Rhodium catechol containing porous organic polymers: Defined catalysis for single-site and supported nanoparticulate materials

Article abstract of DOI:10.1021/om500136k

A single-site, rhodium(I) catecholate containing porous organic polymer was prepared and utilized as an active catalyst for the hydrogenation of olefins in both liquid-phase and gas-phase reactors. Liquid-phase, batch hydrogenation reactions at 50 psi and ambient temperatures result in the formation of rhodium metal nanoparticles supported within the polymer framework. Surprisingly, the Rh(I) complex is catalytically active and stable for propene hydrogenation at ambient temperatures under gas-phase conditions, where reduction of the Rh(I) centers to Rh(0) nanoparticles requires at least 200-250 °C under a flow of hydrogen gas. After high-temperature treatment, the Rh(0) nanoparticles are active arene hydrogenation catalysts that convert toluene to methylcyclohexadiene at a rate of 9.3 × 10^-3 mol g^-1 h^-1 of rhodium metal at room temperature. Conversely, single-site Rh(I) is an active and stable catalyst for the hydrogenation of propylene (but not toluene) under gas-phase conditions at room temperature.

Full text of DOI:10.1021/om500136k

Article
pubs.acs.org/Organometallics
Rhodium Catechol Containing Porous Organic Polymers: Defined
Catalysis for Single-Site and Supported Nanoparticulate Materials
Steven J. Kraft,† Guanghui Zhang,⊥ David Childers,‡ Fulya Dogan,† Jeffrey T. Miller,†
SonBinh T. Nguyen,§ and Adam S. Hock*,†,∥
†Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
‡Department of Chemical Engineering, University of Illinois at Chicago, Chicago, Illinois 60607, United States
§Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
∥Department of Biological and Chemical Sciences, Illinois Institute of Technology, Chicago, Illinois 60616, United States
⊥College of Chemistry & Molecular Sciences, Wuhan University, Wuhan, Hubei 430072, P. R. China
S
* Supporting Information
ABSTRACT: A single-site, rhodium(I) catecholate containing
porous organic polymer was prepared and utilized as an active
catalyst for the hydrogenation of olefins in both liquid-phase
and gas-phase reactors. Liquid-phase, batch hydrogenation
reactions at 50 psi and ambient temperatures result in the
formation of rhodium metal nanoparticles supported within
the polymer framework. Surprisingly, the Rh(I) complex is
catalytically active and stable for propene hydrogenation at
ambient temperatures under gas-phase conditions, where
reduction of the Rh(I) centers to Rh(0) nanoparticles requires
at least 200−250 °C under a flow of hydrogen gas. After high-
temperature treatment, the Rh(0) nanoparticles are active
arene hydrogenation catalysts that convert toluene to
methylcyclohexadiene at a rate of 9.3 × 10−3 mol g−1 h−1 of rhodium metal at room temperature. Conversely, single-site
Rh(I) is an active and stable catalyst for the hydrogenation of propylene (but not toluene) under gas-phase conditions at room
temperature.
coordination environment that does not have freely homoge-
neous analogues.
INTRODUCTION
■
Current interest in metal containing porous organic polymers
(POPs)1−6 is expanding toward many different applications in
catalysis,7−14 gas storage,6,15−20 and gas separations.12,21−23
This rise in research activity can be attributed to these chemical
and thermal stability of these materials related to MOFs and
more tunable binding environments in comparison to zeolitic
environments. The tunability of these materials is reflected in
recent reports concerning a variety of catalytic reactions,
including hydrogenation,24,25 oxidation,7−9,26 reduction,10,24,27
and photochemical transformations11 with a number of
different metal-containing materials.
Our group is currently studying catalytic POPs containing
metal catecholate functionalities, as typical homogeneous metal
catecholate complexes are frequently catalytically inactive due
to their propensity toward the formation of bis- or tris-chelation
motifs for metal stabilization.28−33 Recent publications within
our group and others have utilized a catechol-containing POP,
POP A2B1 (monomer A, 3,6-linked catechol; monomer B,
para-linked tetraphenylmethane),34 and derivatives of such to
stabilize catalytically active single-site metal centers of Fe,24,27
Ta,25 and La.35 These catalysts are unique because a single
catechol ligand supports the metal complex and represents a
Although rhodium is one of the most rare and costly of the
transition metals, a large amount of catalysis research has been
conducted with it because it often exhibits unique and
extraordinary catalytic activity for hydrogenation, hydro-
formylation, and oxidation reactions.36 Special attention must
be placed on metal speciation when studying Rh catalysis to
avoid confusing rhodium metal for molecular or ionic rhodium
species. This is due to the relative ease of reduction of rhodium
salts and organometallic complexes to rhodium metal.36,37 The
study of the actual catalytic site within heterogeneous materials
is often very challenging and can result in improper
identification. The report herein highlights the use of rhodium
for the hydrogenation of simple olefins and toluene supported
in POP A2B1 for the discrimination of the oxidation state of
rhodium (ionic or metallic) within this polymer support under
reaction conditions.
Received: February 6, 2014
Published: May 8, 2014
© 2014 American Chemical Society
2517
dx.doi.org/10.1021/om500136k | Organometallics 2014, 33, 2517−2522

Organometallics
Article
Figure 1. Synthesis of [(COD)Rh(CAT)]2-POP (p = extended polymer network).
Figure 2. X-ray absorption measurements of [(COD)Rh(CAT)]2-POP and standards: (orange line) as-prepared material; (green line) [{t-
BuNC(Ph)CN-t-Bu}Rh(COD)]; (purple line) [(COD)2Rh][BF4]; (black line) Rh foil; (red line) Rh2O3. Calculated models are given in Table 1
material is in the 1+ oxidation state (Figure 2 (left) and
Table 1). For clarity, the spectrum for [(COD)Rh(CAT)]2-
RESULTS AND DISCUSSION
■
Addition of the convenient Rh(I) source [{t-BuNC(Ph)CN-t-
Bu}Rh(COD)]38 (where COD is 1,5-cyclooctadiene and{t-
BuNC(Ph)CN-t-Bu} is N,N′-di-tert-butylphenylamidinate) to a
suspension of POP A2B1 in diethyl ether resulted in complete
uptake of the rhodium complex within 24 h. Analysis of the
washings by 1H NMR spectroscopy reveals 95% of the expected
[t-BuNC(Ph)CN(H)t-Bu] upon Rh ligation. Upon further
washing, the remaining 5% is recovered. Importantly, the
addition of excess [{t-BuNC(Ph)CN-t-Bu}Rh(COD)] to
[(COD)Rh(CAT)]2-POP (Figure 1) does not result in any
appreciable weight change, after washing the solid to remove
entrained rhodium precursor, corroborating full metalation of
the catechol sites. Attempts to generate a homogeneous
rhodium catechol complex in solution by the addition of 1
equiv of 3,6-di-tert-butylcatechol to 1 equiv of [{t-BuNC(Ph)-
CN-t-Bu}Rh(COD)] resulted in the formation of a dinuclear
rhodium complex. This complex is formed even with mixing
the reagents precooled to −78 °C.
Table 1. XAS Results for [(COD)Rh(CAT)]2-POP under
Inert and Oxidizing Conditions
edge energy,
keV
oxidn
state
treatment
CN
R, Å
[(COD)Rh(CAT)]2-POP
(COD)Rh[tBuNC(Ph)NtBu]
[(COD)2Rh][BF4]
Rh foil
23.2273
23.2266
23.2270
23.2200
23.2295
Rh(I)
Rh(I)
Rh(I)
Rh(0)
Rh(III)
4.0
6.0
NA
12
6
2.05
2.08
NA
2.69
2.05
Rh2O3
POP in air is not shown, as the spectrum is identical with the
spectrum obtained under inert conditions. Although metal
catecholate complexes are well-known to undergo oxidation of
either the metal or ligand under mildly oxidizing conditions,
these data indicate that the Rh(I) is not oxidized after brief
exposure to ambient air.
In order to gain insight into the Rh oxidation state and
coordination environment at the Rh centers, X-ray absorption
spectroscopy data (XAS) were obtained under inert conditions
and in air at ambient temperature and pressure. As rhodium
XAS does not contain a discernible pre-edge feature, the energy
of the first derivative of the XANES curve of [(COD)Rh-
(CAT)]2-POP was compared to those of Rh(I) and Rh(III)
standards, clearly showing that the as-prepared rhodium
Analysis of the extended X-ray absorption fine structure
(EXAFS; Figure 2 (right)) reveals that [(COD)Rh(CAT)]2-
POP consists of four-coordinate rhodium centers with average
bond distances of 2.05 Å. Comparisons of coordination
numbers and average bond lengths are given in Table 1.
Such analysis indicates that the Rh centers are in a four-
coordinate environment bound to an anionic oxyphenol, with a
dative η2-olefin COD interaction. Conventional counting of
2518
dx.doi.org/10.1021/om500136k | Organometallics 2014, 33, 2517−2522

Organometallics
Article
organometallic complex coordination numbers would dictate
that a single olefin interaction takes up one coordination site;
however, in comparison with the coordination number of the
precursor, [{t-BuNC(Ph)CN-t-Bu}Rh(COD)], COD olefin
interactions are counted as two neighboring atoms and not
one per olefin bond. This is because the underlying physics of
the XAS experiment probes the nature and number of
coordinated atoms as a whole39,40 and both C atoms of the
olefin are detected in the extended X-ray absorption fine
structure (EXAFS).
(CAT)]2-POP. As mild reduction of rhodium complexes to
rhodium metal has been well established,36,37,45,46 a color
change from orange to black is indicative of such phenomena.
Analysis by scanning transmission electron microscopy
(STEM) spectroscopy shows 1.5−7.0 nm particles of rhodium
metal with a mean size of 3.4 1.0 nm (Figure 4) after liquid-
phase batch reactions were performed, and the material
Rh(NP)(CAT-POP) (NP = nanoparticle) was isolated. Such
reduction is typical of supported Rh complexes in solution.17,18
Additionally, a similar reduction of metal occurs in the
hydrogenation of olefins (i.e., cyclohexene and tetramethyl-
ethylene) and benzonitrile under identical reaction conditions.
To determine the source of nanoparticle formation during
liquid-phase hydrogenation reactions of toluene and unsatu-
rated substrates in THF-d8, the reactions were performed in
deuterated cyclohexane. Upon a change in solvent a drastic
increase in reaction completion time to 8 h occurs for the
hydrogenation of toluene at 50 psi of H2. Additionally,
reactions performed in THF-d8 at 50 psi of H2 lose ∼10 psi
of H2 within 1.5 h, indicative of an induction period for
nanoparticle formation. Alternatively, such a pressure con-
sumption does not occur for reactions with deuterated
cyclohexane until ∼4 h of reaction time, indicating that
solvents play a major role in the time of reduction of
[(COD)Rh(CAT)]2-POP to nanoparticles. Indeed, when the
reaction in deuterated cyclohexane is halted before the
consumption of ∼10 psi of H2 (at 3 h reaction time),
[(COD)Rh(CAT)]2-POP is still orange with no conversion of
toluene to methylcyclohexane. These data may seem contra-
dictory, but it is reasonable to hypothesize that the more
coordinating solvent THF-d8 helps to reduce the energy barrier
to rhodium metal reduction. However, solvent alone is not
sufficient for Rh reduction, since [(COD)Rh(CAT)]2-POP
treated with 50 psi of H2 in only THF-d8 with no aromatic
substrate present does not reduce to rhodium metal: i.e. there is
no visual change in the material and no particles are observed
by STEM. Thus, while coordinating solvent aids in the
reduction of rhodium to metal, the substrate is also necessary
for the reduction of rhodium to metal under liquid-phase
reaction conditions.
Isolated Rh(I) complexes with only one olefin of the COD
bound are rare,41,42 as these complexes typically contain
chelating COD moieties. However, one of these complexes,
(η2-1,2,5,6-cyclooctadiene){η2-[bis(diisopropylamino)-
phosphino][2,6-bis(trifluoromethyl)phenyl]carbene}rhodium
chloride,41 was characterized by 13C NMR spectroscopy and
contains a resonance at 71.7 ppm assigned to the olefin carbons
bound to the rhodium center. For comparison and direct
evidence of η2-COD coordination to the Rh centers, solid-state
(SS) 1H and 13C NMR spectroscopy was performed for
1
[(COD)Rh(CAT)]2-POP. The SS H NMR data (Figure S2,
Supporting Information) reveals an upfield shift of the aromatic
protons within the material consistent with Rh(I) coordination
to catechol sites. Resonances for the COD protons are
observed but are rather broad and nondiscernible as to the
number of varied electronic environments. However, the SS
13C NMR spectrum (Figure 3; a fully deconvoluted spectrum is
Because liquid-phase hydrogenation reactions of toluene
produced nanoparticles with solvent-dependent formation
kinetics, we also tested the hydrogenation of propene and
toluene under gas-phase and solvent-free plug-flow hydro-
genation conditions. Propene hydrogenation was performed
first as a test of the material to perform hydrogenation of a
simple olefin. The results obtained at ambient temperature are
summarized in Table 2. A slight induction period occurs for the
material over the course of 2.5 h, probably due to the removal
of entrained solvent molecules in the POP framework, but the
activity remains stable for over 24 h on stream at maximum
conversion with a TOF of 22.5 h−1, assuming all rhodium(I)
centers are active (or 2.2 × 10−3 mol h−1 g−1). Exposure to
oxygen and reentry into catalysis does not result in oxidation of
the Rh centers or catalyst deactivation, but the conversion
tested over three recycling periods remains the same. In
accordance with Bayram et al.,47 poisoning studies were
attempted with PMe3 to determine the actual number of active
rhodium centers under reaction conditions. However, addition
of PMe3 to [(COD)Rh(CAT)]2-POP results in leeching of
rhodium(I) out of the polymer, not allowing such studies, thus
resulting in the assumption that all rhodium centers are active
for hydrogenation.
1
Figure 3. Solid-state H/13C cross-polarized NMR spectra overlay of
POP A2B1 and [(COD)Rh(CAT)]2-POP, highlighting the COD−Rh
association.
given by Figure S3 in the Supporting Information) shows
clearly defined resonances for olefin carbons bound to Rh(I) at
70.7 ppm consistent per the previous report.41 The unbound
olefinic carbon resonances are observed at 130.6 ppm, and this
asymmetry in the SS NMR spectrum corroborates the XAFS
analysis describing Rh(I) centers with η2-COD interactions.
With a firm picture of the precatalyst Rh structure and the
recent development of hydrogenation catalysts contained
within porous materials,43,44 catalytic activity toward the
hydrogenation of the simple arene toluene was explored.
Reactions were first performed in deuterated tetrahydrofuran
(THF-d8) under a 50 psi H2 atmosphere at ambient
temperature, where full conversion to methylcyclohexane was
observed within 4 h. However, upon reaction completion, a
color change from orange to black occurred for [(COD)Rh-
2519
dx.doi.org/10.1021/om500136k | Organometallics 2014, 33, 2517−2522

Organometallics
Article
Figure 4. (top) Representative STEM images of Rh(NP)(CAT-POP) as prepared (left) and after liquid-phase batch hydrogenation reactions of
toluene with [(COD)Rh(CAT)]2-POP in THF-d8 (middle and right). (bottom) Graph of particle size distribution counting for this material.
mixture of propylene and hydrogen. All three of these
experiments resulted in no change of the spectrum of the
material, as shown in Figure 1, indicating that Rh(I) activates
H2 without the formation of a Rh(III) intermediate or the
equilibrium lies far to the Rh(I) oxidation state. Moreover, XAS
does not show any reduction of the metal at ambient
temperature or up to 175 °C with reactant gases. These
observations are in contrast to those of Gates’ Rh(III) species
Rh(allyl)2SiO2,37 which reduces to rhodium metal after 5 h of
H2 exposure on stream at ambient temperature.
Table 2. Propylene Hydrogenation Results for Plug-Flow
Reactions with [(COD)Rh(CAT)]2-POP
time (min)
Rh TOFav at room temp (h−1
)
0
15.9
20.3
22.1
22.5
60
150
a
max conversion
a
24 hours on-stream.
Analysis of [(COD)Rh(CAT)]2-POP by XAS at elevated
temperatures under hydrogen gas (3.5% in helium) revealed
that the formation of nanoparticles does not occur below 200
°C. Complete conversion to nanoparticles occurs in 30 min at
250 °C to generate Rh(NP)(CAT-POP), as shown in Figure 5.
The gas-phase hydrogenation of propene with [(COD)Rh-
(CAT)]2-POP is rapid, and there is no change in color;
however, visual observation does not preclude the possibility of
reduction of the Rh(I) to Rh(0). Thus, the catalyst was
analyzed by in situ XAS with hydrogen, propylene, and a
Figure 5. X-ray absorption measurements of [(COD)Rh(CAT)]2-POP and Rh(NP)CAT-POP: (orange line) as-prepared material; (black solid
line) Rh foil; (black dashed line) nanoparticle-containing material.
2520
dx.doi.org/10.1021/om500136k | Organometallics 2014, 33, 2517−2522

Organometallics
Article
A comparison of the XAFS spectrum (Figure 5 (right)) with
the Rh foil indicates the presence of nanoparticles ∼5 nm in
size, which corroborates the particle sizes measured by STEM
of [(COD)Rh(CAT)]2-POP after batch hydrogenation re-
actions.
are easily reduced to Rh(0) nanoparticles, which have high
hydrogenation activity for olefins and arenes. The reducibility
of Rh(I) in the liquid phase is dependent on both solvent and
substrate; however, under gas-phase conditions Rh(I) is the
active catalyst species for olefin hydrogenation.
However, it is still possible that a small percent (<5%) of the
rhodium centers, which is below the detection limit of XAS,
have reduced to metal and are the catalytically active species for
olefin hydrogenation in the gas phase. The ability of Rh(0)
nanoparticles to catalytically saturate aromatics provides a
convenient way to test for the onset of metal reduction. Thus,
the Rh(I) single-site catalyst [(COD)Rh(CAT)]2-POP under
conditions where it rapidly hydrogenates propene was also
tested for toluene hydrogenation in the gas phase: i.e., without
solvent. A saturator was attached to the plug-flow system filled
with toluene. The reaction was run at ambient temperature
with a flow of 15 mL/min of 4% H2/96% Ar through the
toluene saturator at 22 Torr. For the same [(COD)Rh-
(CAT)]2-POP catalyst used for propylene hydrogenation, there
was no toluene hydrogenation at room temperature. After high-
temperature reduction of the Rh(I) metal centers to nano-
particles, the catalyst was cooled to room temperature, where
Rh(NP)(CAT-POP) converted toluene quantitatively at 25 °C
to methylcyclohexadiene (TOF of 9.3 × 10−3 mol g−1 h−1).
Methylcyclohexadiene was observed as the product because the
current reactor setup only allows the ratio of H2 to toluene to
be approximately 1:1 under steady-state conditions at this
temperature. Finally, infrared analysis of the Rh(NP)(CAT-
POP) catalyst after toluene saturation shows that the CC
region is unchanged. Thus, the Rh NPs within the polymer
pores are unable to hydrogenate the bulk POP network.
Given the propensity for POP materials to entrain guest
molecules, the effect of physisorbed toluene on the reduction
and catalysis was explored. Interestingly, the toluene is not
removed by the high-temperature H2 treatment used to reduce
the Rh(I) to nanoparticles, but toluene does not appear to
affect the reduction temperature. Presumably, the entrained
toluene concentration is not high enough to produce a truly
“solvated” environment. Furthermore, entrained toluene in the
porous material is saturated by flowing hydrogen through the
Rh(NP)(CAT-POP), resulting in the release of fully converted
methylcyclohexane in flowing H2. These results are consistent
with our assertion that Rh(I) centers are active for room-
temperature, gas-phase propylene hydrogenation and that
Rh(0) NPs are not the active catalytic material in this case.
In liquid-phase hydrogenation with high concentrations of
solvent, Rh(I) centers are much more easily reduced to
nanoparticles, perhaps by an autocatalytic mechanism.48
ASSOCIATED CONTENT
* Supporting Information
Text and figures giving full details of the syntheses and
procedures used and characterization data. This material is
available free of charge via the Internet at http://pubs.acs.org.
■
S
AUTHOR INFORMATION
Notes
The authors declare no competing financial interest.
■
ACKNOWLEDGMENTS
■
The work at Argonne National Laboratory was supported by
the U.S. Department of Energy, Office of Basic Energy
Sciences, Chemical Sciences, under Contract DE-AC-02-06-
CH11357. A.S.H. thanks the Illinois Institute of Technology for
startup funding support. Use of the Advanced Photon Source is
supported by the U.S. Department of Energy, Office of Science
and Office of Basic Energy Sciences, under contract DE-AC-02-
06-CH11357. Materials Research Collaborative Access Team
(MRCAT, Sector 10 μB) operations are supported by the
Department of Energy and the MRCAT member institutions.
REFERENCES
■
(1) Yuan, S.; Desiree, W.; Mason, A.; Reprogle, B.; Ferrandon, M. S.;
Yu, L.; Liu, D.-J. Macromol. Rapid Commun. 2012, 33, 407.
(2) Kaur, P.; Hupp, J. T.; Nguyen, S. T. ACS Catal. 2011, 1, 819.
(3) Yuan, S.; Dorney, B.; White, D.; Kirklin, S.; Zapot, P.; Yu, L.; Liu,
D.-J. Chem. Commun. 2010, 4547.
(4) Farha, O. K.; Bae, Y.-S.; Hauser, B. G.; Spokoyny, A. M.; Snurr, R.
Q.; Mirkin, C. A.; Hupp, J. T. Chem. Commun. 2010, 46, 1056.
(5) Yuan, S.; Kirklin, S.; Dorney, B.; Liu, D.-J.; Yu, L. Macromolecules
2009, 42, 1554.
(6) Cooper, A. I. Adv. Mater. 2009, 21, 1291.
(7) Modak, A.; Mondal, J.; Bhaumik, A. Appl. Catal. A: Gen. 2013,
459, 41.
(8) Saha, B.; Gupta, D.; Abu-Omar, M. M.; Modak, A.; Bhaumik, A. J.
Catal. 2013, 299, 316.
(9) Shultz, A. M.; Farha, O. K.; Hupp, J. T.; Nguyen, S. T. Chem. Sci.
2011, 2, 686.
(10) Jiang, J.-X.; Wang, C.; Laybourn, A.; Hasell, T.; Clowes, R.;
Khimyak, Y. Z.; Xiao, J.; Higgins, S. J.; Adams, D. J.; Cooper, A. I.
Angew. Chem. 2011, 50, 1072.
(11) Xie, Z.; Wang, C.; de Krafft, K. E.; Lin, W. J. Am. Chem. Soc.
2011, 133, 2056.
(12) Jiang, J.-X.; Cooper, A. I. Top. Curr. Chem. 2010, 293, 1.
(13) Zhang, Y.; Riduan, S. N. Chem. Soc. Rev. 2012, 41, 2083.
(14) Ma, L.; Wanderley, M. M.; Lin, W. ACS Catal. 2011, 1, 691.
(15) Xie, L.-H.; Suh, M. P. Chem. Eur. J. 2013, 19, 11800.
(16) Rabbani, M. G.; Reich, T. E.; Kassab, R. M.; Jackson, K. T.; El-
Kaderi, H. M. Chem. Commun. 2012, 48, 1141.
(17) Rabbani, M. G.; El-Kaderi, H. M. Chem. Mater. 2011, 1650.
(18) Yuan, D.; Lu, W.; Zhou, D.; Zhou, H.-C. Adv. Mater. 2011, 23,
3723.
(19) Ben, T.; Ren, H.; Ma, S.; Cao, D.; Lan, J.; Jing, X.; Wang, W.;
Xu, J.; Deng, F.; Simmons, J.; Qiu, S.; Zhu, G. Angew. Chem. 2009, 48,
9457.
(20) Thomas, A.; Kuhn, P.; Weber, J.; Titirici, M.-M.; Antonietti, M.
Macromol. Rapid Commun. 2009, 30, 221.
CONCLUSION
■
The studies reported herein indicate that site-isolated Rh(I)
centers of [(COD)Rh(CAT)]2-POP are active toward the
hydrogenation of propylene to propane under vapor-phase
plug-flow reaction conditions with a TOF of 22.5 h−1 or 2.2 ×
10−3 mol h−1 g−1. The single-site Rh(I) catechol POP is
thermally robust, resulting in no change in catalytic activity
after treatment to 175 °C. Under gas-phase plug-flow
conditions the Rh(I) centers are not active for arene
hydrogenation. These single-site Rh(I) catalysts reduce to
Rh(0) nanoparticles readily at 250 °C under H2 and are then
active for the hydrogenation of toluene to methylcyclohex-
adiene with a TOF of 9.3 × 10−3 mol g−1 h−1 at 25 °C. Single-
site Rh(I) centers under batch (solution) reaction conditions
(21) Lu, W.; Yuan, D.; Sculley, J.; Zhao, D.; Krishna, R.; Zhou, H.-C.
J. Am. Chem. Soc. 2011, 133, 18126.
2521
dx.doi.org/10.1021/om500136k | Organometallics 2014, 33, 2517−2522

Organometallics
Article
(22) Farha, O. K.; Spokoyny, A. M.; Hauser, B. G.; Bae, Y.-S.; Brown,
S. E.; Snurr, R. Q.; Mirkin, C. A.; Hupp, J. T. Chem. Mater. 2009, 21,
3033.
(23) McKeown, N. B.; Budd, P. M. Chem. Soc. Rev. 2006, 35, 675.
(24) Kraft, S. J.; Hu, B.; Zhang, G.; Miller, J. T.; Hock, A. S. Eur. J.
Inorg. Chem. 2013, 2013, 3972.
(25) Tanabe, K. K.; Siladke, N. A.; Broderick, E. M.; Kobayashi, T.;
Goldston, J. F.; Weston, M. H.; Farha, O. K.; Hupp, J. T.; Pruski, M.;
Mader, E. A.; Johnson, M. J. A.; Nguyen, S. T. Chem. Sci. 2013, 4,
2483.
(26) Mackinstosh, H. J.; Budd, P. M.; McKeown, N. B. J. Mater.
Chem. 2008, 18, 573.
́
(27) Kraft, S. J.; Sanchez, R. H.; Hock, A. S. ACS Catal. 2013, 3, 826.
(28) Mialane, P.; Tchertanov, L.; Banse, F.; Sainton, J.; Girerd, J. J.
Inorg. Chem. 2000, 39, 2440.
(29) Raymond, K. N.; Isied, S. S.; Brown, L. D.; Fronczek, F. R.;
Nibert, J. H. J. Am. Chem. Soc. 1976, 98, 1767.
(30) Pierpont, C. G.; Lange, C. W. In Progress in Inorganic Chemistry;
Wiley: Hoboken, NJ, 2007; Vol 57, p 331.
(31) Pierpont, C. G. Inorg. Chem. 2011, 50, 9766.
(32) Comba, P.; Wadepohl, H.; Wunderlich, S. Eur. J. Inorg. Chem.
2011, 2011, 5242.
(33) Halder, P.; Paria, S.; Paine, T. K. Chem. Eur. J. 2012, 18, 11778.
(34) Weston, M. H.; Farha, O. K.; Hauser, B. G.; Hupp, J. T.;
Nguyen, S. T. Chem. Mater. 2012, 24, 1292.
(35) Totten, R. K.; Weston, M. H.; Park, J. K.; Farha, O. K.; Hupp, J.
T.; Nguyen, S. T. ACS Catal. 2013, 3, 1454.
(36) Guerro, M.; Than Chau, N. T.; Noel, S.; Denicourt-Nowicki, A.;
̈
Hapiot, F.; Roucoux, A.; Monflier, E.; Philippot, K. Curr. Org. Chem.
2013, 17, 364.
(37) Foley, H. C.; DeCanio, S. J.; Tau, K. D.; Chao, K. J.; Onuferko,
J. H.; Dybowski, C.; Gates, B. C. J. Am. Chem. Soc. 1983, 105, 3074.
(38) Matioszek, D.; Saffon, N.; Sotiropoulos, J.-M.; Miqueu, K.;
́
Castel, A.; Escudie, J. Inorg. Chem. 2012, 51, 11716.
(39) Nelson, R. C.; Miller, J. T. Catal. Sci. Technol. 2012, 2, 461.
(40) Singh, J.; Lamberti, C.; van Bokhoven, J. A. Chem. Soc. Rev.
2010, 39, 4754.
(41) Despagnet, E.; Miqueu, K.; Gornitzka, H.; Dyer, P. W.;
Bourissou, D.; Bertrand, G. J. Am. Chem. Soc. 2002, 124, 11834.
(42) Sanger, A. R. Can. J. Chem. 1983, 61, 2214.
(43) Genna, D. T.; Wong-Foy, A. G.; Matzger, A. J.; Sanford, M. S. J.
Am. Chem. Soc. 2013, 135, 10586.
(44) Nickerl, G.; Stoeck, U.; Burkhardt, U.; Senkovska, I.; Kaskel, S. J.
Mater. Chem. A 2014, 2, 144.
(45) Mateos-Pedrero, C.; Blerot, B.; Soria, M. A.; Gonzal
S. R.; Ruiz, P. Catal. Today 2013, 203, 176.
(46) Yuan, Y.; Yan, N.; Dyson, P. J. ACS Catal. 2012, 2, 1057.
́ ́
ez-Carrazan,
(47) Bayram, E.; Lu, J.; Aydin, C.; Uzun, A.; Browning, N. D.; Gates,
B. C.; Finke, R. G. ACS Catal. 2012, 2, 1947.
(48) Finney, E. E.; Finke, R. G. Chem. Mater. 2008, 20, 1956.
2522
dx.doi.org/10.1021/om500136k | Organometallics 2014, 33, 2517−2522