Cyclometalated Pd(ii) and Ir(iii) 2-(4-bromophenyl)pyridine complexes with N-heterocyclic carbenes (NHCs) and acetylacetonate (acac): Synthesis, structures, luminescent properties and application in one-pot oxidation/Suzuki coupling of aryl chlorides containing hydroxymethyl

Article abstract of DOI:10.1039/c4dt00833b

A series of cyclopalladated 2-(4-bromophenyl)pyridine (bpp) complexes [Pd(bpp)(NHC)Cl] 1-3, [Pd(bpp)(acac)] 4, cyclometalated iridium(iii) complexes [Ir(bpp)₂Cl]₂5 and [Ir(bpp)₂(acac)] 6 have been synthesized and characterized. Their detailed structures have been determined by X-ray diffraction and many intermolecular C-H...X (Cl, Br, π) and π...π interactions were found in their crystals. Cyclometalated complexes 1-4 and 6 exhibit luminescence with emission peaks of 390-543 nm in dichloromethane solution under UV irradiation. Their application to coupling reactions of aryl chlorides containing hydroxymethyl was also investigated. An efficient 3/Cu cocatalyzed oxidation/Suzuki reaction for the synthesis of biarylaldehydes from chloro-phenylmethanol and arylboronic acids in air has been developed. In addition, a 6/3-cocatalyzed one-pot reaction of acetylferrocene, (2-amino-5-chlorophenyl)methanol, and arylboronic acids provided 6-aryl-2-ferrocenylquinolines in moderate to good yields.

Full text of DOI:10.1039/c4dt00833b

Dalton
Transactions
View Article Online
View Journal | View Issue
PAPER
Cyclometalated Pd(II) and Ir(III) 2-(4-bromophenyl)-
pyridine complexes with N-heterocyclic carbenes
(NHCs) and acetylacetonate (acac): synthesis,
structures, luminescent properties and application
in one-pot oxidation/Suzuki coupling of aryl
chlorides containing hydroxymethyl†
Cite this: Dalton Trans., 2014, 43,
10235
Chen Xu,*a,b Hong-Mei Li,a Zhi-Qiang Xiao,b Zhi-Qiang Wang,a Si-Fu Tang,c
Bao-Ming Ji,a Xin-Qi Hao*b and Mao-Ping Songb
A series of cyclopalladated 2-(4-bromophenyl)pyridine (bpp) complexes [Pd(bpp)(NHC)Cl] 1–3, [Pd(bpp)-
(acac)] 4, cyclometalated iridium(III) complexes [Ir(bpp)2Cl]2 5 and [Ir(bpp)2(acac)] 6 have been synthesized
and characterized. Their detailed structures have been determined by X-ray diffraction and many inter-
molecular C–H⋯X (Cl, Br, π) and π⋯π interactions were found in their crystals. Cyclometalated complexes
1–4 and 6 exhibit luminescence with emission peaks of 390–543 nm in dichloromethane solution under
UV irradiation. Their application to coupling reactions of aryl chlorides containing hydroxymethyl was also
investigated. An efficient 3/Cu cocatalyzed oxidation/Suzuki reaction for the synthesis of biarylaldehydes
from chloro-phenylmethanol and arylboronic acids in air has been developed. In addition, a 6/3-co-
catalyzed one-pot reaction of acetylferrocene, (2-amino-5-chlorophenyl)methanol, and arylboronic
acids provided 6-aryl-2-ferrocenylquinolines in moderate to good yields.
Received 19th March 2014,
Accepted 17th April 2014
DOI: 10.1039/c4dt00833b
www.rsc.org/dalton
applied to the coupling reactions of aryl chlorides. However,
aryl halides containing hydroxymethyl as substrates have been
Introduction
Cyclometalation has become one of the most popular organo- relatively less reported.9 Alcohols are of great importance as
metallic reactions, providing a straightforward entry to cyclo- cheap and readily available materials for the preparation of
metalated complexes that feature a metal–carbon bond.1 pharmaceutical products and fine chemicals. In addition,
Among them, cyclometalated palladium(II),2 iridium(III)3 com- palladium-catalyzed aerobic alcohol oxidation to carbonyl
plexes have been successfully developed as highly active pre- compounds is one of the most common classes of oxidation
catalysts for coupling reactions. For example, Buchwald4 and reactions in organic chemistry.10 Great progress has made
Ishii5 groups have reported the use of dialkylbiaryl phosphine- recently in palladium-catalyzed oxidation by using NHC
palladacycle complexes and [Ir(cod)Cl]2/PPh3 as efficient cata- ligands reported by the group of Sigman.11 We have also deve-
lysts for the Suzuki reaction of unactivated aryl chlorides and loped NHC-palladacycles/Cu12 and cyclometallated Ir/Pd13
the α-alkylation of alcohols. As an alternative, NHCs have cocatalyzed α-alkylation/Suzuki reaction for the synthesis of
proved to be excellent ligands in transition-metal-catalyzed 2,6-diarylquinolines from (2-amino-5-bromophenyl)methanol.
coupling reactions.6 Especially the NHC-palladacycles reported To the best of our knowledge, there are no reports concerning
by the groups of Nolan,7 Herrmann8 have successfully been reactions involving oxidation and the Suzuki reaction for the
synthesis of biarylaldehydes from aryl chlorides containing
hydroxymethyl and arylboronic acids.
On the other hand, cyclometalated iridium complexes have
attracted a great deal of attention due to their possible appli-
cations as organic light-emitting diodes (OLEDs).14 In these
studies, acetylacetonate (acac) is one of the most widely used
ancillary ligands providing additional possibilities for tuning
the electro-optical properties. Furthermore, the use of NHCs as
ancillary ligands has opened up new routes for the design of
aCollege of Chemistry and Chemical Engineering, Luoyang Normal University,
Luoyang, Henan 471022, China. E-mail: xubohan@163.com
bCollege of Chemistry and Molecular Engineering, Zhengzhou University, Zhengzhou,
Henan 450001, China. E-mail: xqhao@zzu.edu.cn
cQingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of
Sciences, Qingdao 266101, China
†CCDC 981473–981478 for 1–6 and 992168 for 9h. For crystallographic data in
CIF or other electronic format see DOI: 10.1039/c4dt00833b
This journal is © The Royal Society of Chemistry 2014
Dalton Trans., 2014, 43, 10235–10247 | 10235

View Article Online
Paper
Dalton Transactions
Scheme 1 Synthesis of palladacycles 1–4 and cyclometalated iridium complexes 5–6.
phosphorescent materials, because of their high stability and the Pd(II), Ir(III) dimers were directly subjected to bridge-split-
excellent color purity.15 However, the luminescence of NHC- ting reactions with acac to produce the mononuclear cyclo-
palladacycles has not been reported to date. As a continuation metalated Pd(II), Ir(III) acac complexes 4 and 6.
of our interest in the application of cyclometalated com-
These complexes were characterized by elemental analysis,
plexes,16 we prepared four new palladacycles 1–4 and two IR, ESI-MS, and H NMR. The H NMR spectra of these com-
cyclometalated Ir complexes 5–6 (Scheme 1) and examined plexes were consistent with the proposed structures. The
their luminescent properties and catalytic activity. Here, we lowest field resonance appear as a doublet at δ 8.43–9.24 ppm,
also reported that the 3/Cu(OAc)2 and 6/3-cocatalyzed one-pot and was assigned to the proton ortho to the nitrogen in the
reaction of aryl chlorides containing hydroxymethyl, provides a pyridyl ring. NHC-palladacycles 1–3 all exhibit singlets for the
1
1
series of biarylaldehydes and 6-aryl-2-ferrocenylquinolines.
methyl groups of the NHCs at δ 2.31, 3.57 and 2.43, 2.29,
2.26 ppm, respectively. In the mass spectra of 1–3, the most
intense peak was attributed to [M − Cl]+. The acac CH proton
is observed as a sharp singlet at δ 5.41 and 5.30 ppm for com-
plexes 4 and 6, respectively. Furthermore, the X-ray molecular
structures of all complexes were determined.
Results and discussion
Synthesis and characterization of the complexes 1–6
The preparation of six new cyclometalated palladium, iridium
complexes 1–6 is as follows (Scheme 1). The cyclopalladation
reaction was carried out with bpp and 1 equivalent of Li2PdCl4
X-ray molecular structures of palladacycles
and NaOAc in methanol at rt for 12 h. The formed yellow Single crystal structure analyses reveal that 1–4 are mono-
solids were collected by filtration, and can be assigned as a nuclear and the palladium centers feature a square planar
chloride-bridged palladacyclic dimer.16a,b Because of its poor coordination geometry. The molecules are shown in Fig. 1–4.
solubility in all common organic solvents, it was not character- The bicyclic system formed by the palladacycle and the pyridyl
ized and directly subjected to bridge-splitting reaction. Three ring is approximately coplanar (dihedral angles of 5.7°, 0.6°,
NHC adducts of palladacycles 1–3 have been easily prepared 3.8° and 1.5°, 0.9° for complexes 1–4, respectively). The Pd–
in situ from the reaction of the above dimer and 1,3-bis(4- Cbpp and Pd–Nbpp bond lengths are elongated to 1.990(2) and
methylphenyl) imidazolium chloride (ITolHCl), 1,3-bis(4- 2.071(2) Å in 1, 1.992(3) and 2.070(2) Å in 2, 1.984(4) and
methoxyphenyl) imidazolium chloride (IMeOHCl) or 1,3-bis- 2.083(3) Å in 3, due to the stronger electron-withdrawing
(2,4,6-trimethylphenyl) imidazolium chloride (IMesHCl) in ability of the chloride anion. The Pd–Ccarb [1.998(3) Å] bond
THF at rt under N2. The chloride-bridged dimer [Ir(bpp)2Cl]2 5 length of 3 is similar to those of related carbene adducts
was synthesized according to the reported procedure.17 Then, [1.992–1.998 Å],18 while it is longer than those of 1–2 [1.976(2)
10236 | Dalton Trans., 2014, 43, 10235–10247
This journal is © The Royal Society of Chemistry 2014

View Article Online
Dalton Transactions
Paper
Fig. 1 The molecular structure of 1 with displacement ellipsoids drawn
at the 50% probability level. H atoms are omitted for clarity. Selected
bonds distances (Å): Pd(1)–C(1) 1.976(2), Pd(1)–C(24) 1.990(2), Pd(1)–
N(3), 2.071(2), Pd(1)–Cl(1), 2.4205(7).
Fig. 4 The molecular structure of 4 with displacement ellipsoids drawn
at the 50% probability level. H atoms are omitted for clarity. Selected
bonds distances (Å): Pd(1)–C(1) 1.958(7), Pd(1)–N(1) 2.006(6), Pd(1)–O(1)
2.010(5), Pd(1)–O(2) 2.088(5), Pd(2)–C(18) 1.955(9), Pd(2)–O(4) 2.015(7),
Pd(2)–N(2) 2.031(7), Pd(2)–O(3) 2.072(7).
and 1.981(3) Å] possibly due to the steric bulk of the IMes
ligand.
ˉ
For 4, it crystallizes in the triclinic P1 space group with two
mononuclear molecules [Pd(bpp)(acac)] in each asymmetric
unit. The two crystallographic independent Pd(II) ions have the
same coordination mode which is chelated by one acac ligand
and one bpp ligand, yielding one five-membered ring
(NCCCPd) and one six-membered ring (OCCCOPd) around the
Pd(II) center (Fig. 4). The Pd–Cbpp and Pd–Nbpp bond lengths
were found to be in the range of 1.958(7)–1.955(9) and 2.006(6)–
2.031(7) Å, respectively, which are comparable to those of other
reported cyclopalladated diketonate complexes.19 In addition,
the bpp and acac ligands are almost coplanar in 4, whereas for
1–3 the imidazole rings of the NHC ligands are almost perpen-
dicular to the bpp plane [76.64(7)° for 1, 87.40(9)° for 2, and
73.08(13)° for 3] for the sake of steric hindrance.
Fig. 2 The molecular structure of 2 with displacement ellipsoids drawn
at the 50% probability level. H atoms and CH2Cl2 are omitted for clarity.
Selected bonds distances (Å): Pd(1)–C(19) 1.981(3), Pd(1)–C(7) 1.992(3),
Pd(1)–N(1) 2.070(2), Pd(1)–Cl(1) 2.4255(10).
Conventional and unconventional hydrogen interactions
are very interesting in crystal engineering and supramolecular
chemistry.20 In 1–3, there are a plenty of C–H⋯Cl and
C–H⋯Br interactions with the D⋯A distances and DHA angles
varying from 3.273(5) to 3.821(4) Å, and 123.2 to 166.4°,
respectively. Besides C–H⋯Cl and C–H⋯Br interactions, there
are also some π⋯π interactions between the metal-involved
rings and aromatic groups of bpp and NHC ligands (Table 1).
A closer look at the structures reveals the presence of C–H⋯π
interactions in 1–2, and 4 (Table 2).
For 1 and 2, both bpp and NHC ligands can serve as
H-donors or acceptors of C–H⋯π interactions (Fig. 5). In the
case of 4, the C–H⋯π interactions are formed between the
methyl groups of the acac ligands and pyridine or the benzene
ring of the bpp ligands with the H⋯centroid (aromatic ring)
and C⋯centroid distances falling in the range of 2.8593(5)–
3.0388(5) and 3.5836(5)–3.9482(5) Å, respectively. The H⋯cen-
troid distances of 4 are longer than those of B(C6F5)3-stabilized
benzene–ammonia and benzene water compounds, but
Fig. 3 The molecular structure of 3 with displacement ellipsoids drawn
at the 50% probability level. H atoms are omitted for clarity. Selected
bonds distances (Å): Pd(1)–C(7) 1.984(4), Pd(1)–C(21) 1.998(3), Pd(1)–
N(1) 2.083(3), Pd(1)–Cl(1) 2.4061(11).
This journal is © The Royal Society of Chemistry 2014
Dalton Trans., 2014, 43, 10235–10247 | 10237

View Article Online
Paper
Dalton Transactions
Table 1 Geometric parameters of the π⋯π interactions in 1–4
Complex
π⋯π
Cga⋯Cg (Å)
αb
βc
Cg⋯plane (Cg2) (Å)
Symm. op. on Cg2
1
2
3
4
C18→N3⋯C18→N3
N1→C5⋯C6→C11
C1→N1⋯C1→N1
Pd2→O4⋯Pd2→N2
Pd1→N1⋯Pd1→O1
3.577(1)
3.747(3)
3.463(1)
3.644(3)
3.621(4)
0
76.49(1)
73.42(2)
82.7(1)
69.69(1)
69.74(1)
3.478(1)
3.591(3)
3.435(1)
3.417(3)
3.397(4)
−x, −y, −z
1.07(2)
0
5.74(3)
3.27(3)
1 − x, 1 − y, 1 − z
1.5 − x, 0.5 −y , 1 – z
1 − x, −y, 1 − z
1 − x, 1 − y, −z
a Cg = centre of gravity of the interacting ring. b α = angle between the planes of the two interacting rings. c β = angle between the Cg⋯Cg line and
the plane of the first interacting ring.
X-ray molecular structures of cyclometalated iridium
Table 2 Geometric parameters of the C–H⋯π interactions in 1–2 and
complexes
4
Although many structures of mononuclear cyclometalated
iridium complexes have been determined,3 there are very
limited reports on the structures of dinuclear Cl-bridged
dimers.11b,22 The dimer 5 adopts the racemate form, rather
than the meso form. Each iridium atom locates at a distorted
octahedral environment with cis-C–C and trans-N–N chelate
dispositions. A two-fold axis passes through both chlorine
atoms, thus, the asymmetric unit consists of half of the mole-
cule (Fig. 7). The central iridium atom in 6 is surrounded by
two bbp and one acac with cis-C–C, trans-N–N and cis-O–O
chelate dispositions (Fig. 8). The Ir–C, Ir–N and Ir–O bond
lengths are similar to the reported values of cyclometalated
2-phenylpyridine (ppy) iridium complex (ppy)2Ir(acac).23 The
crystal structure of 6 is also similar to that of (ppy)2Ir(acac) by
Complex
H⋯centroid (Å)
C⋯centroid (Å)
C–H⋯centroid (°)
1
2.962(1)
2.664(1)
3.069(7)
2.8944(4)
3.0012(4)
2.8593(5)
3.0388(5)
3.775(1)
3.557(2)
3.97(1)
3.7597(5)
3.9482(5)
3.5836(5)
3.9385(6)
143.32(1)
161.09(1)
165.8(3)
150.49(2)
169.15(2)
133.01(2)
156.63(2)
2
4
shorter than that of Cu(II)-carboxylate.21 But in 3, no obvious
C–H⋯π interactions can be found. These unconventional
hydrogen interactions work together and assemble the respect-
ive mononuclear molecules into 3D supramolecular structures
(Fig. 6).
Fig. 5 C–H⋯π interactions found in complexes 1 (a), 2 (b) and 4 (c).
10238 | Dalton Trans., 2014, 43, 10235–10247
This journal is © The Royal Society of Chemistry 2014

View Article Online
Dalton Transactions
Paper
Fig. 6 Three-dimensional packing diagrams of 1 (a), 2 (b), 3 (c) and 4 (d). The π⋯π interactions are shown as dotted lines.
Fig. 7 The molecular structure of 5 with displacement ellipsoids drawn
at the 50% probability level. H atoms and CH2Cl2 are omitted for clarity.
Selected bonds distances (Å): Ir(1)–N(1) 2.070(6), Ir(1)–N(2) 2.077(6),
Ir(1)–C(1) 1.998(12), Ir(1)–C(12) 1.989(10), Ir(1) –Cl(1) 2.494(3), Ir(1)–Cl(2)
2.530(3).
Fig. 8 The molecular structure of 6 with displacement ellipsoids drawn
at the 50% probability level. H atoms and CH2Cl2 are omitted for clarity.
Selected bonds distances (Å): Ir(1)–C(7) 1.994(11), Ir(1)–C(18) 1.996(12),
Ir(1)–N(1) 2.049(10), Ir(1)–N(2) 2.014(11), Ir(1)–O(1) 2.158(8), Ir(1)–O(2)
2.140(8).
the existence of π⋯π interaction with a ca. 3.838 Å face–face
separation between the adjacent ring planes.
and 375 nm, respectively. These absorption bands can all be
assigned to the ligand localized π–π* transitions. Three NHC-
Luminescent properties
The UV-Vis absorption and photoluminescence (PL) spectra of palladacycles all exhibit luminescence in CH2Cl2 at rt. 1 and 3
these complexes in CH2Cl2 at rt are shown in Fig. 9 and 10 and display emission peaks at 390 nm and 394 nm suggesting that
Table 3. The absorption spectra of 1–3 have similar features. steric factors have less influence on the luminescence.
Two intense absorption peaks appear at 220 nm and 295 nm, However, the emission peak (414 nm) of 2 containing –OCH3
and weaker absorptions were also observed between 295 nm is obviously higher than those of 1 and 3 containing –CH3,
This journal is © The Royal Society of Chemistry 2014
Dalton Trans., 2014, 43, 10235–10247 | 10239

View Article Online
Paper
Dalton Transactions
Fig. 11 The cyclic voltammetry spectra of 6.
Fig. 9 Normalized absorption and emission of 1–3 in CH2Cl2 at rt.
an emitting material in yellow OLEDs, but in the fabrication of
white OLEDs combined with blue emitters.
Moreover, the electrochemical property of 6 was investi-
gated by cyclic voltammetry in CH2Cl2 solution containing
0.1 M tetrabutylammonium hexafluorophosphate with a 0.05 V
s−1 scan rate. The cyclic voltammogram shows a reversible oxi-
ox
1/2
dation wave due to iridium(III/IV) with E of 1.04 V vs. Ag/AgCl
(Fig. 11). The highest occupied molecular orbital (HOMO)
energy level was calculated to be −5.36 eV relative to the value
of −4.8 eV for ferrocene (Fc) with respect to the zero vacuum
level.24 The lowest unoccupied molecular orbital (LUMO)
energy level was estimated to be −2.88 eV according to the
HOMO energy level value in combination with the band gap
derived from the absorption band edge.
Fig. 10 Normalized absorption and emission of 4 and 6 in CH2Cl2 at rt.
Pd/Cu cocatalyzed oxidation/Suzuki reaction
Palladium-catalyzed Suzuki coupling is well-known as being
one of the most versatile and utilized reactions for the con-
struction of a C–C bond, in particular for the formation of
biaryls.2,4 Generally, Suzuki coupling of aryl halides containing
hydroxymethyl produced the corresponding biarylalcohols.25
Initially, we examined the catalytic activity of palladacycles 1–4
for the Suzuki reaction of (4-bromophenyl) methanol with phe-
nylboronic acid. Based on our previous experiments in pallada-
cyclic precatalysts for Suzuki coupling,20b,d the reaction was
performed under a nitrogen atmosphere in dioxane in the
presence of Cs2CO3 as base at 110 °C for 18 h. 3 was the most
efficient among these palladacycles 1–4 and produced the
indicating that the inductive effect of the substituents on the
NHC ligand have more effect on the luminescence. The absorp-
tion spectra of cyclometalated acac complexes 4 and 6 are very
different to each other. Complex 4 shows three intense absorp-
tion bands from ligands below 375 nm, in contrast, complex 6
exhibits obvious metal-to-ligand charge transition (MLCT)
absorption bands between 407 nm and 510 nm. Thus, the emis-
sion (λmax = 543 nm) of complex 6 should be phosphorescence,
the emission (λmax = 391 nm) of complex 4 is fluorescence.
Similar to the luminescence of (ppy)2Ir(acac),23 6 shows a yellow
phosphorescence, which implies that it not only can be used as
Table 3 Photophysical data for 1–4 and 6
Complex
λabs/nm (ε × 10−3/M−1 cm−1 a
)
λem(λex)/nm
Stokes shift/nm
Φb (%)
1
2
3
4
6
233 (2.08), 270 (1.13), 317 (0.19), 339 (0.22), 353 (0.16)
235 (2.57), 268 (1.49), 318 (0.34), 339 (0.41), 353 (0.38)
235 (2.25), 270 (1.31), 318 (0.27), 339 (0.29), 353 (0.20)
229 (0.45), 265 (0.27), 316 (0.133), 359 (0.08)
390 (353)
414 (353)
394 (353)
391 (359)
543 (407)
37
51
41
32
136
2.4
3.6
1.7
1.8
6.3
268 (0.96), 337 (0.21), 361 (0.14), 407 (0.10), 454 (0.06), 488 (0.01)
a Measured in CH2Cl2 (10 × 10−5 M). b Measured in CH2Cl2 used 9,10-diphenylanthracene and fac-Ir(ppy)3 as the reference standard for 1–4 and
6, respectively.
10240 | Dalton Trans., 2014, 43, 10235–10247
This journal is © The Royal Society of Chemistry 2014

View Article Online
Dalton Transactions
Paper
Table 4 Suzuki coupling of aryl halides containing hydroxymethyl with phenyl boronic acid catalyzed by palladacyclesa
Entry
X
Catalyst (mol%)
7a Yieldb (%)
7b Yieldb (%)
1
2
3
4
5
6
7
Br
Br
Br
Br
Cl
Cl
Cl
Cl
Cl
Cl
1 (1)
2 (1)
3 (1)
4 (1)
1 (1)
2 (1)
3 (1)
1 (1)
2 (1)
3 (1)
51
58
93
16
Trace
Trace
82
Trace
Trace
47
0
0
0
0
0
0
0
24
29
45
8c
9c
10c
a Reaction conditions: aryl halides containing hydroxymethyl (0.5 mmol), phenylboronic acid (0.75 mmol), Cs2CO3 (1.0 mmol), dioxane (3 mL),
110 °C, 18 h, nitrogen atmosphere. b Isolated yield. c In air.
expected coupled product 7a in 93% with a catalyst loading of more active than the other two systems. Different copper salts/
1 mol% (Table 4, entries 1–4). In the case of (4-chlorophenyl)- palladacycle 3 were then tested (entries 4–6). The results indi-
methanol, 1 and 2 were almost inactive under the same reac- cated that 3/Cu(OAc)2 was among the best of these tested cata-
tion conditions, however, 3 generated 7a in a good yield (82%, lysts (92%, entry 6). Other reaction conditions (entries 7–12)
entry 7). Then, the coupling of (4-chlorophenyl)methanol was such as K2CO3 in dioxane and Cs2CO3 in toluene also afforded
performed in air. It is interesting that an unexpected coupled good yields (85% and 88%, respectively).
product 7b was obtained besides 7a (entries 8–10). The results
indicated that palladacycles can also catalyze aerobic alcohol phenyl)methanol with a variety of electronically and structu-
oxidation in the above reaction. rally diverse arylboronic acids were investigated (Table 6).
To test this procedure, the coupling reactions of (4-chloro-
On the basis of this finding, we were interested to see Electron-donating substrates reacted to give the corresponding
whether the palladacycles could efficiently catalyze the reac- products 7c and 7d, the yields (93% and 95%) are higher
tions involving oxidation and the Suzuki reaction for the syn- than the yields of electron-withdrawing substrates containing
thesis of biarylaldehydes. The results from this study are –CO– and –NO2 groups. A slight decrease in the yields (86% and
summarized in Table 5. Under the same reaction conditions 82%) of meta-substitution products 7e and 7f was observed. The
(Cs2CO3, dioxane, air), the yield was improved by the addition method proved to be effective for pyridinylboronic acids bearing
of copper salts (entries 1–3) suggesting that copper partici- functional groups, including esters (7j) and amines (7k).
pated in the catalytic cycles. The 3/CuCl2 system was obviously
This newly developed coupling protocol was also success-
fully applied to the synthesis of 2-biarylcarboxaldehydes via
oxidation and the Suzuki reaction of (2-chlorophenyl)methanol
(Table 7). Similar to the results of (4-chlorophenyl)methanol,
the corresponding 2-biaryl-carboxaldehydes 8a–8c were also
obtained with good yields (86–91%). On the basis of the
success of this approach, we were interested to see whether
3/Cu(OAc)2 could efficiently cocatalyze double oxidation and
the Suzuki reaction of hydroxymethylphenylboronic acids. The
desired products biphenyldialdehydes 8d–8f were isolated in
moderate yields (53–76%). Compared with the yields of 7i–7k,
the yields of 8g–8i starting from the same arylboronic acid
were slightly decreased possibly due to steric hindrance.
Table 5 Optimization of the reaction conditionsa
Entry
Catalyst (mol%)
Base
Solvent
Yieldb (%)
1
2
3
4
5
6
7
8
1/CuCl2 (1/5)
2/CuCl2 (1/5)
3/CuCl2 (1/5)
3/CuCl (1/5)
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
K2CO3
Na2CO3
K3PO4
Cs2CO3
Cs2CO3
Cs2CO3
Dioxane
Dioxane
Dioxane
Dioxane
Dioxane
Dioxane
Dioxane
Dioxane
Dioxane
Toluene
THF
53
60
81
72
64
92
85
67
56
88
55
62
3/CuI (1/5)
3/Cu(OAc)2 (1/5)
3/Cu(OAc)2 (1/5)
3/Cu(OAc)2 (1/5)
3/Cu(OAc)2 (1/5)
3/Cu(OAc)2 (1/5)
3/Cu(OAc)2 (1/5)
3/Cu(OAc)2 (1/5)
Ir/Pd cocatalyzed α-alkylation and the Suzuki reaction
9
In recent years, there has been significant interest in the
metal-catalyzed hydrogen autotransfer process by alcohols as a
more benign alternative to potentially genotoxic halides.26
Although iridium complexes serve as efficient catalysts for the
hydrogen transfer process,3 cyclometalated iridium acac com-
plexes-catalyzed α-alkylation of alcohols has not been explored
10
11
12
DMF
a Reaction conditions: (4-chlorophenyl)methanol (0.5 mmol),
phenylboronic acid (0.75 mmol), base (1.0 mmol), solvent (3 mL),
110 °C, 18 h, air atmosphere. b Isolated yield.
This journal is © The Royal Society of Chemistry 2014
Dalton Trans., 2014, 43, 10235–10247 | 10241

View Article Online
Paper
Dalton Transactions
a
Table 6 Reaction of (4-chlorophenyl)methanol with arylboronic acids catalyzed by 3/Cu(OAc)2
a Reaction conditions: (4-chlorophenyl)methanol (0.5 mmol), arylboronic acid (0.75 mmol), 3/Cu(OAc)2 (0.005/0.025 mmol), Cs2CO3 (1.0 mmol),
dioxane (3 mL), 110 °C, 18 h, air atmosphere. b Isolated yield.
a
Table 7 Reaction of (2-chlorophenyl)methanol with arylboronic acids catalyzed by 3/Cu(OAc)2
a Reaction conditions: (2-chlorophenyl)methanol (0.5 mmol), arylboronic acid (0.75 mmol), 3/Cu(OAc)2 (0.005/0.025 mmol), Cs2CO3 (1.0 mmol),
dioxane (3 mL), 110 °C, 18 h, air atmosphere. b Isolated yield.
until now. Considering that cyclometalated iridium complexes
are active catalysts for α-alkylation of alcohols,13,16d we hypo-
thesized that the cyclometalated iridium acac complex 6
should catalyze the α-alkylation of acetylferrocene with benzyl
alcohol. Thus, the reaction of (4-bromophenyl)methanol with
acetylferrocene was performed under a nitrogen atmosphere in
dioxane in the presence of 2 mol [Ir]% of 5 or 6 as catalyst and
KOH as base at 110 °C for 12 h (Scheme 2). To our delight, 6
Scheme 2 α-alkylation of acetylferrocene catalyzed by 5 and 6.
10242 | Dalton Trans., 2014, 43, 10235–10247
This journal is © The Royal Society of Chemistry 2014

View Article Online
Dalton Transactions
Paper
Table 8 Synthesis of 2-ferrocenyl-6-phenylquinolinea
Entry
X
Catalyst (mol%)
Yieldb (%)
1
2
3
4
5
6
7
Br
Br
Br
Cl
Cl
Cl
Cl
6/1 (2/1)
6/2 (2/1)
6/3 (2/1)
6/Pd(OAc)2 (2/3)
6/1 (2/1)
6/2 (2/1)
6/3 (2/1)
82
85
94
0
Trace
Trace
87
a Reaction conditions: acetylferrocene (0.5 mmol), (2-amino-5-halophenyl)methanol (0.6 mmol), phenylboronic acid (0.75 mmol), KOH–Cs2CO3
(0.5 mmol/1 mmol), dioxane (3 mL), 110 °C, nitrogen atmosphere. b Isolated yield.
displayed high catalytic activity producing the desired product lyzed oxidation and Suzuki reaction for the synthesis of biaryl-
in an excellent yield (91%). However, the dimer 5 generated aldehydes in air. Cyclometalated Ir acac complex 6 was an
the product only in 40% yield. Furthermore, we also investi- efficient catalyst for the α-alkylation of acetylferrocene. It was
gated the one-pot synthesis of 6-aryl-2-ferrocenylquinolines via also successfully applied to the one-pot synthesis of 6-aryl-2-
Ir/Pd-cocatalyzed α-alkylation/Suzuki reaction, using the ferrocenylquinolines from (2-amino-5-chlorophenyl)methanol
present cyclometalated complexes 1–6 as catalysts.
using palladacycle 3 as cocatalyst.
We have previously shown that PPh3-cyclometallated
iridium hydride is an efficient catalyst for the one-pot synthesis
of 6-aryl-2-ferrocenylquinolines with 3 mol% Pd(OAc)2.13 Under
the same conditions, acetylferrocene, (2-amino-5-bromophenyl)
methanol and phenylboronic acid were efficiently converted to
the 6-phenyl-2-ferrocenylquinoline in high yields (82–94%) with
a catalytic loading as low as 1 mol% palladacycles 1–3, respect-
ively (Table 8, entries 1–3). For cheaper and more readily avail-
able (2-amino-5-chlorophenyl)methanol, Pd(OAc)2, 1 and 2 were
almost inactive (entries 4–6), but 3 displayed high efficiency
(87%, entry 7). The scope of the procedure was further investi-
gated by varying the arylboronic acids (Table 9). The corres-
ponding 6-aryl-2-ferrocenylquinolines 9a–9g were isolated in
good yields (81–93%). The hindered arylboronic acids provided
the products 9h and 9i in moderate yields (72% and 60%,
respectively). The detailed structure of 9h was confirmed by
single-crystal X-ray crystallography (Fig. 12).
Experimental
General information
Solvents were dried and freshly distilled prior to use. All
reagents and substrates were commercially available.
(2-Amino-5-chlorophenyl)methanol was synthesized according
to the reported procedure.27 IR spectra were collected on a
Bruker VECTOR22 spectrophotometer in KBr pellets. Elemen-
tal analyses were determined with a Carlo Erba 1160 Elemental
Analyzer. 1H NMR, 13C NMR spectra were recorded on a Bruker
DPX-400 spectrometer in CDCl3 with TMS as an internal stan-
dard. Mass spectra were measured on a LC-MSD-Trap-XCT
instrument. The absorption and photoluminescence spectra
were recorded on a Hitachi U-3010 UV-Vis spectrophotometer
and a Hitachi F-4500 fluorescence spectrophotometer in
CH2Cl2 at rt, respectively. Cyclic voltammetry was performed
on a CHI620C electrochemical analyzer. The electrolytic cell
was a conventional three-electrode cell consisting of a Pt
bottom working electrode, a Pt wire counter electrode and an
Ag/AgCl reference electrode.
Conclusion
In summary, a series of cyclometallated complexes have been
synthesized and characterized. X-ray diffraction analysis con-
firms that there are a variety of intermolecular C–H⋯X (Cl, Br,
Preparation of complexes 1–3
π) and π⋯π interactions in their crystals. These cyclometallated A mixture of 2-(4-bromophenyl)pyridine (bpp) (1 mmol),
complexes show emissions ranging from the purple to the Li2PdCl4 (1 mmol) and NaOAc (1.1 mmol) in 10 mL of dry
yellow region. Their catalytic activity was evaluated in the coup- methanol was stirred for 12 h at rt. The yellow solids (0.694 g,
ling reactions of aryl chlorides containing hydroxymethyl. We 93%) were collected by filtration and washed several times
have developed an efficient NHC-palladacycle/Cu(OAc)2 cocata- with methanol. A Schlenk tube was charged with the above
This journal is © The Royal Society of Chemistry 2014
Dalton Trans., 2014, 43, 10235–10247 | 10243

View Article Online
Paper
Table 9 One-pot synthesis of 6-aryl-2-ferrocenylquinolinesa
Dalton Transactions
a Reaction conditions: acetylferrocene (0.5 mmol), (2-amino-5-chlorophenyl)methanol (0.6 mmol), arylboronic acids (0.75 mmol), 6/3 (2 mol
%/1 mol%), KOH–Cs2CO3 (0.5 mmol/1 mmol), dioxane (3 mL), 110 °C, nitrogen atmosphere. b Isolated yield.
CDCl3): δ 9.22 (d, J = 5.2 Hz, 1H), 7.89 (d, J = 8.0 Hz, 4H), 7.68
(t, J = 7.6 Hz, 1H), 7.42–7.45 (m, 3H), 7.26 (s, 2H), 7.20 (d, J =
8.0 Hz, 2H), 7.11–7.16 (m, 2H), 7.03 (d, J = 8.0 Hz, 1H), 6.22 (s,
1H), 2.31 (s, 6H). MS (EI) m/z = 586.0 (M − Cl)+. Elemental ana-
lysis calcd (%) for C28H23BrClN3Pd: C 53.96, H 3.72, N 6.74.
Found: C 54.18, H 3.61, N 6.85.
[Pd(bpp)(IMeO)Cl] (2). Yield: 0.601 g, 92%. IR (KBr, cm−1):
3567, 3213, 2949, 1840, 1652, 1521, 1427, 1362, 1284, 1202,
1145, 1025, 948, 920, 855, 801, 737, 703. 1H NMR (400 MHz,
CDCl3): δ 9.13 (d, J = 5.2 Hz, 1H), 7.86 (d, J = 8.0 Hz, 4H), 7.43
Fig. 12 The molecular structure of 9h with displacement ellipsoids
drawn at the 50% probability level. H atoms are omitted for clarity.
(t, J = 7.6 Hz, 1H), 7.35 (s, 2H), 7.04 (d, J = 8.0 Hz, 1H), 6.98 (t,
J = 6.4 Hz, 1H), 6.74–6.85 (m, 6H), 6.15 (s, 1H), 3.57 (s, 6H). MS
(EI) m/z = 618.0 (M − Cl)+. Elemental analysis calcd (%) for
C28H23BrClN3O2Pd: C 51.32, H 3.54, N 6.41. Found: C 51.45,
palladacyclic dimer (0.5 mmol), the corresponding imidazo-
lium salts (1.25 mmol) and KOtBu (2.5 mmol) under nitrogen. H 3.43, N 6.47.
[Pd(bpp)(IMes)Cl] (3). Yield: 0.582 g, 86%. IR (KBr, cm−1):
2921, 2852, 1693, 1603, 1567, 1510, 1484, 1418, 1328, 1252,
Dry THF was added by a cannula and stirred at rt for 3 h. The
product was separated by passing through a short silica gel
column with CH2Cl2 as eluent, the second band was collected 925, 908, 848, 751, 735, 704, 690, 657. 1H NMR (400 MHz,
CDCl3): δ 9.24 (d, J = 5.2 Hz, 1H), 7.84 (d, J = 8.2 Hz, 1H),
7.67–7.73 (m, 1H), 7.57 (d, J = 8.2 Hz, 1H), 7.47 (t, J = 7.6 Hz,
and afforded the corresponding carbene adducts 1–3.
[Pd(bpp)(Itol)Cl] (1). Yield: 0.559 g, 90%. IR (KBr, cm−1):
3073, 2987, 2859, 1697, 1605, 1506, 1454, 1401, 1270, 1109, 1H), 7.25 (s, 1H), 7.02 (d, J = 8.2 Hz, 2H), 6.93 (s, 2H), 6.79 (d,
1046, 1017, 895, 786, 740, 688, 654. 1H NMR (400 MHz,
J = 8.0 Hz, 2H), 6.31 (s, 1H), 2.43 (s, 6H), 2.29 (s, 6H), 2.26 (s,
10244 | Dalton Trans., 2014, 43, 10235–10247
This journal is © The Royal Society of Chemistry 2014

View Article Online
Dalton Transactions
Paper
6H). MS (EI) m/z = 642.1 (M − Cl)+. Elemental analysis calcd data for 3 was measured on a Xcalibur, Eos, Gemini diffracto-
(%) for C32H31BrClN3Pd: C 56.57, H 4.60, N 6.19. Found: meter. Crystal structures were solved by direct methods using
C 56.51, H 4.52, N 6.35.
SHELXS, subsequent difference Fourier analyses and least
[Pd(bpp)(acac)] (4). The above palladacyclic dimer squares refinement with SHELXL-9728 allowed for the location
(0.5 mmol), acac (0.25 mmol), K2CO3 (0.5 mmol), and ethanol of the atom positions. All non-hydrogen atoms were refined ani-
(10 mL) were added into a three-necked flask. The mixture was sotropically. In the final step of the crystal structure refinement
refluxed under nitrogen for 12 h and then cooled to room hydrogen atoms of idealized –CH2 and –CH3 groups were added
temperature. A yellow precipitate was filtered and washed with and treated with the riding atom mode, their isotropic displace-
water and ethanol several times. The resulting yellow solid was ment factor was chosen as 1.2 and 1.5 times the preceding
purified by passing through a short silica gel column with carbon atom, respectively. One CH2Cl2 molecule (Cl3, Cl4, C29)
CH2Cl2 as eluent to give 4. Yield: 0.371 g, 85%. IR (KBr, cm−1): in 2 is disordered over two positions with an occupancy of 0.5,
2971, 2440, 1604, 1511, 1388, 1370, 1260, 1017, 1007, 890, 822, it is also refined isotropically. C23 to C27 in 4 were refined iso-
719, 704, 695, 655. 1H NMR (400 MHz, CDCl3): δ 8.75 (d, J = 5.2 tropically because of their higher thermal parameters.
Hz, 1H), 7.81 (t, J = 7.6 Hz, 1H), 7.66 (s, 1H), 7.58 (d, J = 8.0 Hz,
1H), 7.25 (s, 2H), 7.18 (t, J = 6.4 Hz, 1H), 5.41 (s, 1H), 2.12 (s,
General procedure for synthesis of biarylaldehydes
3H), 2.06 (s, 3H). MS (EI) m/z = 437.9 (M + H)+. Elemental ana-
lysis calcd (%) for C16H14BrNO2Pd: C 43.81, H 3.22, N 3.19. A 10 mL round-bottomed flask was charged with the pre-
Found: C 43.89, H 3.05, N 3.23.
scribed amount of catalyst Pd/Cu, aryl halides containing
hydroxymethyl (0.5 mmol), arylboronic acid (0.75 mmol), the
selected base (1.0 mmol) and solvent (3 mL) in air. The reac-
Preparation of complexes 5–6
Iridium trichloride (0.5 mmol), bpp (1.5 mmol), 2-ethoxyetha- tion mixture was then placed in an oil bath and heated at
nol (15 mL), and water (5 mL) were added into a three-necked 110 °C for 18 h. After removal of the solvent, the resulting
flask. The mixture was refluxed under nitrogen for 24 h and residue was purified by flash chromatography on silica gel
then cooled to rt. A yellow precipitate was filtered and washed using CH2Cl2–petroleum ether (1/1) as eluent. The products
with water and ethanol several times. The resulting yellow 7a,9b 7b,29a 7c,29b 7d,29c 7e–g,29d 7h,29a 7i29e and 8a–c,30a 8d,30b
solid was purified by passing through a short silica gel column 8e–f,30c 8g29e are known compounds except for 7j–k and 8h–i.
with CH2Cl2–ethyl acetate (3 : 1) as eluent to give solid 5. Then,
4-(5-Ethoxycarbonylpyridin-3-yl)benzaldehyde
(7j). Yield:
the complex
5
(0.1 mmol), acac (0.22 mmol), K2CO3 0.194 g, 76%. IR (KBr, cm−1): 2818, 1721, 1701, 1607, 1565,
(0.4 mmol), and 2-ethoxyethanol (10 mL) were added into a 1452, 1362, 1307, 1251, 1216, 1173, 1110, 1022, 915, 829, 762,
1
three-necked flask. The mixture was refluxed under nitrogen 702. H NMR (400 MHz, CDCl3): δ 10.10 (s, 1H), 9.26 (s, 1H),
for 12 h and then cooled to rt. A yellow precipitate was filtered 9.05 (s, 1H), 8.54 (s, 1H), 8.04 (d, J = 6.8 Hz, 2H), 7.82 (d, J =
and washed with water and ethanol several times. The result- 8.0 Hz, 2H), 4.48 (q, 2H), 1.46 (t, 3H). 13C NMR (100 MHz,
ing yellow solid was purified by passing through a short silica CDCl3): δ 191.6, 165.0, 151.7, 150.3, 142.5, 136.1, 135.4, 135.1,
gel column with CH2Cl2 as eluent to give solid 6.
130.5, 127.8, 126.5, 61.8, 14.3. MS (EI) m/z = 254.1 (M+).
[Ir(bpp)2Cl]2 (5). Yield: 0.609 g, 88%. IR (KBr, cm−1): 2768, Elemental analysis calcd (%) for C15H13NO3: C 70.58, H 5.13,
1605, 1564, 1530, 1471, 1418, 1369, 1298, 1160, 1005, 883, 868, N 5.49. Found: C 70.65, H 5.02, N 5.56.
1
766, 749, 719, 711, 644. H NMR (400 MHz, CDCl3): δ 9.11 (d,
4-(4-Dimethylaminopyridin-3-yl)benzaldehyde (7k). Yield:
J = 5.2 Hz, 4H), 7.87(d, J = 8.0 Hz, 4H), 7.81(d, J = 8.0 Hz, 4H), 0.192 g, 85%. IR (KBr, cm−1): 2853, 1690, 1592, 1523, 1503,
1
7.58 (d, J = 7.2 Hz, 4H), 7.48 (t, J = 7.2 Hz, 4H), 6.96 (d, J = 1388, 1282, 1213, 1170, 1067, 1030, 958, 832, 807, 778, 690. H
8.0 Hz, 4H), 6.83 (s, 4H). MS (EI) m/z = 1383.8 (M+). Elemental NMR (400 MHz, CDCl3): δ 9.99 (s, 1H), 8.50 (s, 1H), 7.90 (d, J =
analysis calcd (%) for C44H28Br4Cl2Ir2N4: C 38.08, H 2.03, 7.2 Hz, 2H), 7.73 (d, J = 8.8 Hz, 1H), 7.66 (d, J = 8.4 Hz, 2H),
N 4.04. Found: C 38.15, H 1.98, N 4.01.
6.59 (d, J = 8.8 Hz, 1H), 3.20 (s, 6H). 13C NMR (100 MHz,
[Ir(bpp)2(acac)] (6). Yield: 0.643 g, 85%. IR (KBr, cm−1): CDCl3): δ 191.8, 159.0, 146.7, 144.4, 135.7, 134.3, 130.5, 128.2,
2993, 1816, 1582, 1510, 1474, 1367, 1252, 1228, 1056, 1004, 126.0, 122.5, 105.8, 38.1. MS (EI) m/z = 225.1 (M+). Elemental
879, 868, 788, 766, 748, 722, 714, 693. 1H NMR (400 MHz, analysis calcd (%) for C14H14N2O: C 74.31, H 6.24, N 12.38.
CDCl3): δ 8.43 (d, J = 5.2 Hz, 2H), 7.83 (d, J = 8.0 Hz, 2H), 7.77 Found: C 74.37, H 6.13, N 12.42.
(t, J = 7.8 Hz, 2H), 7.40 (d, J = 8.0 Hz, 2H), 7.19 (t, J = 6.4 Hz,
2-(5-Ethoxycarbonylpyridin-3-yl)benzaldehyde
(8h). Yield:
2H), 7.00 (d, J = 8.0 Hz, 2H), 6.29 (s, 2H), 5.30 (s, 1H), 1.79 (s, 0.181 g, 71%. IR (KBr, cm−1): 2874, 1719, 1596, 1445, 1364,
6H). MS (EI) m/z = 757.0 (M + H)+. Elemental analysis calcd 1294, 1267, 1248, 1198, 1109, 1019, 974, 823, 782, 759, 711. H
1
(%) for C27H21Br2IrN2O2: C 42.81, H 2.79, N 3.70. Found: NMR (400 MHz, CDCl3): δ 9.98 (s, 1H), 9.29 (s, 1H), 8.80 (s,
C 42.89, H 2.71, N 3.77.
1H), 8.34 (s, 1H), 8.07 (d, J = 8.0 Hz, 1H), 7.71–7.75 (m, 1H),
7.62 (m, 1H), 7.45 (d, J = 8.0 Hz, 1H), 4.46 (q, 2H), 1.43 (t, 3H).
13C NMR (100 MHz, CDCl3): δ 190.8, 164.9, 153.4, 150.2, 140.5,
Single-crystal structure determination
Single crystal X-ray diffraction measurements of 1, 2, 4–6 and 137.7, 134.0, 133.7, 131.2, 129.2, 125.9, 61.7, 14.3. MS (EI) m/z
9h were carried out on a Bruker SMART APEX II CCD diffracto- = 254.1 (M+). Elemental analysis calcd (%) for C15H13NO3:
meter (Mo Kα radiation, λ = 71.073 pm) at rt. Crystallographic C 70.58, H 5.13, N 5.49. Found: C 70.63, H 5.06, N 5.54.
This journal is © The Royal Society of Chemistry 2014
Dalton Trans., 2014, 43, 10235–10247 | 10245

View Article Online
Paper
Dalton Transactions
2-(4-Dimethylaminopyridin-3-yl)benzaldehyde
(8i). Yield: Henan Province (122102310452) and the Science Foundation
0.174 g, 77%. IR (KBr, cm−1): 2850, 1687, 1601, 1547, 1515, of Henan Education Department (14A150049).
1479, 1439, 1386, 1320, 1192, 1152, 1063, 957, 828, 812, 768,
1
733. H NMR (400 MHz, CDCl3): δ 10.05 (s, 1H), 8.19 (s, 1H),
8.00 (d, J = 7.2 Hz, 1H), 7.59–7.62 (m, 1H), 7.39–7.49 (m, 3H),
References
6.60 (d, J = 8.8 Hz, 1H), 3.15 (s, 6H). 13C NMR (100 MHz,
CDCl3): δ 192.3, 158.8, 148.6, 143.2, 138.6, 133.8, 130.7, 128.0,
127.3, 120.7, 105.2, 38.1. MS (EI) m/z = 225.1 (M+). Elemental
analysis calcd (%) for C14H14N2O: C 74.31, H 6.24, N 12.38.
Found: C 74.40, H 6.15, N 12.47.
1 M. Albrecht, Chem. Rev., 2010, 110, 576.
2 (a) R. B. Bedford, Chem. Commun., 2003, 1787;
(b) J. Dupont, C. S. Consorti and J. Spencer, Chem. Rev.,
2005, 105, 2527; (c) Palladacycles, ed. J. Dupont and
M. Pfeffer, Wiley-VCH, Weinheim, 2008.
General procedure for synthesis of 6-aryl-2-ferrocenyl-
quinolines
3 (a) Iridium Complexes in Organic Synthesis, ed. L. A. Oro and
C. Claver, Wiley-VCH Verlag GmbH & Co. KgaA, Weinheim,
2009; (b) T. Suzuki, Chem. Rev., 2011, 111, 1825.
4 (a) T. Kinzel, Y. Zhang and S. L. Buchwald, J. Am. Chem.
Soc., 2010, 132, 14073; (b) M. A. Düfert, K. L. Billingsley
and S. L. Buchwald, J. Am. Chem. Soc., 2013, 135, 12877;
(c) N. C. Bruno, M. T. Tudge and S. L. Buchwald, Chem.
Sci., 2013, 4, 916.
5 (a) K. Taguchi, H. Nakagawa, T. Hirabayashi, S. Sakaguchi
and Y. Ishii, J. Am. Chem. Soc., 2004, 126, 72; (b) Y. Iuchi,
Y. Obora and Y. Ishii, J. Am. Chem. Soc., 2010, 132, 2536;
(c) Y. Obora and Y. Ishii, Synlett, 2011, 30.
6 (a) N-Heterocyclic Carbenes in Synthesis, ed. S. P. Nolan,
Wiley-VCH, Weinheim, 2006; (b) D. Enders, O. Niemeier
and A. Henseler, Chem. Rev., 2007, 107, 5606; (c) F. E. Hahn
and M. C. Jahnke, Angew. Chem., Int. Ed., 2008, 47, 3122;
(d) G. C. Fortman and S. P. Nolan, Chem. Soc. Rev., 2011,
40, 5151; (e) S. Gaillard and J. L. Renaud, Dalton Trans.,
2013, 42, 7255.
7 (a) O. Navarro, N. Marion, Y. Oonishi, R. A. Kelly III and
S. P. Nolan, J. Org. Chem., 2006, 71, 685; (b) N. Marion,
O. Navarro, J. G. Mei, E. D. Stevens, N. M. Scott and
S. P. Nolan, J. Am. Chem. Soc., 2006, 128, 4101.
8 (a) W. A. Herrmann, Angew. Chem., Int. Ed., 2002, 41, 1290;
(b) G. D. Frey, J. Schütz, E. Herdtweck and W. A. Herrmann,
Organometallics, 2005, 24, 4416.
9 (a) Y. H. Park, H. R. Ahn, B. Canturk, S. Jeon, S. Lee,
H. Kang, G. A. Molander and J. Ham, Org. Lett., 2008, 10,
1215; (b) A. D. Zotto, F. Amoroso, W. Baratta and P. Rigo,
Eur. J. Org. Chem., 2009, 110; (c) J. Shin, J. Bertoia,
K. R. Czerwinski and C. Bae, Green Chem., 2009, 11, 1576;
(d) F. G. Rivera, I. Angurell, M. D. Rossell, R. Erni, J. Llorca,
N. J. Divins, G. Muller, M. Seco and O. Rossell, Chem. –
Eur. J., 2013, 19, 11963.
10 (a) Oxidation of Alcohols to Aldehydes and ketones, ed.
G. Tojo and M. Fernández, Springer, New York, 2006;
(b) S. Caron, R. W. Dugger, S. G. Ruggeri, J. A. Ragan and
D. H. B. Ripin, Chem. Rev., 2006, 106, 2943.
In a Schlenk tube, a mixture of the acetylferrocene (0.5 mmol),
(2-amino-5-chlorophenyl) methanol (0.6 mmol), KOH
(0.5 mmol), and 6 (0.01 mmol) in dioxane (3 mL) was evacu-
ated and charged with nitrogen. The mixture was heated at
110 °C for 12 h then allowed to cool to rt. The vessel was
opened, and arylboronic acids (0.75 mmol), Cs2CO3
(1.0 mmol), and 3 (0.005 mmol) were added to it under nitro-
gen. The mixture was heated at 110 °C for another 12 h. After
removal of the solvent, the resulting residue was purified by
column chromatography on silica gel using CH2Cl2 as eluent.
The products 6-aryl-2-ferrocenyl quinolines 9c–i13 are known
compounds except for 9a–b.
2-Ferrocenyl-6-(3-methylphenyl)quinoline
(9a).
Yield:
0.179 g, 89%. IR (KBr, cm−1): 2922, 1593, 1478, 1378, 1337,
1287, 1180, 1135, 1104, 1012, 905, 894, 837. 1H NMR
(400 MHz, CDCl3): δ 8.12 (m, 2H), 7.97 (s, 2H), 7.56–7.64 (m,
3H), 7.43 (t, 1H), 7.26 (d, J = 7.6 Hz, 2H), 5.13 (s, 2H), 4.53 (s,
2H), 4.12 (s, 5H), 2.51 (s, 3H). 13C NMR (100 MHz, CDCl3):
δ 159.5, 140.6, 138.6, 138.3, 135.7, 129.3, 129.2, 128.9, 128.3,
128.1, 125.3, 124.5, 119.9, 83.9, 70.5, 69.7, 68.0, 21.6. MS (EI,
70 eV) m/z = 404.1 (M + H)+. Elemental analysis calcd (%) for
C26H21FeN: C 77.43, H 5.25, N 3.47. Found: C 77.57, H 5.10,
N 3.59.
2-Ferrocenyl-6-(4-ethylphenyl)quinoline (9b). Yield: 0.190 g,
91%. IR (KBr, cm−1): 2966, 1594, 1566, 1499, 1460, 1337, 1279,
1133, 1104, 1029, 1014, 900, 826, 733. 1H NMR (400 MHz,
CDCl3): δ 8.07–8.26 (m, 2H), 7.83–7.93 (m, 2H), 7.64 (d, J = 8.0
Hz, 2H), 7.56 (d, J = 8.4 Hz, 1H), 7.31 (d, J = 8.0 Hz, 2H), 5.07
(s, 2H), 4.47 (s, 2H), 4.05 (s, 5H), 2.71 (q, 2H), 1.29 (t, 3H). 13C
NMR (100 MHz, CDCl3): δ 159.4, 147.6, 143.7, 138.1, 138.0,
136.6, 129.3, 128.5, 128.3, 127.3, 127.0, 125.0, 119.9, 84.0, 70.5,
69.7, 68.0, 29.8, 15.7. MS (EI) m/z = 418.1 (M + H)+. Elemental
analysis calcd (%) for C27H23FeN: C 77.71, H 5.56, N 3.36.
Found: C 77.79, H 5.43, N 3.43.
11 (a) D. R. Jensen, M. J. Schultz, J. A. Mueller and
M. S. Sigman, Angew. Chem., Int. Ed., 2003, 42, 3810;
(b) J. A. Mueller, C. P. Goller and M. S. Sigman, J. Am.
Chem. Soc., 2004, 126, 9724; (c) C. N. Cornell and
M. S. Sigman, J. Am. Chem. Soc., 2005, 127, 2796;
(d) C. N. Cornell and M. S. Sigman, Inorg. Chem., 2007, 46,
1903.
Acknowledgements
This work was supported by the National Science Foundation
of China (no. 21272110, 21102135 and 21171173), the Aid
Project for the Leading Young Teachers in Henan Provincial
Institutions of Higher Education of China (2013GGJS-151), the
tackle key problems of science and technology Project of
10246 | Dalton Trans., 2014, 43, 10235–10247
This journal is © The Royal Society of Chemistry 2014

View Article Online
Dalton Transactions
Paper
12 C. Xu, H. M. Li, X. E. Yuan, Z. Q. Xiao, Z. Q. Wang, W. J. Fu,
B. M. Ji, X. Q. Hao and M. P. Song, Org. Biomol. Chem.,
2014, 12, 3114.
2911; (d) C. Xu, Z. Q. Wang, Y. P. Zhang, X. M. Dong,
X. Q. Hao, W. J. Fu, B. M. Ji and M. P. Song, Eur. J. Inorg.
Chem., 2011, 4878.
13 C. Xu, X. Q. Hao, Z. Q. Xiao, Z. Q. Wang, X. E. Yuan, 21 (a) X. P. Wang and P. P. Power, Angew. Chem., Int. Ed., 2011,
W. J. Fu, B. M. Ji and M. P. Song, J. Org. Chem., 2013, 78,
8730.
50, 10965; (b) G. G. Luo, H. B. Xiong and J. C. Dai, Cryst.
Growth Des., 2011, 11, 507.
14 (a) R. C. Evans, P. Douglas and C. J. Winscom, Coord. 22 (a) S. Bettington, M. Tavasli, M. R. Bryce, A. S. Batsanov,
Chem. Rev., 2006, 250, 2093; (b) Z. Q. Chen, Z. Q. Bian and
C. H. Huang, Adv. Mater., 2010, 22, 1534;
(c) J. M. Fernández-Hernández, C. H. Yang, J. Beltrán,
V. Lemaur, F. Polo, R. Fröhlich, J. Cornil and L. Cola, J. Am.
Chem. Soc., 2011, 133, 10543; (d) W. Yang, D. W. Wang,
A. L. Thompson, F. B. Diasb and A. P. Monkman, J. Mater.
Chem., 2006, 16, 1046; (b) L. Q. Chen, C. L. Yang, M. Li,
J. G. Qin, J. Gao, H. You and D. G. Ma, Cryst. Growth Des.,
2007, 7, 39; (c) K. A. McGee and K. R. Mann, Inorg. Chem.,
2007, 46, 7800.
Q. J. Song, S. Zhang, Q. Wang and Y. Q. Ding, Organometal- 23 S. Lamansky, P. Djurovich, D. Murphy, F. Abdel-Razzaq,
lics, 2013, 32, 4130; (e) R. Grisorio, G. P. Suranna,
P. Mastrorilll, M. Mazzeo, S. Colella, S. Carallo and G. Gigli,
Dalton Trans., 2013, 42, 8939.
R. Kwong, I. Tsyba, M. Bortz, B. Mui, R. Bau and
M. E. Thompson, Inorg. Chem., 2001, 40, 1704.
24 (a) J. Pommerehne, H. Vestweber, W. Guss, R. F. Mahrt,
M. Porsch and J. Daub, Adv. Mater., 1995, 7, 551;
(b) M. Thelakkat and H. W. Schmidt, Adv. Mater., 1998, 10,
219; (c) X. W. Zhang, J. Gao, C. L. Yang, L. N. Zhu, Z. A. Li,
K. Zhang, J. G. Qin, H. You and D. G. Ma, J. Organomet.
Chem., 2006, 691, 4312.
15 (a) C. F. Chang, Y. M. Cheng, Y. Chi, Y. C. Chiu, C. C. Lin,
G. H. Lee, P. T. Chou, C. C. Chen, C. H. Chang and
C. C. Wu, Angew. Chem., Int. Ed., 2008, 47, 4542;
(b) L. Mercs and M. Albrecht, Chem. Soc. Rev., 2010, 39,
1903; (c) B. Wiegmann, P. G. Jones, G. Wagenblast,
C. Lennartz, I. Münster, S. Metz, W. Kowalsky and 25 (a) J. P. Wolfe, R. A. Singer and B. H. Yang, J. Am. Chem. Soc.,
H. H. Johannes, Organometallics, 2012, 31, 5223;
(d) N. Darmawan, C. H. Yang, M. Mauro, M. Raynal,
S. Heun, J. Pan, H. Buchholz, P. Braunstein and L. D. Cola,
Inorg. Chem., 2013, 52, 10756.
1999, 121, 9550; (b) L. Botella and C. Nájera, Angew. Chem.,
Int. Ed., 2002, 41, 179; (c) B. Biplab, D. Pankaj, S. Nasifa,
B. Biplab and D. Pankaj, Tetrahedron Lett., 2013, 54, 2886;
(d) G. F. Zhang, Y. X. Luan, X. W. Han, Y. Wang, X. Wen,
C. R. Ding and J. R. Gao, Green Chem., 2013, 15, 2081.
16 (a) C. Xu, Z. Q. Wang, W. J. Fu, X. H. Lou, Y. F. Li, F. F. Cen,
H. J. Ma and B. M. Ji, Organometallics, 2009, 28, 1909; 26 (a) G. Guillena, D. J. Ramón and M. Yus, Angew. Chem., Int.
(b) C. Xu, Y. P. Zhang, Z. Q. Wang, W. J. Fu, X. Q. Hao,
Y. Xu and B. M. Ji, Chem. Commun., 2010, 46, 6852;
(c) J. L. Niu, X. Q. Hao, J. F. Gong and M. P. Song, Dalton
Trans., 2011, 40, 5135; (d) C. Xu, X. M. Dong, Z. Q. Wang,
Ed., 2007, 46, 2358; (b) M. H. S. A. Hamid, P. A. Slatford
and J. M. J. Williams, Adv. Synth. Catal., 2007, 349, 1555;
(c) G. Guillena, D. J. Ramón and M. Yus, Chem. Rev., 2010,
110, 1611.
X. Q. Hao, Z. Li, L. M. Duan, B. M. Ji and M. P. Song, 27 M. Q. Jia and S. L. You, ACS Catal., 2013, 3, 622.
J. Organomet. Chem., 2012, 700, 214.
17 M. Nonoyama, Bull. Chem. Soc. Jpn., 1974, 47, 767.
28 G. M. Sheldrick, Acta Crystallogr., Sect. A: Found. Crystal-
logr., 2008, 64, 112.
18 (a) E. A. B. Kantchev, G. R. Peh, C. J. Zhang and Y. Ying, 29 (a) V. Terrasson, D. Prim and J. Marrot, Eur. J. Inorg. Chem.,
Org. Lett., 2008, 10, 3949; (b) E. A. B. Kantchev and
J. Y. Ying, Organometallics, 2009, 28, 289; (c) J. Nasielski,
N. Hadei, G. Achonduh, E. A. B. Kantchev, C. J. O’Brien,
A. Lough and M. G. Organ, Chem. – Eur. J., 2010, 16, 10844;
(d) Y. Kong, L. Wen, H. Song, S. Xu, M. Yang, B. Liu and
B. Wang, Organometallics, 2011, 30, 153.
2008, 2739; (b) Z. H. Guan, J. L. Hu, Y. L. Gu, H. J. Zhang,
G. X. Li and T. Li, Green Chem., 2012, 14, 1964;
(c) S. L. Mao, Y. Sun, G. A. Yu, C. Zhao, Z. J. Han, J. Yuan,
X. L. Zhu, Q. H. Yang and S. H. Liu, Org. Biomol. Chem.,
2012, 10, 9410; (d) A. Beeby, S. Bettington, I. J. S. Fairlamb,
A. E. Goeta, A. R. Kapdi, E. H. Niemelä and
A. L. Thompson, New J. Chem., 2004, 28, 600; (e) J. F. Yang,
S. J. Liu, J. F. Zheng and J. R. Zhou, Eur. J. Org. Chem.,
2012, 6248.
19 J. L. Serrano, L. García, J. Pérez, E. Pérez, J. García,
G. Sánchez, G. López and M. Liu, Eur. J. Inorg. Chem., 2008,
4797.
20 (a) M. Nishio, CrystEngComm, 2004, 6, 130; (b) C. Xu, 30 (a) S. Wertz, D. Leifert and A. Studer, Org. Lett., 2013, 15,
J. F. Gong, S. F. Yue, Y. Zhu and Y. J. Wu, Dalton Trans.,
2006, 4730; (c) H. Matter, M. Nazaré, S. Güssregen,
D. W. Will, H. Schreuder, A. Bauer, M. Urmann, K. Ritter,
M. Wagner and V. Wehner, Angew. Chem., Int. Ed., 2009, 48,
928; (b) D. Saha, K. Chattopadhyay and B. C. Ranu, Tetra-
hedron Lett., 2009, 50, 1003; (c) J. R. Gardinier,
H. M. Tatlock, J. S. Hewage and S. V. Lindeman, Cryst.
Growth Des., 2013, 13, 3864.
This journal is © The Royal Society of Chemistry 2014
Dalton Trans., 2014, 43, 10235–10247 | 10247