Mononuclear half-sandwich iridium and rhodium complexes through C?H activation: Synthesis, characterization and catalytic activity

Article abstract of DOI:10.1016/j.jorganchem.2017.06.023

A series of mononuclear half-sandwich cyclometalated group 9 (Ir and Rh) metal complexes were synthesized in good yields through metal-mediated C?H bond activation. These air-stable C, N-chelate mode complexes have similar solid state structures. Both experimental results and DFT calculations confirmed that no binuclear complexes were generated in this reaction. The iridium complex 3a exhibited good catalytic activity for the reduction of both electron-rich and electron-poor aryl imines with low catalyst loading in the presence of formic acid/triethylamine (F/T) azeotropic mixture. All complexes were fully characterized by elemental analysis and IR and NMR spectroscopies. The structures of 1a, 1b, 2a, 3a and 4b (see chemical structure formula in Scheme 1 and Scheme 2) were further confirmed by single-crystal X-ray analysis.

Full text of DOI:10.1016/j.jorganchem.2017.06.023

Journal of Organometallic Chemistry 846 (2017) 208e216
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Mononuclear half-sandwich iridium and rhodium complexes through
C‒H activation: Synthesis, characterization and catalytic activity
Zi-Jian Yao*, Kuan Li, Peng Li, Wei Deng**
School of Chemical and Environmental Engineering, Shanghai Institute of Technology, Shanghai 201418, China
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of mononuclear half-sandwich cyclometalated group 9 (Ir and Rh) metal complexes were
synthesized in good yields through metal-mediated C‒H bond activation. These air-stable C, N-chelate
mode complexes have similar solid state structures. Both experimental results and DFT calculations
confirmed that no binuclear complexes were generated in this reaction. The iridium complex 3a
exhibited good catalytic activity for the reduction of both electron-rich and electron-poor aryl imines
with low catalyst loading in the presence of formic acid/triethylamine (F/T) azeotropic mixture. All
complexes were fully characterized by elemental analysis and IR and NMR spectroscopies. The structures
of 1a, 1b, 2a, 3a and 4b (see chemical structure formula in Scheme 1 and Scheme 2) were further
confirmed by single-crystal X-ray analysis.
Received 10 May 2017
Received in revised form
20 June 2017
Accepted 22 June 2017
Available online 24 June 2017
Keywords:
Half-sandwich
Iridium
Rhodium
Catalysis
© 2017 Published by Elsevier B.V.
1. Introduction
cyclopentadienyl groups with metal chlorides; (ii) Cp* or
substituted benzenes as h5 or h6 ligands perfectly shield the
Well-defined metallamacrocycles have attracted considerable
interest during the past few years because of their important
application in molecular recognition, host-guest chemistry, catal-
ysis, drug delivery and so on [1‒10]. Thus the construction of this
type of metal supramolecular assembly became one of the most
active research fields in coordination chemistry and organometallic
chemistry. Different from the preparation of metal-organic frame-
works (MOFs) with infinite structure, the coordination number and
direction of the metal center need to be controlled for the synthesis
of discrete two and three-dimensional metallamacrocycles [11,12].
Large efforts have been paid in this field, and a number of excellent
results which using different transition metal compounds as “metal
corner” (Pt, Pd, Ir, Rh) have been reported by Raymond [13‒15],
Stang [16‒20], Mirkin [21], Fujita [22‒25], and other groups [26‒37]
in recent years.
potentially octahedral hemisphere of the metals, from which the
bonds between the metal and the donor atoms, such as N-, S-, O-, P-
donor groups would benefit; (iii) various types of substituents on
the cyclopentadienyl ring may be used to tune the solubility and
the redox property of the corresponding complexes; (iv) Transition
metal complexes with Cp*Ir fragment is one of the most utilized
catalysts in water splitting process and often exhibits high catalytic
activity [40,41].
On the other hand, ligand choice is also important for the
metallamacrocycles construction because they served as the bridge
to link the metal corners. Among various types of ligands, aromatic
imine ligand has gained major attention in the construction of
coordination driven assembly because of their particular features
(such as inexpensive, easy to access and air and moisture stable).
Systematic work has been done by Jin's group and a series of
organoiridium macrocycles have been furnished [38,39]. However,
most of the cases have been focused on the bis-imine which based
on aryl amines. Herein, we explored the reactivity of half-sandwich
group 9 compounds with the bis-imine ligands based on hydrazine,
and a series of mononuclear complexes were afforded. Although
the experimental results indicated that the metallamacrocycles
could not be formed through this ligand, the obtained mononuclear
iridium complexes showed good catalytic activity for the hydro-
genation of imines. Additionally, mononuclear complexes were
confirmed to be the only products by using DFT study.
Among diverse types of supramolecular coordination com-
plexes, half-sandwich iridium and rhodium ([Cp*MCl2]2 (M ¼ Ir,
Rh), (p-cymene)RuCl2) motif exhibits some particular features in
the coordination-driven assembly (Fig. 1) [38,39]: (i) the starting
materials can be simply synthesized by the interaction of arene or
* Corresponding author.
** Corresponding author.
E-mail address: zjyao@sit.edu.cn (Z.-J. Yao).
http://dx.doi.org/10.1016/j.jorganchem.2017.06.023
0022-328X/© 2017 Published by Elsevier B.V.

Z.-J. Yao et al. / Journal of Organometallic Chemistry 846 (2017) 208e216
209
The complexes are air and moisture stable in their solid state
because of the five-membered chelate rings formation. No
decomposition was observed even after heating in toluene for
several hours. In addition, TGA measurement of these complexes
was conducted to further confirm their thermal stability (see TGA
curves in Supporting Information). The results indicate that all the
complexes are stable at high temperature (300 ꢀC). They are soluble
in toluene and dichloromethane and slightly soluble in diethyl
ether and hexane. The obtained mononuclear complexes were fully
characterized by various spectroscopic techniques and elemental
analysis. The IR spectra of these half-sandwich complexes all
display two typical strong and characteristic C¼N absorptions at
approximately 1620e1500 cmꢁ1, which means that the two C¼N
are not equivalent and the lower wave numbers are caused by the
coordination of the imine nitrogen atom. For complex 1a, different
Fig. 1. Properties of half-sandwich complexes.
chemical shift showed at d 9.19 and 8.59 ppm, which were assigned
to the two protons of CH¼N groups, also indicated that the metal
2. Results and discussion
center only coordinated by one imine group. Six groups of signals in
the aromatic region (
protons in the two phenyl rings, indicated the asymmetric structure
of 1a. The analogous single peaks ( 1.69 (1a) and 1.63 (1b) ppm)
d 8.00e7.00 ppm), which were assigned to the
Schiff base ligands, which are prepared by the condensation
reactions of amine and aldehyde, are the one of the simplest and
oldest reactions in organic chemistry. Ligands L1‒L3 were prepared
in high yields by condensation reaction between hydrazine hydrate
and two equivalents aromatic aldehydes, according to the classic
methods. A few drops of acetic acid were added to the reactions to
promote the condensation. With the ligands in hand, we next
explored the reactivity of these ligands with one equivalent half-
sandwich group 9 metal complexes [Cp*MCl2]2 (M ¼ Ir, Rh) in the
presence of NaOAc. As shown in Scheme 1, all mononuclear com-
plexes were obtained through mono C‒H bond activation in mod-
erate to good isolated yields in methanol at elevated temperature.
No bis-cyclometalated products were found in the reaction. An
excess amount of [Cp*IrCl2]2 was employed in the reaction to
examine whether the bi-nuclear complex could be afforded ac-
cording to the results reported before [42]. However, complex 1a
was still afforded as the only product when the molar ratio of
[Cp*IrCl2]2 and L1 increased to 2: 1. Moreover, no new species were
observed from the reaction of 1a with [Cp*IrCl2]2 in the presence of
NaOAc at 50 ꢀC. The reactions between transition metal precursors
and the ligands with either electron-donating or electron-
withdrawing groups all afforded the C‒H bond activation prod-
ucts smoothly. The mononuclear complexes were also furnished
with lower yields by using CH2Cl2 as solvent.
d
displayed in the 1H NMR spectra of the two complexes suggested
identical environments of the Cp* groups. In comparison with the
1H NMR spectrum of 1a, analogous NMR data of 1b indicated that
the two complexes have similar structures in solution. Similarly, the
1H NMR spectra of 2a, b and 3a, b indicated that all the products are
asymmetric mononuclear complexes through one CeH bond acti-
vation. The spectroscopic data and elemental analysis of these
complexes demonstrate that their structures are similar to each
other.
To unambiguously elaborate the structures of these mono-
nuclear half-sandwich complexes, an X-ray analysis is desired.
Single crystals suitable for X-ray diffraction analysis were obtained
by the slow diffusion of hexane into a saturated solution of them in
dichloromethane (Fig. 2). Selected bond lengths and angles are
listed in Table 1, and their crystallographic data are summarized in
Table 2. Molecular structures of complexes 1a, b, 2a and 3a show
that the geometry at the metal center is that of a three-legged piano
stool with the metal center coordinated by the
N atoms, as well as one chloride ligand. The metal center has a
distorted-octahedral environment, assuming that the
5-Cp* group
occupies three fac coordination sides. The two C¼N bond lengths in
h
5-Cp* and the C and
h
Scheme 1. Synthesis of ligands and mononuclear complexes.

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Z.-J. Yao et al. / Journal of Organometallic Chemistry 846 (2017) 208e216
Fig. 2. Molecular structures of 1a, 1b, 2a and 3a with 30% probability ellipsoids. Hydrogen atoms were omitted for clarity.
all complexes are not equal upon complexes formation revealing
coordination of one imine nitrogen atom. The bond lengths of
C(7)eN(1) are longer than those of C(8)eN(2) in all complexes,
respectively. For complexes 1a and 1b, the M‒CPh bond distances of
2.043(4) (1a) and 2.034(2) Å (1b), respectively, which are both
within the range of known values for these bonds in analogous
complexes [43]. The M‒N bond lengths of 1a and 1b also compares
well with similar bonds found in analogous complexes [42]. The
five-membered ring Ir(1)eC(1)eC(6)eC(7)eN(1) of complex 1a is
almost planar with the dihedral angle of 1.7ꢀ between planes of
N(1)eIr(1)eC(1) and C(1)eC(6)eC(7)eN(1). The sum of the angles
formed by the five-membered ring of 539.9ꢀ further confirmed the

Z.-J. Yao et al. / Journal of Organometallic Chemistry 846 (2017) 208e216
211
Table 1
Crystallographic data and structure refinement parameters for 1a,b, 2a, 3a and 4b.a
1a
1b
2a
3a
4b
Chemical Formula
FW
C24H26ClIrN2
570.12
C24H26ClRhN2
480.83
C26H30ClIrN2O2
630.17
C24H24Cl3IrN2
639.00
C24H24Br2ClN2Rh
638.63
T/[K]
296(2)
173(2)
173(2)
173(2)
173(2)
l
/Å
0.71073
Monoclinic
P2(1)/n
13.8182(14)
8.1748(8)
20.144(2)
90
106.070(2)
90
2186.6(4)
4
1.732
6.240
1112
2.086e26.945
5870
0.71073
Monoclinic
P2(1)/n
7.4677(12)
16.869(3)
17.208(3)
90
101.526(2)
90
2124.1(6)
4
1.504
0.941
984
2.415e26.829
14414
0.71073
Triclinic
Pe1
0.71073
Triclinic
Pe1
0.71073
Monoclinic
P2(1)/c
7.6606(12)
15.912(2)
20.022(3)
90
97.110(3)
90
2421.7(6)
4
1.752
4.129
1256
1.640e27.230
14688
Crystal system
Space group
a/Å
b/Å
c/Å
8.5525(13)
10.9035(17)
13.423(2)
80.809(2)
87.836(2)
77.282(2)
1205.3(3)
2
1.736
5.675
620
2.279e25.999
7763
8.3874(8)
10.8102(11)
13.0378(13)
97.1190(10)
95.250(2)
100.2870(10)
1146.3(2)
2
1.851
6.187
620
1.585e26.998
8007
ꢀ
ꢀ
ꢀ
/
a
b
g
V/Å3
Z
/
/
r
/Mg mꢁ3
m
/mmꢁ1
F(000)
q
range/ꢀ
Reflections collected
Completeness to
q
99.3%
99.6%
97.9%
97.5%
99.0%
Data/restraints/param.
4713/30/258
1.069
R1 ¼ 0.0238
wR2 ¼ 0.0681
0.743/ꢁ0.618
4535/0/258
1.114
R1 ¼ 0.0253,
wR2 ¼ 0.0753
0.472/ꢁ0.410
4654/18/306
1.098
R1 ¼ 0.0306,
wR2 ¼ 0.1190
2.457/ꢁ1.908
4890/0/276
1.111
R1 ¼ 0.0245,
wR2 ¼ 0.0728
1.576/ꢁ1.610
5352/0/276
1.068
Goodness-of-fit on F2
Final R indices [I > 2
s
(I)a]
R1 ¼ 0.0515,
wR2 ¼ 0.1594
4.194/ꢁ1.084
Largest diff.peak/hole (e Åꢁ3
)
a
R1 ¼ SjjF0j-jFcjj/SjF0j (based on reflections with F20>2
s
F2). wR2 ¼ [S[w(F02-Fc2)2]/S[w(F02)2]]1/2; w ¼ 1/[
s
2(F20)þ(0.095P)2]; P ¼ [max(F02, 0)þ2Fc2]/3(also with F02>2
s
F2).
Table 2
Selected bond lengths (Å) and angles (◦) for complexes 1a,b, 2a, 3a and 4b.
Bond lengths (Å) and angles (ꢀ)
1a
1b
2a
3a
4b
M(1)eCl(1)
M(1)eC(1)
M(1)eN(1)
C(7)eN(1)
2.3876(11)
2.043(4)
2.085(3)
1.291(5)
1.255(6)
76.95(15)
117.4(3)
116.0(4)
114.0(4)
115.6(3)
2.4045(7)
2.034(2)
2.094(2)
1.297(3)
1.277(3)
78.12(9)
115.95(17)
116.3(2)
115.0(2)
114.34(17)
2.4017(15)
2.026(6)
2.095(5)
1.283(8)
1.261(8)
77.5(2)
117.6(4)
116.4(6)
112.3(5)
129.1(5)
2.4025(10)
2.048(4)
2.090(4)
1.306(6)
1.277(6)
77.01(15)
117.7(3)
115.2(4)
114.5(4)
115.6(3)
2.4039(15)
2.029(6)
2.118(5)
1.289(8)
1.277(8)
78.2(2)
115.8(4)
116.0(6)
115.3(5)
114.3(4)
C(8)eN(2)
N(1)eM(1)eC(1)
M(1)eN(1)eC(7)
N(1)eC(7)eC(6)
C(7)eC(6)eC(1)
C(6)eC(1)eM(1)
planarity of the cyclemetalated moiety. However, the five-
membered ring Rh(1)eC(1)eC(6)eC(7)eN(1) in 1b is folded with
the dihedral angle of 4.7ꢀ between planes of N(1)eRh(1)eC(1) and
C(1)eC(6)eC(7)eN(1). The backbone of 2a and 3a is very similar to
1a, including Ir‒CPh and Ir‒N bond lengths, and the angles of
cyclemetalated rings.
Besides the reactivity study of para-substituted ligands with
half-sandwich transition metal precursors, interaction between
meta-substituted ligand L4 with [Cp*MCl2]2 was also investigated.
Complexes 4a and 4b were afforded under the same reaction
condition in 75% and 73% yields, respectively. Theoretically, as
shown in Scheme 2, there are two positions available for CeH bond
activation. However, from their 1H NMR spectra, complexes 4a and
4b are found to be the only products obtained in the experiment
because an important characteristic for the formation of isomers is
the splitting of Cp* signals in the 1H NMR spectra (Fig. 3 shows the
1H NMR spectrum of complex 4b). Complex 4b crystalized in
monoclinic space group P2(1)/c and their crystallographic data are
summarized in Tables 1 and 2 (Fig. 4). Crystal structure of 4b in-
dicates that the selective CeH bond activation is probably caused by
the steric hindrance [44,45].
The only products of mononuclear complexes (no binuclear
complexes was obtained) is clearly of great interest and we have
tried to elucidate the reasons using density functional theory
Scheme 2. Selective CeH bond activation of L3.

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Fig. 3. 1H NMR spectrum of complex 4b.
Fig. 4. Molecular structure of 4b with 30% probability ellipsoids. Hydrogen atoms were omitted for clarity.
calculations (DFT). The energy of the mononuclear iridium complex
1 and binuclear iridium complex B1 based on L1 was calculated
(Fig. 5). The results obviously show that the energy needed for the
formation of B1 (
M1 (
E ¼ 16.36 kcal/mol) at room temperature. So it is reasonable
that the binuclear product was not found in the reaction even large
D
E ¼ 413.80 kcal/mol) is much higher than that of
D

Z.-J. Yao et al. / Journal of Organometallic Chemistry 846 (2017) 208e216
213
Fig. 5. Computed reaction energy for the formation of L1, L1′, B1 and B1’.
excess amount of [Cp*IrCl2]2 had been employed. The binuclear
complex will decompose quickly even if it could be prepared. On
the other hand, for the bis-imine ligand with a phenyl bridge L1′,
binuclear iridium complex B1′ could be obtained because of the
slight differences of reaction energy for the formation of 1′ and B1’
(Fig. 5). The different reactivity between the two ligands (L1 and
L1′) is presumably caused by the phenyl bridge which greatly al-
leviates the steric crowding of the binuclear complex molecule.
The reduction of imines has attracted considerable attention in
synthetic chemistry, pharmaceuticals, materials science, and
biotechnology [46e51], not only because of the importance of the
amine products for the chemical science, but also to the reduction
process is the key intermediate of the reductive amination [52].
Compared with the reduction pathway using metal hydride as
reducing reagents, catalytic hydrogenation with late transition
metal complexes represents a sustainable and green chemical
process, crucial for large scale industries. Encouraged by the pre-
vious results of the catalytic activity of the iridium complexes [53],
we explored the catalytic activity of complexes 1ae4a for the ar-
omatic ketimines to the corresponding ketamines. The hydroge-
nation reactions were performed in an azeotropic mixture of formic
acid/triethylamine (F/T) (serve as H donor) [54] in CF3CH2OH using
1 mol% catalyst loading. Preliminary results are summarized in
Table 3. Various imine substrates were employed in the reactions
and the results demonstrated complexes 1a-4a are indeed catalytic
active. Among these iridium catalysts, complex 3a was found to be
the best catalyst for the reaction (Table 3, Entries 1e4). This result
indicates that the electron-deficient iridium center is more proper
for the catalytic hydrogenation, which is consistent with previous
results [52]. Reaction temperature also exhibits influence on the
catalytic hydrogenation and 80 ꢀC is proper for the reaction
(Table 3, Entries 5 and 6). Decreasing the catalyst loading (0.1 mol%)
led to a lower yield of product (Table 3, Entry 3). With the
optimized condition in hand, a series of imines were used in the
reaction and the results showed that these aryl imines could be
reduced to the corresponding amines with high efficiency. Both
electron-withdrawing and electron-donating containing sub-
stances, whether ortho- or para-substituted, afforded the corre-
sponding amines in good yields (Table 3, entries 7e12). Scheme 3
shows the proposed mechanism of this reaction. The cyclo-
metalated iridium catalyst reacted with formic acid to generate the
iridium hydride through the decarboxylation process. Further
interaction between iridium hydride and protonation imine fur-
nished the corresponding amine.
3. Conclusion
A series of mononuclear half-sandwich iridium and rhodium
complexes with bis-imine ligands based on hydrazine were syn-
thesized through one CeH bond activation. All these transition
metal complexes were air- and moisture-stable. DFT calculations
further confirmed the experimental results which binuclear com-
plexes could not be generated probably because of the steric
crowding. Mononuclear iridium complex 3a showed good catalytic
activity for the reduction of both electron-rich and electron-poor
imines with low catalyst loading. The catalytic system exhibited
high efficiency and the corresponding amines were given in good
yields. Further modification of the ligand and their reactivity study
with group 9 metal complexes is currently underway in our lab.
4. Experimental section
4.1. General data
All manipulations were performed under an atmosphere of ni-
trogen using standard Schlenk techniques. Chemicals were used as

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Table 3
4.2. Synthesis of bis-imine ligands L1eL4
Catalytic reduction of imines with iridium complexes 1ae4a.a
Hydrazine hydrate (0.25 g, 5.0 mmol) and corresponding aro-
matic aldehydes (2.5 mmol) were reacted in methanol for 6 h in the
presence of catalytic amount of AcOH. Solvent was removed under
reduced pressure, and the obtained solid was washing with cold
methanol for several times.
L1: yellow solid; 90% yield. 1H NMR (500 MHz, CDCl3, 25 ꢀC):
Entry
1
Catalyst
T/ꢀC
80
Product
Yieldb/%
76
d
8.69 (s, 2H, CH¼N), 7.87e7.85 (m, 4H, Ph), 7.47e7.44 (m, 6H, Ph)
ppm. IR (KBr, disk):
y 2943, 1624, 1444, 1306, 1206, 1018, 953, 856,
1a
750 cmꢁ1. Elemental analysis calcd (%) for C14H12N2: C 80.74, H 5.81,
N 13.45, found: C 80.67, H 5.85, N 13.59.
L2: yellow solid; 93% yield. 1H NMR (500 MHz, CDCl3, 25 ꢀC):
1c
1c
1c
1c
1c
1c
2
3
4
5
6
7
2a
3a
4a
3a
3a
3a
80
80
80
60
90
80
68
d
8.61 (s, 2H, CH¼N), 7.79 (d, J ¼ 8.5 Hz, 4H, Ph), 6.97 (d, J ¼ 8.5 Hz,
91/62c
82
4H, Ph), 3.85 (s, 6H, OMe) ppm. IR (KBr, disk):
y 2925, 1600, 1503,
1297, 1250, 1165, 1021, 832, 617 cmꢁ1. Elemental analysis calcd (%)
for C16H16N2O2: C 71.62, H 6.01, N 10.44, found: C 71.69, H 5.98, N
10.33.
81
90
92
L3: yellow solid; 89% yield. 1H NMR (500 MHz, CDCl3, 25 ꢀC):
d
8.61 (s, 2H, CH¼N), 7.79 (d, J ¼ 8.5 Hz, 4H, Ph), 7.44 (d, J ¼ 8.0 Hz,
1d
1e
1f
8
3a
3a
3a
80
80
80
88
89
82
4H, Ph) ppm. IR (KBr, disk): y 2943, 1624, 1484, 1399, 1313, 1168,
1088, 861, 819 cmꢁ1. Elemental analysis calcd (%) for C14H10Cl2N2: C
60.67, H 3.64, N 10.11, found: C 60.74, H 3.63, N 10.16.
L4: yellow solid; 91% yield. 1H NMR (500 MHz, CDCl3, 25 ꢀC):
9
d
8.57 (s, 2H, CH¼N), 8.03 (s, 2H, Ph), 7.73 (d, J ¼ 7.5 Hz, 2H, Ph), 7.60
(d, J ¼ 8.0 Hz, 2H, Ph), 7.34 (t, J ¼ 7.5 Hz, 2H, Ph) ppm. IR (KBr, disk):
2951, 1624, 1557, 1463, 1422, 1316, 1205, 1065, 956, 778 cmꢁ1
y
.
10
Elemental analysis calcd (%) for C14H10Br2N2: C 45.94, H 2.75, N
7.65, found: C 45.82, H 2.63, N 7.56.
1g
1h
4.3. Synthesis of mononuclear complexes 1e4
11
12
3a
3a
80
80
88
87
A mixture of [Cp*MCl2]2 (0.1 mmol, M ¼ Ir, Rh), NaOAc
(0.6 mmol), and corresponding ligands L1eL4 (0.1 mmol) was
stirred at 50 ꢀC in 15 mL of methanol for 8 h. The mixture was
filtered and evaporated to give the crude products which were
further purified by silica gel column chromatography (CH2Cl2:
EA ¼ 30: 1) to afford pure cyclometalated mononuclear complexes
in yields of 70e85%.
1i
a
Reaction conditions: imines (0.5 mmol), catalyst (1 mol%), CF3CH2OH (2 mL), F/T
(0.5 mL).
1a: red solid, 76% yield. 1H NMR (500 MHz, CDCl3, 25 ꢀC):
d 9.19
b
c
Yield was determined by GC analysis, n-tridecane was used as internal standard.
0.1 mol% catalyst was used.
(s,1H, CH¼N), 8.59 (s,1H, CH¼N), 7.90 (d, J ¼ 7.0 Hz, 2H, Ph), 7.85 (d,
J ¼ 7.5 Hz, 1H, Ph), 7.59 (d, J ¼ 7.5 Hz, 1H, Ph), 7.51e7.46 (m, 3H, Ph),
7.18 (t, J ¼ 7.5 Hz,1H, Ph), 7.06 (t, J ¼ 7.0 Hz,1H, Ph),1.69 (s,15H, Cp*)
ppm. IR (KBr, disk):
y 2909, 1580, 1528, 1447, 1427, 1209, 1021, 864,
721 cmꢁ1. Elemental analysis calcd (%) for C24H26ClIrN2: C 50.56, H
4.60, N 4.91, found: C 50.62, H 4.63, N 4.88.
1b: red solid, 79% yield. 1H NMR (500 MHz, CDCl3, 25 ꢀC):
d 9.31
(s,1H, CH¼N), 8.45 (s,1H, CH¼N), 7.91 (d, J ¼ 6.0 Hz, 2H, Ph), 7.84 (d,
J ¼ 8.0 Hz, 1H, Ph), 7.53e7.48 (m, 4H, Ph), 7.24 (overlapped with
CDCl3, 1H, Ph), 7.09 (t, J ¼ 7.0 Hz, 1H, Ph), 1.63 (s, 15H, Cp*) ppm. IR
(KBr, disk): y .
2912, 1583, 1531, 1467, 1428, 1213, 1021, 869, 721 cmꢁ1
Elemental analysis calcd (%) for C24H26ClRhN2: C 59.95, H 5.45, N
5.83, found: C 59.88, H 5.36, N 5.91.
2a: red solid, 81% yield. 1H NMR (500 MHz, CDCl3, 25 ꢀC):
d 9.04
(s,1H, CH¼N), 8.48 (s,1H, CH¼N), 7.83 (d, J ¼ 8.5 Hz, 2H, Ph), 7.53 (d,
J ¼ 8.5 Hz, 1H, Ph), 7.36 (s, 1H, Ph), 6.98 (d, J ¼ 8.5 Hz, 2H, Ph), 6.62
(d, J ¼ 8.5 Hz, 1H, Ph), 3.90 (s, 3H, OMe), 3.88 (s, 3H, OMe), 1.57 (s,
Scheme 3. Propose mechanism of the transfer hydrogenation.
15H, Cp*) ppm. IR (KBr, disk):
1001, 854, 703 cmꢁ1
26H30ClIrN2O2: C 49.55, H 4.80, N 4.45, found: C 49.58, H 4.73, N
4.49.
2b: red solid, 80% yield. 1H NMR (500 MHz, CDCl3, 25 ꢀC):
y 2901, 1568, 1512, 1422, 1403, 1191,
.
Elemental analysis calcd (%) for
C
commercial products without further purification. 1H NMR
(500 MHz) spectra were measured with a Bruker DMX-500 spec-
trometer. Elemental analysis was performed on an Elementar vario
EL III analyzer. IR (KBr) spectra were measured with the Nicolet FT-
IR spectrophotometer.
d
9.16
(s,1H, CH¼N), 8.33 (s,1H, CH¼N), 7.82 (d, J ¼ 8.5 Hz, 2H, Ph), 7.44 (d,
J ¼ 8.5 Hz, 1H, Ph), 7.36 (s, 1H, Ph), 6.98 (d, J ¼ 8.5 Hz, 2H, Ph), 6.62
(d, J ¼ 8.5 Hz, 1H, Ph), 3.90 (s, 3H, OMe), 3.87 (s, 3H, OMe), 1.62 (s,

Z.-J. Yao et al. / Journal of Organometallic Chemistry 846 (2017) 208e216
215
15H, Cp*) ppm. IR (KBr, disk):
1004, 853, 706 cmꢁ1
Elemental analysis calcd (%) for
26H30ClRhN2O2: C 57.73, H 5.59, N 5.18, found: C 57.82, H 5.65, N
5.21.
3a: red solid, 83% yield. 1H NMR (500 MHz, CDCl3, 25 ꢀC):
y
2895, 1563, 1510, 1423, 1408, 1196,
Program), Local Institutions Capacity Training of Shanghai Science
and Technology Commission, and the Start Funding of Shanghai
Institute of Technology (YJ2016-10).
.
C
d
9.11
Appendix A. Supplementary data
(s, 1H, CH¼N), 8.54 (s, 1H, CH¼N), 7.83 (d, J ¼ 8.5 Hz, 2H, Ph), 7.76 (s,
1H, Ph), 7.51 (s, J ¼ 8.0 Hz, 1H, Ph), 7.46 (d, J ¼ 8.5 Hz, 2H, Ph), 7.05
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.jorganchem.2017.06.023.
(d, J ¼ 8.0 Hz, 1H, Ph), 1.67 (s, 15H, Cp*) ppm. IR (KBr, disk):
y 2906,
1572,1522,1430,1406,1200, 992, 861, 695 cmꢁ1. Elemental analysis
calcd (%) for C24H24Cl3IrN2: C 45.11, H 3.79, N 4.38, found: C 41.88, H
4.23, N 9.21.
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Acknowledgements
€
€
This work was supported by the National Natural Science
Foundation of China (No. 21601125), the Chenguang Scholar of
Shanghai Municipal Education Commission (No. 16CG64), Natural
Science Foundation of Shanghai (No. 16ZR1435700), the Shanghai
Municipal Education Commission (Plateau Discipline Construction

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