Bipyridine- and phenanthroline-based metal-organic frameworks for highly efficient and tandem catalytic organic transformations via directed C-H activation

Article abstract of DOI:10.1021/ja512478y

We report here the synthesis of a series of robust and porous bipyridyl- and phenanthryl-based metal-organic frameworks (MOFs) of UiO topology (BPV-MOF, mBPV-MOF, and mPT-MOF) and their postsynthetic metalation to afford highly active single-site solid catalysts. While BPV-MOF was constructed from only bipyridyl-functionalized dicarboxylate linker, both mBPV- and mPT-MOF were built with a mixture of bipyridyl- or phenanthryl-functionalized and unfunctionalized dicarboxylate linkers. The postsynthetic metalation of these MOFs with [Ir(COD)(OMe)]₂ provided Ir-functionalized MOFs (BPV-MOF-Ir, mBPV-MOF-Ir, and mPT-MOF-Ir), which are highly active catalysts for tandem hydrosilylation of aryl ketones and aldehydes followed by dehydrogenative ortho-silylation of benzylicsilyl ethers as well as C-H borylation of arenes using B₂pin₂. Both mBPV-MOF-Ir and mPT-MOF-Ir catalysts displayed superior activities compared to BPV-MOF-Ir due to the presence of larger open channels in the mixed-linker MOFs. Impressively, mBPV-MOF-Ir exhibited high TONs of up to 17000 for C-H borylation reactions and was recycled more than 15 times. The mPT-MOF-Ir system is also active in catalyzing tandem dehydrosilylation/dehydrogenative cyclization of N-methylbenzyl amines to azasilolanes in the absence of a hydrogen acceptor. Importantly, MOF-Ir catalysts are significantly more active (up to 95 times) and stable than their homogeneous counterparts for all three reactions, strongly supporting the beneficial effects of active site isolation within MOFs. This work illustrates the ability to increase MOF open channel sizes by using the mixed linker approach and shows the enormous potential of developing highly active and robust single-site solid catalysts based on MOFs containing nitrogen-donor ligands for important organic transformations.

Full text of DOI:10.1021/ja512478y

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Article
Bipyridine- and Phenanthroline-Based Metal-Organic
Frameworks for Highly Efficient and Tandem Catalytic
Organic Transformations via Directed C-H Activation
Kuntal Manna, Teng Zhang, Francis X Greene, and Wenbin Lin
J. Am. Chem. Soc., Just Accepted Manuscript • Publication Date (Web): 02 Feb 2015
Downloaded from http://pubs.acs.org on February 2, 2015
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Bipyridine- and Phenanthroline-Based Metal-Organic Frame-
works for Highly Efficient and Tandem Catalytic Organic
Transformations via Directed C-H Activation
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Kuntal Manna,† Teng Zhang,† Francis X. Greene, and Wenbin Lin*
Department of Chemistry, University of Chicago, 929 E 57th St, Chicago, IL 60637, USA
ABSTRACT: We report here the synthesis of a series of robust and porous bipyridylꢀ and phenanthrylꢀbased metalꢀorganic frameꢀ
works (MOFs) of UiO topology (BPVꢀMOF, mBPVꢀMOF and mPTꢀMOF) and their postsynthetic metalation to afford highly acꢀ
tive singleꢀsite solid catalysts. While BPVꢀMOF was constructed from only bipyridylꢀfunctionalized dicarboxyate linker, both
mBPVꢀ and mPTꢀMOF were built with a mixture of bipyridylꢀ or phenanthrylꢀfunctionalized and unfunctionalized dicarboxylate
linkers. The postsynthetic metalation of these MOFs with [Ir(COD)(OMe)]2 provided Irꢀfunctionalized MOFs (BPVꢀMOFꢀIr,
mBPVꢀMOFꢀIr and mPTꢀMOFꢀIr), which are highly active catalysts for tandem hydrosilylation of aryl ketones and aldehydes folꢀ
lowed by orthoꢀsilylation of benzylicsilyl ethers as well as CꢀH borylation of arenes using B2pin2. Both mBPVꢀMOFꢀIr and mPTꢀ
MOFꢀIr catalysts displayed superior activities compared to BPVꢀMOFꢀIr due to the presence of larger open channels in the mixedꢀ
linker MOFs. Impressively, mBPVꢀMOFꢀIr exhibited high TONs of up to 17000 for CꢀH borylation reactions and was recycled
more than 15 times. The mPTꢀMOFꢀIr system is also active in catalyzing tandem dehydrosilylation/dehydrogenative cyclization of
Nꢀmethylbenzyl amines to azasilolanes in the absence of a hydrogenꢀacceptor. Importantly, MOFꢀIr catalysts are significantly more
active (up to 95 times) and stable than their homogeneous counterparts for all three reactions, strongly supporting the beneficial
effects of active site isolation within MOFs. This work illustrates the ability to increase MOF open channel sizes by using the
mixed linker approach and shows the enormous potential of developing highly active and robust singleꢀsite solid catalysts based on
MOFs containing nitrogenꢀdonor ligands for important organic transformations.
chemical sensing,8 biomedical imaging,9 drug delivery10, conꢀ
ductivity/semiconductivity,11 and solar energy harvesting.12 In
particular, MOFs have been established as a highly tunable
platform for developing singleꢀsite solid catalysts for various
organic transformations.13 More recently, we showed that
UiOꢀtype MOFs provide an efficient means for stabilizing
homogeneous catalysts based on simple bipyridyl and salicꢀ
ylaldimine ligands to afford much enhanced catalytic activity
and even lead to catalytic activities that cannot be achieved
with the homogeneous counterparts.14 As MOFs can be synꢀ
thesized from wellꢀdefined molecular building blocks to tune
their pore and channel sizes without change of MOF strucꢀ
tures, further synthetic elaborations of the bipyridylꢀ and pheꢀ
nanthrylꢀderived ligands can afford new MOF catalysts with
much improved activities and efficiencies over the previously
reported simple bipyꢀMOF.
INTRODUCTION
Bipyridines and phenanthrolines have been extensively emꢀ
ployed in the construction of a wide variety of metal complexꢀ
es with great potential in many applications ranging from caꢀ
talysis to therapeutics.1 In particular, owing to their robust
redox stability, ease of functionalization, and entropically faꢀ
vored metal binding, these nitrogen donorꢀbased chelating
ligands have been routinely used in developing catalytic sysꢀ
tems for solar energy conversion and fine chemical synthesis.
However, homogeneous catalysts based on bipyridylꢀ and
phenanthrylꢀderived ligands tend to have more open coordinaꢀ
tion environments than their phosphine counterparts, and as a
result, they are more prone to deactivation via intermolecular
pathways than metalꢀphosphine catalysts. To alleviate this
drawback, steric protection around the metal centers using
modified bulky bipyridylꢀ and phenanthrylꢀderived ligands is
commonly employed to stabilize homogeneous singleꢀsite
catalysts.2 Installation of bulky substituents at the positions
adjacent to the Nꢀdonors can significantly affect the ligandꢀ
binding properties as well as the electronic properties of metꢀ
alꢀligand complexes, which often attenuates the catalytic activꢀ
ities of the resulting metal complexes.3 Alternative strategies
are thus needed to engender enhanced stability and catalytic
activity to homogeneous metal complex catalysts based on
bipyridylꢀ and phenanthrylꢀderived ligands.
In this article, we report the design and synthesis of elongatꢀ
ed bipyridylꢀ and phenanthrylꢀcontaining UiO MOFs with
larger channels and their postsynthetic metalation with an iridꢀ
ium complex to afford highly active and efficient singleꢀsite
solid catalysts for several important organic reactions via diꢀ
rected CꢀH activation. UiOꢀtype MOFs built from Zr6(ꢀ3ꢀ
O)4(ꢀ3ꢀOH)4 secondary building units (SBUs) and linear diꢀ
carboxylate linkers are highly stable under various reaction
conditions, and thus provide an ideal system for exploring
catalytic applications.15 Furthermore, the UiO MOF topology
is amenable to the incorporation of a wide variety of functionꢀ
alities into the dicarboxylate linkers to lead to numerous novel
Over the past fifteen years, metalꢀorganic frameworks
(MOFs) have emerged as an interesting class of porous moꢀ
lecular materials with great potential in many applications
such as gas storage,4 separation,5 catalysis,6 nonlinear optics,7
functional materials for many important applications.16
mixed linker strategy of using both the functionalized linkers
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mPTꢀMOF was synthesized in 45% yield by heating ZrCl4 and a
and catalytically inactive linkers was also developed in this
work to afford mixedꢀlinker MOFs with much larger open
channels and pores to allow for facile diffusion of the subꢀ
strates and products through the MOF channels. These Irꢀ
functionalized MOFs have been employed as active, robust,
and reusable solid catalysts in three important organic transꢀ
formations: CꢀH borylation of arenes, tandem hydrosilylation
of aryl ketones and aldehydes followed by hydroxylꢀdirected
orthoꢀsilylation, and tandem dehydrocoupling of Nꢀ
methylbenzyl amines with Et2SiH2 to (hydrido)silyl amines
and subsequent intramolecular dehydrogenative cyclization.
Analogous homogeneous bipyridylꢀ and phenanthrylꢀiridium
complexes were also prepared in order to compare their cataꢀ
lytic activities with those of the MOFꢀbased catalysts. We
demonstrate that the MOFꢀIr catalysts are significantly more
active than their homogeneous controls in both borylation and
silylation reactions,17 revealing the crucial role of active site
isolation within MOFs. Additionally, these solid MOFꢀ
catalysts can overcome many fundamental difficulties associꢀ
ated with homogeneous catalysts such as capitalꢀ and laborꢀ
intensive ligand design in order to avoid multimolecular cataꢀ
lyst decomposition, leaching of toxic metal ions and complexꢀ
es into the organic products, and the limitation of solvent
choices due to poor solubility of some homogenous catalysts
in nonpolar solvents.
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mixture of H2PT and 4,4’ꢀbis(carboxyphenyl)ꢀ2ꢀnitroꢀ1,1’ꢀ
biphenyl (H2TPHN) in 1:2 molar ratio in a DMF solution in the
presence of TFA at 100 ºC. The presence of bipyridylꢀ and pheꢀ
nanthrylꢀcontaining dicarboxylate linkers in mBPVꢀMOF and
mPTꢀMOF, respectively, was established and quantified by taking
1H NMR spectra of the digested MOFs. NMR studies consistently
revealed that the ratio of biphenyl and bipyridine in the mBPVꢀ
MOF or the ratio of tetraphenyl and phenanthroline in mPTꢀMOF
is approximately 2:1, consistent with the molar ratio in the feed
(Figure S6 and S10, Supporting Information [SI]). Nitrogen sorpꢀ
tion measurements indicate that both mBPVꢀMOF and mPTꢀMOF
are highly porous with a BET surface area of 1207 m2/g and 3834
m2/g respectively (Figure S8 and S12, SI), and pore sizes of 7 Å
and 7.7 Å respectively (Figure S18 and S21, SI).
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The structures of BPVꢀMOF and mBPVꢀMOF were established
by comparing the powder Xꢀray diffraction (PXRD) patterns of
the MOFs with the predicted pattern from a single crystal strucꢀ
ture of BPHVꢀMOF which was synthesized from ZrCl4 and 4,4’ꢀ
bis(carboxyethenyl)ꢀ1,1’ꢀbiphenyl (H2BPHV) linker in the presꢀ
ence of DMF and TFA at 80 ºC (Figure 1). A singleꢀcrystal Xꢀray
diffraction study revealed that BPHVꢀMOF adopts the UiO strucꢀ
ture (Figure 1a), with the Zr6(ꢀ3ꢀO)4(ꢀ3ꢀOH)4 SBUs connected by
the BPHV bridging linkers to afford the 12ꢀconnected fcu topoloꢀ
gy. However, BPHVꢀMOF crystallizes in a lower symmetry space
ꢀ
group of I4 due to the bending nature of the BPHV linker. The
broadening of (101) peak and appearance of several other peaks
suggest structural distortion in the powder samples, which has
been observed in other nanoscale MOFs.10i In the present case, the
bent nature of the BPHV and BPV linkers provides additional
mechanisms for structural distortions from the single crystal strucꢀ
ture. Similarly, the structure of mPTꢀMOF was established by
comparing the PXRD patterns with the simulated pattern from a
single crystal structure of TPHNꢀMOF which was synthesized
from ZrCl4 and 4,4’ꢀbis(carboxyphenyl)ꢀ2ꢀnitroꢀ1,1’ꢀbiphenyl
(H2TPHN) under similar conditions. TPHNꢀMOF adopts a typical
RESULTS AND DISCUSSION
BPVꢀMOF, mBPVꢀMOF, and mPTꢀMOF were constructed
from both bipyridylꢀ or phenanthrylꢀfunctionalized dicarboxylate
linker and the Zrꢀbased SBU to afford UiO frameworks as shown
in Schemes 1 and 2. The bipyridylꢀcontaining dicarboxylate linkꢀ
er, H2BPV, was synthesized from 5,5’ꢀdibromoꢀ2,2’ꢀbipyridine in
two steps (Scheme 1). The Suzuki coupling between 5,5’ꢀ
dibromoꢀ2,2’ꢀbipyridine and methyl acrylate followed by saponiꢀ
fication provided H2BPV in 60% overall yield. The phenanthoꢀ
lineꢀcontaining dicarboxylate linker, H2PT, was prepared from
phenanthroline in three steps in a 22% overall yield (Scheme 2).
ꢀ
UiO structure and crystallizes in the cubic Fm3m space group
(Figure 1).
Scheme 2. Synthesis of mPT-MOFa
Scheme 1. Synthesis of BPV-MOF and mBPV-MOFa
CO2Me
CO2H
CO2H
CO2H
CO2Me
Br
Br
Br
Zr6O4(OH)4(BPV)6
BPV-MOF
iii)
N
N
N
N
N
N
N
i)
ii)
iii)
NO2 iv)
N
N
+
N
N
Zr6O4(OH)4(TPHN)4(PT)2
mPT-MOF
N
ii)
i)
N
iv)
N
Zr6O4(OH)4(BPHV)4(BPV)2
mBPV-MOF
Br
CO2Me
CO2H
H2PT
CO2H
H2TPHN
CO2H
H2BPV
CO2Me
aReagents: (i) Br2, S2Cl2, pyridine, nꢀBuCl, reflux, 12 h; (ii) 4ꢀ
acetylphenylboronic acid, Pd(PPh3)2, CsF, DME, 100 °C, 3 d; (iii)
aq NaOH, EtOH; (iv) ZrCl4, DMF, TFA, 100 °C, 5 d.
aReagents: (i) methyl acrylate, Pd(OAc)2, P(oꢀtol)3, NEt3, DMF,
120 °C, 2 d; (ii) NaOH, EtOH, H2O, reflux; (iii) ZrCl4, DMF,
TFA, 100 °C, 5 d; (iv) H2BPHV, ZrCl4, DMF, TFA, 100 °C, 5 d.
The solvothermal reaction between ZrCl4 and H2BPV in the
presence of dimethylformamide (DMF) and trifluoroacetic acid
(TFA) at 100 ºC afforded BPVꢀMOF with a UiO framework of
Zr6O4(OH)4(BPV)6 in 40% yield. In contrast, mBPVꢀMOF was
synthesized in 40% yield by heating ZrCl4 with H2BPV and 4,4’ꢀ
bis(carboxyethenyl)ꢀ1,1’ꢀbiphenyl (H2BPHV) (in a 1:2 molar
ratio) in the presence of DMF and TFA at 100 ºC. Similarly,
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CO2H
b)
a)
1
2
3
CO2H
4
5
NO2
TFA, DMF
+ ZrCl4
80 °C
6
7
TFA, DMF
80 °C
+ ZrCl4
8
9
10
CO2H
CO2H
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Zr6O4(OH)4(BPHV)6 [BPHVꢀMOF]
Zr6O4(OH)4(TPHN)6 [TPHNꢀMOF]
c)
d)
BPV-MOF-Ir after borylation
BPV-MOF-Ir after silylation
BPV-MOF-Ir
BPV-MOF
BPV-MOF (simulated)
N
N
N
N
[Ir(COD)(OMe)]2
THF
Ir(COD)(OMe)
=
10
20
30
40
BPV-MOF-Ir
2θ
BPV-MOF
e)
f)
mBPV-MOF-Ir
(after run16 in borylation of indole)
mBPV-MOF-Ir
(after run1 in borylation of indole)
mBPV-MOF-Ir
(after run1 in C-H silylation)
mBPV-MOF-Ir
N
N
N
[Ir(COD)(OMe)]2
THF
mBPV-MOF
[Ir]
=
N
10
20
30
40
mBPV-MOF-Ir
mBPV-MOF
2θ
g)
h)
mPT-MOF-Ir after run 1 in silylation
mPT-MOF-Ir after run 16 in silylation
mPT-MOF-Ir after run 1 in silylation
mPT-MOF-Ir
mPT-MOF (fresh)
(
8a
2g
2g
)
(
)
(
)
N
mPT-MOF (simulated)
N
N
[Ir(COD)(OMe)]2
THF
NO2
NO2
[Ir]
=
N
10
20
30
40
mPT-MOF-Ir
mPT-MOF
2θ
Figure 1. (a) Synthesis and singleꢀcrystal Xꢀray structure of BPHVꢀMOF. (b) Synthesis and single crystal Xꢀray structure of TPHNꢀMOF.
(c) Postsynthetic metalation of BPVꢀMOF. (d) PXRD patterns simulated from the CIF file of BPHVꢀMOF (black) and of BPVꢀMOF
(green), BPVꢀMOFꢀIr (purple), BPVꢀMOFꢀIr recovered from CꢀH silylation of 2a (red), and BPVꢀMOFꢀIr recovered from CꢀH borylation
of mꢀxylene (blue). (e) Postsynthetic metalation of mBPVꢀMOF. (f) PXRD patterns of mBPVꢀMOF (black), mBPVꢀMOFꢀIr (red), mBPVꢀ
MOFꢀIr recovered from CꢀH silylation (blue), and mBPVꢀMOFꢀIr recovered from CꢀH borylation of indole after run 1 (green) and after
run 16 (pink). (g) Postsynthetic metalation of mPTꢀMOF. (h) PXRD patterns simulated from CIF file of TPHNꢀMOF (black) and of mPTꢀ
MOF (blue), mPTꢀMOFꢀIr (purple), mPTꢀMOFꢀIr recovered from CꢀH silylation of 2g after run 1 (red) and after run 16 (green), and mPTꢀ
MOFꢀIr recovered from amine directed CꢀH silylation of 8a after run 1 (pink).
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The postsynthetic metalation of BPVꢀMOF was performed by
tion of a stoichiometric amount of H2, which was identified and
treating BPVꢀMOF with 2.0 equiv of [Ir(COD)(OMe)]2 in THF to
afford BPVꢀMOFꢀIr as a deep purple solid (Figure 1c). Similarly,
mBPVꢀMOFꢀIr and mPTꢀMOFꢀIr were prepared as a deep purple
and deep green solid respectively by the treatment of mBPVꢀMOF
and mPTꢀMOF with 1.0 equiv of [Ir(COD)(OMe)]2 in THF (Figꢀ
ure 1e and 1g), respectively. Inductively coupled plasmaꢀmass
spectroscopy (ICPꢀMS) analyses of Ir/Zr ratio of the digested
metalated MOFs revealed the Ir loadings of 65%, 16% and 20%
with respect to the Zr centers for BPVꢀMOFꢀIr, mBPVꢀMOFꢀIr
and mPTꢀMOFꢀIr, respectively. mPTꢀMOF was also metalated
with [IrCl(COD)]2 in THF to obtain mPTꢀMOFꢀIr(COD)ꢀCl as a
green solid at a 12% Ir loading. Because mBPVꢀMOFꢀIr and
mPTꢀMOFꢀIr only contain 1/3 functionalized linkers, these Ir
loadings correspond to the metalation of 48% and 61% of the
BPV and PT linkers in these mMOFs. The crystallinity of all the
MOFs was maintained upon metalation as shown by similar
PXRD patterns of MOFs and MOFꢀIr materials (Figure 1d, 1f and
1h). BPVꢀMOFꢀIr, mBPVꢀMOFꢀIr and mPTꢀMOFꢀIr have BET
surface area of 106, 563, and 1828 m2/g respectively, and pore
sizes of 5.8, 5.9, and 6.7 Å respectively. The smaller surface areas
and pore sizes of metalated MOFs compared to their pristine anaꢀ
logs are due to the presence of Ir and associated ligands in the
MOF cavities.
We performed homogeneous control experiments in order to
identify the Ir species formed from postsynthetic metalation of the
MOFs. Treatment of [Ir(COD)(OMe)]2 with H2BPV or Me2BPV
at room temperature. afforded (H2BPV)Ir(COD)(OMe) and
(Me2BPV)Ir(COD)(OMe), respectively. The identities of both Ir
complexes were established by NMR spectroscopy and mass
spectrometry. These Ir complexes are airꢀ and waterꢀsensitive, and
rapidly decomposed under MOF digestion conditions. However,
because H2BPV or Me2BPV ligands were completely metalated to
form (H2BPV)Ir(COD)(OMe) or (Me2BPV)Ir(COD)(OMe) at
room temperature, we can infer that the identities of the Ir species
in the metalated MOFs as Ir(L)(COD)(OMe) (L=BPV or PT)
complexes.
BPVꢀMOFꢀIr, mBPVꢀMOFꢀIr and mPTꢀMOFꢀIr are all active
in catalyzing the hydrosilylation of aryl ketones to benzylicsilyl
ethers and subsequent intramolecular orthoꢀsilylation of benꢀ
zylicsilyl ethers to give benzoxasiloles (Table 1).18 Benzoxasiloles
are important in organic synthesis and can be converted to pheꢀ
nols by Tamao−Fleming oxidation18ꢀ19 or to biaryl derivatives by
Hiyama crossꢀcoupling reactions.20 In homogeneous catalysis
pioneered by Hartwig and coworkers, the hydrosilylation of keꢀ
tones was catalyzed by [Ir(COD)(OMe)]2, and the subsequent
intramolecular orthoꢀsilylation of benzylicsilyl ethers was cataꢀ
lyzed by phenathrolineꢀderived Ir(I) complex in presence of norꢀ
borene as the hydrogen acceptor.18, 21 This homogeneous reaction
requires relatively high catalyst loadings and the use of a hydroꢀ
gen acceptor. In MOFꢀIr catalyzed silylation reactions, the hyꢀ
drosilylation of ketones proceeded at room temperature, but the
dehydrogenative orthoꢀsilylation of benzylicsilyl ethers required
elevated temperatures. Screening experiments revealed that the
intramolecular orthoꢀsilylation gave the highest turnover frequenꢀ
cy when the reaction mixture was refluxed in nꢀheptane under
nitrogen atmosphere at 115 ºC (Table S2 and Figure S25, SI). At
0.1 mol % Ir loading, BPVꢀMOFꢀIr provided benzylicsilyl ether
2a in complete conversion upon treatment of acetophenone with
1.05 equiv Et2SiH2 in nꢀheptane for 18 h at room temperature.
Refluxing the resultant mixture at 115 ºC for 8 d afforded correꢀ
sponding benzoxasilole 3a with 72% conversion. Under identical
reaction conditions, 0.1 mol % mBPVꢀMOFꢀIr and mPTꢀMOFꢀIr
gave complete conversions of 2a and afforded 3a in good isolated
yields (Table 1, entries 2 and 4). The dehydrogenative orthoꢀ
silylation of benzylicsilyl ethers was accompanied by the generaꢀ
quantified by GC analysis (Figure S27 , SI). Importantly, no H2ꢀ
acceptor was needed, which represents an improvement over the
reported homogeneous CꢀH silylation reactions in terms of atom
economy. The PXRD patterns of MOFs recovered from the silylaꢀ
tion reactions remained the same as those of freshly prepared
MOFꢀIr precatalysts, indicating that the MOF frameworks are
stable under the catalytic conditions (Figures 1d, 1f, and 1g). The
higher catalytic activities of both mBPVꢀMOFꢀIr and mPTꢀMOFꢀ
Ir compared to BPVꢀMOFꢀIr were also observed for other subꢀ
strates (Table 1; Entries 7ꢀ9, 15ꢀ18, 19ꢀ21). The enhanced activity
of mMOF catalysts compared to BPVꢀMOFꢀIr is likely due to the
presence of more open channels, which facilitates diffusion of
substrates and products through the channels of mMOFs. Directly
refluxing a mixture of acetophenone and Et2SiH2 in nꢀheptane at
115 ºC using 0.01 mol % of mPTꢀMOFꢀIr resulted in the comꢀ
plete conversion of 1a, however, afforded benzoxasilole 3a in a
lower yield (82%), presumably due to the decomposition of the Irꢀ
hydride intermediate generated during the hydrosilylation step at
higher temperatures.
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Table 1. MOF-Ir Catalyzed Tandem Hydrosilylation of
Ketones and Intramolecular ortho-Silylation of Ben-
zylicsilyl Ethers to Prepare Benzoxasilolesa
Et
Et
Si
R2
O
O
H
MOF-Ir
1.05 equiv. Et2SiH2
R2
R2
115 °C, t2
O
Si
Et2
-H2
n-Heptane, 23 °C, t1 = 18 h
R1
R1
R1
1
2
3
Entry
Product
MOFꢀIr catalyst
(mol% loading)
BPVꢀMOF (0.1)
mBPVꢀMOF (0.1)
mPTꢀMOF (1.0)
mPTꢀMOF (0.1)
Time
(t2)
8 d
8 d
24 h
7 d
Yield
(%)b
72
100 (93)
100
Me
1
2
3
4
O
Si
100 (86)
Et2
3a
Me
O
5
6
mBPVꢀMOF (0.1)
mPTꢀMOF (0.1)
5 d
4 d
100 (95)
100 (94)
Si
Me
Et2
3b
Et
7
8
9
BPVꢀMOF (0.1)
mBPVꢀMOF (0.1)
mPTꢀMOF (0.1)
7 d
2.5 d
2.5 d
100
100 (94)
100 (95)
O
Si
Et2
3c
3d
n-Pr
10
11
mBPVꢀMOF (0.1)
mPTꢀMOF (0.1)
5 d
4.5 d
100 (96)
100 (94)
O
Si
Et2
Ph
12
13
14
mBPVꢀMOF (0.1)
mPTꢀMOF (1.0)
mPTꢀMOF (0.1)
3 d
15 h
7 d
100
100 (97)
100
O
Si
Et2
3e
Me
O
15
16
17
18
BPVꢀMOF (0.1)
mBPVꢀMOF (0.1)
mPTꢀMOFꢀIr (1.0)
mPTꢀMOF (0.1)
5 d
26
100
100
3.5 d
15 h
4.5 d
Si
MeO
Et2
100 (89)
3f
Me
19
20
21
22
23
BPVꢀMOF (0.1)
mBPVꢀMOF (0.1)
mPTꢀMOF (0.1)
mPTꢀMOF (0.05)
mPTꢀMOF (0.025)
6 d
40 h
35 h
4 d
100 (96)
100 (96)
100 (94)
100 (91)
76
O
Si
Cl
Et2
3g
8 d
ACS Paragon Plus Environment

Page 5 of 10
Journal of the American Chemical Society
Et
O
Et
Si
H
Cl
O
H
1
2
3
4
5
6
7
8
24
25
mPTꢀMOF (0.1)
mPTꢀMOF (0.1)
3 d
100
100
MOF-Ir
1.05 equiv. Et2SiH2
O
115 °C, t2
O
H
Si
Si
Et2
R
-H2
Et2
n-Heptane, 23 °C, t1 = 24 h
3h
MeO
R
R
5
6
4
Me
2 dc
O
Entry
R
H
MOFꢀIr
mBPVꢀMOFꢀIr
mPTꢀMOFꢀIr
Time (t2) Yield (%)b
Si
1
2
4.5 d
3 d
100
Et2
3i
100 (95)
Me
O
3
4
Cl
Br
mBPVꢀMOFꢀIr
mPTꢀMOFꢀIr
4 d
3.5 d
100 (96)
100 (86)
9
17 dd
S
26
mPTꢀMOF (0.1)
100 (93)
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Si
5
mPTꢀMOFꢀIr
4.5 d
100
Et2
3j
aReaction conditions: MOFꢀIr (0.5 mol % Ir), 4.0 mL nꢀheptane,
aReaction conditions: 5.0 mg of MOFꢀIr (0.1 mol % Ir) or other
loadings as specified, 4.0 mL of nꢀheptane, 115 °C, reflux under
N2. bIsolated yield in the parenthesis. ct1 = 42 h. dt1 = 4 d.
115 °C, reflux under N2. bIsolated yield in the parenthesis.
Remarkably, at a 0.5 mol % Ir loading, mPTꢀMOFꢀIr could be
recovered and reused for the intramolecular orthoꢀsilylation of 2g
at least 15 times without loss of MOF crystallinity (Figure 3 and
Figure 1f). Excellent yields (86ꢀ99%) of the benzoxasilole, 3g,
were obtained consistently in the reuse experiments. Importantly,
3g was obtained in high purity simply by removing the solid cataꢀ
lyst and the organic volatiles (without any other workup). The
heterogeneous nature of mPTꢀMOFꢀIr was further confirmed by
several experiments. The PXRD patterns of mPTꢀMOFꢀIr recovꢀ
ered from the 1st and 16th run remained essentially unchanged
from that of freshly prepared mPTꢀMOFꢀIr (Figure 1h). Additionꢀ
ally, ICPꢀMS analyses showed that the amounts of Ir and Zr
leaching into the supernatant after the 1st run were 2.1% and
0.008%, respectively, and the amounts of leached Ir and Zr after
the 5th run were 0.08% and 0.009%, respectively. Moreover, no
further conversion was detected after removal of mPTꢀMOFꢀIr
during the course of the silylation reaction (Scheme S1, SI). These
results collectively indicate that the mPTꢀMOFꢀIr catalyst is very
stable under the catalytic conditions.
Tandem hydrosilylation of aryl ketones and intramolecular
orthoꢀsilylation reactions catalyzed by mBPVꢀMOFꢀIr and mPTꢀ
MOFꢀIr have a broad substrate scope as shown in Table 1. At 0.1
mol % Ir loading, mixedꢀlinker MOFs gave complete conversions
of both the aryl ketones (1a-j) and the in situ generated benꢀ
zylicsilyl ethers (2a-j) in absence of Hꢀacceptor to afford benzoxꢀ
asiloles (3a-j) in excellent yields (86ꢀ100%). Monoalkyl (3a-d),
aryl (3e), alkoxy (3f and 3i), and halogen (3g-h) substituents were
all tolerated under the reaction conditions. Benzoxasiloles could
also be prepared from secꢀbenzyl alcohols by dehydrocoupling of
alcohols to benzylicsilyl ethers at room temperature, followed by
intramolecular cyclization at 115 ºC. For example, 3c was affordꢀ
ed from 1ꢀphenylꢀ1ꢀpropanol (1c) in 94% and 95% yields for
mBPVꢀMOFꢀIr and mPTꢀMOFꢀIr respectively (Table 1, entries 8
and 9). Additionally, heteroaromatic benzoxasilole (3j) was also
obtained in 93% yield with 0.1 mol % of mPTꢀMOFꢀIr (Table 1,
entry 26). Notably, a turnover number (TON) of 3200 was obꢀ
served for mPTꢀMOFꢀIr with 1g as the substrate (Table 1, entry
23).
Irꢀfunctionalized mixedꢀlinker MOFs are also active in catalyzꢀ
ing hydrosilylation of benzaldehydes (4) and in situ cyclization of
the primary (hydrido)silyl ethers (5) under identical reaction conꢀ
ditions to those for aryl ketones (Table 2). Although longer reacꢀ
tion times were required in both steps, full conversions were obꢀ
served and excellent yields of benzoxasiloles (6) were obtained
with 0.5 mol % mBPVꢀMOFꢀIr and mPTꢀMOFꢀIr catalysts. Noꢀ
tably, both mBPVꢀMOFꢀIr and mPTꢀMOFꢀIr catalysts are signifiꢀ
cantly more active in intramolecular orthoꢀsilylation of benꢀ
zylicsilyl ethers than their homogeneous control analogs. Under
identical conditions, 0.5 mol % of {pth}Ir(COD)(OMe) {pth =
3,8ꢀbis(4ꢀmethoxycarbonylphenyl)phenanthroline} afforded 6b in
only 37% conversion in three days, after which no further converꢀ
sion was observed with further heating. In contrast, the conversion
of 5b proceeded linearly with time until completion in the presꢀ
ence of 0.2 mol % of the mPTꢀMOFꢀIr catalyst (Figure 2a). This
result indicates that mPTꢀMOFꢀIr is at least 7 times more active
than the homogeneous control for the intramolecular silylation
reaction. Time dependent GC conversion curves indicated that
mBPVꢀMOFꢀIr was also at least 3 times more active its homogeꢀ
neous control [bpy(CH=CHCO2Me)2]Ir(COD)(OMe) (Figure 2b).
The higher activities of MOF catalysts strongly support the beneꢀ
ficial effect of active site isolation in the MOF framework, which
prevents any intermolecular deactivation pathways.
b)
a)
mBPV-MOF-Ir (0.05 mol % Ir)
[bpy(CH=CHCO2Me)2] Ir(COD)(OMe)
mPT-MOF-Ir (0.2 mol % Ir)
{pth}Ir(COD)(OMe)
(0.5 mol % Ir)
100
80
60
40
20
0
100
(0.05 mol % Ir)
50
0
0
2
4
6
0
1
2
3
4
time (d)
time (d)
Figure 2. (a) Plots of GC conversion (%) vs time for orthoꢀ
silylation of 5b using mPTꢀMOFꢀIr (0.2 mol %) and
{pth}Ir(COD)(OMe) (0.5 mol %) as catalysts in nꢀheptane at 115
°C. (b) Plots of GC conversion (%) vs time for orthoꢀsilylation of
2g
using
mBPVꢀMOFꢀIr
(0.05
mol
%)
and
[bpy(CH=CHCO2Me)2]Ir(COD)(OMe) (0.05 mol %) as catalysts
in nꢀheptane at 115 °C.
Table 2. mBPV-MOF-Ir and mPT-MOF-Ir Catalyzed Tan-
dem Hydrosilylation of Aldehyde and Intramolecular ortho-
Silylation of Benzylicsilyl Ethers to Prepare Benzoxasilolesa
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 6 of 10
homogeneous catalysis, a number of nitrogen and phosphineꢀ
100
80
60
40
20
0
1
2
3
4
5
6
7
8
based iridium(I) catalysts have been reported and generally biꢀ
pyridylꢀderived catalysts are more active compared to those conꢀ
taining phosphine ligands. Recently, efforts to develop heterogeꢀ
neous borylation catalysts have been made based on iridium(0)
nanoparticles,25 insoluble iridium complex,26 or silicaꢀsupported
catalyst.27 The MOFꢀIr catalyzed borylation reactions were first
screened for optimized conditions such as temperature, solvents,
and in neat arenes (without using a solvent) to obtain the best
results. The screening experiments revealed that the highest turnꢀ
over frequencies were observed when the borylation reactions
were performed in neat arene at 115 ºC or refluxed in nꢀheptane at
115 ºC for solid substrates (Table S3 and S4; SI). Longer reaction
time was required when the reaction mixture was heated above
115 ºC, which is likely due to the instability of active catalytic
species at higher temperatures. Under the optimized conditions,
0.1 mol % BPVꢀMOFꢀIr gave 72% of 5ꢀ(4,4,5,5ꢀTetramethylꢀ
1,3,2ꢀdioxaborolanꢀ2ꢀyl)ꢀmꢀxylene (11a) in 5 d from mꢀxylene
and 100% of 2ꢀ(4,4,5,5ꢀtetramethylꢀ1,3,2ꢀdioxaborolanꢀ2ꢀyl)ꢀ1Hꢀ
indole (11h) from indole in 16 h (Table 4, entries 1 and 15). In
contrast, mBPVꢀMOFꢀIr and mPTꢀMOFꢀIr afforded 11a and 11h
in quantitative yields at much shorter reaction times (Table 4;
entries 2, 4, 16, and 18). mPTꢀMOFꢀIr(COD)ꢀCl was about half as
active in CꢀH borylation as mPTꢀMOFꢀIr. The TPHNꢀMOF treatꢀ
ed with [Ir(COD)(OMe)]2 did not give any activity for benzene
borylation, ruling out the involvement of the Zr6(ꢀ3ꢀO)4(ꢀ3ꢀOH)4
SBUs in arene borylation reactions. The faster reaction rates due
to the presence of more open channels within the mMOFꢀIr cataꢀ
lysts led us to investigate the borylation reactions with a broad
range of substrates. Monoꢀborylated arenes were obtained in exꢀ
cellent yields (94ꢀ100%) for a range of activated and unactivated
arenes (Table 4). Halogenꢀ and alkoxyꢀ functional groups were
well tolerated under the reaction conditions. The regioselectivities
of borylated products are the same as those reported for homogeꢀ
neous Irꢀcatalysts.14a, 23d The borylation occurred at the least steriꢀ
cally hindered CꢀH bonds of the unactivated arenes (Table 4, enꢀ
tries 1ꢀ14) and at the 2ꢀposition of heteroarenes such as indole and
benzo[b]furan (Table 4, entries 15ꢀ20). Notably, pure products
were obtained by simply removing the catalyst via centrifugation
followed by removal of the volatiles. Although both mMOFs
afforded borylated arenes in excellent yields, mBPVꢀMOFꢀIr
displayed superior activity over mPTꢀMOFꢀIr. Importantly, TONs
of 17000 and 9000 were obtained for borylation of mꢀxylene and
indole, respectively, with mBPVꢀMOFꢀIr (Table 1; entries 3 and
17). In these two cases, the leached iridium contents in 5ꢀ(4,4,5,5ꢀ
tetramethylꢀ1,3,2ꢀdioxaborolanꢀ2ꢀyl)ꢀmꢀxylene (11a, 1.50 g, 6.46
mmol) and 2ꢀ(4,4,5,5ꢀtetramethylꢀ1,3,2ꢀdioxaborolanꢀ2ꢀyl)ꢀ1Hꢀ
indole (11h, 0.765 g, 3.15 mmol) were 1.22 ppm and 0.3 ppm,
respectively. Therefore, pure borylated products containing very
low residual iridium in 1 ppm or lower levels could be obtained
without any chromatographic purification.
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
2
4
6
8
10
12
14
16
Run
Figure 3. Plot of yield (%) of benzoxasilole at various runs in
the recycle and reuse of mPTꢀMOFꢀIr (0.5 mol % Ir) for or-
thoꢀsilylation of 2g.
The high activity of mPTꢀMOFꢀIr in hydroxylꢀdirected intraꢀ
molecular silylation of arene CꢀH bonds inspired us to investigate
the analogous silylation reactions directed by an amine group. The
dehydrogenative intramolecular silylation of aromatic CꢀH bonds
of (hydrido)silyl amines would generate azasilolanes. The siliconꢀ
heteroatom bonds in azasilolanes could be further functionalized
via oxidation or halogenations. Recently, Hartwig and coꢀworkers
reported Irꢀcatalyzed secondary amine directed silylation of aroꢀ
matic CꢀH bonds, in which (hydrido)silyl amines, generated in
situ by [Ir(COD)(OMe)]2ꢀcatalyzed dehydrocoupling of benzylaꢀ
mine with Et2SiH2, undergo dehydrogenative silylation in presꢀ
ence of norborene as the hydrogen acceptor by 3,4,7,8ꢀ tetrameꢀ
thylꢀ1,10ꢀphenanthrolineꢀderived iridium catalyst.22 Interestingly,
mPTꢀMOFꢀIr afforded azasilolanes directly from Nꢀmethylbenzyl
amines and Et2SiH2 without employing any Hꢀacceptor. Analoꢀ
gous to hydroxylꢀdirected silylation reactions, 0.5 mol % mPTꢀ
MOFꢀIr provided (hydrido)silyl amines in nꢀheptane at room temꢀ
perature in 24 h. Refluxing the resultant mixture at 115 °C affordꢀ
ed azasilolanes in complete conversions (Table 3). Azasilolanes
9a and 9b were obtained in 92% and 82% yields respectively
(Table 3, entries 1 and 2). In contrast, 0.5 mol % of
{pth}Ir(COD)(OMe) afforded 9a from 8a in only 20% conversion
at 115 °C in nꢀheptane and no further conversion was observed
upon refluxing for longer times. The similar PXRD pattern of
recovered mPTꢀMOFꢀIr to that of freshly prepared catalyst indiꢀ
cates that the MOF remained crystalline and stable under the reacꢀ
tion conditions (Figure 1h).
Table 3. mPT-MOF-Ir Catalyzed Tandem Dehydrocoupling
of N-Methylbenzyl Amines and Intramolecular ortho-
Silylation of (Hydrido)silyl Amines to Azasilolanesa
mPT-MOF-Ir (0.5 mol % Ir)
1.05 equiv. Et2SiH2
R
R
Me
Interestingly, both mMOFs catalysts are significantly more
active in CꢀH borylation of arenes than their homogeneous counꢀ
terparts. Time dependent GC conversion curves indicated that
mBPVꢀMOFꢀIr was also at least 95 times more active than its
homogeneous control [bpy(CH=CHCO2Me)2]Ir(COD)(OMe)
(Figure 4a). [bpy(CH=CHCO2Me)2]Ir(COD)(OMe) had a very
low activity in borylation reaction. At 115 ºC in neat mꢀxylene,
0.05 mol % [bpy(CH=CHCO2Me)2]Ir(COD)(OMe) afforded 8a in
only 9% conversion after 2 days, and then no further conversion
was observed with prolonged heating. However, under identical
conditions, mBPVꢀMOFꢀIr gave 11a with a TON of 17000. mPTꢀ
MOFꢀIr also compares favorably to its homogeneous counterpart,
with at least twice as high activity as its homogeneous control
(Figure S32, SI). Therefore, immobilization of molecular catalysts
in the MOF framework dramatically enhances the overall activity
and stability of the catalysts by preventing bimolecular deactivaꢀ
R
N
115 °C, t
NMe
NHMe
SiEt2
Si
Et2
-H2
n-Heptane, 23 °C, 24 h
H
7
8
9
Entry
1
R
Time (t)
Conversion (%)b
100 (92)
H (9a)
6 d
2
Cl (9b)
10 d
100 (82)
aReaction conditions: mPTꢀMOFꢀIr (0.5 mol % Ir), 4.0 mL nꢀ
heptane, 115 °C, reflux under N2. bNMR yield in the parenthesis.
MOFꢀIr catalysts are also active in dehydrogenative borylation
of aromatic CꢀH bonds using B2(pin)2 (pin = pinacolate) as the
borylating agent.23 Borylation of aryl CꢀH bonds provides aryl
boronates, which are versatile reagents in organic synthesis.24 In
ACS Paragon Plus Environment

Page 7 of 10
Journal of the American Chemical Society
tion pathways. Remarkably, at a 0.5 mol % Ir loading, the MOFꢀIr
amounts of Ir and Zr leaching into the supernatant after the 1st run
were 0.132% and 0.029%, respectively, and after the 5th run were
0.016% and 0.012%, respectively. Moreover, no further converꢀ
sion was detected after removal of mBPVꢀMOFꢀIr from the reacꢀ
tion mixture (Scheme S5, SI). mPTꢀMOFꢀIr could also be recyꢀ
cled 15 times for borylation of mꢀxylene (Figure 4c). The PXRD
of recovered mPTꢀMOFꢀIr after run 17 indicated that the MOF
remained crystalline, which suggests that the deactivation of
mPTꢀMOFꢀIr at run 17 is due to the decomposition of the active
Irꢀcatalyst but not the MOF framework. Additionally, ICPꢀMS
analyses showed that the amounts of Ir and Zr leaching into the
supernatant were 0.042% and 0.038% respectively after the 1st
run, 0.08% and 0.009% respectively after the 5th run, and 0.018%
1
2
3
4
5
6
7
8
catalyst was reused more than 15 times in the borylation of indole
without loss of catalytic activity (Figure 4b) or MOF crystallinity
(Figure 1f). Excellent yields (89ꢀ100%) of 2ꢀ(4,4,5,5ꢀtetramethylꢀ
1,3,2ꢀdioxaborolanꢀ2ꢀyl)ꢀ1Hꢀindole (11h) were obtained consistꢀ
ently in the reuse experiments. Notably, 11h was obtained in high
purity simply by removing the solid catalyst and the organic volaꢀ
tiles. The heterogeneity of mBPVꢀMOFꢀIr was confirmed by sevꢀ
eral experiments. The PXRD patterns of mBPVꢀMOFꢀIr recovꢀ
ered from the 1st and 16th run remained the same as that of freshly
prepared mBPVꢀMOFꢀIr (Figure 1f), indicating that the MOF
catalyst is very stable under the catalytic conditions. The leaching
of Ir and Zr into the supernatant was very low during the course of
the borylation reaction as shown by ICPꢀMS analysis. The
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
and
0.014%
respectively
after
the
10th
run.
Table 4: MOF-Ir catalyzed C-H borylation of arenes.a
O
O
O
B
MOF-Ir
115 °C
2 Ar
+ H2
B B
+
2 Ar-H
O
O
O
11
10
Entry
Substrate
Product
MOFꢀIr catalyst
Ir loading (mol %)
Time Yield (%)b
1c
2c
3c
4c
BPVꢀMOFꢀIr
mBPVꢀMOFꢀIr
mBPVꢀMOFꢀIr
mPTꢀMOFꢀIr
0.1
0.1
0.005
0.1
5 d
72
100 (97)
85
16 h
15 d
32 h
100 (96)
Bpin
5c
6c
mBPVꢀMOFꢀIr
mPTꢀMOFꢀIr
0.1
0.1
16 h
35 h
100 (97)
100 (99)
Bpin
7c
8c
Bpin
mBPVꢀMOFꢀIr
mPTꢀMOFꢀIr
0.1
0.1
16 h
18 h
100
100
9c
mPTꢀMOFꢀIr
0.1
18 h
100
(o:m:p =
0:62:38)
Bpin
Cl
Cl
10c
11c
mBPVꢀMOFꢀIr
mPTꢀMOFꢀIr
0.1
0.1
24 h
30 h
100 (94)
100 (95)
Cl
Cl
Cl
Bpin
Cl
Bpin
Cl
12
mPTꢀMOFꢀIr
1.0
24 h
100
Cl
OMe
OMe
13
14
mBPVꢀMOFꢀIr
mPTꢀMOFꢀIr
0.1
0.1
36 h
2 d
100 (96)
100
MeO
MeO
Bpin
Bpin
15
16
17
18
BPVꢀMOFꢀIr
mBPVꢀMOFꢀIr
mBPVꢀMOFꢀIr
mPTꢀMOFꢀIr
0.1
0.1
0.01
0.1
18 h
5 h
9 d
100
100 (98)
90
N
H
N
H
11 h
100 (94)
Bpin
19
mPTꢀMOFꢀIr
0.5
18 h
100
O
O
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aReaction conditions: MOFꢀIr, 0.508 mmol B2pin2, 1.02 mmol of arene, 3.0 mL of nꢀheptane, 115 °C, reflux under
N2. bIsolated yield in the parenthesis. cNeat arene was used.
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Supporting information
5
6
a)
mBPV-MOF-Ir (0.05 mol % Ir)
[bpy(CH=CHCO2Me)2]Ir(COD)(OMe)
b)
100
100
General experimental section; synthesis and characterization of
BPVꢀMOF, mBPVꢀMOF, mPTꢀMOF, BPVꢀMOFꢀIr, mBPVꢀ
MOFꢀIr, and mPTꢀMOFꢀIr; procedures for BPVꢀMOFꢀIr, mBPVꢀ
MOFꢀIr, and mPTꢀMOFꢀIr catalyzed CꢀH borylation of arenes,
tandem hydrosilylation and intramolecular orthoꢀsilylation of
benzylicsilyl ethers, and tandem dehydrocoupling and intramoꢀ
lecular orthoꢀsilylation of (hydrido)silyl amines; recycle proceꢀ
dure of mBPVꢀMOFꢀIr and mPTꢀMOFꢀIr in CꢀH borylation of
arenes and intramolecular orthoꢀsilylation of benzylicsilyl ethers;
GC analysis conditions for all products. This material is available
free of charge via the Internet at http://pubs.acs.org.
(0.05 mol % Ir)
80
60
40
20
0
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8
9
80
60
40
20
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time (d)
Run
mPT-MOF-Ir
(after run17 in borylation of
mPT-MOF-Ir
(after run1 in borylation of
mPT-MOF-Ir
c)100
d)
m
-xylene)
m-xylene)
80
60
40
20
0
mPT-MOF
AUTHOR INFORMATION
Corresponding Author
wenbinlin@uchicago.edu.
Author Contributions
0
2
4
6
8
10
12
14
16
10
20
30
40
2
θ
Run
†These authors contributed equally.
Figure 4. (a) Plots of GC conversion (%) vs time (h) for C−H
Notes
borylation of mꢀxylene using mBPVꢀMOFꢀIr (0.01 mol %) and
[bpy(CH=CHCO2Me)2]Ir(COD)(OMe) (0.05 mol %) as catalysts
under identical conditions. (b) Plots of GC conversion (%) vs time
(h) for various runs in the recycle and reuse of mBPVꢀMOFꢀIr for
borylation of indole. (c) Plots of GC conversion (%) vs time (h)
for various runs in the recycle and reuse of mPTꢀMOFꢀIr for
borylation of mꢀxylene. (d) PXRD patterns of freshly prepared
mPTꢀMOF (black), mPTꢀMOFꢀIr (red), and mPTꢀMOFꢀIr recovꢀ
ered from CꢀH borylation of mꢀxylene after run 1 (blue) and after
run 17 (green).
The authors declare no competing financial interest.
ACKNOWLEDGMENT
This work was supported by NSF (CHEꢀ1111490) and startup
funds from the University of Chicago. We thank Dr. Michaël
Carboni and Dr. Takahiro Sawano for experimental help, Christoꢀ
pher Poon and Carter W. Abney for performing ICPꢀMS experiꢀ
ments, and Kuangda Lu for taking TEM images. Singleꢀcrystal
diffraction studies were performed at ChemMatCARS (Sector
15), APS, Argonne National Laboratory. ChemMatCARS is prinꢀ
cipally supported by the NSF Divisions of Chemistry and Materiꢀ
als Research (CHEꢀ1346572). Use of the Advanced Photon
Source, an Office of Science User Facility operated for the U.S.
DOE Office of Science by ANL, was supported by the U.S. DOE
under Contract No. DEꢀAC02ꢀ06CH11357.
CONCLUSIONS
We have constructed three porous ZrꢀMOFs (BPVꢀMOF,
mBPVꢀMOF and mPTꢀMOF) of UiOꢀtopology with elongated
bipyridylꢀ and phenanthrylꢀcontaining bicarboxylate linkers. The
straightforward postsynthetic metalation of these UiOꢀMOFs with
[Ir(COD)(OMe]2 afforded highly active and robust singleꢀsite
solid catalysts for three important organic transformations via
directed CꢀH activation: tandem hydrosilylation/orthoꢀsilylation
of aryl ketones and aldehydes, tandem dehydrocoupling/orthoꢀ
silylation reactions of Nꢀmethylbenzyl amines, and borylations of
aromatic CꢀH bonds. In all three reactions, mixedꢀlinker MOF
catalysts (mMOFꢀIr) are much more active than BPVꢀMOF conꢀ
taining only functionalized linkers. We believe that mMOF cataꢀ
lysts have much larger open channels due to the doping of bulky
functionalized linkers and their resulting Ir complexes into less
sterically demanding unfunctionalized linkers, which facilitates
the transport of the substrates and products through the MOF
channels. We have also observed that mMOF catalysts show
much enhanced activities and stability when compared to their
homogenous analogues, likely due to active site isolation in MOF
structures which prevents any intermolecular deactivation pathꢀ
ways. In addition, these solid catalysts can be readily recycled and
reused for more than 15 times. Our work thus introduces a simple
and efficient doping strategy to enlarge the open channels of cataꢀ
lytically active MOFs and highlights the enormous potential of
developing MOF catalysts based on nitrogenꢀdonor ligands for
practical synthesis of fine chemicals.
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