Well-Defined Rhodium-Gallium Catalytic Sites in a Metal-Organic Framework: Promoter-Controlled Selectivity in Alkyne Semihydrogenation to E-Alkenes

Article abstract of DOI:10.1021/jacs.8b08550

Promoters are ubiquitous in industrial heterogeneous catalysts. The wider roles of promoters in accelerating catalysis and/or controlling selectivity are, however, not well understood. A model system has been developed where a heterobimetallic active site comprising an active metal (Rh) and a promoter ion (Ga) is preassembled and delivered onto a metal-organic framework (MOF) support, NU-1000. The Rh-Ga sites in NU-1000 selectively catalyze the hydrogenation of acyclic alkynes to E-alkenes. The overall stereoselectivity is complementary to the well-known Lindlar's catalyst, which generates Z-alkenes. The role of the Ga in promoting this unusual selectivity is evidenced by the lack of semihydrogenation selectivity when Ga is absent and only Rh is present in the active site.

Full text of DOI:10.1021/jacs.8b08550

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Article
Well-Defined Rh-Ga Catalytic Sites in a Metal-Organic Framework:
Promoter-Controlled Selectivity in Alkyne Semi-Hydrogenation to E-Alkenes
Sai Puneet Desai, Jingyun Ye, Jian Zheng, Magali S. Ferrandon, Thomas E. Webber, Ana E. Platero-Prats,
Jiaxin Duan, Paula Garcia-Holley, Donald M. Camaioni, Karena W Chapman, Massimiliano Delferro, Omar K.
Farha, John L. Fulton, Laura Gagliardi, Johannes A Lercher, R. Lee Penn, Andreas Stein, and Connie C Lu
J. Am. Chem. Soc., Just Accepted Manuscript • DOI: 10.1021/jacs.8b08550 • Publication Date (Web): 23 Oct 2018
Downloaded from http://pubs.acs.org on October 24, 2018
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Well-Defined Rh-Ga Catalytic Sites in a Metal-Organic Framework: Promoter-Controlled
Selectivity in Alkyne Semi-Hydrogenation to E-Alkenes
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Sai Puneet Desai, Jingyun Ye, Jian Zheng, Magali S. Ferrandon, Thomas E. Webber, Ana E. Platero-
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Prats, Jiaxin Duan, Paula Garcia-Holley, Donald Camaioni, Karena W. Chapman, Massimiliano
Delferro, Omar K. Farha, John L. Fulton, Laura Gagliardi, Johannes A. Lercher, R. Lee Penn,
Andreas Stein and Connie C. Lu *
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1,
1. Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, United States
2. Supercomputing Institute, and Chemical Theory Center, University of Minnesota, Minneapolis, Minnesota 55455,
United States
. Institute for Integrated Catalysis, and Fundamental and Computational Science Directorate, Pacific Northwest
National Laboratory, Richland, Washington 99352, United States
. Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, IL, USA
. X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, United
States
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. Department of Inorganic Chemistry, Universidad Autónoma de Madrid, Spain
. Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
. Department of Chemistry, Faculty of Science, King Abdulaziz University, Jeddah, Saudi Arabia
. Department of Chemistry and Catalysis Research Institute, Technische Universität München, 85748 Garching,
Germany
Abstract
Promoters are ubiquitous in industrial heterogeneous catalysts. The wider roles of promoters in
accelerating catalysis and/or controlling selectivity are, however, not well understood. A model system
has been developed where a heterobimetallic active site comprising an active metal (Rh) and a promoter
ion (Ga) are preassembled and delivered onto a metal-organic framework (MOF) support, NU-1000. The
Rh-Ga sites in NU-1000 selectively catalyze the hydrogenation of acyclic alkynes to E-alkenes. The
overall stereoselectivity is complementary to the well-known Lindlar’s catalyst, which generates Z-
alkenes. The role of the Ga in promoting this unusual selectivity is evidenced by the lack of semi-
hydrogenation selectivity when Ga is absent and only Rh is present in the active site.
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Introduction
Heterogeneous transition-metal catalysts are often enhanced by additive elements or ions, which are by
themselves not catalytically active. These so-called promoters are ubiquitous in industrial heterogeneous
catalysts and ensure the economic viability of most large-scale chemical processes.1-7 However, the
fundamental understanding of how promoters function is limited, hindering the progress of rationally
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designed solid catalysts. We have introduced a simple model system, whereby bimetallic active sites are
preassembled in a dinucleating ligand scaffold and delivered onto NU-1000,9,10 a metal-organic
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framework (MOF) consisting of Zr -oxide nodes and tetrakis(p-benzoate)pyrene linkers. The large 31 Å
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pore diameter of the larger channels in NU-1000 permit easy entry of the bimetallic complexes, which
anchor evenly throughout the MOF particle. These functionalized MOFs, if modular, would allow us to
draw and test structure-function hypotheses that are potentially relevant to metal-promoter interactions in
catalysis. The focus of this work is a bimetallic Rh-Ga active site that is installed post-synthetically onto
NU-1000. This catalytic material exhibits key advantages of both homo- and heterogeneous catalysts:
tunability, uniformity, site-isolation, and recyclability.12-19 Notably, the single-site nature of the Rh-Ga
catalyst has allowed us to elucidate a critical structure-function relationship: the close proximity of Rh
and Ga engenders the selective hydrogenation of alkynes to E-alkenes. By comparison, the single Rh site
generates alkenes and alkane non-selectively.
The chemo- and stereoselective synthesis of alkenes via alkyne hydrogenation has important
applications in the pharmaceutical and polymer industries.20,21 To generate a specific alkene cleanly,
catalysts must preclude formation of both the alkane and the other alkene isomer. Another challenge for
catalyst development is the trade-off between selectivity and activity. For ~50 years, Lindlar’s catalyst
concoction of Pd metal, CaCO , Pb or Ag ions, and quinoline, has been the choice catalyst system for the
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semi-hydrogenation of alkynes to Z-alkenes.6,22 Despite recent advances in single-atom surface-alloy and
intermetallic catalysts for selective alkyne semi-hydrogenations23-31, a similarly versatile catalyst for E-
selective alkenes has yet to be fully realized.32-39 To date, the best single heterogeneous catalyst,
Rh Sb/SiO , hydrogenates diphenylacetylene to E-stilbene in 58% yield, along with the alkane (~38%)
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and Z-stilbene (~4%).40-42 Hence, the activity/selectivity trade-off, the lack of substrate scope, and catalyst
instability all inspire further catalyst development. Here, the MOF-supported Rh-Ga catalyst was tested
using a broad swath of substrates and demonstrated excellent alkyne conversion and high selectivity for
acyclic (E)-alkenes.
Results and Discussion
Synthesis and characterization of 1 and 2
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Post-synthetic grafting of RhGa(py tren) onto NU-1000 was achieved by soaking the MOF in a benzene
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solution of (py tren)GaRhX (X = Me or OPh, Fig. 1a) to afford RhGa(py tren)@NU-1000 (1). Based on a
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host of physicochemical methods, the Rh-Ga complex is selectively grafted onto the MOF nodes with a
nearly ideal stoichiometry of one Rh-Ga complex per Zr -node. ICP-AES analyses of 1 revealed Rh and
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Ga metal loadings of 3.3 wt% and 2 wt% respectively, and a Zr:Rh:Ga mole ratio of 6:1.07:1.01. The
grafting of (H py tren)Rh(C H )OPh onto NU-1000 is similarly selective, affording the Rh-only
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analogue, Rh(C H )(κ -H py tren)@NU-1000 (2), where the Rh loading is 3.5 wt% and the Zr:Rh mole
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ratio is 6:1.20. Powder X-ray diffraction studies and N sorption isotherms further confirm the
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crystallinity and porosity of 1 (1545 cm /g) and 2 (1637 cm /g), cf. 1990 cm /g for NU-1000 (Fig. 1c).
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The H NMR spectra of D SO -digested 1 and 2 each shows D py tren in a mole ratio of 1 ligand per 2
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linkers, which is equivalent to 1 ligand per node (SI, Fig. S9). The HAADF-STEM images of 1 and 2
reveal that the modified MOF particles retain the overall shape and morphology of pristine NU-1000
particles (Fig. 1e). Additionally, STEM-EDS maps of the individual particles of 1 or 2 display a near
conformal distribution of the Rh metal (as well as Ga for 1) throughout the particles.9,10,43
Figure 1. (a) Single-crystal x-ray structures of the RhGa and Rh molecular precursors. (b) DFT-optimized
structures of 1 and 2 in the ca. 8.5Å-pore (see SI for details on DFT models A and G, respectively). (c) N2
sorption isotherms of NU-1000, 1, and 2. (d) DED map of 1. (e) HAADF-STEM image of 1 and STEM-
EDS elemental mapping. Scale bar is 200 nm.
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A combination of synchrotron-based techniques and periodic density functional theory (DFT)
calculations were employed to gain detailed structural insight of 1 and 2. A difference envelope density
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DED) analysis that compares the synchrotron X-ray powder diffraction data between modified and
pristine NU-1000 generates a low-resolution map of the excess electron density introduced into the MOF
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by the post-synthetic modification. The DED maps of 1 and 2 are both consistent with siting of the Rh
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complexes between two Zr -nodes in the ca. 8.5Å-wide pore of NU-1000 (Fig. 1d, SI Fig. S12).
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interrogate the local metal coordination environments, Rh and Ga K-edge XANES and EXAFS studies
were conducted on 1 and on the model complex, (py tren)GaRhCl, whose structure is known (SI Fig S21-
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23). Collectively, the synchrotron X-ray data for 1 and 2 rule out agglomeration of Rh metal. More
importantly, the coordination geometries and electronic environments of the Rh and Ga centers in 1 are
nearly unchanged from their counterparts in (py tren)GaRhCl. For example, the Rh/Ga XANES spectra of
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and (py tren)GaRhCl are strikingly similar (Fig. 2).
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In silico structural models of 1 were obtained by embedding the “(py tren)GaRh” species into the
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ca. 8.5Å-pore of NU-1000, and then using periodic DFT methods to optimize the geometry. The in silico
structure shown in Figure 1b was determined to be the best model of 1 because of the close match
between its simulated and the experimental EXAFS spectra (SI Figs. S13, S25a, and S25b, model A). The
model contains a square pyramidal Rh center that is covalently attached to the Zr -node via a Rh(μ-OH)Zr
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linkage. The grafted Rh-Ga species in 1 is nearly isostructural to (py tren)GaRhCl, with the exception that
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one N−Ga−N bond angle increases by 15 deg to allow for a weak Ga···(μ-OH)Zr interaction. Refinement
of the Rh EXAFS data supports a 5-coordinate Rh atom with 1 Ga and 4 N/O donors (Fig. 2d, Table 1).
Importantly, the Rh−Ga bond is intact in 1 with a distance of 2.35(5) Å, which compares well to the
Rh−Ga bond in (py tren)GaRhCl (c.f. 2.3171(2) Å). Multiple scattering contributions at ~4.1 Å further
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support the ligand remaining intact. This best model is also corroborated by the Ga EXAFS data, wherein
scattering from a single Rh atom is evident, and the Rh−Ga bond length refines to 2.336(15) Å (SI, Fig.
S27 and Table S9). Another closely related in silico model also aligns well with the Rh/Ga EXAFS data
and is predicted to be slightly lower in energy by 4 kcal/mol. In this alternative model, a single proton
shifts from the hydroxyl ligand in Zr(μ-OH)···Ga−N to an amide donor, generating a Zr(μ-O)Ga···NH
linkage (SI Figs. S14, S25c, and S25d, model B). The Rh XANES spectrum of 2 is also highly similar to
that of 1. Importantly, the scattering of a proximal Ga ion is notably absent in the Rh EXAFS spectra of 2
(
Fig. 2c). The best structure for 2 is a Rh(ethylene) complex, as shown in Fig. 1b, based on the Rh
EXAFS data, DFT energies, as well as complementary experiments that suggest the ethylene ligand
remains bound to Rh after grafting (SI Figs. S26g and S26h, model G). Of relevance, the Rh centers in the
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DFT models of 1 and 2 face the 3nm-wide hexagonal channels of NU-1000, allowing good substrate
access.
Pair distribution function (PDF) studies further support the proposed local structures of 1 and 2
(
SI Fig. S28).45,46 A differential analysis that subtracted the PDF measured for pristine NU-1000 from that
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obtained for 1 or 2 highlights additional (or changed) atom-atom correlations associated with grafting of
the Rh-Ga/Rh complexes onto NU-1000. For 2, well defined peaks corresponding to the Rh−N/O bond
and 1-3-Rh···C distance are observed at 2.09 Å and 3.01 Å, respectively. Additional features at 3.65 Å
(Rh···O), 4.28 Å (Rh···Zr), and 4.88Å (Rh···O/Zr), support the grafting of the Rh compound on the Zr6-
node. Similar peaks observed for 1 at 3.67, 4.25, and 4.86 Å are attributed to a similar grafting of the Rh-
Ga complex on the Zr -node (Table S10). A further differential analysis, isolating the differences in the
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PDF data for 1 and 2, was applied to highlight the features associated with the Ga. Features at 1.95 Å and
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.77 Å were assigned to the Ga−N and Ga···(OH)Zr distances, respectively.
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Figure 2. X-ray absorption spectroscopy: (a) Normalized XANES spectra at Rh K-edge of 1, 2,
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py tren)GaRhCl, and Rh O . (b) Normalized XANES spectra at Ga K-edge of 1, (py tren)GaRhCl, and
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Ga O . (c) k -weighted Rh-EXAFS Img[χ(R)] for 1 and 2 showing the similarity in the overall structures
of the catalysts barring the Rh-Ga scattering at ~2 Å (no phase corrections). (d) k -weighted Rh K-edge
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Magχ(R) and Imgχ(R) spectra of 1 and the corresponding FEFF fit that was obtained from DFT modeling.
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Table 1. The results of Rh and Ga EXAFS from the fit of the experimental spectra of 1 and
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py tren)GaRhCl based on the model derived using FEFF9. The values of bond distances quoted in the
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table are corrected for phase shift. Energy shift (E ) and reduction factor (S ) are set by reference to the
standards. The fit is obtained using k-weighting of 2 in the k range of 2.0 Å < k < 12.0 Å (Rh EXAFS)
or 2.0 Å < k < 9.0 Å (Ga EXAFS).
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Entry Scattering pair
Na
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DWFc
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Rh−N/O
Rh−Ga
3.9 ± 0.7
0.8 ± 0.2
2.086 ± 0.0012
2.387 ± 0.057
0.0058 ± 0.0019
0.0035e
0.0094e
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(Rh EXAFS)
Rh−N/O/C (MS)
Ga−N (or O)
Ga−Rh
NA
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1.938 ± 0.023
2.336 ± 0.015
4.2 ± 0.9
0.9 ± 0.4
0.0107 ± 0.0033
0.0035d
(Ga EXAFS)
(Rh EXAFS)
2
Rh−N/O/C
5.1 ± 0.5
2.108 ± 0.001
0.0045 ± 0.001
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N = average coordination number, b R = interatomic distance, c DWF = Debye–Waller Factors, d NA = not available, e Set to value for the
(py tren)GaRhCl complex. Other parameters: amplitude reduction factor (amp) = 0.83 and E = −6.2, R-factors are typically about 0.0045.
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The homogeneity of the Rh-Ga sites in 1 was assessed by treating 1 with 1.2 equiv PPh followed
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by the standard work-up procedure. The solid-state cross-polarization magic-angle-spinning (CP/MAS)
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P NMR spectrum of 1-PPh showed a single resonance at 43.9 ppm, which is consistent with PPh
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coordination to a single Rh-Ga site (SI Fig. S29). For comparison, free PPh displays a P peak at −5.5
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ppm, which shifts downfield to 50.4 ppm in (κ -py tren)GaRh(PPh )Me (JP−Rh=176 Hz, SI Fig. S31).
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Catalysis: Selective Semi-Hydrogenation of Alkynes
The functionalized MOF materials 1 and 2 were tested for the hydrogenation of
diphenylacetylene using standard conditions of 1 mol% catalyst, 5 atm H , and 100 °C in toluene-d .
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Catalyst 1 generated E-stilbene in 93% yield with a high E:Z ratio of 99:1. By contrast, 2 formed bibenzyl
1
in >99% yield. The basis for the different product outcomes was gleaned by H-NMR monitoring of the
reaction for 13 h. For both 1 and 2, Z-stilbene is observed initially, which suggests syn-hydrogenation of
the alkyne, followed by Z-to-E alkene isomerization, and/or hydrogenation of the alkenes to bibenzyl (SI
Fig S35). The semi-hydrogenation and E-alkene selectivity of 1 stems from a ~16-fold slower rate for
bibenzyl formation compared to Z/E-stilbene production; ultimately, E-stilbene, the thermodynamically
favored isomer, prevails. By contrast, 2 shows rapid bibenzyl growth that is competitive with stilbene
production. As a control, treating 1 with Z-stilbene under catalytic conditions generates E-stilbene in high
yield. Moreover, H is critical for the process, because in its absence, the formation of E-stilbene is too
2
slow to be relevant. As negative controls, neither NU-1000 nor the molecular complexes,
(
PhO)RhGa(py tren) and (H py tren)Rh(C H )OPh, are competent for hydrogenation. Upon exposure to
3 3 3 2 4
H , (PhO)RhGa(py tren) and (H py tren)Rh(C H )OPh, both degrade into an insoluble precipitate, which
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is presumably an ill-defined oligomer containing Rh(μ−H)Rh (1JRh-H = 27.4 Hz) groups (SI Figs. S36 and
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S37).47,48 Hence, anchoring the Rh complexes onto the MOF-support is necessary to preclude the
bimolecular decomposition pathway.49
For the selective hydrogenation of diphenylacetylene to E-stilbene, the best single heterogeneous
catalyst, Rh Sb/SiO , generates the desired alkene only in 58% yield. The state-of-the-art heterogeneous
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semi-hydrogenation catalyst system is two-component mixture of Rh Sb/SiO and Pd Pb/SiO , which
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−
1
work in tandem to selectively generate E-stilbene with an overall turnover frequency (TOF) of 6 h at 25
C (per noble metal). Catalyst 1 is equally fast with an identical TOF of 6 h−1 albeit at elevated
°
temperature (100 °C). Notably, catalyst 1 has only a single active site and shows significantly broader
substrate scope (vide supra).
The substrate scope of 1 was tested with terminal and internal alkynes (Figure 3a). Activated
alkynes that are conjugated to aldehyde, ketone and nitrile functionalities are converted into the E-alkenes
in a high E:Z ratio >98:2. Additional functional groups such as propargylic/primary alcohols, boronic
esters, vinyl cyclopropane, amides, lactones, dithiocarbamates, esters, and even peroxides are also well
tolerated. A competitive hydrogenation between PhC≡CH and PhCH=CH2 gave clean alkyne
consumption with minimal formation of ethylbenzene (<2%), even when the initial mixture was 15:1 in
favor of styrene. Substrate limitations include sterically hindered ortho-substituted aryl alkynes, which
result in low conversion (< 20% yield), and linear terminal alkynes, which result in a mixture of internal
E-alkenes.
Catalyst 1 also successfully hydrogenates terminal alkynes incorporated into biologically active
molecules to the corresponding alkenes in >80% yields (Figure 3a). Excitingly, 1 even catalytically
hydrogenates internal alkynes within 12 to 14-membered lactone rings (Figure 3b), to the corresponding
Z-products in high yields and good selectivities (>95%, E:Z ratio ~95:5). The observed selectivities are
remarkable because the E/Z-alkene products are predicted to be nearly isoenergetic (ΔΔG <1-2
5
0
kcal/mol). Moreover, the production of macrocyclic Z-alkene is consistent with syn-hydrogenation as
the initial step. The reversal of selectivity can be explained by considering a typical alkene isomerization
mechanism that involves: Z-alkene insertion into a metal hydride, C−C bond rotation, and β-hydride
elimination to yield the E-isomer. For macrocyclic substrates, considerable ring strain in the C−C bond
rotation step may raise the reaction barrier sufficiently to preclude Z-to-E alkene isomerization (SI Fig.
S52).
To gauge the general catalytic applicability of 1 versus 2, gas-phase hydrogenation of propyne
was performed under air-free conditions using a 16-parallel fixed-bed flow reactors Flowrence system
(SI). The overall optimum catalytic semi-hydrogenation performance was observed at 200 °C, employing
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mg of catalyst (NU-1000, 1, or 2), with a total pressure of 1 atm, and excess of H . Under these
2
conditions, both 1 and 2 convert propyne (94% and >99%, respectively; Figure 3c), albeit to different
major products. In the case of 1, propylene is generated in good yield (82%) and in high selectivity
(88%)51-59 (overall TOF = 3.1 min ), whereas complete hydrogenation was achieved with 2 (>99%
−1
−
1
propane yield, TOF = 3.6 min ). By comparison, the propane TOF for 1 is nearly a magnitude lower (0.4
1
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min ), which is consistent with its selectivity for propylene. These results reinforce the significance of
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the Ga “promoter” in altering catalyst selectivity.
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Figure 3. Catalytic semi-hydrogenation: For the alkyne semi-hydrogenation catalyst 1 (a) E-selective
synthesis of diverse alkenes and Z-selective synthesis of macrocyclic alkenes, and (b) conversion of
propyne(g) to propylene . Deviations from standard conditions include: i. 10 mol% 1, 323 K, 4.3 atm H ,
(g)
2
1
5
5 h; ii. 2 mol% 1, 373 K, 5 atm H , 12 h; iii. 5 mol% 1, 323 K, 4.3 atm H , 18 h; iv. 2.5 mol% 1, 373 K,
2
2
atm H , 16 h.
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At 1 mol% loading, catalyst 1 was recovered and reused up to 5 times without any significant loss
in either activity or selectivity in the semi-hydrogenation of diphenylacetylene (SI Figs. S42 and S43).
EXAFS and XANES analysis of the post-catalytic material showed an intact Rh⟶Ga bond (2.400(11) Å,
SI Fig. S21). HAADF-STEM images collected after 5 catalytic runs showed no observable nanoparticle
1
formation (SI Fig. S44). Moreover, H NMR and ICP-AES analyses of the digested material after 5
1
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catalytic runs confirmed that a nearly similar loading of the RhGa(py tren) unit is retained with a
3
Rh:Ga:py tren mole ratio of 1.01:0.89:0.94 per Zr -node (Table S12). However, the 10% decrease in the
3
6
Ga mole ratio after five runs suggests minor catalyst decomposition, presumably via undesired hydrolysis
of the Ga-amide bonds. Lastly, attribution of activity to the solid catalyst 1, opposed to any soluble Rh
species that might have leached into solution, was tested by filtering the catalytic mixture at 50%
conversion of the diphenylacetylene. Subjecting the supernatant to the catalytic conditions did not yield
any further conversion (SI Figs. S46).
Periodic DFT Mechanistic Studies
To better understand the effect of Ga in promoting selective semi-hydrogenation, periodic DFT
calculations were conducted to compare the catalytic mechanisms of 1 and 2 for hydrogenating the C≡C
and C=C bonds of 2-butyne and Z-2-butene, respectively (see Methods and SI). The general framework of
their mechanisms comprises three steps: H activation to generate a Rh hydride; insertion of the C≡C (or
2
C=C) functionality into the Rh−H bond to form a Rh vinyl (or Rh alkyl) species; and, release of the
alkene (or alkane). The full catalytic mechanism and the reaction coordinate diagram for 1 is shown in
Figure 4, with enthalpy as the energy axis. Starting from the DFT structure of model B, H physisorbs
2
near the Rh center, prior to adding across the Rh−Npyr bond. Hence, metal-ligand cooperativity results in
the heterolytic cleavage of H , where the hydride and proton are simultaneously delivered to Rh and
2
I
δ−
pyridine, respectively. The resulting Rh hydride is also stabilized by two non-classical H-bonds: RhH ---
δ+
H N, where the N donor represents both the pyridine and amine functionalities on the free ligand arm.
Overall, H heterolysis is slightly endothermic (1.4 kcal/mol) with an enthalpic barrier of 11.0 kcal/mol.
2
The next step is the favorable physisorption of 2-butyne, followed by the rate-determining insertion of the
I
alkyne to generate a Rh -vinyl intermediate. By comparison, the insertion of 2-butene has an even larger
enthalpic barrier (34.1 kcal/mol), which is 14.4 kcal/mol higher than that of 2-butyne (c.f. 19.7 kcal/mol).
Hence, these results rationalize the semi-hydrogenation selectivity shown by 1. In the last step,
2
3
intramolecular proton transfer to the Rh-bound sp -C (or sp -C) atom releases the butene (or butane),
respectively, with a lower barrier of 5 (or 9) kcal/mol. Notably, the Rh−Ga bond remains intact
throughout the catalytic cycle.
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The full mechanism for 2 is shown in the SI (Fig. S48). Several notable differences in mechanism
emerge (Fig. 4, inset). Catalyst 2 binds 2-butyne strongly prior to H activation, which occurs via
2
oxidative addition to generate a RhIII dihydride with no enthalpic barrier. In support, a mixture of 1:1
H :D (4 atm, 298 K, toluene-d ) is rapidly scrambled to give HD when 2 is present (< 10 min); whereas,
2
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8
under similar conditions, H/D-scrambling with 1 requires a longer incubation time of 6 h (SI Figs. S49
and S50). In the next step, chemisorbed 2-butyne undergoes insertion with a barrier of 21.2 kcal/mol,
which is rate-limiting. The analogous insertion of Z-2-butene is significantly lower at 13.5 kcal/mol.
Hence, the inversion of the energy barriers to favor C=C insertion rationalizes the preference for alkane
production by 2. Moreover, the lower insertion barriers for 2 compared to 1 is consistent with the faster
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hydrogenation rate of 2. In the last step, reductive elimination from the Rh vinyl hydride to release Z-2-
butene is also rate-determining with a 20.8 kcal/mol barrier. The corresponding reductive elimination of
n-butane has a lower barrier of 12.6 kcal/mol, reinforcing the preference for n-butane production over 2-
butene.
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Figure 4. For catalyst 1, (a) DFT-calculated mechanism for the hydrogenation of 2-butyne (in red) and 2-
butene (in blue) and the corresponding (b) reaction energy coordinate. Selected distances (Å) are shown
in gray. (c) For pre-catalyst 2, the DFT-calculated alkyne/alkene insertion.
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To achieve chemoselective hydrogenation of alkynes to alkenes, the consensus has been that the
free energy barrier for alkene desorption must be lower than that for alkene hydrogenation.23 Indeed,
DFT calculations for 1 predict that the enthalpic barrier for (Z)-2-butene desorption is 20 kcal/mol lower
than that for alkene insertion into the Rh−H bond. Notably, our catalytic results demonstrate the
importance of the GaIII promoter in determining the overall hydrogenation selectivity by altering the
mechanism and the corresponding reaction energy profile.
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III
It is feasible that the Ga promoter plays both an electronic and a structural role. Since Ga is a
Lewis acid,60 the Rh electron density in 1 should be decreased relative to that in 2. Indeed, a charge
analysis indicates that the Rh center is more electropositive in 1 than in 2 (SI, Table S13). This electronic
tuning may explain the switchover to a H heterolysis mechanism in 1, rather than the classical H
2
2
2
oxidative addition that operates for more electron-rich metal centers, such as in 2. In support, the H /D
2
scrambling experiments suggest that both H activation and/or the nature of the Rh−H intermediate are
2
III
different for 1 and 2. Also, the Ga ion may serve as a structural promoter by limiting the number of
available coordination sites at Rh. While the Rh center has only two open coordination sites in 1, three
III
2
binding sites are available in 2, which allow for stabilization of the Rh (H) (η -alkene) intermediate. One
2
consequence is that the enthalpic barrier for (Z)-2-butene desorption is only 4 kcal/mol lower than that for
alkene insertion. Hence, alkene hydrogenation (over desorption) is predicted to be 5-fold less disfavored
for 1 than for 2, making the latter a significantly better semi-hydrogenation catalyst.
Conclusion
Using a post-functionalization of NU-1000, well-defined Rh and Rh-Ga active sites were
III
installed uniformly with a stoichiometry of one Rh/Rh-Ga site per Zr -node. The Ga promoter ion that is
6
directly bonded to Rh enables high selectivity in the Rh-catalyzed semi-hydrogenation of non-cyclic
alkynes to E-alkenes. Impressively, lactone-based macrocycles bearing reactive alkyne groups are
converted to the corresponding Z-alkenes in good yields; and, the Rh-Ga active site is a good catalyst for
the gas-phase semi-hydrogenation of propyne to propylene. Compared to state-of-the-art heterogeneous
systems, the unique aspect of the single Rh-Ga site is that it is responsible for both the chemoselective
hydrogenation of alkynes (over alkenes) and the stereoselective alkene isomerization to acyclic E-alkenes.
Collectively, this work is a powerful demonstration of tailoring single-site reactivity and
selectivity on a solid support by using a covalently bonded, Lewis acidic group 13 promoter. The
simplicity of our model system highlights the structure-activity relationship between the metal-promoter
interaction and its impact on catalyst selectivity. Future work will focus on a detailed mechanistic analysis
of 1. A lingering question regards how/why alkene isomerization is favored over alkene hydrogenation.
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We will also broadly investigate the impact of the organic scaffold and other promoter elements in tuning
these MOF-supported bimetallic active sites.
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Experimental Section
Additional information is provided in the Supporting Information.
Synthesis of (py tren)GaRhMe. A 1 mL THF solution of MeLi (93 µL, 0.102 mmol, 1.1 M in Et O) was
3
2
added to a 50 mL THF slurry of (py tren)GaRhCl (59 mg, 0.102 mmol) at – 78 ºC. The reaction mixture
was allowed to warmup to rt overnight and the volatiles were removed under vacuo. The crude solid was
dissolved in 15 mL of benzene, filtered over Celite and layered with pentane to obtain orange crystals of
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(
py tren)GaRhMe (34 mg, 59% yield). Single crystals for x-ray diffraction were grown from slow
3
evaporation of a concentrated acetonitrile solution of (py tren)GaRhMe. Anal
3
Synthesis of (H py tren)Rh(C H )OPh. A 1 mL THF solution of H py tren (100 mg, 0.265 mmol) was
3
3
2
4
3
3
added to a vial charged with [(C H ) RhCl] (51.5 mg, 0.132 mmol) at room temperature. The reaction
2
4 2
2
mixture was heated to 40 °C for 2 h and immediately filtered over Celite into a vial containing a 5 mL
THF solution of NaOPh (31 mg, 0.265 mmol). After stirring for 12 h, the volatiles were removed under
vacuo. The crude solid was dissolved in 10 mL of benzene, filtered over Celite and layered with pentane
to obtain single crystals of (H py tren)Rh(C H )OPh (103 mg, 65% yield). Anal. Calcd. for
3
3
2
4
C H N RhO: C, 58.17; H, 5.55; N, 16.38. Found: C, 58.10; H, 6.11; N, 16.10.
2
9
33
7
Calcd. for C H N GaRh: C, 47.30; H, 4.33; N, 17.56. Found: C, xx; H, xx; N, xx.
2
2
24
7
Synthesis of 1. Microcrystalline NU-1000 (29.2 mg, 0.014 mmol) was added to a 20 mL benzene
solution of (py tren)GaRhMe (19.6 mg, 0.035 mmol) or (py tren)GaRhOPh (22.3 mg, 0.035 mmol) at
3
3
room temperature. After stirring for 12 h, the heterogeneous mixture was filtered using a fine porosity
glass frit. The resulting solids were washed with copious amounts of benzene (~ 20 mL). The solids were
soaked overnight in 20 mL benzene and washed with fresh benzene (4  1 mL) and pentane (5  1 mL).
The overnight soaking and rinsing procedure was repeated once more. Finally, the solids were dried under
dynamic vacuum (< 100 mTorr) for 5 h. Yield: 36 mg (97%).
Synthesis of 2. The synthetic procedure is identical to that of 1 except (H py tren)Rh(C H )OPh (21.5
3
3
2
4
mg, 0.035 mmol) was used. The reaction between (H py tren)Rh(C H )OPh and NU-1000 was monitored
3
3
2
4
1
by H NMR spectroscopy in a sealed J. Young NMR tube. No ethylene was observed, suggesting that
ethylene remains bound to the anchored Rh site. Yield: 37 mg (98%).
General procedure for semi-hydrogenation catalysis. In a typical catalytic run, a J. Young NMR tube
was loaded with 0.6 mL of d -toluene, 0.0007 mmol of catalyst, 10 µL of mesitylene (0.072 mmol,
internal standard) and desired amount of alkyne. The J. Young NMR tube was then subjected to 3 freeze-
pump-thaw cycles. Finally, 1 atm of H was admitted into the NMR tube at 77 K and the gas was allowed
8
2
to expand by warming to rt resulting in 4 atm of H . After heating the reaction mixture for 15-24 h at 100
2
°
C, the solids were separated from the supernatant by using a fine porosity glass frit. The solids were
washed with 5 mL of benzene and the resulting filtrate was combined with the supernatant and dried in
vacuo. Percent conversions and yields are reported for the crude reaction mixture based on H NMR
spectroscopy. All catalytic runs were repeated in triplicate.
1
Semi-hydrogenation of propyne. Semi-hydrogenation of propyne was performed in a 16 fixed bed
reactors system (Flowrence, Avantium). Typically, 5 mg of catalyst was diluted with 50 mg high-purity
grade silica gel (230-400 mesh, Sigma-Aldrich) and loaded into quartz reactor (ID=2 mm, OD=3 mm,
L=300 mm). Catalyst materials were loaded in a nitrogen-filled glovebox (oxygen and moisture less than
0
.1 ppm), and capped with paraffin film prior loading them in the Avantium system, which was closed
immediately after to avoid contamination with air. Reactions were performed between 50 and 250 °C and
between 1 and 7.5 atm. All gases were purchased from Airgas and UHP grade. 2% propyne in argon was
used together with either 3% hydrogen in argon or pure hydrogen and helium as the GC standard. Total
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flowrate was around 15 mL/min per reactor. The effluent of each reactor was analyzed sequentially by a
gas chromatograph (7890B, Agilent Technologies), equipped with a thermal conductivity detector (TCD)
and 2 flame ionization detectors (FID).
Computational Methods. Periodic density functional calculations were carried out using the CP2K
6
1
62
63
code. The PBE functional with Grimme et al.’s D3 dispersion corrections was used to calculate the
exchange–correlation energy. The DZVP-MOLOPT basis set was used with Geodecker et al.’s
1
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pseudopotentials with a plane wave cutoff energy of 360 Ry.
ASSOCIATED CONTENT
Supporting Information
The Supporting Information is available free of charge on the ACS Publications website at DOI:


X-ray crystallographic data for Rh compounds (CIF)
Experimental procedures, characterization and spectroscopic data, computational methods, and
calculated structures (PDF)
Corresponding Author
clu@umn.edu
Notes
X-ray crystallographic data have been deposited in the Cambridge Crystallographic Data Centre
database (CCDC 1842577 to 1842581).
Acknowledgments
We acknowledge Dr. Camille Malonzo May (UMN), Dr. David Kaphan (Argonne), Dr. Tata
Gopinath (UMN), and Dr. Zhanyong Li (NW) for experimental assistance, and Dr. Dale Pahls
for preliminary theoretical calculations. This work was supported as part of the Inorganometallic
Catalyst Design Center, an Energy Frontier Research Center funded by the U.S. Department of
Energy, Office of Science, Basic Energy Sciences under Award No. DE-SC0012702. This
research used resources of: (1) the Advanced Photon Source, a U.S. Department of Energy
(DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne
National Laboratory under Contract No. DE-AC02-06CH11357; and, (2) the University of
Minnesota Characterization Facility, which is supported by the NSF through the MRSEC, ERC,
MRI, and NNIN programs.
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References
(1)
Koel, B. E.; KIm, J.: Promoters and Poisons. In Promoters and Poisons: Handbook of
Heterogeneous Catalysis; Wiley-VCH Verlag GmbH & Co. KGaA: Handbook of Heterogeneous
Catalysis, 2008.
(
2)
heterogeneous catalysis: The role of Cl on ethylene epoxidation over Ag. J. Catal. 2014, 312, 12-16.
3) Wang, L.; Guan, E.; Zhang, J.; Yang, J.; Zhu, Y.; Han, Y.; Yang, M.; Cen, C.; Fu, G.;
Rocha, T. C. R.; Hävecker, M.; Knop-Gericke, A.; Schlögl, R. Promoters in
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
(
Gates, B. C.; Xiao, F.-S. Single-site catalyst promoters accelerate metal-catalyzed nitroarene
hydrogenation. Nat. Commun. 2018, 9, 1362.
(4)
Willis, J. J.; Goodman, E. D.; Wu, L.; Riscoe, A. R.; Martins, P.; Tassone, C. J.;
Cargnello, M. Systematic Identification of Promoters for Methane Oxidation Catalysts Using Size- and
Composition-Controlled Pd-Based Bimetallic Nanocrystals. J. Am. Chem. Soc. 2017, 139, 11989-11997.
(5)
Enache, D. I.; Edwards, J. K.; Landon, P.; Solsona-Espriu, B.; Carley, A. F.; Herzing, A.
A.; Watanabe, M.; Kiely, C. J.; Knight, D. W.; Hutchings, G. J. Solvent-Free Oxidation of Primary
Alcohols to Aldehydes Using Au-Pd/TiO2 Catalysts. Science 2006, 311, 362-365.
(
6)
insights from density functional theory. Chem. Commun. 2012, 48, 1379-1391.
(7) Dahl, S.; Logadottir, A.; Jacobsen, C. J. H.; Nørskov, J. K. Electronic factors in catalysis:
Lopez, N.; Vargas-Fuentes, C. Promoters in the hydrogenation of alkynes in mixtures:
the volcano curve and the effect of promotion in catalytic ammonia synthesis. Appl. Catal., A 2001, 222,
19-29.
(
8)
Applications. Angew. Chem. Int. Ed. 2016, 55, 6112-6113.
9) Thompson, A. B.; Pahls, D. R.; Bernales, V.; Gallington, L. C.; Malonzo, C. D.; Webber,
Avelino, C. Heterogeneous Catalysis: Understanding for Designing, and Designing for
(
T.; Tereniak, S. J.; Wang, T. C.; Desai, S. P.; Li, Z.; Kim, I. S.; Gagliardi, L.; Penn, R. L.; Chapman, K.
W.; Stein, A.; Farha, O. K.; Hupp, J. T.; Martinson, A. B. F.; Lu, C. C. Installing Heterobimetallic
Cobalt–Aluminum Single Sites on a Metal Organic Framework Support. Chem. Mater. 2016, 28, 6753-
6
762.
(10)
Desai, S. P.; Malonzo, C. D.; Webber, T.; Duan, J.; Thompson, A. B.; Tereniak, S. J.;
DeStefano, M. R.; Buru, C. T.; Li, Z.; Penn, R. L.; Farha, O. K.; Hupp, J. T.; Stein, A.; Lu, C. C.
Assembly of dicobalt and cobalt-aluminum oxide clusters on metal-organic framework and nanocast
silica supports. Faraday Discuss 2017, 201, 287-302.
(11)
Mondloch, J. E.; Bury, W.; Fairen-Jimenez, D.; Kwon, S.; DeMarco, E. J.; Weston, M.
H.; Sarjeant, A. A.; Nguyen, S. T.; Stair, P. C.; Snurr, R. Q.; Farha, O. K.; Hupp, J. T. Vapor-Phase
Metalation by Atomic Layer Deposition in a Metal-Organic Framework. J. Am. Chem. Soc. 2013, 135,
10294-10297.
(12)
Organic Framework Materials as Catalysts. Chem. Soc. Rev. 2009, 38, 1450-1459.
(13) Corma, A.; García, H.; Llabrés i Xamena, F. X. Engineering Metal Organic Frameworks
for Heterogeneous Catalysis. Chem. Rev. 2010, 110, 4606-4655.
14) Diercks, C. S.; Liu, Y.; Cordova, K. E.; Yaghi, O. M. The role of reticular chemistry in
the design of CO2 reduction catalysts. Nat. Mater. 2018, 17, 301-307.
15) Li, Z.; Peters, A. W.; Platero-Prats, A. E.; Liu, J.; Kung, C.-W.; Noh, H.; DeStefano, M.
Lee, J.; Farha, O. K.; Roberts, J.; Scheidt, K. A.; Nguyen, S. T.; Hupp, J. T. Metal-
(
(
R.; Schweitzer, N. M.; Chapman, K. W.; Hupp, J. T.; Farha, O. K. Fine-Tuning the Activity of Metal–
Organic Framework-Supported Cobalt Catalysts for the Oxidative Dehydrogenation of Propane. J. Am.
Chem. Soc. 2017, 139, 15251-15258.
(
16)
progress report. Chem. Soc. Rev. 2011, 40, 498-519.
17) Xiao, D. J.; Bloch, E. D.; Mason, J. A.; Queen, W. L.; Hudson, M. R.; Planas, N.;
Tanabe, K. K.; Cohen, S. M. Postsynthetic modification of metal–organic frameworks—a
(
Borycz, J.; Dzubak, A. L.; Verma, P.; Lee, K.; Bonino, F.; Crocellà, V.; Yano, J.; Bordiga, S.; Truhlar, D.
18
ACS Paragon Plus Environment

Page 19 of 21
Journal of the American Chemical Society
1
2
3
4
5
6
7
8
9
G.; Gagliardi, L.; Brown, C. M.; Long, J. R. Oxidation of ethane to ethanol by N2O in a metal–organic
framework with coordinatively unsaturated iron(II) sites. Nat. Chem. 2014, 6, 590.
(
18)
frameworks. Chem. Soc. Rev. 2009, 38, 1248-1256.
19) Manna, K.; Ji, P.; Lin, Z.; Greene, F. X.; Urban, A.; Thacker, N. C.; Lin, W.
Ma, L.; Abney, C.; Lin, W. Enantioselective catalysis with homochiral metal–organic
(
Chemoselective single-site Earth-abundant metal catalysts at metal–organic framework nodes. Nat.
Commun. 2016, 7, 12610.
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
(
20)
Edition. Vol. 1–8. Edited by G. Ertl, H. Knözinger, F. Schüth, and J. Weitkamp. Angew. Chem. Int. Ed.
009, 48, 3390-3391.
21) Molnár, Á.; Sárkány, A.; Varga, M. Hydrogenation of carbon–carbon multiple bonds:
chemo-, regio- and stereo-selectivity. J. Mol. Catal. A: Chem. 2001, 173, 185-221.
Meurig, T. J. Handbook Of Heterogeneous Catalysis. 2., completely revised and enlarged
2
(
(22)
H., L. Ein neuer Katalysator für selektive Hydrierungen. Helv. Chim. Acta 1952, 35, 446-
450.
(23)
Studt, F.; Abild-Pedersen, F.; Bligaard, T.; Sørensen, R. Z.; Christensen, C. H.; Nørskov,
J. K. Identification of Non-Precious Metal Alloy Catalysts for Selective Hydrogenation of Acetylene.
Science 2008, 320, 1320-1322.
(
24)
Intermetallic Compounds as Highly Selective Semihydrogenation Catalysts. J. Am. Chem. Soc. 2010, 132,
4745-14747.
25)
Armbrüster, M.; Kovnir, K.; Behrens, M.; Teschner, D.; Grin, Y.; Schlögl, R. Pd−Ga
1
(
Armbrüster, M.; Kovnir, K.; Friedrich, M.; Teschner, D.; Wowsnick, G.; Hahne, M.;
Gille, P.; Szentmiklósi, L.; Feuerbacher, M.; Heggen, M.; Girgsdies, F.; Rosenthal, D.; Schlögl, R.; Grin,
Y. Al13Fe4 as a low-cost alternative for palladium in heterogeneous hydrogenation. Nat. Mater. 2012,
1
1, 690-693.
26)
(
Köhler, D.; Heise, M.; Baranov, A. I.; Luo, Y.; Geiger, D.; Ruck, M.; Armbrüster, M.
Synthesis of BiRh Nanoplates with Superior Catalytic Performance in the Semihydrogenation of
Acetylene. Chem. Mater. 2012, 24, 1639-1644.
(27)
Feng, Q.; Zhao, S.; Wang, Y.; Dong, J.; Chen, W.; He, D.; Wang, D.; Yang, J.; Zhu, Y.;
Zhu, H.; Gu, L.; Li, Z.; Liu, Y.; Yu, R.; Li, J.; Li, Y. Isolated Single-Atom Pd Sites in Intermetallic
Nanostructures: High Catalytic Selectivity for Semihydrogenation of Alkynes. J. Am. Chem. Soc. 2017,
139, 7294-7301.
(28)
2, 65-81.
(29)
Wang, A.; Li, J.; Zhang, T. Heterogeneous single-atom catalysis. Nat. Rev. Chem. 2018,
Zhou, H.; Yang, X.; Li, L.; Liu, X.; Huang, Y.; Pan, X.; Wang, A.; Li, J.; Zhang, T. PdZn
Intermetallic Nanostructure with Pd–Zn–Pd Ensembles for Highly Active and Chemoselective Semi-
Hydrogenation of Acetylene. ACS Catal. 2016, 6, 1054-1061.
(30)
Pei, G. X.; Liu, X. Y.; Wang, A.; Lee, A. F.; Isaacs, M. A.; Li, L.; Pan, X.; Yang, X.;
Wang, X.; Tai, Z.; Wilson, K.; Zhang, T. Ag Alloyed Pd Single-Atom Catalysts for Efficient Selective
Hydrogenation of Acetylene to Ethylene in Excess Ethylene. ACS Catal. 2015, 5, 3717-3725.
(31)
Albani, D.; Shahrokhi, M.; Chen, Z.; Mitchell, S.; Hauert, R.; López, N.; Pérez-Ramírez,
J. Selective ensembles in supported palladium sulfide nanoparticles for alkyne semi-hydrogenation. Nat.
Commun. 2018, 9, 2634.
(
32)
Co–H2 Catalyst: A H2 Spin on Isomerization and E-Selectivity. J. Am. Chem. Soc. 2016, 138, 13700-
3705.
Tokmic, K.; Fout, A. R. Alkyne Semihydrogenation with a Well-Defined Nonclassical
1
(
33)
Catalyzed, Environmentally Benign, E-Selective Semi-Hydrogenation of Alkynes. Angew. Chem. Int. Ed.
013, 125, 14381-14384.
(34) Radkowski, K.; Sundararaju, B.; Fürstner, A. A Functional-Group-Tolerant Catalytic
Srimani, D.; Diskin-Posner, Y.; Ben-David, Y.; Milstein, D. Iron Pincer Complex
2
transꢀHydrogenation of Alkynes. Angew. Chem. Int. Ed. 2013, 52, 355-360.
19
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Journal of the American Chemical Society
Page 20 of 21
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
(
35)
Guthertz, A.; Leutzsch, M.; Wolf, L. M.; Gupta, P.; Rummelt, S. M.; Goddard, R.; Farès,
C.; Thiel, W.; Fürstner, A. Half-Sandwich Ruthenium Carbene Complexes Link trans-Hydrogenation and
gem-Hydrogenation of Internal Alkynes. J. Am. Chem. Soc. 2018, 140, 3156-3169.
(36)
Neumann, K. T.; Klimczyk, S.; Burhardt, M. N.; Bang-Andersen, B.; Skrydstrup, T.;
Lindhardt, A. T. Direct trans-Selective Ruthenium-Catalyzed Reduction of Alkynes in Two-Chamber
Reactors and Continuous Flow. ACS Catal. 2016, 6, 4710-4714.
(
37)
Heterobimetallic Catalysis. J. Am. Chem. Soc. 2015, 137, 14598-14601.
38) Burch, R. R.; Shusterman, A. J.; Muetterties, E. L.; Teller, R. G.; Williams, J. M.
Coordinately unsaturated clusters. A novel catalytic reaction. J. Am. Chem. Soc. 1983, 105, 3546-3556.
39) Tseng, K.-N. T.; Kampf, J. W.; Szymczak, N. K. Modular Attachment of Appended
Karunananda, M. K.; Mankad, N. P. E-Selective Semi-Hydrogenation of Alkynes by
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
(
(
Boron Lewis Acids to a Ruthenium Pincer Catalyst: Metal–Ligand Cooperativity Enables Selective
Alkyne Hydrogenation. J. Am. Chem. Soc. 2016, 138, 10378-10381.
(40)
Alkenes, Using Ordered Alloys as Catalysts. ACS Catal. 2016, 6, 2121-2125.
(41) Furukawa, S.; Yokoyama, A.; Komatsu, T. Efficient Catalytic System for Synthesis of
trans-Stilbene from Diphenylacetylene Using Rh-Based Intermetallic Compounds. ACS Catal. 2014, 4,
581-3585.
42)
Furukawa, S.; Komatsu, T. Selective Hydrogenation of Functionalized Alkynes to (E)-
3
(
Liu, Y.; Liu, X.; Feng, Q.; He, D.; Zhang, L.; Lian, C.; Shen, R.; Zhao, G.; Ji, Y.; Wang,
D.; Zhou, G.; Li, Y. Intermetallic NixMy (M = Ga and Sn) Nanocrystals: A Non-precious Metal Catalyst
for Semi-Hydrogenation of Alkynes. Adv. Mater. 2016, 28, 4747-4754.
(
43)
Modulator in the Synthesis of Phase-Pure NU-1000. ACS Appl. Mater. Interfaces 2017, 9, 39342-39346.
44) Gallington, L. C.; Kim, I. S.; Liu, W.-G.; Yakovenko, A. A.; Platero-Prats, A. E.; Li, Z.;
Webber, T. E.; Liu, W.-G.; Desai, S. P.; Lu, C. C.; Truhlar, D. G.; Penn, R. L. Role of a
(
Wang, T. C.; Hupp, J. T.; Farha, O. K.; Truhlar, D. G.; Martinson, A. B. F.; Chapman, K. W.
Regioselective Atomic Layer Deposition in Metal–Organic Frameworks Directed by Dispersion
Interactions. J. Am. Chem. Soc. 2016, 138, 13513-13516.
(45)
Platero-Prats, A. E.; Mavrandonakis, A.; Gallington, L. C.; Liu, Y.; Hupp, J. T.; Farha, O.
K.; Cramer, C. J.; Chapman, K. W. Structural Transitions of the Metal-Oxide Nodes within Metal–
Organic Frameworks: On the Local Structures of NU-1000 and UiO-66. J. Am. Chem. Soc. 2016, 138,
4178-4185.
(46)
Platero-Prats, A. E.; Li, Z.; Gallington, L. C.; Peters, A.; Hupp, J. T.; Farha, O. K.;
Chapman, K. W. Addressing the characterisation challenge to understand catalysis in MOFs: the case of
nanoscale Cu supported in NU-1000. Faraday Discuss 2017, 201, 337-350.
(
47)
Rhodium(III) Hydride. J. Am. Chem. Soc. 2014, 136, 5938-5948.
48) Wayland, B. B.; Balkus, K. J.; Farnos, M. D. Organometallic reactions of rhodium
Hu, Y.; Norton, J. R. Kinetics and Thermodynamics of H–/H•/H+ Transfer from a
(
octaethylporphyrin species in pyridine. Heterolytic cleavage of [(OEP)Rh]2 and metalloanion activation
of carbon monoxide. Organometallics 1989, 8, 950-955.
(49)
Burch, R. R.; Muetterties, E. L.; Teller, R. G.; Williams, J. M. Selective formation of
trans olefins by a catalytic hydrogenation of alkynes mediated at two adjacent metal centers. J. Am. Chem.
Soc. 1982, 104, 4257-4258.
(50)
Zhang, H.; Yu, E. C.; Torker, S.; Schrock, R. R.; Hoveyda, A. H. Preparation of
Macrocyclic Z-Enoates and (E,Z)- or (Z,E)-Dienoates through Catalytic Stereoselective Ring-Closing
Metathesis. J. Am. Chem. Soc. 2014, 136, 16493-16496.
(
51)
to Enhanced Alkene Selectivity in Alkyne Hydrogenation. J. Am. Chem. Soc. 2010, 132, 4321-4327.
52) Bridier, B.; López, N.; Pérez-Ramírez, J. Partial hydrogenation of propyne over copper-
based catalysts and comparison with nickel-based analogues. J. Catal. 2010, 269, 80-92.
(53) Abelló, S.; Verboekend, D.; Bridier, B.; Pérez-Ramírez, J. Activated takovite catalysts
Bridier, B.; Pérez-Ramírez, J. Cooperative Effects in Ternary Cu−Ni−Fe Catalysts Lead
(
for partial hydrogenation of ethyne, propyne, and propadiene. J. Catal. 2008, 259, 85-95.
20
ACS Paragon Plus Environment

Page 21 of 21
Journal of the American Chemical Society
1
2
3
4
5
6
7
8
9
(
54)
Vilé, G.; Bridier, B.; Wichert, J.; Pérez-Ramírez, J. Ceria in Hydrogenation Catalysis:
High Selectivity in the Conversion of Alkynes to Olefins. Angew. Chem. Int. Ed. 2012, 51, 8620-8623.
55) Vilé, G.; Baudouin, D.; Remediakis, I. N.; Copéret, C.; López, N.; Pérez-Ramírez, J.
(
Silver Nanoparticles for Olefin Production: New Insights into the Mechanistic Description of Propyne
Hydrogenation. ChemCatChem 2013, 5, 3750-3759.
(
56)
A.; Pérez-Ramírez, J. Promoted ceria catalysts for alkyne semi-hydrogenation. J. Catal. 2015, 324, 69-78.
57) McCue, A. J.; Gibson, A.; Anderson, J. A. Palladium assisted copper/alumina catalysts
Vilé, G.; Dähler, P.; Vecchietti, J.; Baltanás, M.; Collins, S.; Calatayud, M.; Bonivardi,
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
(
for the selective hydrogenation of propyne, propadiene and propene mixed feeds. Chemical Engineering
Journal 2016, 285, 384-391.
(58)
McCue, A. J.; Guerrero-Ruiz, A.; Rodríguez-Ramos, I.; Anderson, J. A. Palladium
sulphide – A highly selective catalyst for the gas phase hydrogenation of alkynes to alkenes. J. Catal.
2016, 340, 10-16.
(59)
Wehrli, J. T.; Thomas, D. J.; Wainwright, M. S.; Trimm*, D. L.; Cant, N. W. Selective
hydrogenation of propyne over supported copper catalysts: influence of support. Applied Catalysis 1991,
70, 253-262.
(
60)
for Catalytic Olefin Hydrogenation. J. Am. Chem. Soc. 2015, 137, 12486-12489.
61) Jürg, H.; Marcella, I.; Florian, S.; Joost, V. cp2k: atomistic simulations of condensed
matter systems. Wiley Interdisciplinary Reviews: Computational Molecular Science 2014, 4, 15-25.
62) Perdew, J. P.; Burke, K.; Ernzerhof, M. Generalized Gradient Approximation Made
Simple. Phys. Rev. Lett. 1997, 78, 1396-1396.
63) Grimme, S.; Antony, J.; Ehrlich, S.; Krieg, H. A consistent and accurate ab initio
Cammarota, R. C.; Lu, C. C. Tuning Nickel with Lewis Acidic Group 13 Metalloligands
(
(
(
parametrization of density functional dispersion correction (DFT-D) for the 94 elements H-Pu. J. Chem.
Phys. 2010, 132, 154104.
(64)
Goedecker, S.; Teter, M.; Hutter, J. Separable dual-space Gaussian pseudopotentials.
Phys. Rev. B 1996, 54, 1703-1710.
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