Metallopolymerization as a Strategy to Translate Ligand-Modulated

Article Cite This: Organometallics XXXX, XXX, XXX−XXX

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Metallopolymerization as a Strategy to Translate Ligand-Modulated Chemoselectivity to Porous Catalysts Wen-Yang Gao,† Andrew A. Ezazi,† Chen-Hao Wang,† Jisue Moon,‡,§ Carter Abney,‡ Joshua Wright,∥ and David C. Powers*,† †

Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States § Department of Chemical Engineering and Materials Science, University of California−Irvine, Irvine, California 92697, United States ∥ Illinois Institute of Technology, Chicago, Illinois 60616, United States Downloaded by UNIV AUTONOMA DE COAHUILA at 13:00:21:741 on May 23, 2019 from https://pubs.acs.org/doi/10.1021/acs.organomet.9b00162.

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S Supporting Information *

ABSTRACT: Porous catalysts have garnered substantial interest as potential platforms for group-transfer catalysis due to the ability to noncovalently colocalize substrates in proximity to site-isolated reactive intermediates. In contrast to soluble molecular catalysts, the limited synthetic toolbox available to prepare porous catalysts presents a formidable challenge to controlling the primary coordination sphere of lattice-confined catalysts and thus modulating the electronic structures of reactive catalyst intermediates. Here, we utilize Sonogashira cross-coupling chemistry to prepare a family of porous metallopolymers in the primary coordination sphere of Ru2 sites. The newly synthesized materials are characterized by IR, elemental analysis, gas sorption, powder X-ray diffraction, thermogravimetric analysis, X-ray absorption spectroscopy, and diffuse-reflectance UV−vis-NIR spectroscopy. The resulting porous materials are catalysts for nitrene-transfer chemistry, and the chemoselectivity for allylic amination versus olefin aziridination can be tuned by modulating the primary coordination sphere of the catalyst sites. The demonstration of metallopolymerization as a rational synthetic strategy enables ligandmodulated chemoselectivity to be achieved with porous catalysts and represents a new opportunity to tailor the functionality of heterogeneous catalyst materials.

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INTRODUCTION The ability to control the chemoselectivity of substrate functionalization reactions by systematic ligand perturbation is a hallmark of molecular catalyst design. For example, selection for allylic C−H amination versus aziridination products during Ru2-catalyzed nitrene-transfer reactions intimately depends on the primary ligand sphere of the Ru2 catalyst.1 On the basis of the potential to noncovalently colocalize substrates in proximity to site-isolated catalyst sites, metal−organic frameworks (MOFs) have garnered substantial interest as catalyst platforms for both intra- and intermolecular C−H functionalization. Efforts to exert rational synthetic control over the chemoselectivivity of group transfer reactions effected by MOF catalysts are hampered by the current inability to rationally control the primary coordination sphere of catalyst sites, and thus the electronic structure of latticeconfined reactive intermediates. For example, a single porous Ru2-based MOF with open Ru sites has been reported and the Ru2 sites are supported by carboxylate ligands.2,3 Synthesis of crystalline MOFs is predicated on reversible metal−ligand (M−L) bond-forming chemistry, which simulta© XXXX American Chemical Society

neously assembles the porous network and establishes the primary coordination sphere of the lattice-confined transition metal ions.4−6 The necessity for reversible M−L bond formation to achieve material crystallinity limits the diversity of ligands that can be utilized to generate potential catalyst MOFs. Pyridyl-, carboxylate-, and azolate-derived ligandsall of which are fairly weak-field ligands that engender high-spin electronic configurationsare ubiquitous in the chemistry of MOFs (Figure 1a).7 In contrast, strongly basic donors, such as amido, amidinate, and alkoxide ligandscommon ligands in molecular transition metal catalystsare rarely encountered in the coordination chemistry of MOFs.8,9 Porous organic materials,10,11 such as crystalline covalent organic frameworks (COFs),12−14 amorphous porous organic polymers (POPs),15−19 and organic cage compounds20,21 are comprised of exclusively organic components connected via Special Issue: Organometallic Chemistry within Metal-Organic Frameworks Received: March 11, 2019

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DOI: 10.1021/acs.organomet.9b00162 Organometallics XXXX, XXX, XXX−XXX

Organometallics

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RESULTS AND DISCUSSION Synthesis of Molecular Complexes. A family of molecular Ru2[II,III] complexes bearing iodinated bridging ligands was prepared by thermally promoted ligand exchange with Ru2(OAc)4Cl (Figure 2). Exchange reactions were carried

Figure 1. (a) The pKa values (in DMSO) of a series of proligands (the pKa values of carboxylic acid, amide, and amidine refer to those of benzoic acid, benzamide, and benzamidine, respectively). (b) There is a single Ru2-based MOF, and it is based on bridging carboxylate linkers. This work demonstrates metallopolymerization as a synthetic strategy that allows a family of porous Ru2-based catalysts to be prepared with tuned primary coordination spheres.

Figure 2. Five Ru2L4BF4 complexes, featuring carboxylate (L = 4-IOBz), amidate (L = 4-I-HNBz), 2-oxypyridinate (L = 4-I-hp or 5-Ihp), and 2-aminopyridinate (L = 4-I-ap) ligands, were prepared by a two-step procedure of ligand substitution and anion exchange.

out with 4-iodobenzoic acid (4-I-HOBz), 4-iodobenzamide (4I-H2NBz), 2-hydroxy-4-iodopyridine (4-I-hp), 2-hydroxy-5iodopyridine (5-I-hp), and 2-amino-4-iodopyridine (4-I-ap) to provide Ru2(4-I-OBz)4Cl, Ru2(4-I-HNBz)4Cl, Ru2(4-Ihp)4Cl, Ru2(5-I-hp)4Cl, and Ru2(4-I-ap)4Cl, respectively. In each case, ligand substitution reactions were followed by electrospray ionization mass spectrometry (ESI-MS; negative mode), which provided a value of m/z that corresponded to the mass of [Ru2L4Cl2]−. Structurally, these Ru2[II,III] complexes are comprised of a binuclear core supported by four bridging ligands; charge balance of the Ru2[II,III] mixedvalent core is achieved with an axially bound chloride ligand (see, for example, the structure of Ru2(4-I-HNBz)4Cl derived from single-crystal X-ray diffraction, Figure S1 and Table S1). The electronic absorption spectra of the iodinated Ru2 complexes are well-matched to the spectral data for noniodinated analogues (Figure S2). In addition, the 1H NMR spectrum of Ru2(4-I-OBz)4Cl (Figure S3) displays similar paramagnetically shifted signals as Ru2(OBz)4Cl.35 Ru2(4-Ihp)4Cl, Ru2(5-I-hp)4Cl, and Ru2(4-I-ap)4Cl do not display 1H NMR signals when measured in DMSO at 295 K. The formation of Ru−Cl−Ru chains in the solid-state structures of Ru2L4Cl complexes typically leads to poor solubility in many organic solvents (see, for example, the structure of Ru2(4-I-HNBz)4Cl, Figure S1 and Table S1). To increase the solubility of these complexes, we replaced the axially bound chloride ligand with tetrafluoroborate by treatment with silver tetrafluoroborate. The anion exchange process was monitored by IR spectroscopy, which showed the characteristic broad B−F stretch of BF4− at 1050 cm−1 (Figure S4), and elemental analysis. Single-crystal X-ray diffraction analysis of Ru2(HNBz)4BF4 (Figure S5 and Table S2) reveals the two axial positions of the Ru2 unit are occupied by a water and a THF ligand, respectively. The electronic absorption spectra and 1H NMR spectra of the tetrafluoroborate complexes are similar to those of the related chloride complexes (Figures S2, S6, and S7). Synthesis of Ru2-Based Polymers. A mixture of Ru2(4-Ihp)4BF4 and 1,3,5-triethynylbenzene (A) in 1:1 N,Ndimethylformamide (DMF) and diisopropylamine (DIPA) was heated at 80 °C for 24 h under a N2 atmosphere (Table 1 and details in Table S3). The harvested orange material, i.e.,

covalent bonds. A diverse set of reactions, including imine and boronic ester condensations,22−24 nitrile cyclotrimerizations,25 nucleophilic substitutions,26−28 C−C cross-coupling reactions,29−33 and Huisgen cycloadditions,34 have been applied to the synthesis of porous organic materials. With interest in developing platforms for selective group-transfer catalysis,35−37 we were attracted by the potential to utilize the polymerization strategies pioneered in POPs, in combination with preformed metallomonomers containing the specific metal coordination site of interest, to generate new porous materials in which the primary coordination sphere, and thus the electronic structure of site-isolated catalysts, could be systematically tuned.38,39 Because the envisioned synthetic logic is based on retrosynthetic disconnection of covalent bonds within the organic linkers, and not on the M−L bonds, we speculated that such a synthetic approach would provide access to families of catalyst materials in which the primary coordination sphere of the catalyst sites could be systematically tuned via a common synthetic protocol.40 Here we report the synthesis of a family of porous polymer materials featuring Ru2 sites supported by a diverse family of bridging ligands, including carboxylate, amidate, 2-hydroxypyridinate, and 2-aminopyridinate. The materials are readily accessed by Sonogashira cross-coupling chemistry between preformed molecular Ru2 monomers decorated with aryl iodide functionality and polyalkynes. Consistent with the irreversible Sonogashira reactions utilized to generate these materials, 27 the new Ru 2 -based porous polymers are amorphous. These new porous materials are competent nitrene-transfer catalysts in intramolecular C−H amination. Importantly, in the context of intramolecular nitrene transfer in olefinic substrates, the selectivity for allylic amination versus olefin aziridination displays ligand-dependent selectivity analogous to the selectivity achieved by soluble molecular catalysts. We anticipate that the synthetic strategy described herein, which provides access to porous materials that combine the site isolation of catalyst sites characteristic of MOF chemistry with the atomistic control over the primary coordination sphere characteristic of molecular catalysis, will provide new opportunities to develop porous catalysts for chemoselective group-transfer chemistry. B

DOI: 10.1021/acs.organomet.9b00162 Organometallics XXXX, XXX, XXX−XXX

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Organometallics Table 1. BET (Langmuir) Surface Area Values (m2/g) for Each Obtained Polymeric Materialb

a The synthesis of these materials was not attempted. bRu2-based porous polymers were synthesized from Sonogashira cross-coupling reaction between Ru2 metallomonomers and alkyne-based linkers A, B, and C. The surface areas of these materials were probed by N2 adsorption isotherm at 77 K.

[A4/3(Ru24‑hp)]n, did not dissolve in any common solvents, such as dimethyl sulfoxide (DMSO), methanol (MeOH), and tetrahydrofuran (THF). Soxhlet extraction using MeOH was carried out to ensure complete removal of any unincorporated monomer units. The obtained solid did not display an IR feature of alkyne C−H stretching at 3288 cm−1 (Figure S8a) and showed trace amounts of iodine by elemental analysis, consistent with a high degree of polymerization via Sonogashira cross-coupling.41 The developed polymerization chemistry is modular; both the polyalkyne and the Ru2 monomer can be replaced by different reaction partners. In addition to tris-alkyne A, we have carried out polymerization reactions with 1,3,5-tris(4ethynylphenyl)benzene (B), an extended version of A, and tetra(4-ethnylphenyl)methane (C), which features a tetrahedrally disposed array of terminal alkynes (Table 1). In addition to polymerization with Ru2(4-I-hp)4BF4, we have carried out metallopolymerization reactions with each of the iodinated Ru2 complexes described above. In each case, insoluble materials were obtained and IR analysis (Figure S8) indicated a high degree of polymerization. On the basis of powder X-ray diffraction (PXRD) analysis, all of the prepared materials are amorphous (PXRD data for the five polymers prepared from linker B are collected in Figure S9), which is consistent with previous reports that Sonogashira cross-coupling reactions provide access to amorphous POPs.34,42 Thermogravimetric analysis (TGA) revealed this family of materials is thermally stable to above 200 °C (Figure S10). For example, [B4/3(Ru24‑hp)]n is stable up to 250 °C after which temperature continuous weight loss is observed (Figure S10c). Gas Sorption. N2 adsorption isotherms were collected at 77 K for each of the Ru2-based polymers in order to evaluate the porosity of these materials; data are collected in Table 1

and Figure S11. Pore size distribution analysis is summarized in Figure S11j. Each material was preactivated at 150 °C under reduced pressure ( [B4/3(Ru2HNBz)]n > [B4/3(Ru2OBz)]n. This set of experiments demonstrates that the developed Sonogashira coupling strategy for polymerization of metallomonomers provides a platform to translate the chemoselectivity of molecular catalysts to recyclable porous material platforms. Comparison of the chemoselectivity for 4- and 5-substituted hp complexes suggests that, in addition to the primary coordination sphere, confinement effects within porous E

DOI: 10.1021/acs.organomet.9b00162 Organometallics XXXX, XXX, XXX−XXX

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the structure and function of metal−organic frameworks via linker design. Chem. Soc. Rev. 2014, 43, 5561−5593. (5) Cook, T. R.; Zheng, Y.-R.; Stang, P. J. Metal−Organic Frameworks and Self-Assembled Supramolecular Coordination Complexes: Comparing and Contrasting the Design, Synthesis, and Functionality of Metal−Organic Materials. Chem. Rev. 2013, 113, 734−777. (6) Furukawa, H.; Cordova, K. E.; O’Keeffe, M.; Yaghi, O. M. The Chemistry and Applications of Metal−Organic Frameworks. Science 2013, 341, 1230444. (7) Hendon, C. H.; Rieth, A. J.; Korzyński, M. D.; Dincǎ, M. Grand Challenges and Future Opportunities for Metal−Organic Frameworks. ACS Cent. Sci. 2017, 3, 554−563. (8) Catarineu, N. R.; Schoedel, A.; Urban, P.; Morla, M. B.; Trickett, C. A.; Yaghi, O. M. Two Principles of Reticular Chemistry Uncovered in a Metal−Organic Framework of Heterotritopic Linkers and Infinite Secondary Building Units. J. Am. Chem. Soc. 2016, 138, 10826− 10829. (9) Masciocchi, N.; Galli, S.; Tagliabue, G.; Sironi, A.; Castillo, O.; Luque, A.; Beobide, G.; Wang, W.; Romero, M. A.; Barea, E.; Navarro, J. A. R. Thermally Induced Interconversions of Metal− Pyrimidine-4,6-dicarboxylate Polymers: A Structural, Spectroscopic, and Magnetic Study. Inorg. Chem. 2009, 48, 3087−3094. (10) Das, S.; Heasman, P.; Ben, T.; Qiu, S. Porous Organic Materials: Strategic Design and Structure−Function Correlation. Chem. Rev. 2017, 117, 1515−1563. (11) Slater, A. G.; Cooper, A. I. Function-led design of new porous materials. Science 2015, 348, aaa8075. (12) Diercks, C. S.; Yaghi, O. M. The atom, the molecule, and the covalent organic framework. Science 2017, 355, eaal1585. (13) Ding, S.-Y.; Wang, W. Covalent organic frameworks (COFs): from design to applications. Chem. Soc. Rev. 2013, 42, 548−568. (14) Huang, N.; Wang, P.; Jiang, D. Covalent organic frameworks: a materials platform for structural and functional designs. Nat. Rev. Mater. 2016, 1, 16068. (15) Chaoui, N.; Trunk, M.; Dawson, R.; Schmidt, J.; Thomas, A. Trends and challenges for microporous polymers. Chem. Soc. Rev. 2017, 46, 3302−3321. (16) Sun, Q.; Dai, Z.; Meng, X.; Xiao, F.-S. Porous polymer catalysts with hierarchical structures. Chem. Soc. Rev. 2015, 44, 6018−6034. (17) Xu, Y.; Jin, S.; Xu, H.; Nagai, A.; Jiang, D. Conjugated microporous polymers: design, synthesis and application. Chem. Soc. Rev. 2013, 42, 8012−8031. (18) Kaur, P.; Hupp, J. T.; Nguyen, S. T. Porous Organic Polymers in Catalysis: Opportunities and Challenges. ACS Catal. 2011, 1, 819− 835. (19) Zou, L.; Sun, Y.; Che, S.; Yang, X.; Wang, X.; Bosch, M.; Wang, Q.; Li, H.; Smith, M.; Yuan, S.; Perry, Z.; Zhou, H.-C. Porous Organic Polymers for Post-Combustion Carbon Capture. Adv. Mater. 2017, 29, 1700229. (20) Zhang, G.; Mastalerz, M. Organic cage compounds − from shape-persistency to function. Chem. Soc. Rev. 2014, 43, 1934−1947. (21) Tozawa, T.; Jones, J. T.; Swamy, S. I.; Jiang, S.; Adams, D. J.; Shakespeare, S.; Clowes, R.; Bradshaw, D.; Hasell, T.; Chong, S. Y.; Tang, C.; Thompson, S.; Parker, J.; Trewin, A.; Bacsa, J.; Slawin, A. M. Z.; Steiner, A.; Cooper, A. I. Porous organic cages. Nat. Mater. 2009, 8, 973−978. (22) Côté, A. P.; Benin, A. I.; Ockwig, N. W.; O’Keeffe, M.; Matzger, A. J.; Yaghi, O. M. Porous Crystalline, Covalent Organic Frameworks. Science 2005, 310, 1166−1170. (23) Uribe-Romo, F. J.; Hunt, J. R.; Furukawa, H.; Klöck, C.; O’Keeffe, M.; Yaghi, O. M. A Crystalline Imine-Linked 3-D Porous Covalent Organic Framework. J. Am. Chem. Soc. 2009, 131, 4570− 4571. (24) Schwab, M. G.; Fassbender, B.; Spiess, H. W.; Thomas, A.; Feng, X.; Müllen, K. Catalyst-free Preparation of Melamine-Based Microporous Polymer Networks through Schiff Base Chemistry. J. Am. Chem. Soc. 2009, 131, 7216−7217.

expand the suite of porous catalyst materials that can be evaluated for chemoselective C−H functionalization chemistry.

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ASSOCIATED CONTENT

* Supporting Information S

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.organomet.9b00162. Experimental details, characterization data including NMR, electronic absorption, and IR spectra, PXRD patterns, TGA plots, N2 adsorption isotherms, and X-ray absorption spectroscopy data (PDF) Accession Codes

CCDC 1873925−1873926 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by emailing [email protected], or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. ORCID

Wen-Yang Gao: 0000-0002-9879-1634 Andrew A. Ezazi: 0000-0002-3884-3500 Chen-Hao Wang: 0000-0003-3416-4452 Jisue Moon: 0000-0002-1210-6342 Carter Abney: 0000-0002-1809-9577 Joshua Wright: 0000-0002-6217-3084 David C. Powers: 0000-0003-3717-2001 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS We thank Texas A&M University, the Welch Foundation (A1907), and the U.S. Department of Energy (DE-SC0018977) for financial support. XAS data were collected at Sector 10, MRCAT, of the Advanced Photon Source at Argonne National Laboratory. MRCAT operations are supported by the Department of Energy and the MRCAT member institutions. This research used resources of 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-AC0206CH11357.

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REFERENCES

(1) Harvey, M. E.; Musaev, D. G.; Du Bois, J. A Diruthenium Catalyst for Selective, Intramolecular Allylic C−H Amination: Reaction Development and Mechanistic Insight Gained through Experiment and Theory. J. Am. Chem. Soc. 2011, 133, 17207−17216. (2) Wade, C. R.; Dincǎ, M. Investigation of the synthesis, activation, and isosteric heats of CO2 adsorption of the isostructural series of metal−organic frameworks M3(BTC)2 (M = Cr, Fe, Ni, Cu, Mo, Ru). Dalton Trans. 2012, 41, 7931−7938. (3) Kozachuk, O.; Yusenko, K.; Noei, H.; Wang, Y.; Walleck, S.; Glaser, T.; Fischer, R. A. Solvothermal growth of a ruthenium metal− organic framework featuring HKUST-1 structure type as thin films on oxide surfaces. Chem. Commun. 2011, 47, 8509−8511. (4) Lu, W.; Wei, Z.; Gu, Z.-Y.; Liu, T.-F.; Park, J.; Park, J.; Tian, J.; Zhang, M.; Zhang, Q.; Gentle, T., III; Bosch, M.; Zhou, H.-C. Tuning F

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Article

Organometallics (25) Kuhn, P.; Antonietti, M.; Thomas, A. Porous, Covalent Triazine-Based Frameworks Prepared by Ionothermal Synthesis. Angew. Chem., Int. Ed. 2008, 47, 3450−3453. (26) Ong, W. J.; Swager, T. M. Dynamic self-correcting nucleophilic aromatic substitution. Nat. Chem. 2018, 10, 1023−1030. (27) Zhang, B.; Wei, M.; Mao, H.; Pei, X.; Alshmimri, S. A.; Reimer, J. A.; Yaghi, O. M. Crystalline Dioxin-Linked Covalent Organic Frameworks from Irreversible Reactions. J. Am. Chem. Soc. 2018, 140, 12715−12719. (28) Farha, O. K.; Spokoyny, A. M.; Hauser, B. G.; Bae, Y.-S.; Brown, S. E.; Snurr, R. Q.; Mirkin, C. A.; Hupp, J. T. Synthesis, Properties, and Gas Separation Studies of a Robust Diimide-Based Microporous Organic Polymer. Chem. Mater. 2009, 21, 3033−3035. (29) Chen, L.; Honsho, Y.; Seki, S.; Jiang, D. Light-Harvesting Conjugated Microporous Polymers: Rapid and Highly Efficient Flow of Light Energy with a Porous Polyphenylene Framework as Antenna. J. Am. Chem. Soc. 2010, 132, 6742−6748. (30) Jiang, J.-X.; Trewin, A.; Adams, D. J.; Cooper, A. I. Band gap engineering in fluorescent conjugated microporous polymers. Chem. Sci. 2011, 2, 1777−1781. (31) Cheng, G.; Hasell, T.; Trewin, A.; Adams, D. J.; Cooper, A. I. Soluble Conjugated Microporous Polymers. Angew. Chem., Int. Ed. 2012, 51, 12727−12731. (32) Ben, T.; Ren, H.; Ma, S.; Cao, D.; Lan, J.; Jing, X.; Wang, W.; Xu, J.; Deng, F.; Simmons, J. M.; Qiu, S.; Zhu, G. Targeted Synthesis of a Porous Aromatic Framework with High Stability and Exceptionally High Surface Area. Angew. Chem., Int. Ed. 2009, 48, 9457−9460. (33) Jiang, J.-X.; Su, F.; Trewin, A.; Wood, C. D.; Campbell, N. L.; Niu, H.; Dickinson, C.; Ganin, A. Y.; Rosseinsky, M. J.; Khimyak, Y. Z.; Cooper, A. I. Conjugated Microporous Poly(aryleneethynylene) Networks. Angew. Chem., Int. Ed. 2007, 46, 8574−8578. (34) Holst, J. R.; Stöckel, E.; Adams, D. J.; Cooper, A. I. High Surface Area Networks from Tetrahedral Monomers: Metal-Catalyzed Coupling, Thermal Polymerization, and “Click” Chemistry. Macromolecules 2010, 43, 8531−8538. (35) Wang, C.-H.; Das, A.; Gao, W.-Y.; Powers, D. C. Probing Substrate Diffusion in Interstitial MOF Chemistry with Kinetic Isotope Effects. Angew. Chem., Int. Ed. 2018, 57, 3676−3681. (36) Xiao, D. J.; Bloch, E. D.; Mason, J. A.; Queen, W. L.; Hudson, M. R.; Planas, N.; Borycz, J.; Dzubak, A. L.; Verma, P.; Lee, K.; Bonino, F.; Crocellà, V.; Yano, J.; Bordiga, S.; Truhlar, D. 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, 590−595. (37) Wang, L.; Agnew, D. W.; Yu, X.; Figueroa, J. S.; Cohen, S. M. A Metal−Organic Framework with Exceptional Activity for C−H Bond Amination. Angew. Chem., Int. Ed. 2018, 57, 511−515. (38) For a similar metallopolymerization strategy to access phosphine-based materials by polymerization of metal phosphine monomers, see: (a) Bentz, K. C.; Cohen, S. M. Supramolecular Metallopolymers: From Linear Materials to Infinite Networks. Angew. Chem., Int. Ed. 2018, 57, 14992−15001. (b) He, J.; Waggoner, N. W.; Dunning, S. G.; Steiner, A.; Lynch, V. M.; Humphrey, S. M. A PCP Pincer Ligand for Coordination Polymers with Versatile Chemical Reactivity: Selective Activation of CO2 Gas over CO Gas in the Solid State. Angew. Chem., Int. Ed. 2016, 55, 12351−12355. (c) Sikma, R. E.; Kunal, P.; Dunning, S. G.; Reynolds, J. E., III; Lee, J. S.; Chang, J.S.; Humphrey, S. M. Organoarsine Metal−Organic Framework with cis-Diarsine Pockets for the Installation of Uniquely Confined Metal Complexes. J. Am. Chem. Soc. 2018, 140, 9806−9809. (d) Bohnsack, A. M.; Ibarra, I. A.; Bakhmutov, V. I.; Lynch, V. M.; Humphrey, S. M. Rational Design of Porous Coordination Polymers Based on Bis(phosphine)MCl2 Complexes That Exhibit High-Temperature H2 Sorption and Chemical Reactivity. J. Am. Chem. Soc. 2013, 135, 16038−16041. (e) Burgess, S. A.; Kassie, A.; Baranowski, S. A.; Fritzsching, K. J.; Schmidt-Rohr, K.; Brown, C. M.; Wade, C. R. Improved Catalytic Activity and Stability of a Palladium Pincer Complex by Incorporation into a Metal−Organic Framework. J. Am. Chem. Soc. 2016, 138, 1780−1783. (f) Reiner, B. R.; Mucha, N. T.;

Rothstein, A.; Temme, J. S.; Duan, P.; Schmidt-Rohr, K.; Foxman, B. M.; Wade, C. R. Zirconium Metal-Organic Frameworks Assembled from Pd and Pt PNNNP Pincer Complexes: Synthesis, Postsynthetic Modification, and Lewis Acid Catalysis. Inorg. Chem. 2018, 57, 2663− 2672. (g) He, J.; Bohnsack, A. M.; Waggoner, N. W.; Dunning, S. G.; Lynch, V. M.; Kaska, W. C.; Humphrey, S. M. 1-D and 2-D phosphine coordination materials based on a palladium(II) PCP pincer metalloligand. Polyhedron 2018, 143, 149−156. (39) Metallopolymerization of metalloporphyrin-based monomers has been utilized to generate metalloporphyrin-based polymers that can be utilized as heterogeneous catalysts. See: (a) Chen, L.; Yang, Y.; Jiang, D. CMPs as Scaffolds for Constructing Porous Catalytic Frameworks: A Built-in Heterogeneous Catalyst with High Activity and Selectivity Based on Nanoporous Metalloporphyrin Polymers. J. Am. Chem. Soc. 2010, 132, 9138−9143. (b) Ji, G.; Yang, Z.; Zhao, Y.; Zhang, H.; Yu, B.; Xu, J.; Xu, H.; Liu, Z. Synthesis of metalloporphyrin-based conjugated microporous polymer spheres directed by bipyridine-type ligands. Chem. Commun. 2015, 51, 7352−7355. (c) McKeown, N. B.; Hanif, S.; Msayib, K.; Tattershall, C. E.; Budd, P. M. Porphyrin-based nanoporous network polymers. Chem. Commun. 2002, 2782−2783. (d) Shultz, A. M.; Farha, O. K.; Hupp, J. T.; Nguyen, S. T. Synthesis of catalytically active porous organic polymers from metalloporphyrin building blocks. Chem. Sci. 2011, 2, 686−689. (e) Feng, L.-J.; Chen, Q.; Zhu, J.-H.; Liu, D.-P.; Zhao, Y.C.; Han, B.-H. Adsorption performance and catalytic activity of porous conjugated polyporphyrins via carbazole-based oxidative coupling polymerization. Polym. Chem. 2014, 5, 3081−3088. (40) Recently, polymerization of metal−organic polyhedrals has been demonstrated to provide access to amorphous polymers with embedded transition metal sites. See: Carné-Sánchez, A.; Craig, G. A.; Larpent, P.; Guillerm, V.; Urayama, K.; Maspoch, D.; Furukawa, S. Angew. Chem., Int. Ed. 2019, 58, 6347−6350. (41) A variety of conditions have been reported for the synthesis of porous organic materials by Sonogashira-based step-growth polymerization. We have investigated both the impact of the relative stoichiometry of Ru2L4BF4 (L = 4-I-OBz, 4-I-HNBz, 4-I-hp, 5-I-hp, and 4-I-ap) and 1,3,5-tris(4-ethynylphenyl)benzene (B) as well as polymerization under Cu-free conditions and have found the surface area of the resulting materials to be similar to or lower than that prepared by these methods (Figure S11h,i and Table S4). See: (a) Laybourn, A.; Dawson, R.; Clowes, R.; Hasell, T.; Cooper, A. I.; Khimyak, Y. Z.; Adams, D. J. Network formation mechanisms in conjugated microporous polymers. Polym. Chem. 2014, 5, 6325− 6333. (b) Kim, B.; Park, N.; Lee, S. M.; Kim, H. J.; Son, S. U. Insights into the low surface area of conjugated microporous polymers and methodological suggestion for the enhancement of porosity. Polym. Chem. 2015, 6, 7363−7367. (c) Trunk, M.; Herrmann, A.; Bildirir, H.; Yassin, A.; Schmidt, J.; Thomas, A. Copper-Free Sonogashira Coupling for High-Surface-Area Conjugated Microporous Poly(aryleneethynylene) Networks. Chem. - Eur. J. 2016, 22, 7179−7183. (42) Jiang, J.-X.; Su, F.; Trewin, A.; Wood, C. D.; Niu, H.; Jones, J. T. A.; Khimyak, Y. Z.; Cooper, A. I. Synthetic Control of the Pore Dimension and Surface Area in Conjugated Microporous Polymer and Copolymer Networks. J. Am. Chem. Soc. 2008, 130, 7710−7720. (43) Roy, S. G.; Haldar, U.; De, P. Remarkable Swelling Capability of Amino Acid Based Cross-Linked Polymer Networks in Organic and Aqueous Medium. ACS Appl. Mater. Interfaces 2014, 6, 4233−4241. (44) Sonmez, H. B.; Wudl, F. Cross-Linked Poly(orthocarbonate)s as Organic Solvent Sorbents. Macromolecules 2005, 38, 1623−1626. (45) Zhang, W.; Freitag, K.; Wannapaiboon, S.; Schneider, C.; Epp, K.; Kieslich, G.; Fischer, R. A. Elaboration of a Highly Porous RuII,II Analogue of HKUST-1. Inorg. Chem. 2016, 55, 12492−12495. (46) Clark, R. J. H.; Franks, M. L. Resonance Raman spectra of chlorotetra-acetato- and chlorotetrabutyrato-diruthenium. J. Chem. Soc., Dalton Trans. 1976, 1825−1828. (47) Kornecki, K. P.; Berry, J. F.; Powers, D. C.; Ritter, T. Metal− Metal Bond-Containing Complexes as Catalysts for C−H Functionalization. Prog. Inorg. Chem. 2014, 58, 225−302. G

DOI: 10.1021/acs.organomet.9b00162 Organometallics XXXX, XXX, XXX−XXX

Article

Organometallics (48) Aquino, M. A. S. Diruthenium and diosmium tetracarboxylates: synthesis, physical properties and applications. Coord. Chem. Rev. 1998, 170, 141−202. (49) Barral, M. C.; Herrero, S.; Jiménez-Aparicio, R.; Torres, M. R.; Urbanos, F. A. A Spin-Admixed Ruthenium Complex. Angew. Chem., Int. Ed. 2005, 44, 305−307. (50) Miskowski, V. M.; Gray, H. B. Electronic Spectra of Ru2(carboxylate)4+ Complexes. Higher Energy Electronic Excited States. Inorg. Chem. 1988, 27, 2501−2506. (51) Miskowski, V. M.; Loehr, T. M.; Gray, H. B. Electronic and Vibrational Spectra of Ru2(carboxylate)4+ Complexes. Characterization of a High-Spin Metal−Metal Ground State. Inorg. Chem. 1987, 26, 1098−1108. (52) Wilson, C. R.; Taube, H. Acetate Complexes of Dirhodium and Diruthenium. Aquation and Reduction-Oxidation. Inorg. Chem. 1975, 14, 2276−2279. (53) Gao, W.-Y.; Cardenal, A. D.; Wang, C.-H.; Powers, D. C. In Operando Analysis of Diffusion in Porous Metal-Organic Framework Catalysts. Chem. - Eur. J. 2019, 25, 3465−3476. (54) Fiori, K. W.; Du Bois, J. Catalytic Intermolecular Amination of C−H Bonds: Method Development and Mechanistic Insights. J. Am. Chem. Soc. 2007, 129, 562−568. (55) Davies, H. M. L.; Manning, J. R. Catalytic C−H functionalization by metal carbenoid and nitrenoid insertion. Nature 2008, 451, 417−424. (56) Meunier, B.; de Visser, S. P.; Shaik, S. Mechanism of Oxidation Reactions Catalyzed by Cytochrome P450 Enzymes. Chem. Rev. 2004, 104, 3947−3980. (57) Newcomb, M.; Toy, P. H. Hypersensitive Radical Probes and the Mechanisms of Cytochrome P450-Catalyzed Hydroxylation Reactions. Acc. Chem. Res. 2000, 33, 449−455.

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DOI: 10.1021/acs.organomet.9b00162 Organometallics XXXX, XXX, XXX−XXX