A Bifunctional Iridium Catalyst Modified for Persistent Hydrogen

Research Article pubs.acs.org/acscatalysis

A Bifunctional Iridium Catalyst Modified for Persistent Hydrogen Generation from Formic Acid: Understanding Deactivation via Cyclometalation of a 1,2-Diphenylethylenediamine Motif Asuka Matsunami,† Shigeki Kuwata,†,‡ and Yoshihito Kayaki*,† †

Department of Chemical Science and Engineering, School of Materials and Chemical Technology, Tokyo Institute of Technology, 2-12-1-E4-1 O-okayama, Meguro-ku, Tokyo 152-8552, Japan ‡ PRESTO, Japan Science and Technology Agency (JST), 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan S Supporting Information *

ABSTRACT: Thermal degradation of a bifunctional Ir complex with a 1,2-diphenylethylenediamine (DPEN) framework was investigated, which is relevant to catalyst deactivation in the acceptorless dehydrogenation of formic acid. The welldefined hydridoiridium complex 1b, derived from N-triflyl-1,2diphenylethylenediamine (TfDPEN), proved to be solely transformed at the reflux temperature of 1,2-dimethoxyethane (DME) into two iridacycles (2 and 3) via C−H bond cleavage at the ortho carbon atoms of the phenyl substituents on the diamine backbone. These products were successfully isolated and characterized by NMR, elemental analysis, and X-ray crystallography. The iridacycle formation was significantly enhanced in the presence of water, possibly due to facile deprotonative orthometalation via a hydroxidoiridium intermediate. To prevent the deactivation process caused by the cyclometalation of the DPEN moiety, a hydridoiridium complex (5b) without phenyl substituents was synthesized from N-triflylethylenediamine (TfEN). The modified complex 5b showed a pronounced ability to catalyze hydrogen evolution from formic acid in a 1/1 mixed solvent of water and DME even in the absence of base additives. The initial rate was maintained for a longer time relative to 1b, and thus formic acid was mostly converted within 80 min under the conditions of a HCOOH/5b ratio of 15900 at 60 °C. KEYWORDS: iridium, hydrogen generation, formic acid, cyclometalation, bifunctional catalyst

■

INTRODUCTION Hydrogen is a promising clean energy carrier in stationary and transportation power applications for the future.1 However, the storage and transportation of large-scale amounts of hydrogen pose a serious risk due to its highly flammable and explosive nature.2 Generating hydrogen gas from other safe alternatives just before use has drawn much attention, as it is less hazardous and potentially more cost effective.3 Formic acid is an attractive hydrogen carrier because of its relatively high gravimetric hydrogen content (4.4 wt %).4 Various homogeneous catalysts, including Ru,5 Ir,5k,o,6,7 Rh,5m,8 Fe,9 and other10 transitionmetal complexes, have been reported to show the selective transformation of formic acid into hydrogen and carbon dioxide without carbon monoxide contamination.11 Among them, Ir complexes with proton-responsive ligands achieved excellent results. For example, Himeda and Fujita reported a very high turnover frequency (TOF) of 228000 h−1 at 90 °C using a binuclear Ir catalyst bearing a bipyrimidine ligand in the presence of sodium formate.6d Li and co-workers developed a water-soluble iridium catalyst with an N,N′-diimine ligand, which attained the best TOF of 487500 h−1 at 90 °C without base additives.6j As a limited example of exceptionally high © XXXX American Chemical Society

turnover rates under mild conditions, Xiao’s bifunctional Ir complex bearing a cyclometalated 2-aryl-imidazoline ligand demonstrated an excellent TOF of 147000 h−1 for the initial 10 s at 40 °C in an azeotropic mixture of formic acid and triethylamine (5/2).6f In our recent studies on bifunctional catalysts possessing a proton-responsive metal/NH group, Cp*Ir complexes derived from N-sulfonylated DPEN proved to be effective for catalyzing the evolution of hydrogen from formic acid.7 The substituted DPEN ligand has been shown to facilitate Ru-, Rh-, and Ircatalyzed asymmetric transfer hydrogenation,12 H2 hydrogenation of ketones,13 and oxidation of alcohols14 via a H+/ H− delivery with the interconversion between hydrido-amine and amido complexes, as depicted in Scheme 1.15 The function of the catalysts was found to be switchable from hydrogen transfer to acceptorless dehydrogenation. In particular, TfDPEN-derived Ir catalysts 1a,b showed appreciably high activity with a TOF up to 6090 h−1 for the initial 5 min at 35 Received: April 1, 2017 Revised: May 19, 2017 Published: May 24, 2017 4479

DOI: 10.1021/acscatal.7b01068 ACS Catal. 2017, 7, 4479−4484

Research Article

ACS Catalysis Scheme 1. Efficient Proton/Hydride Delivery System for Bifunctional Iridium Complexes

°C without base additives. The conversion of formic acid was accelerated by the NH moiety on the ligand as well as an aqueous mixed solvent, possibly due to the effective protonation of the metal hydride via a plausible proton-relay mechanism (Scheme 2). Scheme 2. Acceptorless Dehydrogenation from Formic Acid Using TfDPEN-Derived Iridium Catalysts 1a,b

Figure 1. Time course of turnover numbers in the dehydrogenation of formic acid using the iridium complex 1a at 25, 35, and 60 °C.

The thermal stability of the hydridoiridium complex 1b, which is a key intermediate in the rate-determining hydrogen evolution step,7 was investigated by heating in refluxing DME for 38 h. The 1H NMR spectrum of the resulting mixture in CD2Cl2 indicated that 1b was transformed entirely into two new products, exhibiting two singlet signals centered at 1.83 and 1.84 ppm due to the methyl protons of the Cp* ligand at a ratio of 1/4.6. These complexes were successfully separated by silica gel column chromatography with hexane/diethyl ether (1/2) as eluent. As depicted in Scheme 3, the two isomeric iridacycles 2 and 3 were identified from the result of 1H, 19F, and 13C{1H} NMR analyses and X-ray crystallography. As shown in Figures 2 and 3, each iridacycle adopts a three-legged piano-stool structure around the Ir(III) atom with Cp*, amine, sulfonylamido, and phenyl ligands. These iridacycles are dehydrogenative cyclometalation products where the ortho carbon atom of each phenyl substituent on the DPEN is attached to the Ir metal. Complex 2 was formed via an intramolecular C−H bond cleavage of the phenyl group A proximal to the NTf moiety, and complex 3 was the product metalated at the phenyl group B proximal to the NH2 moiety. Both structures display similar bond lengths and bond angles around the Ir centers, as shown in Table S1 in the Supporting Information. Although the underlying mechanism of the metallacycle formation is obscure, the release of hydrogen gas could be confirmed by a 1H NMR monitoring experiment for the thermolysis of 1b in refluxing THF-d8. Dehydrogenative cyclometalation was recently reported in a rhodacycle system based on 2-(di-tert-butylphosphinomethyl)-6-phenylpyridine and utilized for the catalytic hydrogen evolution from formic acid.8c The cyclometalation of a hydridorhodium intermediate with a bidentate PN coordination mode was proposed as a clue to H2 elimination accompanied by formation of the PNC pincer structure. The reverse decyclometalation was also demonstrated by treatment of the rhodacycle with formic acid to give a formatorhodium complex with a premetalated aryl moiety. Differently from the reversible nature of the PNCpincer Rh complex conferred from the hemilabile aryl group, the TfDPEN-derived iridacycles 2 and 3 kept intact in a THF-

For most of the catalysts used in the evolution of hydrogen from formic acid, it is difficult to maintain their excellent initial efficiencies. The same was true for our catalysts 1a,b; for example, the rate of hydrogen evolution at 35 °C decreased as time passed. On the other hand, catalyst deterioration was suppressed at 0 °C and the highest turnover number (TON) of 6780 was achieved after 53 h. On the basis of these results, we have shed light on the thermal degradation pathway of the TfDPEN-Ir complexes toward making a more robust and reliable dehydrogenation catalyst.

■

RESULTS AND DISCUSSION We initially investigated the temperature dependence of the catalytic activities of dehydrogenation using the amidoiridium complex 1a. Formic acid (3 mL, 79.5 mmol) was continuously introduced via a syringe pump at a rate of 0.3 mL/min to 1a (0.001 mmol) in a mixed solvent of DME (6 mL) and water (6 mL), according to our reported procedure.7 The rate of gas evolution was accurately estimated by a mass flowmeter for 1 h. As shown in Figure 1, the initial catalytic efficiency was enhanced by increasing the reaction temperature. A very high TOF of 11110 h−1 was achieved at 60 °C within the first 5 min of the reaction, but the hydrogen generation decreased after 15 min and plateaued at a TON of 2270 for 1 h. When the reaction was conducted at a lower temperature of 25 °C, the TON for 1 h was increased to 3190. The initial TOF of 3490 h−1 was not as high as that at 35 or 60 °C, but the TOF remained nearly the same for over 1 h. These results strongly indicate that catalyst deactivation stemming from thermolysis of the catalytic species occurred during dehydrogenation at higher temperatures. 4480


Research Article

ACS Catalysis Scheme 3. Thermal Transformation of Hydridoiridium Complex 1b to Iridacycles 2 and 3

and water, was completed within 50 min to produce a mixture of 2 and 3 with a ratio of 1/6.3. Koike and Ikariya reported a similar acceleration effect of phenols or acidic alcohols on the cyclometalation of bifunctional Ru, Rh, and Ir complexes containing a TsDPEN ligand.16 In addition to the products resulting from ortho metalation of the Ts group, C−H bond metalation on the phenyl group proximal to the NH2 moiety was exemplified by the reaction of the Ru complex. Detailed kinetic and mechanistic studies revealed that ortho metalation is promoted via alkoxido intermediates accessible from the starting amido complexes with alcoholic compounds. Analogously, the C−H activation of 1b should be facilitated by water via a hydroxidoiridium intermediate,17 as shown in Scheme 4. Iridacycles 2 and 3 exhibited limited catalytic activity for the hydrogen evolution in comparison with that of the amidoiridium complex 1a, suggesting that the cyclometalation is closely related to the deterioration of the hydrogen generation. The reaction profile shown in Figure 4 illustrates a substantial

Figure 2. ORTEP structure of the iridacycle 2. The hydrogen atoms, except for the coordinating amine protons, are omitted for clarity. Thermal ellipsoids represent the 30% probability level.

Figure 3. ORTEP structure of the iridacycle 3. The hydrogen atoms, except for the coordinating amine protons, are omitted for clarity. Thermal ellipsoids represent the 30% probability level.

d8 solution at room temperature after treatment with 5 molar equiv of formic acid. Interestingly, the cyclometalation was strongly influenced by water. The formation of the iridacycles was accelerated in aqueous DME, which is the optimized reaction solvent for the acceptorless dehydrogenation system. In contrast to the aforementioned cyclometalation in DME that required 38 h (Scheme 3), thermolysis of 1b, in a 1/1 mixed solvent of DME

Figure 4. Time versus TON plots for the catalytic hydrogen production from formic acid using complexes 1a, 2, and 3.

decrease in the catalytic function of 2 and 3, especially at the initial stage. The iridacycles catalyzed the dehydrogenation with

Scheme 4. Plausible Cyclometalation Mechanism of 1b via a Hydroxidoiridium Intermediate

4481


Research Article

ACS Catalysis the addition of excess formic acid but with a lower performance in comparison with that of the parent complex 1a. The regeneration of catalysis may involve the liberation of the NTf moiety from the iridacycles, as deduced from the 19F NMR spectra of the reaction mixture displaying new signals around −78 ppm.18 After approximately 20 min passed in the reaction, the sum of the signal intensities ascribed to the free NTf was 9 times as much as the peak at −76 ppm of the remaining NTf moiety of 3, whereas almost half of the starting iridacycle remained untouched in the case of the less active 2. These results corroborate the catalytic behavior of 2 and 3. The NTf ligand on the six-membered chelate ring of 3 would be susceptible to its dissociation relative to the rigid fivemembered ring of 2. To prevent the cyclometalation process of the DPEN moiety, we designed a new Ir system, derived from N-triflylethylenediamine (TfEN). The precatalyst chloridoiridium complex 4 was synthesized from [Cp*IrCl2]2 and the TfEN ligand in the presence of triethylamine with 58% yield after recrystallization from dichloromethane/diethyl ether, as shown in Scheme 5a.19

Figure 5. Time versus TON plots for the catalytic acceptorless dehydrogenation from formic acid using complexes 1a and 5b at 35 °C.

125 min. Furthermore, the catalytic deactivation was evidently suppressed even at a higher temperature. When the reaction using 5b was carried out at 60 °C with a total substrate/catalyst molar ratio of 15900, 97% of the added formic acid was converted within 80 min, as depicted in Figure S2 in the Supporting Information.

Scheme 5. Synthesis of (a) the Chloridoiridium Complex 4 Derived from TfEN and (b) the Hydridoiridium Complex 5b via the Coordinately Unsaturated Amidoiridium 5a

■

CONCLUSIONS The well-defined bifunctional hydridoiridium complex 1b, derived from TfDPEN, was thermally transformed into iridacycles 2 and 3, both of which were isolated and characterized. The formation of the iridacycle was markedly enhanced in an aqueous solvent in a manner identical with that for the dehydrogenation. Judging from the catalytic behavior of 2 and 3, the cyclometalation process hampers the catalytic performance for the dehydrogenation from formic acid. Actually, the rationally designed hydridoiridium complex 5b derived from non-phenyl-substituted TfEN showed excellent catalytic activity in the absence of base additives with no noticeable retardation even at elevated temperature. Formic acid was mostly consumed at 60 °C within 80 min to achieve a TON of 15400. The findings on the thermal behavior of DPEN-based complexes should contribute to develop more efficient and robust bifunctional catalysts for a range of asymmetric and nonasymmetric processes.

After transformation of 4 into the amidoiridium complex 5a in situ by treatment with aqueous KOH at 0 °C, subsequent addition of formic acid resulted in the hydridoiridium complex 5b in an isolated yield of 69% (Scheme 5b). The amidoiridium complex 5a was not stable and easily decomposed at room temperature. The chlorido complex 4 and hydrido complex 5b were characterized by 1H, 19F, and 13C NMR spectroscopy and X-ray crystallography. The ORTEP structure of the hydridoiridium complex 5b clearly shows that the metal is bound to Cp*, amine, and sulfonamide ligands in the typical three-legged piano-stool coordination environment, although the hydrido ligand is not located in the electron density map, as depicted in Figure S4 in the Supporting Information. The bond lengths and bond angles around the iridium center of complex 5b were similar to those of the hydridoiridium complex 1b derived from the TfDPEN (see Table S2 in the Supporting Information). Finally, in order to assess the catalytic potential of the new hydridoiridium complex 5b derived from TfEN, flow monitoring experiments of the hydrogen generation from formic acid were performed at 35 and 60 °C. As shown in Figure 5, 5b showed excellent performance with an initial TOF of 5590 h−1 at 35 °C, on par with that of the Ir catalyst 1a derived from TfDPEN. As expected, 5b kept its high performance for a far longer period in comparison to the prototype 1a, achieving a TON of 6850 (86% conversion) after

■

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acscatal.7b01068. Experimental procedures and characterization data, including NMR spectra of new compounds, and singlecrystal X-ray diffraction data for compounds 2, 3, 4· CH2Cl2, and 5b (PDF) Crystallographic data (CIF) Crystallographic data (CIF) Crystallographic data (CIF) Crystallographic data (CIF)

■

AUTHOR INFORMATION

Corresponding Author

*E-mail for Y.K.: [email protected]. 4482


Research Article

ACS Catalysis ORCID

Pan, C.-L.; Zhang, Y.; Li, H.; Min, S.; Guo, X.; Zheng, B.; Chen, H.; Anders, A.; Lai, Z.; Zheng, J.; Huang, K.-W. Chem. - Asian J. 2016, 11, 1357−1360. (w) Mellone, I.; Bertini, F.; Peruzzini, M.; Gonsalvi, L. Catal. Sci. Technol. 2016, 6, 6504−6512. (x) Guan, C.; Zhang, D.-D.; Pan, Y.; Iguchi, M.; Ajitha, M. J.; Hu, J.; Li, H.; Yao, C.; Huang, M.-H.; Min, S.; Zheng, J.; Himeda, Y.; Kawanami, H.; Huang, K.-W. Inorg. Chem. 2017, 56, 438−445. (y) Siek, S.; Burks, D. B.; Gerlach, D. L.; Liang, G.; Tesh, J. M.; Thompson, C. R.; Qu, F.; Shankwitz, J. E.; Vasquez, R. M.; Chambers, N.; Szulczewski, G. J.; Grotjahn, D. B.; Webster, C. E.; Papish, E. T. Organometallics 2017, 36, 1091−1106. (6) (a) Himeda, Y. Green Chem. 2009, 11, 2018−2022. (b) Himeda, Y.; Miyazawa, S.; Onozawa-Komatsuzaki, N.; Hirose, T.; Kasuga, K. Dalton Trans. 2009, 32, 6286−6750. (c) Tanaka, R.; Yamashita, M.; Chung, L. W.; Morokuma, K.; Nozaki, K. Organometallics 2011, 30, 6742−6750. (d) Hull, J. F.; Himeda, Y.; Wang, W.-H.; Hashiguchi, B.; Periana, R.; Szalda, D. J.; Muckerman, J. T.; Fujita, E. Nat. Chem. 2012, 4, 383−388. (e) Maenaka, Y.; Suenobu, T.; Fukuzumi, S. Energy Environ. Sci. 2012, 5, 7360−7367. (f) Barnard, J. H.; Wang, C.; Berry, N. G.; Xiao, J. Chem. Sci. 2013, 4, 1234−1244. (g) Oldenhof, S.; de Bruin, B.; Lutz, M.; Siegler, M. A.; Patureau, F. W.; van der Vlugt, I. J. I.; Reek, J. N. H. Chem. - Eur. J. 2013, 19, 11507−11511. (h) Manaka, Y.; Wang, W.-H.; Suna, Y.; Kambayashi, H.; Muckerman, J. T.; Fujita, E.; Himeda, Y. Catal. Sci. Technol. 2014, 4, 34−37. (i) Wang, W.-H.; Xu, S.; Manaka, Y.; Suna, Y.; Kambayashi, H.; Muckerman, J. T.; Fujita, E.; Himeda, Y. ChemSusChem 2014, 7, 1976−1983. (j) Wang, Z.; Lu, S.-M.; Li, J.; Wang, J.; Li, C. Chem. - Eur. J. 2015, 21, 12592− 12595. (k) Barrett, S. M.; Slattery, S. A.; Miller, A. J. M. ACS Catal. 2015, 5, 6320−6327. (l) Onishi, N.; Ertem, M. Z.; Xu, S.; Tsurusaki, A.; Manaka, Y.; Muckerman, J. T.; Fujita, E.; Himeda, Y. Catal. Sci. Technol. 2016, 6, 988−992. (m) Iguchi, M.; Himeda, Y.; Manaka, Y.; Kawanami, H. ChemSusChem 2016, 9, 2749−2753. (n) Papp, G.; Ö levti, G.; Horváth, H.; Kathó, Á .; Joó, F. Dalton Trans. 2016, 45, 14516−14519. (o) Li, J.; Li, J.; Zhang, D.; Liu, C. ACS Catal. 2016, 6, 4746−4754. (p) Czaun, M.; Kothandaraman, J.; Goeppert, A.; Yang, B.; Greenberg, S.; May, R. B.; Olah, G. A.; Prakash, G. K. S. ACS Catal. 2016, 6, 7475−7484. (q) Celaje, J. J. A.; Lu, Z.; Kedzie, E. A.; Terrile, N. J.; Lo, J. N.; Williams, T. J. Nat. Commun. 2016, 7, 11308−11313. (7) Matsunami, A.; Kayaki, Y.; Ikariya, T. Chem. - Eur. J. 2015, 21, 13513−13517. (8) (a) Fukuzumi, S.; Kobayashi, T.; Suenobu, T. ChemSusChem 2008, 1, 827−834. (b) Wang, Z.; Lu, S.-M.; Wu, J.; Li, C.; Xiao, J. Eur. J. Inorg. Chem. 2016, 2016, 490. (c) Jongbloed, L. S.; de Bruin, B.; Reek, J. N. H.; Lutz, M.; van der Vlugt, J. I. Catal. Sci. Technol. 2016, 6, 1320−1327. (9) (a) Boddien, A.; Loges, B.; Gärtner, F.; Torborg, C.; Fumino, K.; Junge, H.; Ludwig, R.; Beller, M. J. Am. Chem. Soc. 2010, 132, 8924− 8934. (b) Boddien, A.; Gärtner, F.; Jackstell, R.; Junge, H.; Spannenberg, A.; Baumann, W.; Ludwig, R.; Beller, M. Angew. Chem., Int. Ed. 2010, 49, 8993−8996. (c) Boddien, A.; Mellmann, D.; Gärtner, F.; Jackstell, R.; Junge, H.; Dyson, P. J.; Laurenczy, G.; Ludwig, R.; Beller, M. Science 2011, 333, 1733−1736. (d) Zell, T.; Butschke, B.; Ben-Devid, Y.; Milstein, D. Chem. - Eur. J. 2013, 19, 8068−8072. (e) Mellmann, D.; Barsch, E.; Bauer, M.; Grabow, K.; Boddien, A.; Kammer, A.; Sponholz, P.; Bentrup, U.; Jackstell, R.; Junge, H.; Laurenczy, G.; Ludwig, R.; Beller, M. Chem. - Eur. J. 2014, 20, 13589−13602. (f) Bielinski, E. A.; Lagaditis, P. O.; Zhang, Y.; Mercado, B. Q.; Christian, W.; Bernskoetter, W. H.; Hazari, N.; Schneider, S. J. Am. Chem. Soc. 2014, 136, 10234−10237. (g) Bertini, F.; Mellone, I.; Ienco, A.; Peruzzini, M.; Gonsalvi, L. ACS Catal. 2015, 5, 1254−1265. (h) Mellone, I.; Gorgas, N.; Bertini, F.; Peruzzini, M.; Kirchner, K.; Gonsalvi, L. Organometallics 2016, 35, 3344−3349. (10) (a) Rieckborn, T. P.; Huber, E.; Karakoc, E.; Prosenc, M. H. Eur. J. Inorg. Chem. 2010, 2010, 4757−4761. (b) Jeletic, M. S.; Helm, M. L.; Hulley, E. B.; Mock, M. T.; Appel, A. M.; Linehan, J. C. ACS Catal. 2014, 4, 3755−3762. (c) Vogt, M.; Nerush, A.; Diskin-Posner, Y.; Ben-Devid, Y.; Milstein, D. Chem. Sci. 2014, 5, 2043−2051. (d) Enthaler, S.; Brück, A.; Kammer, A.; Junge, H.; Irran, E.; Gülak, S. ChemCatChem 2015, 7, 65−69. (e) Neary, M. C.; Parkin, G. Chem, Sci. 2015, 6, 1859−1865.

Shigeki Kuwata: 0000-0002-3165-9882 Yoshihito Kayaki: 0000-0002-4685-8833 Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS This study was financially supported by JSPS KAKENHI Grant Number 24350079 and 26621043 and in part by Grant for Engineering Research from Mizuho Foundation for the Promotion of Sciences. A.M. is grateful to the Japan Society for the Promotion of Science (JSPS) for a Research Fellowship for Young Scientists (No. 17J09484).

■

REFERENCES

(1) (a) Armaroli, N.; Balzani, V. Angew. Chem., Int. Ed. 2007, 46, 52− 66. (b) Lubitz, W.; Tumas, W. Chem. Rev. 2007, 107, 3900−3903. (2) (a) Eberle, U.; Felderhoff, M.; Schüth, F. Angew. Chem., Int. Ed. 2009, 48, 6608−6630. (b) Yadav, M.; Xu, Q. Energy Environ. Sci. 2012, 5, 9698−9725. (3) (a) Fukuzumi, S. Eur. J. Inorg. Chem. 2008, 2008, 1351−1362. (b) Dalebrook, A. F.; Gan, W.; Grasemann, M.; Moret, S.; Laurenczy, G. Chem. Commun. 2013, 49, 8735−8735. (c) Papp, C.; Wasserscheid, P.; Libuda, J.; Steinrück, H.-P. Chem. Rec. 2014, 14, 879−896. (d) Zhu, Q.-L.; Xu, Q. Energy Environ. Sci. 2015, 8, 478−512. (e) Preuster, P.; Papp, C.; Wasserscheid, P. Acc. Chem. Res. 2017, 50, 74−85. (4) (a) Joó, F. ChemSusChem 2008, 1, 805−808. (b) Enthaler, S.; von Langermann, J.; Schmidt, T. Energy Environ. Sci. 2010, 3, 1207−1217. (c) Grasemann, M.; Laurenczy, G. Energy Environ. Sci. 2012, 5, 8171− 8181. (d) Alsabeh, P. G.; Mellmann, D.; Junge, H.; Beller, M. Top. Organomet. Chem. 2014, 48, 45−80. (e) Mellmann, D.; Sponholz, P.; Junge, H.; Beller, M. Chem. Soc. Rev. 2016, 45, 3954−3988. (f) Singh, A. K.; Singh, S.; Kumar, A. Catal. Sci. Technol. 2016, 6, 12−40. (5) (a) Boddien, A.; Loges, B.; Junge, H.; Beller, M. ChemSusChem 2008, 1, 751−758. (b) Loges, B.; Boddien, A.; Junge, H.; Beller, M. Angew. Chem., Int. Ed. 2008, 47, 3962−3965. (c) Fellay, C.; Dyson, P. J.; Laurenczy, G. Angew. Chem., Int. Ed. 2008, 47, 3966−3968. (d) Junge, H.; Boddien, A.; Capitta, F.; Loges, B.; Noyes, J. R.; Gladiali, S.; Beller, M. Tetrahedron Lett. 2009, 50, 1603−1606. (e) Fellay, C.; Yan, N.; Dyson, P. J.; Laurenczy, G. Chem. - Eur. J. 2009, 15, 3752−3760. (f) Loges, B.; Boddien, A.; Junge, H.; Noyes, J. R.; Baumann, W.; Beller, M. Chem. Commun. 2009, 28, 4185−4187. (g) Boddien, A.; Loges, B.; Junge, H.; Gärtner, F.; Noyes, J. R.; Beller, M. Adv. Synth. Catal. 2009, 351, 2517−2520. (h) Scholten, J. D.; Prechtl, M. H. G.; Dupont, J. ChemCatChem 2010, 2, 1265−1270. (i) Fukuzumi, S.; Kobayashi, T.; Suenobu, T. J. Am. Chem. Soc. 2010, 132, 1496−1497. (j) Gan, W.; Fellay, C.; Dyson, P. J.; Laurenczy, G. J. Coord. Chem. 2010, 63, 2685−2694. (k) Majewski, A.; Morris, D. J.; Kendall, K.; Wills, M. ChemSusChem 2010, 3, 431−434. (l) Boddien, A.; Gärtner, F.; Federsel, C.; Sponholz, P.; Mellmann, D.; Jackstell, R.; Junge, H.; Beller, M. Angew. Chem., Int. Ed. 2011, 50, 6411−6414. (m) Himeda, Y.; Miyazawa, S.; Hirose, T. ChemSusChem 2011, 4, 487−493. (n) Czaun, M.; Goeppert, A.; May, R.; Haiges, R.; Prakash, G. K. S.; Olah, G. A. ChemSusChem 2011, 4, 1241−1248. (o) Wang, W.-H.; Hull, J. F.; Muckerman, J. T.; Fujita, E.; Hirose, T.; Himeda, Y. Chem. - Eur. J. 2012, 18, 9397−9404. (p) Boddien, A.; Federsel, C.; Sponholz, P.; Mellmann, D.; Jackstell, R.; Junge, H.; Laurenczy, G.; Beller, M. Energy Environ. Sci. 2012, 5, 8907−8911. (q) Gan, W.; Snelders, D. J. M.; Dyson, P. J.; Laurenczy, G. ChemCatChem 2013, 5, 1126−1132. (r) Czaun, M.; Goeppert, A.; Kothandaraman, J.; May, R. B.; Haiges, R.; Prakash, G. K. S.; Olah, G. A. ACS Catal. 2014, 4, 311− 320. (s) Filonenko, G. A.; van Putten, R.; Schulpen, E. N.; Hensen, E. J. M.; Pidko, E. A. ChemCatChem 2014, 6, 1526−1530. (t) Guerriero, A.; Bricout, H.; Sordakis, K.; Peruzzini, M.; Monflier, E.; Hapiot, F.; Laurenczy, G.; Gonsalvi, L. ACS Catal. 2014, 4, 3002−3012. (u) Thevenon, A.; Frost-Pennington, E.; Weijia, G.; Dalebrook, A. F.; Laurenczy, G. ChemCatChem 2014, 6, 3146−3152. (v) Pan, Y.; 4483


Research Article

ACS Catalysis (11) Review articles: (a) Enthaler, S. ChemSusChem 2008, 1, 801− 804. (b) Loges, B.; Boddien, A.; Gärtner, F.; Junge, H.; Beller, M. Top. Catal. 2010, 53, 902−914. (c) Enthaler, S.; Langermann, J.; Schmidt, T. Energy Environ. Sci. 2010, 3, 1207−1217. (d) Johnson, T. C.; Morris, D. J.; Wills, M. Chem. Soc. Rev. 2010, 39, 81−88. (e) Fukuzumi, S.; Suenobu, T. Dalton Trans. 2013, 42, 18−28. (f) Fujita, E.; Muckerman, J. T.; Himeda, Y. Biochim. Biophys. Acta, Bioenerg. 2013, 1827, 1031−1038. (12) (a) Hashiguchi, S.; Fujii, A.; Takehara, J.; Ikariya, T.; Noyori, R. J. Am. Chem. Soc. 1995, 117, 7562−7563. (b) Fujii, A.; Hashiguchi, S.; Uematsu, N.; Ikariya, T.; Noyori, R. J. Am. Chem. Soc. 1996, 118, 2521−2522. (c) Mashima, K.; Abe, T.; Tani, K. Chem. Lett. 1998, 27, 1199−1200. (d) Mashima, K.; Abe, T.; Tani, K. Chem. Lett. 1998, 27, 1201−1202. (e) Murata, K.; Ikariya, T. J. Org. Chem. 1999, 64, 2186− 2187. (13) (a) Ohkuma, T.; Utsumi, N.; Tsutsumi, K.; Murata, K.; Sandoval, C.; Noyori, R. J. Am. Chem. Soc. 2006, 128, 8724−8725. (b) Moritani, J.; Kayaki, Y.; Ikariya, T. RSC Adv. 2014, 4, 61001− 61004. (14) (a) Haack, K.-J.; Hashiguchi, S.; Fujii, A.; Ikariya, T.; Noyori, R. Angew. Chem., Int. Ed. Engl. 1997, 36, 285−288. (b) Arita, S.; Koike, T.; Kayaki, Y.; Ikariya, T. Angew. Chem., Int. Ed. 2008, 47, 2447−2449. (c) Wills, M. Angew. Chem., Int. Ed. 2008, 47, 4264−4267. (d) Moritani, J.; Hasegawa, Y.; Kayaki, Y.; Ikariya, T. Tetrahedron Lett. 2014, 55, 1188−1191. (15) (a) Muñiz, K. Angew. Chem., Int. Ed. 2005, 44, 6622−6627. (b) Ikariya, T. Bull. Chem. Soc. Jpn. 2011, 84, 1−16. (c) Zhao, B.; Han, Z.; Ding, K. Angew. Chem., Int. Ed. 2013, 52, 4744−4788. (16) Koike, T.; Ikariya, T. Organometallics 2005, 24, 724−730. (17) (a) Kamezaki, S.; Akiyama, S.; Kayaki, Y.; Kuwata, S.; Ikariya, T. Tetrahedron: Asymmetry 2010, 21, 1169−1172. (b) Dub, P. A.; Wang, H.; Matsunami, A.; Gridnev, I. D.; Kuwata, S.; Ikariya, T. Bull. Chem. Soc. Jpn. 2013, 86, 557−568. (18) Ito, M.; Endo, Y.; Tejima, N.; Ikariya, T. Organometallics 2010, 29, 2397−2399. (19) The ORTEP structure and crystallographic data for 4 are given in Figure S3 and Table S4 in the Supporting Information.

4484


A Bifunctional Iridium Catalyst Modified for Persistent Hydrogen

Recommend Documents