ferguson, J. Chem. Soc. A 1968, 2059–2063.
A. Bondi, J. Phys. Chem. 1964, 68, 441–451.
M. Mantina, A. C. Chamberlin, R. Valero, C. J. Cramer, D. G. Truhlar, J. Phys.
Chem. A 2009, 113, 5806–5812.
A. E. Reed, L. A. Curtiss, F. Weinhold, Chem. Rev. 1988, 88, 899–926.
R. F. W. Bader. Atoms in Molecules: A Quantum Theory, Oxford University
Press, 1990.
K. Hoshino, T. Ogawa, S. Yasuike, H. Seki, J. Kurita, T. Tokunaga, K. Yama-
guchi, J. Phys. Chem. B 2004, 108, 18698–18704.
C. E. Housecroft, A. G. Sharpe. Inorganic Chemistry, 4th Edition, Pearson,
2012.
P. Pyykkö, Chem. Rev. 1988, 88, 563–594.
X. Chen, X. S. Hao, C. E. Goodhue, J. Yu, J. Am. Chem. Soc. 2006, 128,
6790–6791.
G. M. Sheldrick, Acta Crystallogr., Sect. A 2008, 64, 112–122.
G. M. Sheldrick, Acta Crystallogr., Sect. C 2015, 71, 3–8.
M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria, M. A. Robb, J. R.
Cheeseman, G. Scalmani, V. Barone, B. Mennucci, G. A. Petersson, H. Na-
katsuji, M. Caricato, X. Li, H. P. Hratchian, A. F. Izmaylov, J. Bloino, G.
Zheng, J. L. Sonnenberg, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hase-
gawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, T. Vreven, J. A.
Montgomery Jr., J. E. Peralta, F. Ogliaro, M. Bearpark, J. J. Heyd, E. Broth-
ers, K. N. Kudin, V. N. Staroverov, R. Kobayashi, J. Normand, K. Raghava-
chari, A. Rendell, J. C. Burant, S. S. Iyengar, J. Tomasi, M. Cossi, N. Rega,
J. M. Millam, M. Klene, J. E. Knox, J. B. Cross, V. Bakken, C. Adamo, J.
Jaramillo, R. Gomperts, R. E. Stratmann, O. Yazyev, A. J. Austin, R. Cammi,
C. Pomelli, J. W. Ochterski, R. L. Martin, K. Morokuma, V. G. Zakrzewski,
G. A. Voth, P. Salvador, J. J. Dannenberg, S. Dapprich, A. D. Daniels, Ö.
Farkas, J. B. Foresman, J. V. Ortiz, J. Cioslowski, D. J. Fox, Gaussian 09,
Revision D.01, Gaussian, Inc., Wallingford CT, 2013.
Acknowledgments
[35]
[36]
[37]
[38]
[39]
[40]
[41]
[42]
[43]
This work was supported in part by the Ministry of Education,
Culture, Sports, Science and Technology of Japan (MEXT) with
a Grant-in-Aid for Scientific Research (24550060). The authors
thank Prof. Dr. T. Nishinaga (Tokyo Metropolitan University) for
support with the CV measurements.
Keywords: Main group elements · Structure elucidation ·
Pnictogens · Intramolecular coordination · Density
functional calculations
[1] L. D. Freedman, G. O. Doak, Chem. Rev. 1982, 82, 15–57.
[2] C. Silvestru, H. J. Breunig, H. Althaus, Chem. Rev. 1999, 99, 3277–3327.
[3] H. Suzuki; Y. Matano. Organobismuth Chemistry. Elsevier, Amsterdam,
2001.
[4] A. Gagnon, J. Dansereau, A. Le Roch, Synthesis 2017, 49, 1707–1745.
[5] A. P. M. Robertson, P. A. Gray, N. Burford, Angew. Chem. Int. Ed. 2014, 53,
6050–6069; Angew. Chem. 2014, 126, 6162.
[6] P. A. Gray, N. Burford, Coord. Chem. Rev. 2016, 324, 1–16.
[7] S. Benz, A. I. Poblador-Bahamonde, N. Low-Ders, S. Matile, Angew. Chem.
Int. Ed. 2018, 57, 5408–5412; Angew. Chem. 2018, 130, 5506.
[8] M. Yang, D. Tofan, C. H. Chen, K. M. Jack, F. P. Gabbaï, Angew. Chem. Int.
Ed. 2018, 57, 13868–13872; Angew. Chem. 2018, 130, 14064.
[9] Á. García-Romero, A. J. Plajer, D. Miguel, D. S. Wright, A. D. Bond, C. M.
Álvarez, R. García-Rodríguez, Inorg. Chem. 2020, 59, 7103–7116.
[10] S. S. Chitnis, H. A. Sparkes, V. T. Annibale, N. E. Pridmore, A. M. Oliver, I.
Manners, Angew. Chem. Int. Ed. 2017, 56, 9536–9540; Angew. Chem.
2017, 129, 9664.
[44]
[45]
[46]
[47]
[48]
[49]
[50]
[51]
[52]
[11] A. Koppaka, S. H. Park, B. G. Hashiguchi, N. J. Gunsalus, C. R. King, M. M.
Konnick, D. H. Ess, R. A. Periana, Angew. Chem. Int. Ed. 2019, 58, 2241–
2245; Angew. Chem. 2019, 131, 2263.
[12] M. Yang, N. Pati, G. Bélanger-Chabot, M. Hirai, F. P. Gabbaï, Dalton Trans.
2018, 47, 11843–11850.
[53]
[54]
[55]
[13] R. Arias Ugarte, D. Devarajan, R. M. Mushinski, T. W. Hudnall, Dalton Trans.
2016, 45, 11150–11161.
[14] R. Arias Ugarte, T. W. Hudnall, Green Chem. 2017, 19, 1990–1998.
[15] M. Hirai, J. Cho, F. P. Gabbaï, Chem. Eur. J. 2016, 22, 6537–6541.
[16] B. Pan, F. P. Gabbaï, J. Am. Chem. Soc. 2014, 136, 9564–9567.
[17] M. Yang, F. P. Gabbaï, Inorg. Chem. 2017, 56, 8644–8650.
[18] I.-S. Ke, M. Myahkostupov, F. N. Castellano, F. P. Gabbaï, J. Am. Chem. Soc.
2012, 134, 15309–15311.
[19] M. Hirai, F. P. Gabbaï, Chem. Sci. 2014, 5, 1886–1893.
[20] M. Hirai, F. P. Gabbaï, Angew. Chem. Int. Ed. 2015, 54, 1205–1209; Angew.
Chem. 2015, 127, 1221.
[21] M. Hirai, M. Myahkostupov, F. N. Castellano, F. P. Gabbaï, Organometallics
2016, 35, 1854–1860.
[22] A. M. Christianson, F. P. Gabbaï, Chem. Commun. 2017, 53, 2471–2474.
[23] A. Kumar, M. Yang, M. Kim, F. P. Gabbaï, M. H. Lee, Organometallics 2017,
36, 4901–4907.
[56]
J. P. Perdew, J. A. Chevary, S. H. Vosko, K. A. Jackson, M. R. Pederson, D. J.
Singh, C. Fiolhais, Phys. Rev. B 1992, 46, 6671–6687.
A. D. Becke, J. Chem. Phys. 1993, 98, 5648–5652.
B. Metz, H. Stoll, M. Dolg, J. Chem. Phys. 2000, 113, 2563–2569.
K. A. Peterson, J. Chem. Phys. 2003, 119, 11099–11112.
P. C. Hariharan, J. A. Pople, Theor. Chim. Acta 1973, 28, 213–222.
[57]
[58]
[59]
[60]
[24] A. M. Christianson, F. P. Gabbaï, Organometallics 2017, 36, 3013–3015.
[25] H. Yang, F. P. Gabbaï, J. Am. Chem. Soc. 2015, 137, 13425–13432.
[26] I.-S. Ke, J. S. Jones, F. P. Gabbaï, Angew. Chem. Int. Ed. 2014, 53, 2633–
2637; Angew. Chem. 2014, 126, 2671.
Eur. J. Inorg. Chem. 2020, 4373–4379
www.eurjic.org
4378
© 2020 Wiley-VCH GmbH

Full Paper
doi.org/10.1002/ejic.202000795
EurJIC
European Journal of Inorganic Chemistry
[61]
[64] E. D. Glendening, A. E. Reed, J. E. Carpenter, F. Weinhold. NBO 3.1, Theo-
B. P. Pritchard, D. Altarawy, B. Didier, T. D. Gibson, T. L. Windus, J. Chem.
Inf. Model. 2019, 59, 4814–4820.
retical Chemistry Institute, University of Wisconsin, Madison, 1995.
[65] T. A. Keith. AIMAll (Version 19.10.12), TK Gristmill Software, Overland Park,
KS, USA, 2013.
[62] D. Feller, J. Comput. Chem. 1996, 17, 1571–1586.
[63] K. L. Schuchardt, B. T. Didier, T. Elsethagen, L. Sun, V. Gurumoorthi,
J. Chase, J. Li, T. L. Windus, J. Chem. Inf. Model. 2007, 47, 1045–1052.
Received: August 24, 2020
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