Base-Promoted C-O Bond Cleavage of Primary Alcohols by Iridium(III) Porphyrin Chloride

Article abstract of DOI:10.1021/acs.organomet.0c00100

Various Ir(por)-benzyls and Ir(por)-alkyls (por = porphyrinato dianion ligand) were successfully synthesized with benzyl and 1° alkyl alcohols by C-O bond cleavage with Ir(ttp)(CO)Cl (ttp = 5,10,15,20-tetraphenylporphyrinato dianion) in alkaline media. The alkylation products were afforded in up to 92% yields. Mechanistic investigations suggest that both the Ir(ttp)- anion and Ir(ttp)H are key intermediates via a hydrogen-borrowing pathway.

Full text of DOI:10.1021/acs.organomet.0c00100

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Base-Promoted C−O Bond Cleavage of Primary Alcohols by
Iridium(III) Porphyrin Chloride
Yongjun Bian, Xingyu Qu, and Kin Shing Chan*
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ABSTRACT: Various Ir(por)-benzyls and Ir(por)-alkyls (por = porphyrinato
dianion ligand) were successfully synthesized with benzyl and 1° alkyl alcohols by
C−O bond cleavage with Ir(ttp)(CO)Cl (ttp = 5,10,15,20-tetraphenylporphyrinato
dianion) in alkaline media. The alkylation products were afforded in up to 92%
yields. Mechanistic investigations suggest that both the Ir(ttp)− anion and Ir(ttp)H are key intermediates via a hydrogen-borrowing
pathway.
OH).7 Therefore, both acid-catalyzed nucleophilic substitu-
INTRODUCTION
Iridium porphyrin alkyls, Ir(por)R (por = porphyrinato
■
tions and conversion of the hydroxyl group into better leaving
groups followed by substitution are popular strategies.8 We
dianion ligand), as intriguing organometallic complexes have
previously have reported the direct cleavage of the C−OH
been widely utilized in many fields, including molecular
recognition, anticancer drugs, sensors, catalysis, etc.1 Serving as
bond in methanol by Ir(ttp)(CO)Cl to give Ir(ttp)Me under
solvent-free and basic conditions, in which Ir(ttp)H was
catalysts, they can activate various chemical bonds. For
proposed as the active species to cleave the C−O bond likely
example, they can effectively catalyze the N−H, C−H, and
via σ-bond metathesis to give Ir(ttp)Me.9 In this work, we have
Si−H bond insertion with ethyl diazoacetate in high yields.1d,e
successfully expanded the scope of the alcohols to benzyl
Ir(por)R are also effective and robust catalysts for the
cyclopropanation of olefin with diazo compounds.1f More
alcohols and other aliphatic alcohols with β hydrogens.
Ir(ttp)(CO)Cl can efficiently cleave the benzylic C−OH
interestingly, iridium porphyrin alkyls can catalyze the
bond in toluene solvent or aliphatic C−OH bond in
hydrogenolysis of the carbon−carbon σ bond of [2.2]-
benzonitrile solvent to give Ir(ttp)Bn or Ir(ttp)-alkyls,
paracyclophane with H2O as the hydrogen source under
respectively.
neutral conditions. Mechanistic investigations reveal that the
active catalyst is the iridium porphyrin hydride.2 Hence,
RESULTS AND DISCUSSION
developing efficient strategies to access various iridium
porphyrin alkyls remain an attractive research field.
■
Reaction Discovery. Previously, we reported that Rh-
The synthesis of iridium porphyrin alkyls was first reported
by Ogoshi in 1978 involving the transmetalation between
Ir(oep)(CO)Cl (oep = 2,3,7,8,12,13,17,18-octaethylporphyr-
inato dianion) and MeLi or nucleophilic substitution between
Ir(oep)− and MeI to generate Ir(oep)Me (Scheme 1a).3 The
oxidative addition of alkyl C−H bonds by [Ir(por)]2
represents another important method to form iridium
porphyrin alkyls, which was discovered by Wayland in 1986
(Scheme 1b).4 In 2008, our group developed the base-
promoted benzylic C−H bond activation of various PhCH3
species by Ir(ttp)(CO)Cl (ttp = 5,10,15,20-tetraphenylpor-
phyrinato dianion) providing different Ir(ttp)Bn species
(Scheme 1c).5 Recently, we have expanded the scope of
alkylating substrates to alkyl halides, including 1°, 2°, and 3°
alkyls, for the preparation of Ir(ttp)-alkyls from Ir(ttp)(CO)Cl
in good yields under user-friendly aerobic conditions (Scheme
1c).6
(ttp)Cl could cleave the C−OH bond of benzyl alcohols and
aliphatic alcohols in benzonitrile solvent under basic
conditions at 120 °C to form Rh(ttp)Bn and Rh(ttp)-alkyls,
respectively.10 Considering the analogous reactivity of Ir(por)
complexes to Rh(por) complexes in bond activation, we
anticipated that the C−O bonds of various alcohols could be
cleaved with Ir(ttp)(CO)Cl (1a) under the above conditions.
When we examined the reaction between Ir(ttp)(CO)Cl
(1a) and benzyl alcohol (2a) with K2CO3 as a base in
benzonitrile solvent at 120 °C under an N2 atmosphere, to our
delight, the C−O cleavage product, Ir(ttp)Bn (3a), was
isolated in 29% yield (eq 1). Then, we further pursued
optimizing the reaction conditions.
Received: February 11, 2020
Generally, under neutral or basic conditions alkyl alcohols
are not good alkylating agents due to the poor leaving ability of
hydroxide and the strong carbon−OH bond strengths (such as
92.0 kcal/mol in Me−OH and 79.9 kcal/mol in PhCH2−
https://dx.doi.org/10.1021/acs.organomet.0c00100
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temperature. Subsequently, various solvents were further
examined to optimize the reaction conditions. When the
reaction proceeded under solvent-free conditions, the product
Ir(ttp)Bn (3a) was afforded in 50% yield after 48 h (Table 1,
entry 3). Only a trace amount of Ir(ttp)Bn (3a) was observed
in acetonitrile or isopropyl alcohol solvent (Table 1, entries 4
and 5). Using anisole as the solvent, a 4% yield of Ir(ttp)Bn
(3a) was produced with a 17% yield of Ir(ttp)CH3 from the
cleavage of the alkyl PhO−Me bond (Table 1, entry 6).11 The
optimal result was obtained in benzene solvent, and Ir(ttp)Bn
(3a) was formed in 84% yield after 48 h (Table 1, entry 7).
Therefore, we chose benzene as the optimal solvent to further
optimize the reaction conditions.
Scheme 1. Synthesis of Ir(por)R (por = Porphyrinato
Dianion, R = Alkyls)
Base and Base-Loading Effects. Without any base,
Ir(ttp)(CO)Cl (1a) did not react with benzyl alcohol (2a) at
150 °C for 48 h with quantitative recovery of 1a (Table 2,
Table 2. Base and Base-Loading Effects on the C−O
Cleavage of Benzyl Alcohol
a
entry
base
n
time/h
yield/%
1
2
3
4
5
0
48
48
2
2
2
0
84
89
88
80
K2CO3
KOH
KOH
KOH
10
10
20
5
a
Isolated yield.
entry 1). When 10 equiv of KOH was used instead of K2CO3
as the base, the reaction gave a higher product yield of 89%
with a shorter reaction time of only 2 h (Table 2, entry 3).
There was not an obvious influence on the yield and reaction
time when the loading of KOH was increased from 10 to 20
equiv (Table 2, entry 4). A slightly lower yield of 80% was
afforded when 5 equiv of KOH was added. The yield did not
vary greatly, probably because the solubility of KOH in
benzene is low and the solution is already saturated with 5
equiv of KOH. A 10 equiv amount of KOH was thus found to
be suitable.
Temperature and Solvent Effect. When the reaction
temperature was increased from 120 to 150 °C, the yield of the
desired product Ir(ttp)Bn (3a) did not obviously change but
there was a higher reaction rate (Table 1, entries 1 and 2).
Therefore, 150 °C was chosen to be the optimal reaction
Benzyl Alcohol Loading Effects. When both 50 and 30
equiv of benzyl alcohol were used in this transformation, the
reaction efficiency was similar to that of 100 equiv of benzyl
alcohol in rates and yields (Table 3, entries 1−3). A lower
Table 1. Temperature and Solvent Effects on the C−O
Cleavage of Benzyl Alcohol
Table 3. Benzyl Alcohol Loading Effects on the C−O
Cleavage of Benzyl Alcohol
a
entry
solvent
temp/°C
time/h
yield/%
1
2
3
4
5
6
7
benzonitrile
benzonitrile
120
150
150
150
150
150
150
19
5
29
28
50
48
24
24
48
48
a
entry
n
time/h
yield/%
acetonitrile
isopropyl alcohol
anisole
trace
trace
1
2
3
4
100
50
30
2
2
2
5
89
89
88
81
bc
,
4
benzene
84
10
a
b
c
Isolated yield. 1H NMR yield. A 17% NMR yield of Ir(ttp)CH3
was afforded.
a
Isolated yield.
B
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benzyl alcohol loading of 10 equiv resulted in a slightly lower
yield of Ir(ttp)Bn (3a) (81%) in 5 h (Table 3, entry 4).
Therefore, 30 equiv of benzyl alcohol loading was used in
further studies.
Table 5. Scope of Alkyl Alcohols
Substrate Scope. The optimal reaction conditions were
found to require Ir(ttp)(CO)Cl, 30 equiv of benzyl alcohol,
and 10 equiv of KOH as a base in benzene at 150 °C. Various
substituted benzyl alcohols were then investigated under the
optimal conditions. The results demonstrated that the reaction
could tolerate various functional groups such as methyl,
methoxyl, tert-butyl, and trifluoromethyl (Table 4). Both
a
entry
ROH
time/h
yield/%
1
2
3
4
5
6
7
CH3OH (2f)
EtOH (2g)
2
24
24
24
24
24
24
88 (3f)
83 (3g)
79 (3h)
73 (3i)
71 (3j)
70 (3k)
64 (3l)
n-PrOH (2h)
n-BuOH (2i)
n-pentanol (2j)
n-octanol (2k)
5-hexen-1-ol (2l)
Table 4. Scope of Substituted Benzyl Alcohols
a
Isolated yield.
the presence of KOH.11,12a We propose that Ir(ttp)(CO)Cl
(1a) first undergoes ligand dissociation and ligand substitution
with KOH to give Ir(ttp)OH, which then undergoes fast
reductive dimerization to form Ir2(ttp)2 and H2O2. Excess
KOH could reduce Ir2(ttp)2 to Ir(ttp)−. Meanwhile, Ir(ttp)− is
also protonated to Ir(ttp)H by residual water in the solvent.12a
These three Ir(ttp) species are possible dominant active
intermediates for the various bond activations and exist in
equilibria under basic conditions, as depicted in Scheme 2.3,12a
a
entry
R
yield/%
1
2
3
4
5
H (2a)
88 (3a)
92 (3b)
87 (3c)
84 (3d)
86 (3e)
4-t-Bu (2b)
4-Me (2c)
4-OMe (2d)
4-CF3 (2e)
a
Isolated yield.
electron-rich and electron-poor benzyl alcohols 2a−e gave
good yields of the corresponding C−O cleavage products 3a−
e (Table 4, entries 1−5). 4-Methylbenzyl alcohol (2c) reacted
to give the desired Ir(ttp)CH2C6H4(4-Me) (3c) in 87% yield
without any benzylic C−H activation products (Table 4, entry
3). 4-Methoxybenzyl alcohol (2d) underwent chemoselective
C−O cleavage to produce Ir(ttp)CH2C6H4(4-OMe) (3d) in
62% yield (Table 4, entry 4).11 Halogen-containing benzyl
alcohols were not suitable, presumably because the aryl
carbon−halogen bonds were more easily cleaved than alkyl
carbon−oxygen bonds with iridium porphyrin complexes
under the basic conditions.12
To expand the synthetic application of this alkylating
methodology, other 1° alkyl alcohols were then investigated.
Under the above optimal conditions, MeOH (2f) was first
attempted. but no desired Ir(ttp)Me (3f) product was
observed. In view of the fact that benzonitrile as a solvent is
successful in the reaction of Rh(ttp)Cl cleaving the C−O bond
of alkyl alcohols, we again ran the reaction between
Ir(ttp)(CO)Cl (1a) and 100 equiv of MeOH in benzonitrile
solvent. To our delight, the reaction was complete in 2 h and
gave Ir(ttp)Me (3f) in 88% yield (Table 5, entry 1), which was
higher than that under the previously reported solventless
conditions giving a 70% yield.9 Using these conditions, other
alkyl alcohols with β-hydrogens, such as EtOH, n-PrOH, n-
BuOH, n-pentanol, and n-octanol, were also screened, and
moderate to good yields of Ir(ttp)-alkyls 3g−l were obtained
in 24 h (Table 5, entries 2−6). The yields slightly decreased
with increasing alkyl chain length, possibly due to product
decomposition by the facile β-hydride elimination.13 5-Hexen-
1-ol was also a suitable substrate even with a reactive alkene
moiety and gave the corresponding alkylating product in 64%
yield, suggesting that this approach can potentially be used to
prepare more valuable and functionalized Ir(ttp)-alkyls (Table
5, entry 7).
Scheme 2. Equilibria between Iridium Porphyrin
Intermediates
In addition, [Ir(ttp)]2 has been ruled out to be an intermediate
in the C−O cleavage of MeOH by Ir(ttp)(CO)Cl in alkaline
media.9 Therefore, we proposed that similar mechanistic
pathways operate in benzene or benzonitrile solvent. There-
fore, the reactivities of only Ir(ttp)− and Ir(ttp)H as the
probable intermediates toward C−O bond cleavage of benzyl
alcohol were examined individually.
When Ir(ttp)H (1b) was reacted with 30 equiv of benzyl
alcohol at 150 °C in C6D6 for 24 h under N2, no C−O bond
cleavage product Ir(ttp)CH2Ph (3a) was observed (Scheme
3A). Thus, Ir(ttp)H (1b) alone is unlikely to be the active
intermediate.
Ir(ttp)− was then generated in situ from the deprotonation
of Ir(ttp)H (1b) (the pKa of Ir(ttp)H is 15)9 with KOH in
C6D6 and reacted with 30 equiv of benzyl alcohol to form the
C−O cleavage product Ir(ttp)Bn in 78% yield in 2 h (Scheme
3,B). These outcomes imply two mechanistic possibilities: (1)
the Ir(ttp)− anion directly cleaves the C−O bond of benzyl
alcohol possibly by an SN2-like pathway and (2) KOH is
essential and plays a promoting role in the C−O cleavage
reaction with Ir(ttp)H. We support the second mechanistic
proposal because hydroxide is a very poor leaving group under
basic conditions.
In order to gain some mechanistic understanding of the
electronic effects of C−O bond cleavage, a series of
competition experiments using an equimolar mixture of 4-
substituted benzyl alcohol and benzyl alcohol with Ir(ttp)-
Mechanistic Studies. It has been reported that Ir(ttp)-
(CO)Cl could readily be reduced to [Ir(ttp)]2 and Ir(ttp)− in
C
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Scheme 3. Reaction of Ir(ttp)H and Ir(ttp)− toward the C−
O bond Cleavage of Benzyl Alcohol
Scheme 4. Proposed Reaction Mechanism
(CO)Cl and KOH (30 equiv) at 150 °C in benzene were
conducted.
Table 6 summarizes the results. On the basis of these results,
a Hammett plot was then constructed and showed that the
Table 6. Competition Reaction between Substituted BnOH
and BnOH with Ir(ttp)Cl(CO)
a
and benzaldehyde.14,15 Ir(ttp)− can also be protonated to
Ir(ttp)H (1b) by H2O (the pKa of Ir(ttp)H is 15).9,16
Subsequently, the nucleophilic Ir(ttp)− anion attacks the
carbonyl carbon in benzaldehyde to give the α-hydroxyalkyl
complex Ir(ttp)CH(OH)Ph upon protonation with H2O.9,17
Finally, Ir(ttp)CH(OH)Ph can be reduced by Ir(ttp)H (1b)
to the desired C−O cleavage product Ir(ttp)CH2Ph (3a) and
Ir(ttp)OH, probably via σ-bond metathesis.10 Then, Ir(ttp)-
OH is either reused to react with PhCH2OH (2a) or converted
directly to the Ir(ttp)− anion according to the pathway in
Scheme 2. In benzonitrile solvent for aliphatic alcohols, the
(PhCN)Ir(ttp)− anion is formed by the solvent ligation of the
Ir(ttp)− anion and serves as a nucleophile, because the
(PhCN)Ir(ttp)− anion is more nucleophilic than the Ir(ttp)−
anion.10,16
yield/%
entry
FG
σp
3a
3
log(kFG/kH)
1
2
3
CH3
OCH3
CF3
−0.17
−0.27
0.54
35
21
52
60
57
44
0.230
0.431
−0.079
a
NMR yield.
electron-withdrawing group (−CF3) decreased the rate of C−
O cleavage (Figure 1). This finding also disfavors the SN2-like
pathway, since an electron-withdrawing group is a better
leaving group.
CONCLUSION
■
In short, the alkylation of Ir(por)s was successfully achieved
with benzyl and alkyl alcohols as the alkylating reagents. This
C−O bond cleavage reaction could proceed smoothly in
benzene or benzonitrile solvent under basic conditions and
gave up to a 92% yield of Ir(ttp) complexes. Mechanistic
investigations suggest that both the Ir(ttp)− anion and Ir(ttp)
H are key intermediates for this C−O cleavage. The reaction
involves a hydrogen-borrowing pathway via Ir(ttp)H.
Figure 1. Hammett plot of base-promoted Bn−OH cleavage using the
Hammett constants.
EXPERIMENTAL SECTION
On the basis of the above experimental findings and the
previous investigations on the C−O bond cleavage of
CH3OH,9 a possible mechanism is proposed for the C−O
cleavage in primary alcohols using benzyl alcohol as an
example (Scheme 4). First, a small amount of PhCH2O− anion
is produced by deprotonation of PhCH2OH (2a) with KOH
and reacts with Ir(ttp)(CO)Cl (1a) via ligand substitution to
generate the Ir(ttp)OCH2Ph intermediate.14 Alternatively,
Ir(ttp)OCH2Ph can be generated by the reaction between
PhCH2OH (2a) and Ir(ttp)OH from the ligand substitution of
Ir(ttp)(CO)Cl (1a) and KOH. Ir(ttp)OCH2Ph then under-
goes β-H elimination with KOH to yield the Ir(ttp)− anion
■
Unless otherwise noted, all materials were purchased from
commercial suppliers and directly used without further purification.
Benzene for the reaction was distilled from sodium. Hexane for
chromatography was distilled from anhydrous calcium chloride. All
reactions were protected from light by wrapping with aluminum foil.
The reaction mixtures in Teflon screw-capped pressure tubes were
heated in heat blocks on heaters and monitored by thin-layer
chromatography (TLC) performed on Merck precoated silica gel 60
F254 plates. Silica gel (Merck, 70−230 and 230−400 mesh) was used
for column chromatography in air. Ir(ttp)Cl(CO) (1a)13 and It(ttp)
H (1b)5 have been characterized and were prepared according to the
literature processes.
D
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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). All Ir(ttp)-
alkyl compounds are known compounds, and their characterization
data are in accordance with those previously reported.5,6,11,13 Unless
otherwise specified, the coupling constant J refers to H−H coupling.
Reaction of Ir(ttp)Cl(CO) and Benzyl Alcohol with K2CO3 in
PhCN at 120 °C. Ir(ttp)Cl(CO) (1a; 11.6 mg, 0.0125 mmol),
K2CO3 (17.3 mg, 0.125 mmol), and benzyl alcohol (2a; 135.2 mg,
1.25 mmol) were added into benzonitrile (1.5 mL) in a Teflon screw-
capped tube, degassed for three freeze−pump−thaw cycles, refilled
with N2, and heated at 120 °C for 19 h. After the excess benzyl
alcohol and benzonitrile were removed by vacuum distillation, the
solid mixture was then extracted with CH2Cl2 and filtered through a
short pipet column chromatograph on silica gel with CH2Cl2 to give
the red crude product. The crude product was further purified by a
precoated silica gel TLC plate with CH2Cl2/hexane (1/1) to give
Ir(ttp)Bn5 (3a; 3.5 mg, 0.0037 mmol) in 19% yield. 1H NMR
(CDCl3, 400 MHz): δ −3.97 (s, 2 H), 2.71 (s, 12 H), 3.18 (d, 2 H, J
= 7.4 Hz), 5.92 (t, 2 H, J = 7.6 Hz), 6.49 (t, 1 H, J = 7.2 Hz), 7.55 (t,
8 H, J = 6.8 Hz), 7.99 (d, 4 H, J = 7.4 Hz), 8.04 (d, 4 H, J = 7.1 Hz),
8.49 (s, 8 H).
Reaction of Ir(ttp)Cl(CO) and Benzyl Alcohol with K2CO3 in
PhCN at 150 °C. Ir(ttp)Cl(CO) (1a; 11.6 mg, 0.0125 mmol),
K2CO3 (17.3 mg, 0.125 mmol), and benzyl alcohol (2a; 135.2 mg,
1.25 mmol) were added into benzonitrile (1.5 mL) in a Teflon screw-
capped tube, degassed for three freeze−pump−thaw cycles, refilled
with N2, and heated at 150 °C for 5 h. After the excess benzyl alcohol
and benzonitrile were removed by vacuum distillation, the solid
mixture was then extracted with CH2Cl2 and filtered through a short
pipet column chromatograph on silica gel with CH2Cl2 to give the red
crude product. The crude product was further purified by a precoated
silica gel TLC plate with CH2Cl2/hexane (1/1) to give Ir(ttp)Bn (3a;
3.3 mg, 0.0035 mmol) in 28% yield.
K2CO3 (17.3 mg, 0.125 mmol), and benzyl alcohol (2a; 135.2 mg,
1.25 mmol) were added into anisole (1.5 mL) in a Teflon screw-
capped tube, degassed for three freeze−pump−thaw cycles, refilled
with N2, and heated at 150 °C for 48 h. After the excess benzyl
alcohol was removed by vacuum distillation, the solid mixture was
then extracted with CH2Cl2 and filtered through a short pipet column
chromatograph on silica gel with CH2Cl2 to give the red crude
product. The NMR yield of Ir(ttp)Bn (3a) was determined to be 4%
using dichloroethane as the internal standard.
Reaction of Ir(ttp)Cl(CO) and Benzyl Alcohol with K2CO3 in
Benzene at 150 °C. Ir(ttp)Cl(CO) (1a; 11.6 mg, 0.0125 mmol),
K2CO3 (17.3 mg, 0.125 mmol), and benzyl alcohol (2a; 135.2 mg,
1.25 mmol) were added into benzene (1.5 mL) in a Teflon screw-
capped tube, degassed for three freeze−pump−thaw cycles, refilled
with N2, and heated at 150 °C for 48 h. After the excess benzyl
alcohol and benzene were removed by vacuum distillation, the solid
mixture was then extracted with CH2Cl2 and filtered through a short
pipet column chromatograph on silica gel with CH2Cl2 to give the red
crude product. The crude product was further purified by a precoated
silica gel TLC plate with CH2Cl2/hexane (1/1) to give Ir(ttp)Bn (3a;
10.0 mg, 0.0035 mmol) in 84% yield.
Reaction of Ir(ttp)Cl(CO) and Benzyl Alcohol without Base.
Ir(ttp)Cl(CO) (1a; 11.6 mg, 0.0125 mmol) and benzyl alcohol (2a;
41.0 mg, 0.375 mmol) were added into benzene (1.5 mL) in a Teflon
screw-capped tube, degassed for three freeze−pump−thaw cycles,
refilled with N2, and heated at 150 °C for 48 h. No desired Ir(ttp)Bn
1
was formed, as determined by TLC and H NMR.
Reaction of Ir(ttp)Cl(CO) and Benzyl Alcohol with KOH (10
equiv) at 150 °C. Ir(ttp)Cl(CO) (1a; 11.6 mg, 0.0125 mmol), KOH
(7.0 mg, 0.125 mmol), and benzyl alcohol (2a; 135.2 mg, 1.25 mmol)
were added into benzene (1.5 mL) in a Teflon screw-capped tube,
degassed for three freeze−pump−thaw cycles, refilled with N2, and
heated at 150 °C for 2 h. After the excess benzyl alcohol and benzene
were removed by vacuum distillation, the solid mixture was then
extracted with CH2Cl2 and filtered through a short pipet column
chromatograph on silica gel with CH2Cl2 to give the red crude
product. The crude product was further purified by a precoated silica
gel TLC plate with CH2Cl2/hexane (1/1) to give Ir(ttp)Bn (3a; 10.6
mg, 0.0111 mmol) in 89% yield.
Reaction of Ir(ttp)Cl(CO) and Benzyl Alcohol with KOH (20
equiv) at 150 °C. Ir(ttp)Cl(CO) (1a; 11.6 mg, 0.0125 mmol), KOH
(14.0 mg, 0.250 mmol), and benzyl alcohol (2a; 135.2 mg, 1.25
mmol) were added into benzene (1.5 mL) in a Teflon screw-capped
tube, degassed for three freeze−pump−thaw cycles, refilled with N2,
and heated at 150 °C for 2 h. The desired Ir(ttp)Bn (3a; 10.5 mg,
0.011 mmol) was obtained in 88% yield.
Reaction of Ir(ttp)Cl(CO) and Benzyl Alcohol with KOH (5
equiv) at 150 °C. Ir(ttp)Cl(CO) (1a; 11.6 mg, 0.0125 mmol), KOH
(3.5 mg, 0.0625 mmol), and benzyl alcohol (2a; 135.2 mg, 1.25
mmol) were added into benzene (1.5 mL) in a Teflon screw-capped
tube, degassed for three freeze−pump−thaw cycles, refilled with N2,
and heated at 150 °C for 2 h. The desired Ir(ttp)Bn (3a; 9.5 mg,
0.010 mmol) was obtained in 80% yield.
Reaction of Ir(ttp)Cl(CO) and Benzyl Alcohol (50 equiv) at
150 °C. Ir(ttp)Cl(CO) (1a; 11.6 mg, 0.0125 mmol), KOH (7.0 mg,
0.125 mmol), and benzyl alcohol (2a; 67.6 mg, 0.625 mmol) were
added into benzene (1.5 mL) in a Teflon screw-capped tube, degassed
for three freeze−pump−thaw cycles, refilled with N2, and heated at
150 °C for 2 h. After the excess benzyl alcohol and benzene were
removed by vacuum distillation, the solid mixture was then extracted
with CH2Cl2 and filtered through a short pipet column chromato-
graph on silica gel with CH2Cl2 to give the red crude product. The
crude product was further purified by a precoated silica gel TLC plate
with CH2Cl2/hexane (1/1) to give Ir(ttp)Bn (3a; 10.6 mg, 0.0111
mmol) in 89% yield.
Reaction of Ir(ttp)Cl(CO) and Benzyl Alcohol with K2CO3 at
150 °C. Ir(ttp)Cl(CO) (1a; 11.6 mg, 0.0125 mmol) and K2CO3
(17.3 mg, 0.125 mmol) were added into benzyl alcohol (1.5 mL) in a
Teflon screw-capped tube, degassed for three freeze−pump−thaw
cycles, refilled with N2, and heated at 150 °C for 48 h. After the excess
benzyl alcohol was removed by vacuum distillation, the solid mixture
was then extracted with CH2Cl2 and filtered through a short pipet
column chromatograph on silica gel with CH2Cl2 to give the red
crude product. The crude product was further purified by a precoated
silica gel TLC plate with CH2Cl2/hexane (1/1) to give Ir(ttp)Bn (3a;
6.0 mg, 0.0063 mmol) in 50% yield.
Reaction of Ir(ttp)Cl(CO) and Benzyl Alcohol with K2CO3 in
CH3CN at 150 °C. Ir(ttp)Cl(CO) (1a; 11.6 mg, 0.0125 mmol),
K2CO3 (17.3 mg, 0.125 mmol), and benzyl alcohol (2a; 135.2 mg,
1.25 mmol) were added into acetonitrile (1.5 mL) in a Teflon screw-
capped tube, degassed for three freeze−pump−thaw cycles, refilled
with N2, and heated at 150 °C for 24 h. After the excess benzyl
alcohol and acetonitrile were removed by vacuum distillation, the
solid mixture was then extracted with CH2Cl2 and filtered through a
short pipet column chromatograph on silica gel with CH2Cl2 to give
1
the red crude product. The H NMR spectrum was recorded for the
crude product. Ir(ttp)Bn (3a) was formed in trace amounts.
Reaction of Ir(ttp)Cl(CO) and Benzyl Alcohol with K2CO3 in
Isopropyl Alcohol at 150 °C. Ir(ttp)Cl(CO) (1a; 11.6 mg, 0.0125
mmol), K2CO3 (17.3 mg, 0.125 mmol), and benzyl alcohol (2a; 135.2
mg, 1.25 mmol) were added into isopropyl alcohol (1.5 mL) in a
Teflon screw-capped tube, degassed for three freeze−pump−thaw
cycles, refilled with N2, and heated at 150 °C for 24 h. After the excess
benzyl alcohol and isopropyl alcohol were removed by vacuum
distillation, the solid mixture was then extracted with CH2Cl2 and
filtered through a short pipet column chromatograph on silica gel with
1
CH2Cl2 to give the red crude product. The H NMR spectrum was
Reaction of Ir(ttp)Cl(CO) and Benzyl Alcohol (30 equiv) at
150 °C. Ir(ttp)Cl(CO) (1a; 11.6 mg, 0.0125 mmol), KOH (7.0 mg,
0.125 mmol), and benzyl alcohol (2a; 41.0 mg, 0.375 mmol) were
added into benzene (1.5 mL) in a Teflon screw-capped tube, degassed
for three freeze−pump−thaw cycles, refilled with N2, and heated at
recorded for the crude product. Ir(ttp)Bn (3a) was formed in trace
amounts.
Reaction of Ir(ttp)Cl(CO) and Benzyl Alcohol with K2CO3 in
Anisole at 150 °C. Ir(ttp)Cl(CO) (1a; 11.6 mg, 0.0125 mmol),
E
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150 °C for 2 h. The desired Ir(ttp)Bn (3a; 10.5 mg, 0.011 mmol) was
obtained in 88% yield.
Reaction of Ir(ttp)Cl(CO) and Methanol. Ir(ttp)Cl(CO) (1a;
11.6 mg, 0.0125 mmol), KOH (7.0 mg, 0.125 mmol), and methanol
(2f; 40.1 mg, 1.25 mmol) were added into benzonitrile (1.5 mL) in a
Teflon screw-capped tube, degassed for three freeze−pump−thaw
cycles, refilled with N2, and heated at 150 °C for 2 h. After the excess
alcohol and benzonitrile were removed by vacuum distillation, the
solid mixture was then extracted with CH2Cl2 and filtered through a
short pipet column chromatograph on silica gel with CH2Cl2 to give
the red crude product. The crude product was further purified by a
precoated silica gel TLC plate with CH2Cl2/hexane (1/1) to give
Ir(ttp)Me6 (3f; 9.6 mg, 0.0110 mmol) in 88% yield. 1H NMR
(CDCl3, 400 MHz): δ −6.28 (s, 3 H), 2.70 (s, 12 H), 7.54 (d, 8 H, J
= 7.8 Hz), 8.05−8.00 (m, 8 H), 8.54 (s, 8 H).
Reaction of Ir(ttp)Cl(CO) and Ethanol. Ir(ttp)Cl(CO) (1a;
11.6 mg, 0.0125 mmol), KOH (7.0 mg, 0.125 mmol), and ethanol
(2g; 57.5 mg, 1.25 mmol) were added into benzonitrile (1.5 mL) in a
Teflon screw-capped tube, degassed for three freeze−pump−thaw
cycles, refilled with N2, and heated at 150 °C for 24 h. After the excess
alcohol and benzonitrile were removed by vacuum distillation, the
solid mixture was then extracted with CH2Cl2 and filtered through a
short pipet column chromatograph on silica gel with CH2Cl2 to give
the red crude product. The crude product was further purified by a
precoated silica gel TLC plate with CH2Cl2/hexane (1/1) to give
Ir(ttp)Et13 (3g; 9.2 mg, 0.0103 mmol) in 83% yield. 1H NMR
(CDCl3, 400 MHz): δ −5.49 (s, 2 H), −4.58 (t, 3 H, J = 8.4 Hz), 2.70
(s, 12 H), 7.53 (t, 8 H, J = 6.4 Hz),7.99 (d, 4 H, J = 7.5 Hz), 8.05 (d,
4 H, J = 7.2 Hz), 8.52 (s, 8 H).
Reaction of Ir(ttp)Cl(CO) and Benzyl Alcohol (10 equiv) at
150 °C. Ir(ttp)Cl(CO) (1a; 11.6 mg, 0.0125 mmol), KOH (7.0 mg,
0.125 mmol), and benzyl alcohol (2a; 13.5 mg, 0.125 mmol) were
added into benzene (1.5 mL) in a Teflon screw-capped tube, degassed
for three freeze−pump−thaw cycles, refilled with N2, and heated at
150 °C for 5 h. The desired Ir(ttp)Bn (3a; 9.6 mg, 0.010 mmol) was
obtained in 88% yield.
Reaction of Ir(ttp)Cl(CO) and 4-tert-Butylbenzyl Alcohol.
Ir(ttp)Cl(CO) (1a; 11.6 mg, 0.0125 mmol), KOH (7.0 mg, 0.125
mmol), and 4-tert-butylbenzyl alcohol (2b; 61.6 mg, 0.375 mmol)
were added into benzene (1.5 mL) in a Teflon screw-capped tube,
degassed for three freeze−pump−thaw cycles, refilled with N2, and
heated at 150 °C for 2 h. After the excess alcohol and benzene were
removed by vacuum distillation, the solid mixture was then extracted
with CH2Cl2 and filtered through a short pipet column chromato-
graph on silica gel with CH2Cl2 to give the red crude product. The
crude product was further purified by a precoated silica gel TLC plate
with CH2Cl2/hexane (1/1) to give Ir(ttp)(4-t-Bu)Bn5 (3b; 11.6 mg,
0.0115 mmol) in 92% yield. 1HNMR (CDCl3, 400 MHz): δ −3.99 (s,
2 H), 1.02 (s, 9 H), 2.72 (s, 12 H), 3.18 (d, 2 H, J = 8.1 Hz), 5.97 (d,
2 H, J = 8.1 Hz), 7.55 (t, 8 H, J = 6.7 Hz),8.03 (t, 8 H, J = 6.9 Hz),
8.47 (s, 8 H).
Reaction of Ir(ttp)Cl(CO) and 4-Methylbenzyl Alcohol.
Ir(ttp)Cl(CO) (1a; 11.6 mg, 0.0125 mmol), KOH (7.0 mg, 0.125
mmol), and 4-methylbenzyl alcohol (2c; 45.8 mg, 0.375 mmol) were
added into benzene (1.5 mL) in a Teflon screw-capped tube, degassed
for three freeze−pump−thaw cycles, refilled with N2, and heated at
150 °C for 2 h. After the benzene were removed by vacuum
distillation, the solid mixture was then extracted with CH2Cl2 and
filtered through a short pipet column chromatograph on silica gel with
CH2Cl2 to give the red crude product. The crude product was further
purified by a precoated silica gel TLC plate with CH2Cl2/hexane (1/
1) to give Ir(ttp)(4-Me)Bn5 (3c; 10.5 mg, 0.0109 mmol) in 87%
yield. 1H NMR (CDCl3, 400 MHz): δ −4.00 (s, 2 H), 1.71 (s, 3 H),
2.71 (s, 12 H), 3.11 (d, 2 H, J = 7.9 Hz), 5.72 (d, 2 H, J = 7.8 Hz),
7.55 (t, 8 H, J = 6.2 Hz),7.95 (d, 4 H, J = 6.3 Hz), 8.05 (d, 4 H, J =
7.3 Hz), 8.48 (s, 8 H).
Reaction of Ir(ttp)Cl(CO) and n-Propanol. Ir(ttp)Cl(CO) (1a;
11.6 mg, 0.0125 mmol), KOH (7.0 mg, 0.125 mmol), and n-propanol
(2h; 75.1 mg, 1.25 mmol) were added into benzonitrile (1.5 mL) in a
Teflon screw-capped tube, degassed for three freeze−pump−thaw
cycles, refilled with N2, and heated at 150 °C for 24 h. After the excess
alcohol and benzonitrile were removed by vacuum distillation, the
solid mixture was then extracted with CH2Cl2 and filtered through a
short pipet column chromatograph on silica gel with CH2Cl2 to give
the red crude product. The crude product was further purified by a
precoated silica gel TLC plate with CH2Cl2/hexane (1/1) to give
1
Ir(ttp)(n-Pr)13 (3h; 8.9 mg, 0.0098 mmol) in 79% yield. H NMR
(CDCl3, 400 MHz): δ −5.56 (s, 2 H), −4.36 (sext, 2 H, J = 7.6 Hz),
−1.65 (t, 3 H, J = 7.3 Hz), 2.70 (s, 12 H), 7.53 (t, 8 H, J = 7.6 Hz),
8.02 (dd, 8 H, J = 13.8, 6.8 Hz), 8.52 (s, 8 H).
Reaction of Ir(ttp)Cl(CO) and 4-Methoxylbenzyl Alcohol.
Ir(ttp)Cl(CO) (1a; 11.6 mg, 0.0125 mmol), KOH (7.0 mg, 0.125
mmol), and 4-methoxylbenzyl alcohol (2d; 51.8 mg, 0.375 mmol)
were added into benzene (1.5 mL) in a Teflon screw-capped tube,
degassed for three freeze−pump−thaw cycles, refilled with N2, and
heated at 150 °C for 2 h. After the excess alcohol and benzene were
removed by vacuum distillation, the solid mixture was then extracted
with CH2Cl2 and filtered through a short pipet column chromato-
graph on silica gel with CH2Cl2 to give the red crude product. The
crude product was further purified by a precoated silica gel TLC plate
with CH2Cl2/hexane (1/1) to give Ir(ttp)(4-OMe)Bn11 (3d; 10.3
Reaction of Ir(ttp)Cl(CO) and n-Butanol. Ir(ttp)Cl(CO) (1a;
11.6 mg, 0.0125 mmol), KOH (7.0 mg, 0.125 mmol), and n-butanol
(2i; 92.7 mg, 1.25 mmol) were added into benzonitrile (1.5 mL) in a
Teflon screw-capped tube, degassed for three freeze−pump−thaw
cycles, refilled with N2, and heated at 150 °C for 24 h. After the excess
alcohol and benzonitrile were removed by vacuum distillation, the
solid mixture was then extracted with CH2Cl2 and filtered through a
short pipet column chromatograph on silica gel with CH2Cl2 to give
the red crude product. The crude product was further purified by a
precoated silica gel TLC plate with CH2Cl2/hexane (1/1) to give
1
1
Ir(ttp)(n-Bu)6 (3i; 8.4 mg, 0.0091 mmol) in 73% yield. H NMR
mg, 0.0105 mmol) in 84% yield. H NMR (CDCl3, 400 MHz): δ
−4.04 (s, 2 H), 2.71 (s, 12 H), 3.14 (d, 2 H, J = 8.6 Hz), 3.46 (s, 3
H), 5.47 (d, 2 H, J = 8.5 Hz), 7.55 (d, 8 H, J = 7.4 Hz),7.97 (dd, 4 H,
J = 7.8, 2.2 Hz), 8.04 (dd, 4 H, J = 7.8, 2.2 Hz), 8.48 (s, 8 H).
Reaction of Ir(ttp)Cl(CO) and 4-Trifluoromethylbenzyl
Alcohol. Ir(ttp)Cl(CO) (1a; 11.6 mg, 0.0125 mmol), KOH (7.0
mg, 0.125 mmol), and 4-trifluoromethylbenzyl alcohol (2e; 66.1 mg,
0.375 mmol) were added into benzene (1.5 mL) in a Teflon screw-
capped tube, degassed for three freeze−pump−thaw cycles, refilled
with N2, and heated at 150 °C for 2 h. After the excess alcohol and
benzene were removed by vacuum distillation, the solid mixture was
then extracted with CH2Cl2 and filtered through a short pipet column
chromatograph on silica gel with CH2Cl2 to give the red crude
product. The crude product was recrystallized from CH2Cl2/MeOH
to give Ir(ttp)(4-CF3)Bn11 (3e; 11.0 mg, 0.0108 mmol) in 86% yield.
1H NMR (CDCl3, 400 MHz): δ −3.91 (s, 2 H), 2.72 (s, 12 H), 3.18
(CDCl3, 400 MHz): δ −5.52 (t, 2 H, J = 8.1 Hz), −4.44 (quint, 2 H, J
= 7.9 Hz), −1.48 (sext, 2 H, J = 7.5 Hz), −0.75 (t, 3 H, J = 7.4 Hz),
2.70 (s, 12 H), 7.53 (t, 8 H, J = 6.0 Hz), 7.98 (d, 4 H, J = 7.4 Hz),
8.05 (d, 4 H, J = 7.4 Hz), 8.51 (s, 8 H).
Reaction of Ir(ttp)Cl(CO) and 1-Pentanol. Ir(ttp)Cl(CO) (1a;
11.6 mg, 0.0125 mmol), KOH (7.0 mg, 0.125 mmol), and 1-pentanol
(2j; 110.0 mg, 1.25 mmol) were added into benzonitrile (1.5 mL) in a
Teflon screw-capped tube, degassed for three freeze−pump−thaw
cycles, refilled with N2, and heated at 150 °C for 24 h. After the excess
alcohol and benzonitrile were removed by vacuum distillation, the
solid mixture was then extracted with CH2Cl2 and filtered through a
short pipet column chromatograph on silica gel with CH2Cl2 to give
the red crude product. The crude product was further purified by a
precoated silica gel TLC plate with CH2Cl2/hexane (1/1) to give
1
Ir(ttp)(n-pentyl)6 (3j; 8.3 mg, 0.0089 mmol) in 71% yield. H NMR
(d, 2 H, J = 7.9 Hz), 6.14 (d, 2 H, J = 8.0 Hz), 7.55 (d, 8 H, J = 6.8
(CDCl3, 400 MHz): δ −5.54 (t, 2 H, J = 8.4 Hz), −4.44 (quint, 2 H, J
= 7.6 Hz), −1.52 (quint, 2 H, J = 7.5 Hz), −0.42 (sext, 2 H, J = 7.4
Hz), −0.19 (t, 3 H, J = 7.3 Hz), 2.70 (s, 12 H), 7.53 (t, 8 H, J = 6.4
Hz), 7.94 (d, 4 H, J = 7.4 Hz), 8.03 (d, 4 H, J = 7.2 Hz), 8.51 (s, 8
H).
F
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Hz), 7.98 (d, 4 H, J = 7.3 Hz), 8.05 (d, 4 H, J = 7.2 Hz), 8.51 (s, 8
H).
orcid.org/0000-0002-1112-6819; Email: ksc@
cuhk.edu.hk
Reaction of Ir(ttp)Cl(CO) and n-Octanol. Ir(ttp)Cl(CO) (1a;
11.6 mg, 0.0125 mmol), KOH (7.0 mg, 0.125 mmol) and n-octanol
(2k; 162.8 mg, 1.25 mmol) were added into benzonitrile (1.5 mL) in
a Teflon screw-capped tube, degassed for three freeze−pump−thaw
cycles, refilled with N2, and heated at 150 °C for 24 h. After the excess
alcohol and benzonitrile were removed by vacuum distillation, the
solid mixture was then extracted with CH2Cl2 and filtered through a
short pipet column chromatograph on silica gel with CH2Cl2 to give
the red crude product. The crude product was further purified by a
precoated silica gel TLC plate with CH2Cl2/hexane (1/1) to give
Ir(ttp)(n-octyl) (3k; 8.5 mg, 0.0087 mmol) in 70% yield. H NMR
(CDCl3, 400 MHz): δ −5.54 (t, 2 H, J = 8.4 Hz), −4.44 (quint, 2 H, J
= 7.8 Hz), −1.51 (quint, 2 H, J = 7.5 Hz), −0.46 (quint, 2 H, J = 7.6
Hz), 0.10 (quint, 2 H, J = 7.6 Hz), 0.55 (quint, 2 H, J = 7.6 Hz), 0.63
(t, 3 H, J = 7.2 Hz), 0.87 (sext, 2 H, J = 7.8 Hz), 2.70 (s, 12 H), 7.53
(t, 8 H, J = 6.9 Hz), 7.98 (d, 4 H, J = 7.6 Hz), 8.05 (d, 4 H, J = 7.6
Hz), 8.51 (s, 8 H).
Authors
Yongjun Bian − College of Chemistry and Chemical Engineering,
Jinzhong University, Yuci 030619, People’s Republic of China;
Department of Chemistry, The Chinese University of Hong
Kong, Hong Kong, People’s Republic of China; orcid.org/
0000-0001-9433-974X
Xingyu Qu − College of Chemistry and Chemical Engineering,
Jinzhong University, Yuci 030619, People’s Republic of China;
Department of Chemistry, The Chinese University of Hong
Kong, Hong Kong, People’s Republic of China
6
1
Complete contact information is available at:
https://pubs.acs.org/10.1021/acs.organomet.0c00100
Notes
Reaction of Ir(ttp)Cl(CO) and 5-Hexen-1-ol. Ir(ttp)Cl(CO)
(1a; 11.6 mg, 0.0125 mmol), KOH (7.0 mg, 0.125 mmol), and 5-
hexen-1-ol (2l; 125.2 mg, 1.25 mmol) were added into benzonitrile
(1.5 mL) in a Teflon screw-capped tube, degassed for three freeze−
pump−thaw cycles, refilled with N2, and heated at 150 °C for 24 h.
After the excess alcohol and benzonitrile were removed by vacuum
distillation, the solid mixture was then extracted with CH2Cl2 and
filtered through a short pipet column chromatograph on silica gel with
CH2Cl2 to give the red crude product. The crude product was further
purified by a precoated silica gel TLC plate with CH2Cl2/hexane (1/
1) to give Ir(ttp)(5-hexenyl)6 (3l; 7.5 mg, 0.0081 mmol) in 64%
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
We thank the Research Grants Council of Hong Kong for
financial support (GRF No. 14300115), the Scientific and
Technological Innovation Programs of Higher Education
Institutions in Shanxi (No. 2019L0879 and No. 2019L0894),
the Construction Plan of “1331” engineering Photoelectric
Material Innovation Team of Jinzhong University (No.
2017007), and the Shanxi “1331” project Key Innovative
Research Team (No. PY201817),
1
yield. H NMR (CDCl3, 400 MHz): δ −5.53 (t, 2 H, J = 8.2 Hz),
−4.41 (quint, 2 H, J = 7.5 Hz), −1.41 (quint, 2 H, J = 7.3 Hz), 0.31
(q, 2 H, J = 7.1 Hz), 2.70 (s, 12 H), 4.10 (d, 1 H, J = 15.9 Hz), 4.37
(d, 1 H, J = 10.1 Hz), 4.64−4.74 (m, 1H), 7.53 (d, 8 H, J = 6.2
Hz),7.99 (d, 4 H, J = 7.3 Hz), 8.05 (d, 4 H, J = 7.2 Hz), 8.52 (s, 8 H).
Reaction of Ir(ttp)H and Benzyl Alcohol without KOH.
Ir(ttp)H (1b; 10.8 mg, 0.0125 mmol) and benzyl alcohol (2a; 41.0
mg, 0.375 mmol) were added into benzene-d6 (C6D6) (1.5 mL) in a
Teflon screw-capped tube, degassed for three freeze−pump−thaw
cycles, refilled with N2, and heated at 150 °C for 24 h. No desired
REFERENCES
■
(1) (a) Yanagisawa, M.; Tashiro, K.; Yamasaki, M.; Aida, T. Hosting
Fullerenes by Dynamic Bond Formation with an Iridium Porphyrin
Cyclic Dimer: A “Chemical Friction” for Rotary Guest Motions. J.
Am. Chem. Soc. 2007, 129, 11912−11913. (b) Koren, K.; Borisov, S.
M.; Saf, R.; Klimant, I. Strongly Phosphorescent Iridium(III)−
Porphyrins − New Oxygen Indicators with Tuneable Photophysical
Properties and Functionalities. Eur. J. Inorg. Chem. 2011, 2011, 1531−
1
Ir(ttp)Bn was formed, as determined by TLC and H NMR.
́
Reaction of Ir(ttp)H and Benzyl Alcohol with KOH. Ir(ttp)H
(1b; 10.8 mg, 0.0125 mmol), KOH (7.0 mg, 0.125 mmol), and benzyl
alcohol (2a; 41.0 mg, 0.375 mmol) were added into benzene-d6
(C6D6) (1.5 mL) in a Teflon screw-capped tube, degassed for three
freeze−pump−thaw cycles, refilled with N2, and heated at 150 °C for
2 h. After the excess benzyl alcohol and C6D6 were removed by
vacuum distillation, the solid mixture was then extracted with CH2Cl2
and filtered through a short pipet column chromatograph on silica gel
with CH2Cl2 to give the red crude product. The crude product was
further purified by a precoated silica gel TLC plate with CH2Cl2/
hexane (1/1) to give Ir(ttp)Bn (3a; 9.3 mg, 0.0098 mmol) in 78%
yield.
1534. (c) Hearn, J. M.; Romero-Canelon, I.; Qamar, B.; Liu, Z.;
Hands-Portman, I.; Sadler, P. J. Organometallic Iridium(III)
Anticancer Complexes with New Mechanisms of Action: NCI-60
Screening, Mitochondrial Targeting, and Apoptosis. ACS Chem. Biol.
2013, 8, 1335−1343. (d) Anding, B. J.; Woo, L. K. Iridium Porphyrin
Catalyzed N−H Insertion Reactions: Scope and Mechanism.
Organometallics 2013, 32, 2599−2607. (e) Wang, J.-C.; Xu, Z.-J.;
Guo, Z.; Deng, Q.-H.; Zhou, C.-Y.; Wan, X.-L.; Che, C.-M. Highly
enantioselective intermolecular carbene insertion to C−H and Si−H
bonds catalyzed by a chiral iridium (iii) complex of a D4-symmetric
Halterman porphyrin ligand. Chem. Commun. 2012, 48, 4299−4301.
(f) Anding, B. J.; Ellern, A.; Woo, L. K. Olefin Cyclopropanation
Catalyzed by Iridium(III) Porphyrin Complexes. Organometallics
2012, 31, 3628−3635. (g) Wang, J.-C.; Zhang, Y.; Xu, Z.-J.; Lo, V. K.-
Y.; Che, C.-M. Enantioselective Intramolecular Carbene C−H
Insertion Catalyzed by a Chiral Iridium(III) Complex of D4-
Symmetric Porphyrin Ligand. ACS Catal. 2013, 3, 1144−1148.
(2) To, C. T.; Tam, C. M.; Chan, K. S. Iridium-Catalyzed Carbon-
Carbon σ-Bond Hydrogenation with Water: Rate Enhancement with
Iridium Hydride. ACS Catal. 2015, 5, 4333−4336.
ASSOCIATED CONTENT
* Supporting Information
■
sı
The Supporting Information is available free of charge at
https://pubs.acs.org/doi/10.1021/acs.organomet.0c00100.
1
Competition reactions, H NMR spectra, and substrate
scope (PDF)
(3) Ogoshi, H.; Setsure, J.-I.; Yoshida, Z.-I. Syntheses and reactions
of iridium complexes of octaethylporphyrin. J. Organomet. Chem.
1978, 159, 317−328.
AUTHOR INFORMATION
Corresponding Author
■
(4) Del Rossi, K. J.; Wayland, B. B. Formation and organometallic
reactivity of iridium (II) octaethylporphyrin dimer. J. Chem. Soc.,
Chem. Commun. 1986, 1653−1655.
Kin Shing Chan − Department of Chemistry, The Chinese
University of Hong Kong, Hong Kong, People’s Republic of
China; School of Chemistry and Chemical Engineering, Nanjing
University, Nanjing 210046, People’s Republic of China;
(5) Cheung, C. W.; Chan, K. S. Base-Promoted Selective Activation
of Benzylic Carbon-Hydrogen Bonds of Toluenes by Iridium (III)
Porphyrin. Organometallics 2008, 27, 3043−3055.
G
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Organometallics
pubs.acs.org/Organometallics
Article
(6) Zuo, H.; Liu, Z.; Yang, W.; Zhou, Z.; Chan, K. User-friendly
aerobic reductive alkylation of iridium (III) porphyrin chloride with
potassium hydroxide: scope and mechanism. Dalton Trans. 2015, 44,
20618−20625.
(7) Luo, Y. R. Comprehensive Handbook of Chemical Bond Energies;
CRC Press: Boca Raton, FL, 2007.
(8) (a) Emer, E.; Sinisi, R.; Capdevila, M. G.; Petruzziello, D.;
DeVincentiis, F.; Cozzi, P. G. Direct Nucleophilic SN1-Type
Reactions of Alcohols. Eur. J. Org. Chem. 2011, 2011, 647−666.
(b) Henderson, L. C.; Thornton, M. T.; Byrne, N.; Fox, B. L.; Waugh,
K. D.; Squire, J. S.; Servinis, L.; Delaney, J. P.; Brozinski, H. L.;
Andrighetto, L. M.; Altimari, J. M. Protic ionic liquids as recyclable
solvents for the acid catalyzed synthesisof diphenyl methyl thioethers.
C. R. Chim. 2013, 16, 634−639. (c) Miller, K. J.; Abu-Omar, M. M.
Palladium-Catalyzed SN1 Reactions of Secondary Benzylic Alcohols:
Etherification, Amination, and Thioetherification. Eur. J. Org. Chem.
2003, 2003, 1294−1299. (d) Rackl, D.; Kais, V.; Kreitmeier, P.;
Reiser, O. Visible light photoredox-catalyzed deoxygenation of
alcohols. Beilstein J. Org. Chem. 2014, 10, 2157−2165. (e) Herrmann,
̈
J. M.; Konig, B. Reductive Deoxygenation of Alcohols: Catalytic
Methods Beyond Barton-McCombie Deoxygenation. Eur. J. Org.
Chem. 2013, 2013, 7017−7027.
(9) Cheung, C. W.; Fung, H. S.; Lee, S. Y.; Qian, Y. Y.; Chan, Y. W.;
Chan, K. S. Reactivity Studies of Iridium (III) Porphyrins with
Methanol in Alkaline Media. Organometallics 2010, 29, 1343−1354.
(10) Bian, Y.; Tam, C. M.; To, C. T.; Qu, X.; Chan, K. S. Alkylation
of Rhodium Porphyrin Complexes with Primary Alcohols under Basic
Conditions. Organometallics 2019, 38, 3662−3670.
(11) Chen, C.; Chan, K. S. Alkyl Carbon-Oxygen Bond Cleavage of
Aryl Alkyl Ethers by Iridium-Porphyrin and Rhodium-Porphyrin
Complexes in Alkaline Media. Organometallics 2017, 36, 3456−3464.
(12) (a) Cheung, C. W.; Chan, K. S. Base-Promoted Selective Aryl
C-Cl Cleavage by Iridium (III) Porphyrins via a Metalloradical Ipso
Addition-Elimination Mechanism. Organometallics 2011, 30, 4999−
5009. (b) Cheung, C. W.; Chan, K. S. Base-Promoted Selective Aryl
Carbon-Bromine Bond Cleavage by Iridium(III) Porphyrin for
Iridium(III) Porphyrin Aryl Synthesis: A Metalloradical Ipso
Addition-Elimination Mechanism. Organometallics 2011, 30, 1768−
1771. (c) Cheung, C. W.; Chan, K. S. Base-Promoted Selective Aryl
C−Br and C−I Bond Cleavage by Iridium (III) Porphyrin: Reduction
of IrIII−OH to IrII for Metalloradical Ipso Substitution of Aryl−
Halogen Bonds. Organometallics 2011, 30, 4269−4283. (d) Qian, Y.
Y.; Li, B. Z.; Chan, K. S. Competitive Aryl−Fluorine and Aryl−
Halogen (Halogen = Cl, Br) Bond Cleavage with Iridium Porphyrin
Complexes. Organometallics 2013, 32, 1567−1570.
(13) Yeung, S. K.; Chan, K. S. Selective Oxidation of (Porphyrinato)
iridium (III) Arylethyls by Nitroxide: Evidence for Stabilization of
Carbon-Centered Ir-CH2-CHR • Radicals by Iridium. Organometallics
2005, 24, 6426−6430.
(14) Kloek, S. M.; Heinekey, D. M.; Goldberg, K. I. Stereoselective
Decarbonylation of Methanol to Form a Stable Iridium(III) trans-
Dihydride Complex. Organometallics 2006, 25, 3007−3011.
(15) Blum, O.; Milstein, D. Mechanism of a Directly Observed β-
Hydride Elimination Process of Iridium Alkoxo Complexes. J. Am.
Chem. Soc. 1995, 117, 4582−4594.
(16) (a) Pearson, R. G. Basicity and Nucleophilicity of Transition
Metal Complexes. Adv. Chem. Ser. 1987, 215, 233−244. (b) Giedyk,
M.; Goliszewska, K.; Gryko, D. Vitamin B12 catalysed reactions. Chem.
Soc. Rev. 2015, 44, 3391−3404.
(17) Wayland, B. B.; Vanvoorhees, S. L.; Wilker, C. Organometallic
Chemistry of Rhodium Tetraphenylporphyrin Derivatives: Formyl,
Hydroxymethyl, and Alkyl Complexes. Inorg. Chem. 1986, 25, 4039−
4042.
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Organometallics XXXX, XXX, XXX−XXX