Alkyl Carbon-Oxygen Bond Cleavage of Aryl Alkyl Ethers by Iridium-Porphyrin and Rhodium-Porphyrin Complexes in Alkaline Media

Article abstract of DOI:10.1021/acs.organomet.7b00386

Alkyl C-O bond cleavage in aryl alkyl ethers was achieved with Rh(ttp)Cl (1a; ttp = 5,10,15,20-tetrakis(p-tolyl)porphyrinato dianion) together with competitive alkyl C-H bond activation in alkaline media. In contrast, selective alkyl C-O bond cleavage occurred with the iridium-porphyrin Ir(ttp)(CO)Cl (1b)/KOH. Mechanistic investigations indicate the coexistence of M^I(ttp)^- and M₂^II(ttp)₂ (M = Rh, Ir) under basic conditions. With a weaker Rh(ttp)-Rh(ttp) bond, Rh^II(ttp)· metalloradical exists in an appreciable amount to cleave the alkyl C-H bond, competing with the alkyl C-O bond cleavage via Rh^I(ttp)^-. In contrast, the more nucleophilic Ir^I(ttp)^- cleaves the alkyl C-O bond exclusively.

Full text of DOI:10.1021/acs.organomet.7b00386

Article
pubs.acs.org/Organometallics
Alkyl Carbon−Oxygen Bond Cleavage of Aryl Alkyl Ethers by
Iridium−Porphyrin and Rhodium−Porphyrin Complexes in Alkaline
Media
Chen Chen and Kin Shing Chan*
Department of Chemistry, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, People’s Republic of China
S
* Supporting Information
ABSTRACT: Alkyl C−O bond cleavage in aryl alkyl ethers was
achieved with Rh(ttp)Cl (1a; ttp = 5,10,15,20-tetrakis(p-tolyl)-
porphyrinato dianion) together with competitive alkyl C−H bond
activation in alkaline media. In contrast, selective alkyl C−O
bond cleavage occurred with the iridium−porphyrin Ir(ttp)(CO)
Cl (1b)/KOH. Mechanistic investigations indicate the coexistence of MI(ttp)− and M2 (ttp)2 (M = Rh, Ir) under basic con-
II
ditions. With a weaker Rh(ttp)−Rh(ttp) bond, RhII(ttp)· metalloradical exists in an appreciable amount to cleave the alkyl
C−H bond, competing with the alkyl C−O bond cleavage via RhI(ttp)−. In contrast, the more nucleophilic IrI(ttp)− cleaves the
alkyl C−O bond exclusively.
methods on etheric C(sp3)−O bond cleavage have seldom
INTRODUCTION
■
been reported.14
The carbon−oxygen (C−O) bond is among the most common
Group 9 MI(por)− (M = Rh, Ir; por = porphyrinato dianion)
linkages in nature.1 Recently, C−O bond cleavage has drawn
anions show “super nucleophilic”15 character toward alkyl
much attention due to its application in natural product syn-
iodide, lactones, and epoxides in these substitution reactions.16
thesis and biomass utilization.2 Ether cleavage or O-dealkylation
The typical method to generate MI(por)−, however, requires
is primarily used as a deprotection method of the hydroxyl group
in synthetic chemistry,3 such as the debenzylation of PhOBn
an anaerobic atmosphere and expensive NaBH4 to reduce
MIII(por)Cl.16 Recently, our group has developed a more con-
with H2 catalyzed by Pd/C.4
venient method by using KOH as the reducing agent to gen-
Etheric C−O cleavage is usually a Brønsted- or Lewis-acid-
erate MI(por)− in aerobic conditions. MI(por)− is in equilibria
catalyzed process by activating the C−O bond with protonation
with MII(por)· and M(por)H under basic conditions.17 Both
Rh(ttp)Cl and Ir(ttp)(CO)Cl in the presence of KOH can
cleave the C−O bond of CH3−OH to give M(ttp)CH3.
IrI(ttp)− is the proposed nucleophile to displace hydroxide in
CH3−OH, while Rh(ttp)H undergoes σ-bond metathesis with
CH3−OH to give Rh(ttp)CH3.18 Wayland has also demon-
strated the water-soluble IrI(tspp)− (tspp = tetra(p-sulfo-
natophenyl)porphyrinato dianion) catalyzed the C−O bond
cleavage of CD3OD with Ir(tspp)D to give Ir(tspp)CD3.19
However, the activation of the reactive O−H bond competed
with the alkyl C−O bond in the reaction process.18,19 In aryl
alkyl ethers, the PhO− is a better leaving group than OH− in
CH3−OH, and the C(sp2)−O bond is inert toward nucleo-
philic substitution;20 the alkyl C(sp3)−O bond is therefore more
likely to be selectively substituted by MI(por)− (M = Rh, Ir)
anions. As far as we know, such a metal-centered anion-
complex-mediated nucleophilic substitution of aryl alkyl ethers
with the displacement of phenoxide under alkaline conditions
remains unusual. In addition, the generated M(por)alkyls may
serve as intermediates for alkyl C−O bond hydrogenolysis
through M(por)−C bond hydrogenation with water.21 Herein,
we report the KOH-promoted alkyl C−O bond activation of
or coordination.5,6 In the absence of acids, extremely basic
conditions are needed, such as in the case of the [1,2]-Wittig
rearrangement of ethers to give secondary or tertiary alcohols in
the presence of alkyl lithium compounds.7
The transition-metal-mediated C−O bond activation of
ethers has been widely investigated due to the importance of
this fundamental step both in catalytic and stoichiometric trans-
formations.5,8 The C(sp2)−O bond activation of aryl ethers by
transition-metal complexes via oxidative addition has been
systematically studied,8,9 while the C(sp3)−O bond activation is
less commonly encountered.10 Ittel and Tolman reported the
alkyl C−O bond activation of anisole via oxidative addition by a
Fe0(dmpe)2 (dmpe = Me2PCH2CH2PMe2) intermediate in
1978 (Scheme 1A).11 Later, Milstein and co-workers dis-
covered that an electrophilic Pd(II) or Ni(II) species was likely
to function as a Lewis acid to promote the alkyl C−O bond
cleavage of a bisphosphinated aryl methyl ether (Scheme 1B).8
A unique C−O cleavage mode induced by C−H oxida-
tive addition with an iridium PCP-type pincer ligand has
been disclosed by Goldman and co-workers (Scheme 1C).12
Recently, Gryko and co-workers reported a nucleophilic
substitution of (allyloxy)arenes with reduced Vitamine B12
species (CoI) to cleave the alkyl C−O bond (Scheme 1D).13
However, this method is limited to allyl aryl ethers. Aside from
the above strategies for C(sp3)−O bond activation, other
Received: May 24, 2017
© XXXX American Chemical Society
A
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Scheme 1. Transition-Metal-Mediated C(sp3)−O Bond Cleavage
aryl alkyl ethers with rhodium−porphyrin and iridium−
porphyrin complexes to yield the corresponding M(por)alkyls
via the proposed MI(por)− (M = Rh, Ir)-anion-mediated dis-
placement of phenoxide.
are usually stable under basic conditions.6 Figures 1,2 illustrate
the molecular structures of 3a and 3c. The collection and
RESULTS AND DISCUSSION
■
Alkyl C−O Bond Cleavage of Aryl Alkyl Ethers by
Rhodium−Porphyrin Complexes. On the basis of the
optimal reaction conditions in the reported C−O bond
cleavage of methanol with Rh(ttp)Cl (1a),18b 10 equiv of
K2CO3 at 150 °C and solvent-free conditions were applied for
the investigation of the alkyl C−O bond cleavage of anisole
(2a). However, only alkyl C−H bond activation (CHA)
occurred to give 70% yield of 3a (eq 1). Compounds with
Figure 1. ORTEP drawing of Rh(ttp)CH2OPh·0.5CHCl3
(3a·0.5CHCl3), with 50% probability displacement ellipsoids. 3a
selected bond length (Å): Rh(1)−C(61): 2.031(6).
processing parameters of single-crystal data for 3a and 3c are
shown in the Supporting Information.
On the basis of the reported mechanism on the alkyl C−H
bond activation with RhII(por)·23 and the alkyl C−O bond
activation with RhI(por)−,16c,17a Scheme 2 depicts the proposed
mechanism for the reaction between aryl alkyl ethers with
Rh(por) complexes. In basic media, Rh(ttp)Cl (1a) undergoes
ligand substitution with OH− to form Rh(ttp)OH, which then
similar structures have been reported in our previous work.22
When the stronger base of KOH was employed, the alkyl C−O
bond-activation (COA) product was achieved (3b) in 46%
yield as well as alkyl C−H activation product (3a) in 24% yield
(eq 2). A similar result was obtained when the more reac-
tive benzyl phenyl ether (2b) was employed with 3c and 3d,
obtained in 17% and 45% yields, respectively (eq 3). This alkyl
C−O bond cleavage is distinct, since the C−O bonds of ethers
generates RhII (ttp)2 and H2O2 through reductive dimeriza-
2
tion.24 RhII (ttp)2 reacts with excess OH− to yield an equilib-
2
rium mixture of RhI(ttp)− and Rh(ttp)OH.25,17a Rh2(ttp)2 dis-
sociates into a RhII(ttp)· metalloradical, which then undergoes
bimetalloradical C−H bond activation to give Rh(ttp)alkyl and
Rh(ttp)H, analogous to that of CH4 and toluene (Scheme 2,
Pathway A).23 Alternatively, the nucleophilic RhI(ttp)− undergoes
B
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Alkyl C−O Bond Cleavage of Aryl Alkyl Ethers by
Iridium−Porphyrin Complexes. With the partial success of
alkyl C−O bond cleavage between aryl alkyl ethers and Rh(ttp)
Cl (1a)/KOH, we then examined the chemistry with more
nucleophilic IrI(ttp)−, generated from the reaction of Ir(ttp)-
(CO)Cl (1b) with KOH, in order to achieve selective alkyl
C−O bond cleavage. We adapted the reaction conditions of the
C−O cleavage of MeOH18a by using 20 equiv of KOH at
200 °C in solvent-free conditions to investigate the alkyl C−O
bond cleavage of anisole (2a) with Ir(ttp)(CO)Cl (1b). To our
delight, the alkyl C−O bond activation of anisole proceeded
selectively to give Ir(ttp)CH3 (3e) with a high yield of 83%
(eq 6). With this initial success, the reaction conditions were
further optimized.
Figure 2. ORTEP drawing of Rh(ttp)CHPh(OPh)·CHCl3
(3c·CHCl3), with 50% probability displacement ellipsoids. 3c selected
bond length (Å): Rh(1)−C(61): 2.059(6).
Reaction Conditions Optimization. Temperature Effect.
The reaction temperature was first optimized. At 120 °C, the
reaction required 4 h to give Ir(ttp)CH3 (3e) in 55% yield
(Table 1, entry 1). When the temperatures were raised to
Scheme 2. Proposed Mechanism for COA and CHA of Aryl
Alkyl Ethers with Rhodium−Porphyrin Complexes
a
Table 1. Temperature Effect
entry
temp/°C
time/h
yield/%
1
2
3
4
120
150
180
200
4
2
1
1
55
87
87
83
a
Ir(ttp)(CO)Cl (1b) (0.010 mmol) with 1.0 mL of anisole.
150−200 °C, the reactions took 1 to 2 h to complete to give
similar yields of 3e (Table 1, entries 2 to 4). Therefore, 150 °C
was chosen as the optimal temperature to allow milder conditions.
Base and Base-Loading Effects. Without any base,
Ir(ttp)(CO)Cl (1b) did not react with anisole (2a) at 150 °C
for 14 h with quantitative recovery of 1b (Table 2, entry 1).
When a weak base of K2CO3 was employed, Ir(ttp)CH3 (3e)
was only obtained in 6% yield (Table 2, entry 3). Thus, KOH
was found to be the optimal base (Table 2, entry 2). When
10 equiv of KOH was added, Ir(ttp)Me (3e) was obtained in
82% yield at 150 °C for 2 h (Table 2, entry 5). A lower KOH
parallel nucleophilic substitution at the alkyl carbon center to
cleave the C−O bond (Scheme 2, Pathway B).16c,17a
Since rhodium−porphyrin alkyls undergo hydrolysis with
water to give the corresponding alkanes,26 the hydrolysis of
3a and 3c in basic conditions was further examined for the
regeneration of 2a and 2b from 3a and 3c, respectively.
Rh(ttp)CH2OPh (3a) was found to be very stable toward
hydrolysis at 200 °C for 82 h without any anisole (2a)
formed (eq 4). The hydrolysis rate of 3c, being a Rh(ttp)-2°
a
Table 2. Base and Base-Loading Effects
entry
base
n
time/h
yield/%
b
1
KOH
KOH
K2CO3
KOH
KOH
KOH
0
14
2
0
2
3
4
5
6
20
20
5
87
6
10
2
alkyl, was much faster to regenerate 50% of benzyl phenyl
ether (2b) in 18 h (eq 5). However, the hydrolysis rate
was still too slow compared with the formation rate of
CHA product 3c. Thus, it was difficult to eliminate C−H
bond-activation product through hydrolysis in the reaction
process.
71
82
81
10
30
2
2
a
Ir(ttp)(CO)Cl (1b) (0.010 mmol) with 1.0 mL of anisole.
Ir(ttp)(CO)Cl (1b) recovered quantitatively.
b
C
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loading of 5 equiv resulted in a 71% yield of Ir(ttp)CH3 (3e),
also in 2 h (Table 2, entry 4). With higher loadings of KOH at
20 and 30 equiv, the reaction efficiency was similar in rates and
yields (Table 2, entries 2, 5, and 6). Therefore, 10−30 equiv of
KOH were all effective, and 10 equiv of KOH was used in
further studies.
Substrate Scope. Various primary alkyl aryl ethers were
then investigated. Alkyl C−O bond cleavage occurred selectively
to give high product yields with Ir(ttp)(CO)Cl (1b)/KOH
(Table 3, entries 1 to 4). The reaction with low melting-point
Figure 3. ORTEP drawing of Ir(ttp)CH2CH3 (3f), with 50%
probability displacement ellipsoids. 3f selected bond length (Å):
Ir(1)−C(41): 1.969(12).
a
Table 3. Substrate Scope for Alkyl C−O Bond Cleavage
Scheme 3. Equilibria between Iridium−Porphyrin
Intermediates under the Optimized Reaction Conditions
entry
R
time/h
yield/%
1
2
3
Me (2a)
Et (2c)
nPr (2d)
Bn (2b)
allyl (2e)
2
2
2
2
4
82 (3e)
87 (3f)
85 (3g)
b
4
82 (3h)
Ir(ttp)nPr (3g): 35%
c
5
a
Ir(ttp)(CO)Cl (1b) (0.010 mmol) with 1 mL of substrate in solvent-
b
free conditions. BnOPh (2b) (10 equiv) in benzene solvent.
c
Ir(ttp)CH2CH2CH2OPh (3i) (20%) was also isolated.
ligand dissociation and ligand substitution with OH− to give
Ir(ttp)OH, which undergoes fast reductive dimerization to gen-
erate Ir2(ttp)2 and H2O2 at 150 °C.28 Ir2(ttp)2 will be reduced
by excess OH− to give IrI(ttp)H−,29 and it can be protonated
by residual water to form Ir(ttp)H.16a Therefore, Ir2(ttp)2 (1d),
IrI(ttp)−, and Ir(ttp)H (1c) are the three dominant possible
intermediates coexisting in the reaction mixture. The reactivity
of the three possible intermediates toward alkyl C−O bond
cleavage were then examined individually.
solid PhOBn (2b) (mp = 39−41 °C) (10 equiv) was con-
ducted in benzene solvent and completed in 2 h to afford
Ir(ttp)Bn (3h) in 82% yield (Table 3, entry 4). When allyl
Table 4. Alkyl C−O Bond Cleavage of PhOBn(p-FG) in
a
Benzene
Ir(ttp)H (1c) reacted with anisole at 150 °C for 2 h to give
only trace amounts of Ir(ttp)Me (3e) and the aromatic CHA
product 3m (Scheme 4A). The reaction of Ir(ttp)H (1c) with
PhOBn (2b) gave the benzylic C−H activation product 3n in
around 60% yield (Scheme 4A), similar to the benzylic CHA of
PhCH3 by Ir(ttp)H to afford Ir(ttp)CH2Ph.30Alkyl C−O bond
cleavage of both anisole (2a) and PhOBn (2b) does not occur
with Ir(ttp)H. Therefore, Ir(ttp)H (1c) is unlikely to be the
intermediate to cleave the alkyl C−O bond.
b
entry
FG
yield /%
1
2
3
OMe (2f)
Cl (2g)
71 (3j)
66 (3k)
68 (3l)
CF3 (2h)
a
b
Ir(ttp)(CO)Cl (1b) (0.010 mmol) with 1.0 mL of benzene. NMR
yield calculated using diphenylmethane as the internal standard.
phenyl ether was employed, 35% of Ir(ttp)nPr (3g) was isolated
together with 20% yield of Ir(ttp)CH2CH2CH2OPh (3i)
formed from the 1,2-insertion with Ir(ttp)H.19,27 (Table 3,
entry 5) As for the 2° alkyl phenyl ether of isopropyl phenyl
ether, no Ir(ttp)alkyl was observed. The nucleophilic
substitution of the isopropyl group is likely too sterically
demanding. Ir(ttp)Et (3f) was further characterized by single-
crystal X-ray diffraction, and its structure is shown in Figure 3.
When the para-substituted aryl phenyl ethers PhOBn(p-FG)
(FG = OMe, Cl, CF3) (2f−h) reacted with Ir(ttp)(CO)Cl
(1b), Ir(ttp)Bn(p-FG) was achieved in moderate to high yields
from 66−71% (Table 4, entries 1 to 3) with high chemoselec-
tivity. The substrate-bearing aryl C−Cl bond (2g) underwent
selective alkyl C−O bond cleavage without interference from
C−Cl bond activation, which has been reported by our group
before.28
Ir2(ttp)2 (1d) reacted with anisole (2a) to give trace amounts
of Ir(ttp)Me (3e) (Scheme 4B). The reaction of Ir2(ttp)2 (1d)
with PhOBn (2b) gave the benzylic C−H bond-activation pro-
duct (3n) in 40% yield in 2 h with no Ir(ttp)Bn (3h) formed
(Scheme 4B). Thus, Ir2(ttp)2 (1d) is also not the intermediate
for alkyl C−O bond cleavage.
IrI(ttp)− was prepared independently from the deprotona-
tion of Ir(ttp)H with KOH18a and reacted with 2a and 2b,
respectively, to give the corresponding C−O cleavage products
in 54 and 22% yield in 2 h (Scheme 4C). The results strongly
support that IrI(ttp)− is the intermediate to cleave the alkyl
C−O bond.
To gain further understanding on the stereoelectronic nature
of the alkyl C−O bond-cleavage process, the competition experi-
ments between equal molar mixtures of PhOMe (2a), PhOEt
(2c), and PhOnPr (2d) were conducted (Table 5, entries 1 to 3).
The relative reactivity followed the trend: 2a/2c/2d = 1:1.7:3.2,
which is not consistent with a typical SN2 process. The reac-
tion between Ir(ttp)Me (3e) and PhOnPr (2d) gave 5% of
Ir(ttp)nPr (3g) with mostly 95% yield recovery of 3e; thus, the
Mechanistic Investigation. Like the Rh(ttp) analogue, the
four Ir(ttp) species: IrI(ttp)−, IrII(ttp)·, Ir(ttp)H, and Ir(ttp)-
OH have been reported to exist in equilibria in basic conditions
as depicted in Scheme 3.16a,28,29 Ir(ttp)(CO)Cl (1b) undergoes
D
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ratios were close to 1 (Table S1). Thus, no significant reactivity
difference was observed and para-substituents on the benzyl
group have little electronic effect on the alkyl C−O bond-
cleavage process.
Scheme 4. Reactivity of Three Possible Intermediates toward
Alkyl C−O Bond Cleavage
Therefore, further efforts were taken for the reaction with
BnOPh(p-FG) (FG = OMe, CN) (2i, 2j) to compare the
reaction times of each substrate for a qualitative understanding
of the electronic effect on the alkyl C−O bond-cleavage rate.
BnOPh(p-CN) (2j), with a strong electron-withdrawing group,
showed the fastest reaction rate, taking 0.5 h to complete, while
the reaction of BnOPh(p-OMe) (2i) required 3 h. (Table 6,
Table 6. Comparison of Reaction Time of Ir(ttp)(CO)Cl
a
with BnOPh(p-FG)
b
entry
FG
time (h)
yield (%)
1
2
3
OMe (2i)
H (2b)
3
2
71
82
CN (2j)
0.5
81
a
b
Ir(ttp)(CO)Cl (1b) (0.010 mmol) with 1.0 mL of benzene. Yield
calculated using diphenylmethane as the internal standard.
entries 1 to 3) On the basis of these findings, an SN2-like
transition state is deduced for the C−O cleavage process
(Figure 4). The IrI(ttp)− anion attacks the benzylic carbon with
a
Table 5. Relative Reactivity of Primary Alkyl Phenyl Ethers
Figure 4. Alkyl C−O bond cleavage via an SN2-like transition state.
b
a heterolytic C−O cleavage. The incipient phenoxide is
stabilized by an electron-withdrawing group, such as a CN
group in the transition state to result in a shorter reaction
time.
entry
R1
R2
1 yield: 2 yield
total yield (%)
1
2
3
Me
Me
Et
Et
3e/3f = 1:1.7
3e/3g = 1:3.2
63
79
71
nPr
nPr
3f/3g = 1:1.8
Comparison of Rhodium−Porphyrins and Iridium−
Porphyrins in Alkyl C−O Bond Cleavage. Alkyl C−O bond
cleavage with Ir(ttp)(CO)Cl (1b)/KOH was achieved with
high chemoselectivity. However, C−H bond activation
occurred parallel with alkyl C−O bond activation in the
rhodium case. We rationalize that IrI(ttp)− is more nucleophilic
than RhI(ttp)− in basic conditions, allowing it to more easily
substitute the alkyl C−O bond because of the higher pKa of
Ir(ttp)H (∼15)16a compared with that of Rh(ttp)H (∼11).31
Alternatively, with a stronger Ir−Ir bond (∼24 kcal/mol),32
a
b
Ir(ttp)(CO)Cl (1b), 0.010 mmol. Ratio calculated according to the
1H NMR of the crude mixture.
ratios measured were the kinetic ones. We do not fully under-
stand the underlying reason for the reactivity trend at this
stage.
In the reaction process, the starting material Ir(ttp)(CO)Cl
(1b) was completely consumed rapidly within the first 10 min,
while the formation of product was much slower and took
about 2 h. Therefore, the C−O bond-cleavage step is the rate-
determining step in the multistepwise reaction. Competition
reactions between para-substituted PhOBn(p-FG) (2f−h) and
PhOBn (2b) were conducted to investigate on the electronic
nature of the C−O cleavage step. The reaction between
Ir(ttp)Bn (3h) and PhOBn(p-CF3) (2h) under the optimized
reaction conditions gave quantitative recovery of Ir(ttp)Bn
(3h) and without any potential Ir(ttp)Bn(p-CF3) (3l) formed,
so the product ratios measured were the kinetic ratios (eq S1).
Then, competition experiments between an equimolar mix-
ture of PhOBn(p-FG) (FG = OMe, Cl and CF3) (2f−h) and
PhOBn (2b) with Ir(ttp)(CO)Cl (1b) and KOH in benzene
were conducted and yielded the product ratio between
Ir(ttp)CH2C6H4(p-FG) and Ir(ttp)CH2Ph. The calculated
IrII (ttp)2 cannot dissociate into IrII(ttp)· as fast and exten-
2
sively as the rhodium−porphyrin analogue (Rh−Rh bond:
∼16 kcal/mol)33 to activate the C−H bond.
CONCLUSION
■
The alkyl C−O bond cleavage of aryl alkyl ethers was
successfully achieved by Rh(ttp)Cl (1a) and Ir(ttp)(CO)Cl
(1b) in basic media. Competitive alkyl C−H bond activation
occurred with Rh(ttp)Cl (1a), while selective alkyl C(sp3)−O
bond cleavage was achieved exclusively with Ir(ttp)(CO)Cl
(1b). MI(ttp)− (M = Rh, Ir) was proposed to be the inter-
mediate to cleave the alkyl C(sp3)−O bond via nucleophilic
substitution.
E
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1H NMR (CDCl3, 400 MHz, 314 K) δ −0.30 (d, 1 H, 2JRh−H = 4.1 Hz,
EXPERIMENTAL SECTION
■
3
CH), 2.71 (s, 12 H), 3.20 (brs, 2 H), 4.26 (d, 2 H, JH−H = 8.1 Hz),
Unless otherwise noted, all of the reagents were purchased from
commercial suppliers and directly used without further purification.
Hexane was distilled from anhydrous calcium chloride. Benzene was
distilled over sodium under nitrogen. All reactions were protected
from light by wrapping with aluminum foil. The reaction in Teflon
screw-capped pressure tubes were heated in heating blocks on heaters
and monitored by thin-layer chromatography (TLC), whereas the
reactions in sealed NMR tubes were heated in GC ovens. TLC was
performed on precoated silica gel 60 F254 plates. Rh(ttp)Cl (1a),34
Ir(ttp)Cl(CO) (1b),35 Ir(ttp)H (1c),30 and Ir2(ttp)2 (1d)30 have been
characterized and were prepared according to the literature process.
Para-substituted benzyl phenyl ethers: BnOPh(p-FG) (FG = OMe,
CN) (2i, 2j) and PhOBn(p-FG) (FG = OMe, Cl, CF3) (2f, 2g, 2h)
have also been characterized and were prepared according to the
literature method.36 Silica gel (Merck, 70−230 and 230−400 mesh)
was used in column chromatography.
3
6.04 (t, 2 H, JH−H = 7.6 Hz), 6.39−6.49 (m, 4 H), 7.50−7.56
(m, 8 H), 7.98 (m, 8 H), 8.64 (s, 8 H). 13C NMR (CDCl3, 100 MHz)
δ 21.6, 63.9 (1JRh−C = 29.9 Hz), 113.0, 119.7, 122.6, 124.7, 125.8,
127.4, 127.5, 127.9, 131.4, 134.0, 134.2, 137.1, 139.5, 139.8, 143.3,
143.4, 153.4. HRMS (m/z) (ESI-MS): [M]+ calcd for C61H47N4RhO
954.2799; found 954.2784.
Reaction of Rh(ttp)Cl and Benzyl Phenyl Ether with KOH.
Rh(ttp)Cl (1a; 9.7 mg, 0.012 mmol), KOH (7.2 mg, 0.12 mmol) and
PhOBn (2b; 19.2 mg, 0.11 mmol) were added in benzene (1.0 mL).
The mixture was degassed for three freeze−pump−thaw cycles, refilled
with N2, and heated to 150 °C for 1 h until reaction completion.
Benzene solvent was removed by vacuum distillation. Anisole (5 μL)
was added as the internal standard to calculate the NMR yields of
products. Rh(ttp)Bn (3d)23a in 16%, and Rh(ttp)CHPh(OPh) (3c) in
41% were achieved.
Hydrolysis of Rh(ttp)CH2OPh in Alkaline Media. Rh(ttp)-
CH2OPh (3a; 0.88 mg, 0.001 mmol), KOH (0.56 mg, 0.01 mmol),
H2O (18 μL, 1 mmol), and benzene-d6 (0.5 mL) were added in a
Teflon screw-capped NMR tube. The mixture was degassed for three
freeze−pump−thaw cycles and then sealed in the NMR tube under
vacuum. It was heated at 200 °C in the dark for 82 h. It was monitored
1H NMR spectra were recorded on a Bruker AV400 instrument at
400 MHz. Chemical shifts were referenced with the residual solvent
protons in CDCl3 (δ 7.26 ppm) and C6D6 (δ 7.15 ppm). 13C NMR
spectra were recorded on a Bruker AV400 (100 MHz) or a Bruker
AV700 (176 MHz) spectrometer with reference to CDCl3 (δ 77.1 ppm)
as an internal standard. 19F NMR spectra were recorded on a Bruker
AV400 instrument at 376 MHz with reference to fluorobenzene
(δ −113.15 ppm) as an internal standard. Chemical shifts (δ) are
reported as parts per million (ppm) in δ scale downfield from TMS.
Coupling constants (J) are reported in Hertz (Hz). High-resolution
mass spectrometry (HRMS) was performed on a Bruker SolariX 9.4 T
FTICR MS instrument in electrospray ionization (ESI) mode using
MeOH/CH2Cl2 (1/1) as the solvent or on Bruker Autoflex speed
MALDI-TOF instrument using a trans-2-[3-(4-tert-butylphenyl)-2-
methyl-2-propenylidene]malononitrile (DCTB) matrix and CH2Cl2 as
the solvent.
1
with H NMR spectroscopy, and the NMR yields were measured.
Rh(ttp)CH2OPh was recovered in 90% yield without any organic
product formed.
Hydrolysis of Rh(ttp)CHPh(OPh) in Alkaline Media. Rh(ttp)-
CHPh(OPh) (3c; 0.95 mg, 0.001 mmol), KOH (0.56 mg,
0.01 mmol), H2O (18 μL, 1 mmol), and benzene-d6 (0.5 mL) were
added in a Teflon screw-capped NMR tube. The mixture was degassed
for three freeze−pump−thaw cycles and then sealed in the NMR tube
under vacuum. It was heated at 200 °C in the dark for 18 h. It was
1
monitored with H NMR spectroscopy, and the NMR yields were
measured. PhOBn (2b) was formed in 50% yield.
Single crystals were grown using a vapor diffusion method. The
compound was dissolved in a solvent in a small open vial. The vial was
then placed into a larger vial containing a precipitant solvent, and the
outer vial was then sealed.
Reaction of Ir(ttp)(CO)Cl and Anisole with KOH (20 Equiv) at
200 °C. Ir(ttp)(CO)Cl (1b; 9.7 mg, 0.010 mmol), KOH (11.9 mg,
0.21 mmol), and anisole (2a; 1.0 mL) were added in a Teflon screw-
capped tube. The mixture was degassed for three freeze−pump−thaw
cycles, refilled with N2, and heated to 200 °C for 1 h until reaction
completion. Excess anisole was removed by vacuum distillation. The
residue was purified by pipet column chromatography on silica
gel with CH2Cl2/hexane (1:1) to give Ir(ttp)Me18a (3e; 7.3 mg,
0.0083 mmol) in 83% yield. Ir(ttp)Me (3e): Rf: 0.70 (hexane/CH2Cl2:
Reaction of Rh(ttp)Cl and Anisole with K2CO3. Rh(ttp)Cl
(1a; 11.3 mg, 0.014 mmol), K2CO3 (18.8 mg, 0.14 mmol) and anisole
(2a; 1.0 mL) were added in a Teflon screw-capped tube. The mixture
was degassed for three freeze−pump−thaw cycles, refilled with N2,
and heated at 150 °C for 1 h until reaction completion. Excess anisole
was removed by vacuum distillation. The residue was purified by pipet
column chromatography on silica gel with CH2Cl2/hexane (1:7) to
give the first fraction as Rh(ttp)CH2OPh (3a; 9.2 mg, 0.0105 mmol)
in 72% yield. Rf: 0.65 (hexane/CH2Cl2: 1/1). 1H NMR (CDCl3,
1
1/1). H NMR (CDCl3, 400 MHz) δ −6.28 (s, 3 H, CH3), 2.68
(s, 12 H), 7.50−7.53 (m, 8 H), 7.98−8.03 (m, 8 H), 8.51 (s, 8 H).
Reaction of Ir(ttp)(CO)Cl and Anisole with KOH (20 Equiv) at
120 °C. Ir(ttp)(CO)Cl (1b; 10.6 mg, 0.011 mmol), KOH (11.8 mg,
0.21 mmol), and anisole (2a; 1.0 mL) were added in a Teflon screw-
capped tube. The mixture was degassed for three freeze−pump−thaw
cycles, refilled with N2, and heated to 120 °C for 4 h to give Ir(ttp)Me
(3e; 5.3 mg, 0.006 mmol) in 55% yield.
2
400 MHz) δ −1.74 (d, 2 H, JRh−H = 3.4 Hz, CH2), 2.70 (s, 12 H),
3.65−3.70 (m, 2 H), 6.37−6.45 (m, 3 H), 7.51−7.56 (m, 8 H), 7.98−
8.03 (m, 8 H), 8.69 (s, 8 H). 13C NMR (CDCl3, 100 MHz) δ 21.8,
51.9 (1JRh−C = 29.5 Hz), 112.2, 120.0, 122.6, 127.6, 127.7, 127.9, 131.7,
134.3, 134.4, 137.4, 139.6, 143.5, 154.0. HRMS (m/z) ( MALDI-MS):
[M]+ calcd for C55H43N4RhO 878.2486; found 878.2450.
Reaction of Ir(ttp)(CO)Cl and Anisole with KOH (20 Equiv) at
150 °C. Ir(ttp)(CO)Cl (1b; 9.8 mg, 0.010 mmol), KOH (11.9 mg,
0.21 mmol), and anisole (2a; 1.0 mL) were added in a Teflon screw-
capped tube. The mixture was degassed for three freeze−pump−thaw
cycles, refilled with N2, and heated to 150 °C for 2 h to give Ir(ttp)Me
(3e; 7.6 mg, 0.087 mmol) in 87% yield.
Reaction of Ir(ttp)(CO)Cl and Anisole with KOH (20 Equiv) at
180 °C. Ir(ttp)(CO)Cl (1b; 10.3 mg, 0.011 mmol), KOH (12.3 mg,
0.22 mmol), and anisole (2a; 1.0 mL) were added in a Teflon screw-
capped tube. The mixture was degassed for three freeze−pump−thaw
cycles, refilled with N2, and heated to 180 °C for 1 h to give Ir(ttp)Me
(3e; 8.5 mg, 0.0097 mmol) in 88% yield.
Reaction of Ir(ttp)(CO)Cl and Anisole without KOH at 150 °C.
Ir(ttp)(CO)Cl (1b; 9.6 mg, 0.010 mmol) and anisole (2a; 1.0 mL)
were added in a Teflon screw-capped tube. The mixture was degassed
for three freeze−pump−thaw cycles, refilled with N2, and heated to
150 °C for 14 h with Ir(ttp)(CO)Cl recovered quantitatively.
Reaction of Ir(ttp)(CO)Cl and Anisole with K2CO3 (20 Equiv)
at 150 °C. Ir(ttp)(CO)Cl (1b; 9.1 mg, 0.010 mmol), K2CO3 (28.5 mg,
Reaction of Rh(ttp)Cl and Anisole with KOH. Rh(ttp)Cl (1a;
9.5 mg, 0.012 mmol), KOH (6.3 mg, 0.011 mmol), and anisole (2a;
1.0 mL) were added in a Teflon screw-capped tube. The mixture was
degassed for three freeze−pump−thaw cycles, refilled with N2, and
heated to 150 °C for 1 h until reaction completion. The two products
were purified by column chromatography on silica gel eluting with
CH2Cl2/hexane (1:1). Rh(ttp)Me (3b)23a in 46%, and Rh(ttp)-
CH2OPh (3a) in 24% were achieved.
Independent Synthesis of Rh(ttp)CHPh(OPh). Rh(ttp)Cl (1a;
9.7 mg, 0.012 mmol), K2CO3 (16.2 mg, 0.12 mmol) and PhOBn (2b;
19.2 mg, 0.11 mmol) were added in benzene (1.0 mL). The mixture
was degassed for three freeze−pump−thaw cycles, refilled with
N2, and heated to 150 °C for 1 h until reaction completion. Benzene
solvent was removed by vacuum distillation. The red residue was
purified by column chromatography on silica gel eluting with CH2Cl2/
hexane (1:8) to give red solid product Rh(ttp)CHPh(OPh) (3c;
5.2 mg, 0.0054 mmol) in 45% yield. Rf: 0.77 (hexane/CH2Cl2: 1/1).
F
DOI: 10.1021/acs.organomet.7b00386
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
0.20 mmol), and anisole (2a; 1.0 mL) were added in a Teflon screw-
capped tube. The mixture was degassed for three freeze−pump−thaw
cycles, refilled with N2, and heated to 150 °C for 10 h to give complex
products. Ir(ttp)Me (3e) was estimated to be in 6% yield.
Reaction of Ir(ttp)(CO)Cl and Anisole with KOH (5 Equiv) at
150 °C. Ir(ttp)(CO)Cl (1b; 10.7 mg, 0.011 mmol), KOH (3.2 mg,
0.057 mmol), and anisole (2a; 1.0 mL) were added in a Teflon screw-
capped tube. The mixture was degassed for three freeze−pump−thaw
cycles, refilled with N2, and heated to 150 °C for 2 h to give Ir(ttp)Me
(3e; 7.2 mg, 0.0082 mmol) in 71% yield.
Reaction of Ir(ttp)(CO)Cl and Anisole with KOH (10 Equiv) at
150 °C. Ir(ttp)(CO)Cl (1b; 11.9 mg, 0.013 mmol), KOH (6.6 mg,
0.12 mmol), and anisole (2a; 1.0 mL) were added in a Teflon screw-
capped tube. The mixture was degassed for three freeze−pump−thaw
cycles, refilled with N2, and heated to 150 °C for 2 h to give Ir(ttp)Me
(3e; 9.3 mg, 0.011 mmol) in 82% yield.
Reaction of Ir(ttp)(CO)Cl and Anisole with KOH (30 Equiv) at
150 °C. Ir(ttp)(CO)Cl (1b; 9.2 mg, 0.010 mmol), KOH (18 mg,
0.32 mmol), and anisole (2a; 1.0 mL) were added in a Teflon screw-
capped tube. The mixture was degassed for three freeze−pump−thaw
cycles, refilled with N2, and heated to 150 °C for 2 h to give Ir(ttp)Me
(3e; 7.1 mg, 0.0081 mmol) in 81% yield.
Reaction of Ir(ttp)(CO)Cl and Ethoxybenzene with KOH (10
Equiv) at 150 °C. Ir(ttp)(CO)Cl (1b; 11.7 mg, 0.013 mmol), KOH
(7.7 mg, 0.14 mmol), and ethoxybenzene (2c; 1.0 mL) were added in
a Teflon screw-capped tube. The mixture was degassed for three
freeze−pump−thaw cycles, refilled with N2, and heated to 150 °C for
2 h to give Ir(ttp)Et35 (3f; 9.8 mg, 0.011 mmol) in 87% yield.
Reaction of Ir(ttp)(CO)Cl and Propoxybenzene with KOH (10
Equiv) at 150 °C. Ir(ttp)(CO)Cl (1b; 10.6 mg, 0.011 mmol), KOH
(6.7 mg, 0.12 mmol), and propoxybenzene (2d; 1.0 mL) were added
in a Teflon screw-capped tube. The mixture was degassed for three
freeze−pump−thaw cycles, refilled with N2, and heated to 150 °C for
2 h to give Ir(ttp)nPr35 (3g; 8.8 mg, 0.0097 mmol) in 85% yield.
Reaction of Ir(ttp)(CO)Cl and Benzyl Phenyl Ether with KOH
(10 Equiv) at 150 °C. Ir(ttp)(CO)Cl (1b; 9.3 mg, 0.010 mmol),
KOH (6.2 mg, 0.11 mmol), PhOBn (2b; 18.8 mg, 0.10 mmol), and
benzene (1.0 mL) were added in a Teflon screw-capped tube. The
mixture was degassed for three freeze−pump−thaw cycles, purged
with N2, and heated to 150 °C for 2 h until reaction completion.
Benzene solvent was removed with vacuum distillation. Diphenyl-
methane (10 μL) was added as the internal standard. The NMR yield
of Ir(ttp)Bn (3h)30 was determined to be 82% by comparing the
benzylic protons with the methylene protons of diphenylmethane.
Ir(ttp)Bn (3h): Rf: 0.6 (hexane/CH2Cl2: 1/1). 1H NMR (CDCl3,
400 MHz) δ −3.99 (s, 2 H, CH2), 2.68 (s, 12 H), 3.16 (d, 2 H, 3JH−H
= 7.7 Hz), 5.90 (t, 2 H, 3JH−H = 7.5 Hz), 5.47 (t, 1 H, 3JH−H = 7.3 Hz),
7.50−7.54 (m, 8 H), 7.95−8.02 (m, 8 H), 8.46 (s, 8 H).
7.29 mmol) were added in a Teflon screw-capped tube. The mixture
was degassed for three freeze−pump−thaw cycles, refilled with N2,
and heated to 150 °C for 4 h until reaction completion. Excess allyl
phenyl ether was removed with vacuum distillation. The residue was
purified by pipet column chromatography on silica gel with CH2Cl2/
hexane (1:7) to give Ir(ttp)nPr (3g; 4.0 mg, 0.0044 mmol) in 35%
yield as the first fraction and CH2Cl2/hexane (1:5) as eluent to give
Ir(ttp)CH2CH2CH2OPh (3i; 2.7 mg, 0.0027 mmol) in 20% yield.
Independent Synthesis of Ir(ttp)Bn(p-OMe). Ir(ttp)(CO)Cl
(1b; 10.1 mg, 0.011 mmol), KOH (6.0 mg, 0.11 mmol), 4-meth-
oxybenzyl phenyl ether (2f; 23.4 mg, 0.11 mmol), and methanol
(1.0 mL) were degassed for three freeze−pump−thaw cycles in a
Teflon screw-capped tube. The reaction was heated in 150 °C under
N2 in the dark for 0.5 h until reaction completion. Methanol solvent
was removed with vacuum distillation. The residue was further washed
with methanol to give Ir(ttp)Bn(p-OMe) (3j; 6.8 mg, 0.007 mmol) as
1
red purple solid in 63% yield. Rf: 0.63 (hexane:CH2Cl2 = 1/1). H
NMR (CDCl3, 400 MHz) δ −4.06 (s, 2 H, CH2), 2.67 (s, 12 H), 3.12
(d, 2 H, 3JH−H = 8.6 Hz), 3.44 (s, 3 H), 5.45 (d, 2 H, 3JH−H = 8.5 Hz),
7.53 (d, 8 H, 3JH−H = 7.5 Hz), 7.86−8.12 (m, 8 H), 8.45 (s, 8 H). 13
C
NMR (CDCl3, 100 MHz) δ −13.5, 21.8, 55.1, 112.0, 124.3, 125.2,
127.7, 127.8, 131.5, 133.9, 134.0, 137.4, 139.1, 143.5, 155.4. HRMS
(m/z) (ESI-MS): [M]+ calcd for (C56H45IrN4O) 982.3217; found
982.3222.
Reaction of Ir(ttp)(CO)Cl and PhOBn(p-OMe). Ir(ttp)(CO)Cl
(1b; 9.2 mg, 0.010 mmol), KOH (6.0 mg, 0.11 mmol), 4-meth-
oxybenzyl phenyl ether (2f; 18.8 mg, 0.095 mmol), and benzene
(1.0 mL) were added in a Teflon screw-capped tube. The mixture was
degassed for three freeze−pump−thaw cycles, refilled with N2, and
heated to 150 °C for 2 h until reaction completion. Benzene solvent
was removed with vacuum distillation. The NMR yield of Ir(ttp)Bn
(p-OMe) (3j) was determined to be 71% using 10 μL of dipheny-
lmethane as the internal standard.
Reaction between Ir(ttp)(CO)Cl and PhOBn(p-Cl). Ir(ttp)(CO)
Cl (1b; 9.9 mg, 0.010 mmol), KOH (6.0 mg, 0.11 mmol), 4-chlo-
robenzyl phenyl ether (2g; 23.1 mg, 0.106 mmol), and benzene
(1.0 mL) were added in a Teflon screw-capped tube. The mixture was
degassed for three freeze−pump−thaw cycles, refilled with N2, and
heated to 150 °C for 2 h until reaction completion. Benzene solvent
was removed with vacuum distillation. The NMR yield of Ir(ttp)Bn(p-
Cl)(3k)28 was determined to be 66% using 10 μL of diphenylmethane
as the internal standard.
Independent Synthesis of Ir(ttp)Bn(p-CF3). Ir(ttp)(CO)Cl (1b;
9.6 mg, 0.010 mmol), KOH (6.0 mg, 0.11 mmol), 4-(trifluoromethyl)-
benzyl phenyl ether (2h; 25.7 mg, 0.010 mmol), and methanol
(1.0 mL) were added in a Teflon screw-capped tube. The mixture was
degassed for three freeze−pump−thaw cycles, refilled with N2, and
heated to 150 °C for 0.5 h until reaction completion. Methanol solvent
was removed with vacuum distillation. The residue was further washed
with methanol to give Ir(ttp)Bn(p-CF3) (3l; 8.8 mg, 0.008 mmol) as
Independent Synthesis of Ir(ttp)CH2CH2CH2OPh. Ir(ttp)(CO)
Cl (1b; 23.7 mg, 0.026 mmol), KOH (14.4 mg, 0.26 mmol), allyl
phenyl ether (2e; 35 μL, 0.25 mmol), and benzene (1.0 mL) were
added in a Teflon screw-capped tube. The mixture was degassed for
three freeze−pump−thaw cycles, refilled with N2, and heated to
150 °C for 2 h until reaction completion. Benzene and excess allyl
phenyl ether were removed with vacuum distillation. The residue was
purified by pipet column chromatography on silica gel with CH2Cl2/
hexane (1:5) to give Ir(ttp)CH2CH2CH2OPh (3i; 16.4 mg,
1
purple solid in 85% yield. Rf: 0.69 (hexane:CH2Cl2 = 1/1). H NMR
(CDCl3, 400 MHz) δ −3.97 (s, 2 H, CH2), 2.71 (s, 12 H), 3.13 (d, 2
H, 3JH−H = 7.9 Hz), 6.11 (d, 2 H, 3JH−H = 7.9 Hz), 7.54 (d, 8 H, 3JH−H
3
3
= 7.8 Hz), 7.88 (d, 4 H, JH−H = 6.9 Hz), 8.01 (d, 4 H, JH−H
=
6.6 Hz), 8.44 (s, 8 H).19F NMR (CDCl3, 376 MHz) δ −62.6. 13C
NMR (CDCl3, 100 MHz) δ −16.2, 21.6, 123.0, 123.9, 124.0, 124.8
(q, 1JC−F = 269.0 Hz), 127.6, 137.3, 138.7, 143.1, 146.5. HRMS (m/z)
(MALDI-MS): [M]+ calcd for (C56H42IrF3N4) 1020.2989; found
1020.2985.
1
0.0165 mmol) in 64% yield. Rf: 0.64 (hexane:CH2Cl2 = 1/1). H NMR
3
(CDCl3, 400 MHz) δ −5.44 (t, 2 H, JH−H = 8 Hz, CH2CH2CH2OPh),
−3.75- −4.06 (m, 2 H, CH2CH2CH2OPh), 1.0 (t, 2 H, 3JH−H = 6.8 Hz,
CH2CH2CH2OPh), 2.69 (s, 12 H), 5.80 (d, 2 H, 3JH−H = 8.0 Hz), 6.63
(t, 1 H, 3JH−H = 7.3 Hz), 6.87 (t, 2 H, 3JH−H = 7.9 Hz), 7.52 (m, 8 H),
Reaction between Ir(ttp)(CO)Cl and PhOBn(p-CF3). Ir(ttp)-
(CO)Cl (1b; 10.7 mg, 0.011 mmol), KOH (6.0 mg, 0.11 mmol),
4-(trifluoromethyl)benzyl phenyl ether (2h; 26.6 mg, 0.105 mmol),
and benzene (1.0 mL) were degassed for three freeze−pump−thaw
cycles in a Teflon screw-capped tube. The reaction was heated in
150 °C under N2 in the dark for 2 h until reaction completion.
Benzene solvent was removed with vacuum distillation. The NMR
yield of Ir(ttp)Bn(p-CF3) (3l) was determined to be 68% using 10 μL
of diphenylmethane as the internal standard.
7.93 (d, 4 H, 3JH−H = 7.6 Hz), 8.02−8.03 (m, 4 H), 8.51 (s, 8 H). 13
C
NMR (CDCl3, 100 MHz): δ -20.3, 21.8, 25.8, 63.2, 114.3, 120.1,
124.4, 127.8, 129.1, 131.6, 133.7, 134.2, 137.4, 138.9, 143.6, 158.0.
HRMS (m/z) (MALDI-MS): [M]+ calcd for (C57H47IrN4O)
996.3378; found 996.3362.
Reaction of Ir(ttp)(CO)Cl and Allyl Phenyl Ether with KOH
(10 Equiv) at 150 °C. Ir(ttp)(CO)Cl (1b; 10.6 mg, 0.011 mmol),
KOH (6.4 mg, 0.11 mmol), and allyl phenyl ether (2e; 1.0 mL,
Reaction of Ir(ttp)H with Anisole in Solvent-Free Conditions.
Ir(ttp)H (1c; 10.3 mg, 0.012 mmol) and anisole (2a; 1.0 mL) were
G
DOI: 10.1021/acs.organomet.7b00386
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degassed for three freeze−pump−thaw cycles in a Teflon screw-capped
tube, refilled with N2, and heated to 150 °C for 2 h until reaction
cycles in a Teflon screw-capped tube. The reaction was heated in
150 °C under N2 in the dark for 17 h. Ir(ttp)nPr (3g) was formed in
5% yield with 90% of Ir(ttp)Me (3e) recovered.
1
completion. Excess anisole was removed with vacuum. The H NMR
Reaction of Ir(ttp)Cl(CO) with Ethoxybenzene and Propox-
ybenzene. Ir(ttp)(CO)Cl (1b; 10.9 mg, 0.012 mmol), KOH
(11.6 mg, 0.21 mmol), ethoxybenzene (2c; 0.506 mL, 4.0 mmol),
and propoxybenzene (2d; 0.586 mL, 4.0 mmol) were degassed for
three freeze−pump−thaw cycles in a Teflon screw-capped tube. The
reaction was heated in 150 °C under N2 in the dark for 2 h until
reaction completion to give Ir(ttp)Et (3f; 2.7 mg) in 25% yield and
Ir(ttp)nPr (3g; 5.0 mg) in 46% yield. The two products were purified
by pipet column chromatography on silica gel eluting with CH2Cl2/
spectrum was recorded for the residue. Ir(ttp)Me (3e) and
Ir(ttp)C6H4(p-OMe) (3m)29a were formed in trace amounts.
Independent Synthesis of Ir(ttp)CHPh(OPh). Ir(ttp)(CO)Cl
(1b; 10.6 mg, 0.011 mmol), K2CO3 (14.8 mg, 0.11 mmol), PhOBn
(2b; 10.8 mg, 0.058 mmol), and benzene (1.0 mL) were added in a
Teflon screw-capped tube. The mixture was degassed for three freeze−
pump−thaw cycles, refilled with N2, and heated to 200 °C for 15 h.
Benzene solvent was removed with vacuum distillation. The residue
was purified by a precoated silica gel TLC plate with CH2Cl2/hexane
(1:1) to give Ir(ttp)CHPh(OPh) (3n; 5.4 mg, 0.005 mmol) in 45%
yield. Rf: 0.58 (hexane:CH2Cl2 = 1/1). 1H NMR (CDCl3,
400 MHz) δ −0.82 (s, 1 H, CH), 2.70 (s, 12 H), 3.31 (brs, 2 H),
4.37 (d, 2 H, 3JH−H = 8.0 Hz), 6.07 (t, 2 H, 3JH−H = 7.5 Hz), 6.32 (t, 1
1
hexane (1:1). The yield of each product was determined by an H
NMR spectrum from the integration of ethyl protons of the iridium−
ethyl group of Ir(ttp)Et and the propyl protons of the iridium−propyl
group of Ir(ttp)nPr.
3
Reaction of Ir(ttp)Cl(CO) with Anisole and Ethoxybenzene.
Ir(ttp)(CO)Cl (1b; 10.5 mg, 0.011 mmol), KOH (12.6 mg,
0.22 mmol), ethoxybenzene (2c; 0.506 mL, 4.0 mmol), and anisole
(2a; 0.435 mL, 4.0 mmol) were degassed for three freeze−pump−
thaw cycles in a Teflon screw-capped tube. The reaction was heated in
150 °C under N2 in the dark for 2 h until reaction completion to give
Ir(ttp)Et (3f; 4.5 mg) in 40% yield and Ir(ttp)Me (3e; 2.6 mg) in 23%
yield. The two products were purified by pipet column chromatog-
raphy on silica gel eluting with CH2Cl2/hexane (1:1). The yield of
each product was determined by an 1H NMR spectrum from the
integration of ethyl protons of the iridium−ethyl group of Ir(ttp)Et
and the methyl protons of the iridium−methyl group of Ir(ttp)Me.
Reaction of Ir(ttp)Cl(CO) with Anisole and Propoxybenzene.
Ir(ttp)(CO)Cl (1b; 9.3 mg, 0.010 mmol), KOH (11.3 mg, 0.20 mmol),
propoxybenzene (2d; 0.586 mL, 4.0 mmol), and anisole (2a;
0.435 mL, 4.0 mmol) were degassed for three freeze−pump−thaw
cycles in a Teflon screw-capped tube. The reaction was heated in
150 °C under N2 in the dark for 2 h to give Ir(ttp)nPr (3g; 5.5 mg) in
61% yield and Ir(ttp)Me (3e; 2.0 mg) in 23% yield. The two products
were purified by pipet column chromatography on silica gel eluting
with CH2Cl2/hexane (1:1). The yield of each product was determined
by an 1H NMR spectrum from the integration of propyl protons of the
iridium−propyl group of Ir(ttp)nPr and the methyl protons of the
iridium−methyl group of Ir(ttp)Me.
H, JH−H = 7.2 Hz), 6.41−6.50 (m, 3 H), 7.51−7.56 (m, 8 H), 7.93
(d, 4 H, 3JH−H = 7.5 Hz), 7.99 (d, 4 H, 3JH−H = 7.6 Hz), 8.46 (s, 8 H).
13C NMR (CDCl3, 100 MHz): δ 21.6, 33.6, 113.2, 119.1, 124.0, 124.1,
125.9, 127.5, 127.8, 131.2, 133.8, 133.9, 137.1, 139.0, 140.2,
143.2, 154.0. HRMS (m/z) (ESI-MS): [M + Na]+ calcd for
(C61H47IrN4ONa) 1067.3285; found 1067.3276.
Reaction of Ir(ttp)H with PhOBn in Benzene. Ir(ttp)H (1c;
8.4 mg, 0.010 mmol), PhOBn (2b; 18 mg, 0.10 mmol), and benzene
(1.0 mL) were added in a Teflon screw-capped tube. The mixture was
degassed for three freeze−pump−thaw cycles, refilled with N2, and
heated to 150 °C in the dark for 0.5 h until reaction completion.
Benzene solvent was removed with vacuum distillation. Diphenyl-
methane (10 μL) was added as the internal standard, and the NMR
yield of Ir(ttp)CHPh(OPh) (3n) was calculated to be 60%.
Reaction of Ir2(ttp)2 with Anisole in Solvent-Free Conditions.
Ir(ttp)H (1c; 3.0 mg, 0.003 mmol) and 2,2,6,6- tetramethylpiper-
idinooxy (TEMPO) (0.8 mg, 0.005 mmol) were added into a Teflon
screw-capped tube under N2. Degassed benzene (1.0 mL) was added
into the tube with an airtight syringe, and the reaction mixture
changed to deep brown instantaneously. Benzene solvent was removed
with vacuum distillation, and the residue was further dried under
vacuum for 24 h to remove the solvent, unreacted TEMPO, and
TEMPOH coproduct. Degassed anisole (2a, 1.0 mL) was then added
into the tube under N2, and the mixture was heated to 150 °C in the
dark for 2 h until reaction completion. Excess anisole was removed
with vacuum. Ir(ttp)Me (3e) was formed in trace amounts.
Reaction of Ir(ttp)(CO)Cl and BnOPh(p-OMe) at 150 °C.
Ir(ttp)(CO)Cl (1b; 10.5 mg, 0.011 mmol), KOH (6.0 mg, 0.11 mmol),
4-(benzyloxy)anisole (2i; 23.3 mg, 0.11 mmol), and benzene (1.0 mL)
were added in a Teflon screw-capped tube. The mixture was degassed
for three freeze−pump−thaw cycles, refilled with N2, and heated to
150 °C for 3 h until reaction completion. Benzene solvent was
removed with vacuum distillation. The NMR yield of Ir(ttp)Bn (3h)
was determined to be 71% using diphenylmethane as the internal
standard.
Reaction of Ir2(ttp)2 with PhOBn in Benzene. Ir2(ttp)2 (1d;
8.1 mg, 0.009 mmol), PhOBn (2b; 17.3 mg, 0.09 mmol), and degassed
benzene (1.0 mL) were added into the tube under N2. The reaction
mixture was heated to 150 °C for 2 h until reaction completion.
Benzene solvent was removed with vacuum distillation. Diphenyl-
methane (10 μL) was added as the internal standard, and the NMR
yield of Ir(ttp)CHPh(OPh) (3n) was calculated to be 40%.
Reaction of Ir(ttp)(CO)Cl and BnOPh(p-CN) at 150 °C.
Ir(ttp)(CO)Cl (1b; 9.2 mg, 0.010 mmol), KOH (6.0 mg, 0.11 mmol),
4-(benzyloxy)benzonitrile (2j; 20.5 mg, 0.10 mmol), and benzene
(1.0 mL) were added in a Teflon screw-capped tube. The mixture was
degassed for three freeze−pump−thaw cycles, refilled with N2, and
heated to 150 °C for 0.5 h until reaction completion. Benzene solvent
was removed with vacuum distillation. The NMR yield of Ir(ttp)Bn
(3h) was determined to be 81% using diphenylmethane as the internal
standard.
Reaction of Ir(ttp)H with Anisole and KOH in Solvent-Free
Conditions. Ir(ttp)H (1c; 8.8 mg, 0.010 mmol), KOH (6.0 mg,
0.010 mmol), and anisole (2a; 1.0 mL) were added into a Teflon
screw-capped tube, and the reaction mixture was degassed for three
freeze−pump−thaw cycles, refilled with N2, and heated to 150 °C in
the dark for 2 h until reaction completion. Excess anisole was removed
with vacuum. The residue was recrystallized from MeOH/DCM and
washed with MeOH three times. Ir(ttp)Me (3e) was achieved in
54% yield.
Reaction of Ir(ttp)H with PhOBn and KOH in Benzene. Ir(ttp)
H (1c; 9.5 mg, 0.011 mmol), KOH (6.0 mg, 0.010 mmol), PhOBn
(2b; 20.3 mg, 0.11 mmol), and benzene (1.0 mL) were added into a
Teflon screw-capped tube, and the reaction mixture was degassed for
three freeze−pump−thaw cycles, refilled with N2, and heated to 150 °C
in the dark for 2 h until reaction completion. Benzene solvent was
removed with vacuum distillation. Diphenylmethane (10 μL) was added
as the internal standard, and the NMR yield of Ir(ttp)CHPh(OPh) (3n)
was calculated to be 11% with Ir(ttp)Bn (3h) in 22% yield.
ASSOCIATED CONTENT
■
S
* Supporting Information
The Supporting Information is available free of charge on the ACS
Publications website at DOI: 10.1021/acs.organomet.7b00386.
1
Competition reactions; H and 13C NMR spectra; tables
and figures outlining X-ray crystallographic data for
Rh(ttp)CH2OPh (3a), Rh(ttp)CHPh(OPh) (3c), and
Ir(ttp)Et (3f); HRMS spectra for Rh(ttp)CH2OPh (3a),
Rh(ttp)CHPh(OPh) (3c), Ir(ttp)CH2CH2CH2OPh
Reaction of Ir(ttp)Me with Propoxybenzene. Ir(ttp)Me (3e;
10.6 mg, 0.012 mmol), KOH (7.4 mg, 0.13 mmol), and propoxy-
benzene (2d; 1.0 mL) were degassed for three freeze−pump−thaw
H
DOI: 10.1021/acs.organomet.7b00386
Organometallics XXXX, XXX, XXX−XXX

Organometallics
(3i), Ir(ttp)Bn(p-OMe) (3j), Ir(ttp)Bn(p-CF3) (3l), and
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Ir(ttp)CHPh(OPh) (3n) (PDF)
Accession Codes
CCDC 1552670−1552672 contain the supplementary crystal-
lographic data for this paper. These data can be obtained free of
charge via www.ccdc.cam.ac.uk/data_request/cif, or by email-
ing data_request@ccdc.cam.ac.uk, or by contacting The
Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
AUTHOR INFORMATION
Corresponding Author
*E-mail: ksc@cuhk.edu.hk
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ORCID
Kin Shing Chan: 0000-0002-1112-6819
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
We thank Research Grants Council (GRF No. 14300115) of
Hong Kong SAR for financial support.
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DOI: 10.1021/acs.organomet.7b00386
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