Unexpected transfer of phenyl from a phenylbismuth complex to iridium in [Cp*IrCl2]2

Article abstract of DOI:10.1080/00958972.2014.908189

Tetranuclear [PhBi(pyzc)₂]₄2(H₂O) (1) (where pyzc. = 2-pyrazinecarboxylic acid) is easily obtained via reaction of BiPh₃ and Hpyzc under reflux. Treatment of 1 with [Cp*IrCl ₂]₂ affords phenyliridium complex [Cp*Ir(Ph)(2- (NC₄H₃N)CO₂)] (2). Unexpected transfer of phenyl from 1 to iridium occurs. The structures of 1 and 2 are established by single-crystal X-ray diffraction. Each bismuth in 1 is in the center of distorted pentagonal pyramidal geometry, equatorially coordinating one κ²-N,O and one μ²-(κ²-N,O),O' pyzc, axially binding to phenyl. Complex 2 displays a typical piano-stool geometry with the metal center coordinated by Cp*, a terminal phenyl, and a chelating N,O-ligand. The UV.vis spectrum of 2 is described.

Full text of DOI:10.1080/00958972.2014.908189

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Unexpected transfer of phenyl from a
phenylbismuth complex to iridium in
[Cp*IrCl2]2
Xiao-Hui Hua, Wen-Zhong Fanga, Min Yanga, Chen Lia & Xiao-Yi Yia
a Key Laboratory of Resources Chemistry of Nonferrous Metals,
Ministry of Education, School of Chemistry and Chemical
Engineering, Central South University, Changsha, PR China
Accepted author version posted online: 26 Mar 2014.Published
online: 22 Apr 2014.
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To cite this article: Xiao-Hui Hu, Wen-Zhong Fang, Min Yang, Chen Li & Xiao-Yi Yi (2014)
Unexpected transfer of phenyl from a phenylbismuth complex to iridium in [Cp*IrCl2]2, Journal of
Coordination Chemistry, 67:5, 779-786, DOI: 10.1080/00958972.2014.908189
To link to this article: http://dx.doi.org/10.1080/00958972.2014.908189
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Journal of Coordination Chemistry, 2014
Vol. 67, No. 5, 779–786, http://dx.doi.org/10.1080/00958972.2014.908189
Unexpected transfer of phenyl from a phenylbismuth complex
to iridium in [Cp*IrCl2]2
XIAO-HUI HU, WEN-ZHONG FANG, MIN YANG, CHEN LI and XIAO-YI YI*
Key Laboratory of Resources Chemistry of Nonferrous Metals, Ministry of Education, School of
Chemistry and Chemical Engineering, Central South University, Changsha, PR China
(Received 30 October 2013; accepted 27 February 2014)
Tetranuclear [PhBi(pyzc)2]4·2(H2O) (1) (where pyzc− = 2-pyrazinecarboxylic acid) is easily obtained
via reaction of BiPh3 and Hpyzc under reflux. Treatment of 1 with [Cp*IrCl2]2 affords phenyliridi-
um complex [Cp*Ir(Ph)(2-(NC4H3N)CO2)] (2). Unexpected transfer of phenyl from 1 to iridium
occurs. The structures of 1 and 2 are established by single-crystal X-ray diffraction. Each bismuth in
1 is in the center of distorted pentagonal pyramidal geometry, equatorially coordinating one κ2-N,O
and one μ2-(κ2-N,O),O′ pyzc, axially binding to phenyl. Complex 2 displays a typical piano-stool
geometry with the metal center coordinated by Cp*, a terminal phenyl, and a chelating N,O-ligand.
The UV–vis spectrum of 2 is described.
Keywords: Tetranuclear; Bismuth; Iridium; Pyrazinecarboxylate; Phenyl transfer
1. Introduction
The cleavage of phenyl groups from PPh3, SbPh3, and BiPh3 and its phenyl transfer to tran-
sition metals have been reported [1–4]. Although BiPh3 could react with transition metal
complexes to form transition metal–bismuth and/or transition metal phenyl complexes,
examples involved in phenyl transfer are still rare, limited to rhenium–bismuth and
osmium–bismuth complexes [5–8]. For example, Adams et al. reported reaction of
triosmium carbonyl complexes with BiPh3 to yield a series of osmium–bismuth complexes-
containing Bi or BiPh from cleavage of all or part of the phenyl groups from the BiPh3 with
*Corresponding author. Email: xyyi@csu.edu.cn
© 2014 Taylor & Francis

780
X.-H. Hu et al.
osmium–carbonyl complexes-containing phenyl, benzoyl, and benzyne ligands derived from
the phenyl group that were transferred from BiPh3 [6, 7]. Rhenium carbonyl complexes-
containing bridging BiPh2 from cleavage of phenyl from BiPh3 have also been reported.
These complexes have shown to be good catalysts for ammoxidation of 3-picoline to
3-cyanopyridine [8].
We have now investigated the synthesis of [PhBi(pyzc)2]4·2(H2O) (1) (where Hpyzc =
2-pyrazinecarboxylic acid) from BiPh3 and the reaction of 1 with [Cp*IrCl2]2. The phenylir-
idium product [Cp*Ir(Ph)(pyzc)] (2) has been obtained. The results of these studies are
reported herein.
2. Experimental
2.1. General
All manipulations were carried out under nitrogen by standard Schlenk techniques unless
1
otherwise stated. Solvents were purified, distilled, and degassed prior to use. H NMR spec-
tra were recorded on a Bruker AV 400 spectrometer operating at 400 MHz and chemical
shifts (δ, ppm) were reported with reference to SiMe4. Infrared spectra (KBr) were recorded
on a Perkin-Elmer 16 PC FT-IR spectrophotometer. Elemental analyses were performed by
a PE240C elemental analyzer. Chemicals were obtained from J&K Scientific Ltd.
[Cp*IrCl2]2 was prepared according to the literature method [9].
2.2. Synthesis of [PhBi(pyzc)2]4·2(H2O) (1)
A mixture of BiPh3 (44 mg, 0.1 mM) and Hpyzc (24.8 mg, 0.2 mM) in water and ethanol
(v : v = 3 mL : 3 mL) was refluxed for 2 h. After cooling, the volatiles in the mixture were
removed in vacuo followed by washing with water, ethanol, and diethyl ether to obtain
white solid of 1, which is pure enough for elemental analysis. The white solid was re-dis-
solved in the hot mixture of ethanol and water. When left undisturbed, it gave colorless
block crystals which were suitable for X-ray single-crystal diffraction. Yield: 21.6 mg
(40%). IR (KBr, cm−1): 3236.1–3143.6(br), 1670.1(vs), 1546.7(m), 1465.7(w), 1385.0(s),
1338.4(vs), 1168.7(m), 10431.9(s), 849.0(s), 794.6(s), 736.7(s), 628.7(vw), 535.9(vs), 459
(s). Anal. Calcd for C64H48Bi4N16O18: C, 35.50; H, 2.23; N, 10.35. Found: C, 36.03; H,
2.14; N, 10.71.
2.3. Synthesis of [Cp*Ir(Ph)(pyzc)] (2)
A mixture of 1 (21 mg, 0.01 mM) and [Cp*IrCl2]2 (16 mg, 0.02 mM) in MeOH and THF
(v : v = 2 mL : 2 mL) was stirred overnight, during which the color of the solution changed
to darkish red in 10 min, and then to orange in 1 h. The mixture was filtered. Slow evapora-
tion of the filtrate afforded orange crystals, which were suitable for X-ray diffraction. Yield:
1
15 mg (71%). H NMR (CDCl3): δ 1.51 (s, 15H, -Me), 1.75 (m, 2H, THF), 3.64 (m, 2H,
THF), 6.72 (t, 1H, -Ph), 6.82 (t, 2H, -Ph), 7.04 (d, 2H, -Ph), 7.26 (s, 1H, -pyrazine), 8.42
(t, 1H, -pyrazine), 8.89 (t, 1H, -pyrazine) ppm. UV–vis(CH3CN) [λmax, nm (ε, M−1 cm−1)]:
260 (2190), 395 (560), 459 (440). IR (KBr, cm−1): 1655(vs), 1581(m), 1545(m), 1408(w),
1378(w), 1322(m), 1273(w), 1168(m), 1055(w), 853(m), 795(m), 735(s), 699(m), 652(w).

Phenyl transfer
781
Anal. Calcd for C21H23IrN2O2·THF: C, 50.07; H, 5.34; N, 4.67. Found: C, 49.88; H, 5.01;
N, 4.89.
2.4. X-ray crystallography
Diffraction data of 1 and 2 were recorded on a Bruker CCD diffractometer with monochro-
mated Mo-Kα radiation (λ = 0.71073 Å). The collected frames were processed with SAINT.
The absorption correction was treated with SADABS [10]. Structures were solved by direct
methods and refined by full-matrix least-squares on F2 using the SHELXTL software pack-
age [11]. Atom positions of non-hydrogen atoms were refined with anisotropic parameters.
All hydrogens were introduced at their geometric positions and refined as riding. In 2, the
unit cell includes a large region of disordered THF solvent molecules, which could not be
modeled as discrete atomic sites. We employed PLATON/SQUEEZE [12] to calculate the
diffraction contribution of solvent THF molecules and, thereby, to produce a set of solvent-
free diffraction intensities. The SQUEEZE calculations showed a total solvent accessible
area volume of 940.3 Å3 in 2 and the residual electron density amounted to 56e per unit
cell, corresponding to nearly 1.4 molecules of THF per asymmetric unit, which is consistent
1
with the H NMR characterization.
3. Results and discussion
Treatment of BiPh3 with two equivalents of Hpyzc leads to isolation of tetranuclear bismuth
complex [PhBi(pyzc)2]·2(H2O) (1) in medium yield (scheme 1). 1 is isolated with yield of
20–35% based on bismuth when the molar ratios of Bi : ligand vary from 2 : 1 to 1 : 3.
O
N
O
Ph
N
N
N
Bi
N
O
N
O
O
O
O
Ph
N
O
O
Bi
CH3CH2OH
H2O
N
OH
4 BiPh3
8
8 C6H6
(1)
N
O
N
N
Ph
O
Bi
O
N
N
O
N
O
N
N
N
O
Bi
Ph
O
N
O
1
Ir
O
CH3OH, THF
1 + [Cp*IrCl2]2
(2)
O
N
2
N
Scheme 1.

782
X.-H. Hu et al.
Similar reaction of BiPh3 with other organic carboxylic acid or sulfonic acid, such as
2,3-pyrazinedicarboxylic acid, 3,5-pyrazoledicarboxylic acid, 8-quinolinesulfonic acid,
8-hydroxyquinoline-5-sulfonic acid, and 4-pyridineethanesulfonic acid, only gives insoluble
white precipitate. That hinders us in characterization and for further studying their
reactivity.
Treatment of 1 with [Cp*IrCl2]2 affords the phenyliridium complex [Cp*Ir(Ph)(pyzc)]
(2). To our knowledge, it is the first example of phenyl transfer from BiPh complex to irid-
ium. In comparison, the reaction between BiPh3 and [Cp*IrCl2]2 only yields intractable
brown precipitate; no phenyliridium complex is isolated. Complexes 1 and 2 are air stable
and are characterized by IR, elemental analyses, and X-ray diffraction. The IR spectra of 1
and 2 show strong sharp bands at 1670 and 1655 cm−1, respectively, assigned to stretching
modes of the carboxyl groups, comparable with the literature values [13, 14]. Complex 1
cannot be characterized by NMR spectra due to very poor solubility in organic solvents,
including DMF and DMSO. 1H NMR spectrum of 2 in CDCl3 displays strong pyrazine pro-
ton signals at δ = 7.26, 8.42, and 8.89 ppm, together with C5Me5 and phenyl protons at δ =
1.51 and 6.72–7.04 ppm, respectively. The co-crystallized tetrahydrofuran protons resonate
at δ = 1.75 and 3.64 ppm.
The crystallographic data and experimental details for 1 and 2 are shown in table 1.
Selected bond distances and angles are listed in tables 2 and 3. Complex 1 crystallizes in
triclinic space group P-1 with one half of a tetrameric aggregate comprising the asymmetric
unit and one co-crystallized water. The structure of 1, as shown in figure 1, is similar with
that for the tetrameric phenylbismuth di-picolinate complex [PhBi(2-(C5H4N)CO2)2]4 [15].
The only difference is pyrazinecarboxylate in 1 instead of picolinate. BiIII ions in 1 are
located at the center of distorted pentagonal pyramidal geometry, equatorially bound to
Table 1. Crystallographic data and experimental details for 1 and 2.
1
2
Formula
Fw
Crystal system
Space group
a, Å
b, Å
c, Å
α, °
β, °
C64H48Bi4N16O18
2165.10
Triclinic
P-1
12.242 (2)
12.623 (3)
13.328 (3)
104.59 (3)
115.29 (3)
100.02 (3)
1706.3(6)
1
C21H23Ir1N2O2
1055.23
Monoclinic
P21/c
16.1361 (7)
14.3958 (6)
22.7058 (9)
120.437 (3)
γ, °
V, Å3
Z
4547.5 (3)
8
1.541
ρ
Calcd, g cm−3
2.107
T, K
293 (2)
10.366
1020
17340
7724
0.0930
1.018
0.0635, 0.0837
0.1232, 0.0974
293 (2)
5.886
2048
30412
10324
0.0325
1.023
0.0470, 0.1253
0.0819, 0.1333
μ, mm−1
F (0 0 0)
No. of refln.
No. of indep. refln.
Rint
GoFa
R1,b wR2 [I > 2σ(I)]
c
R1, wR2 (all data)
½
aGoF = [Σw(|Fo| − |Fc|)2/(Nobs − Nparam)] .
bR1 = Σ||Fo| − |Fc||/Σ|Fo|.
cwR2 = [(Σw|Fo| − |Fc|)2/Σw2|Fo|2]½.

Phenyl transfer
783
Table 2. Selected bond distances (Å) and angles (°) of 1.
Bi1–C1
Bi1–O1
Bi1–O3
Bi1–O8A
Bi1–N1
Bi1–N3
2.235 (10)
2.369 (6)
2.425 (7)
2.417 (6)
2.580 (8)
2.602 (8)
Bi2–C21
Bi2–O4
Bi2–O5
Bi2–O7
Bi2–N5
Bi2–N7
2.273 (10)
2.421 (6)
2.311 (7)
2.520 (6)
2.658 (8)
2.558 (8)
C1–Bi1–O1
C1–Bi1–O3
C1–Bi1–O8A
C1–Bi1–N1
C1–Bi1–N3
O1–Bi1–O3
O1–Bi1–O8A
O1–Bi1–N1
O1–Bi1–N3
O3–Bi1–O8A
O3–Bi1–N1
O3–Bi1–N3
O8A–Bi1–N1
O8A–Bi1–N3
N1–Bi1–N3
87.4 (3)
87.2 (3)
80.2 (3)
88.1 (3)
83.4 (3)
140.5 (2)
141.5 (2)
66.6 (3)
75.9 (2)
75.5 (2)
152.1 (2)
64.6 (2)
76.6 (2)
137.4 (2)
141.9 (2)
C21–Bi2–O4
C21–Bi2–O5
C21–Bi2–O7
C21–Bi2–N5
C21–Bi2–N7
O4–Bi2–O5
O4–Bi2–O7
O4–Bi2–N5
O4–Bi2–N7
O5–Bi2–O7
O5–Bi2–N5
O5–Bi2–N7
O7–Bi2–N5
O7–Bi2–N7
N7–Bi2–N5
85.4 (3)
90.6 (3)
82.3 (3)
86.1 (3)
86.2 (3)
75.1 (2)
139.1 (2)
76.7 (2)
141.6 (3)
143.5 (2)
151.7 (2)
67.5 (3)
63.8 (2)
76.3 (2)
139.9 (3)
Symmetry transformations used to generate equivalent atoms: A−x + 1, −y + 1, −z + 1.
Table 3. Selected bond distances (Å) and angles (°) of 2.
Ir1–C11
2.069 (7)
Ir2–C41
2.069(7)
Ir1–N1
Ir1–O1
2.065 (8)
2.169 (6)
Ir2–N3
Ir2–O3
2.089 (8)
2.178 (6)
C11–Ir1–N1
C11–Ir1–O1
N1–Ir1–O1
86.3 (3)
86.2 (2)
75.1 (3)
C41–Ir2–N3
C41–Ir2–O3
N3–Ir2–O3
84.5 (3)
86.4 (2)
77.3 (3)
three oxygens and two nitrogens from two pyzc ligands, and axially with phenyl. Two coor-
dination modes of κ2-N,O and μ2-(κ2-N,O),O′ for pyzc are observed. The Bi–N and Bi–O
bond distances are 2.580(8)–2.658(8) Å and 2.311(7)–2.520(6) Å, respectively, analogous
with those observed in other phenylbismuth complexes [15–17]. Bi–C bond distance in 1 is
2.254 Å. The Bi is out of the N2O3 pentagonal meridian plane by 0.214 Å toward the apical
carbon due to lone pair repulsion of Bi along the Bi–C bond.
Complex 2 crystallizes in the space group P21/c. Its structure with atom labeling is
shown in figure 2. Complex 2 displays a typical piano-stool geometry with the metal center
coordinated by Cp*, a terminal phenyl, and a κ2-N,O-chelating pyzc. The distance between
iridium and Cp* is 1.825 Å, which is comparable with that for Cp*Ir complexes [18, 19].
The average Ir–C, Ir–N, and Ir–O bond distances are 2.069, 2.077, and 2.174 Å, respec-
tively. The N1–Ir1–O1 and N3–Ir2–O3 bond angles of 2 are 75.1(3)° and 77.3(3)°. Com-
plex 2 is co-crystallized with tetrahydrofuran molecules, which are squeezed out using
Platon program due to their serious disorder.
The UV–vis spectrum of 2 is displayed in figure 3. Clearly, 2 follows the normal trends
observed in the electronic spectrum of metal complex with phenyl and pyrazinecarboxylate,
with metal-to-ligand charge transfer and a ligand based π–π* transition. The low-spin d6
configuration of 2 provides filled orbitals at IrIII, which can interact with low-lying π*

784
X.-H. Hu et al.
Figure 1. The molecular structure of 1 (hydrogens are omitted for clarity. Probability ellipsoids of 50% are
shown).
Figure 2. The molecular structure of 2 (hydrogens are omitted for clarity. Probability ellipsoids of 50% are
shown).

Phenyl transfer
785
Figure 3. The UV–vis spectrum of 2.
orbitals of the ligand. Therefore, the medium intensity bands at 395 and 459 nm in the
electronic spectrum can be assigned to metal-to-ligand charge transfer transition. The
high-energy band at 260 nm is attributable to intra-ligand π–π* transition.
4. Conclusion
We have synthesized and characterized 1 by reaction of BiPh3 with 2-pyrazinecarboxylic
acid. Bismuth is at the center of a distorted pentagonal pyramid. Phenyl is at the axial posi-
tion. Two pyzc bind to bismuth in κ2-N,O and μ2-(κ2-N,O),O′ manner. The phenyl transfer
from 1 to iridium in [Cp*IrCl2]2 generates phenyliridium complex 2, of which X-ray
diffraction shows a typical piano-stool geometry with the iridium coordinated by Cp*, a
terminal phenyl, and a κ2-N,O-chelating pyzc.
Supplementary material
Electronic Supplementary Information (ESI) available: Crystallographic data for 1 and 2, have been
deposited with the Cambridge Crystallographic Data Center as supplementary publication no. CCDC
965724- and 965725, respectively. Copies of the data can be obtained free of charge on application to
CCDC, 12 Union Road, Cambridge CB2 1EZ, UK.
Acknowledgement
This work was supported by the National Natural Science Foundation of China (project 21001118),
Hunan Provincial Science and Technology Department (S2012R1040), and the Test Fund of Central
South University for valuable equipments.

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X.-H. Hu et al.
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