Supporting Information

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1 Supporting Information Efficient Reversible ydrogen Carrier System Based on Amine Reforming of Methanol Jotheeswari Kothandaraman, Sayan Kar, Raktim Sen, Alain Goeppert, George A. Olah* and G. K. Surya rakash* Loker ydrocarbon Research Institute and Department of Chemistry, University of Southern California, University ark, Los Angeles, California , United States. 1. Materials and methods All experiments were carried out under inert atmosphere using standard schlenk techniques with the exclusion of moisture. Complexes Ru-Macho -B (C-1) (Strem Chemicals, 98%), Ru- Macho (C-2) (Strem Chemicals, 98%), Carbonylhydrido[6-(di-t-butylphosphinomethylene)-2- (,-diethylaminomethyl)-1,6-dihydropyridine]ruthenium(ii) (C-4) (Strem Chemicals, 98%), (R,R)-Ts-DEEB (C-7) (Strem Chemicals, 16% Ru), (R)-RUCY -xylbia (C-8) (Strem Chemicals, 8% Ru), and anhydrous K 3 O 4 (Aldrich, 97%) were weighed inside an argon filled glove box without any further purification (Figure S1). Complexes RuCl Me h (CO) (C-3) 1, RuCl ir (CO) (C-5) 2, FeBr ir (CO) (C-6) 3 were prepared by previously reported methods., -Dimethylethylenediamine (7) (Combi-Blocks, 98%) was sparged with 2 for 2 hours and stored in a schlenk flask. Amines 1 (Aldrich, 99%), 2 (Aldrich, 99%), 3 (Aldrich, 99%), 4 (Aldrich, 99%), 6 (Aldrich, 99%) were purified through distillation and amine 5 (Aldrich, 99%) through sublimation prior to use. Methanol (DriSolv) and toluene (DriSolv) were sparged with 2 for 2 hours and stored over 3 Å molecular sieves. Freshly distilled 1,4-dioxane S1

2 was used. 1,3,5-Trimethoxybenzene (TMB) (Aldrich, >99%), DMSO-d 6 (CIL, D-99.9%), and toluene-d 8 (Aldrich, D-99+%) were used without any further purification. 1 and 13 C MR spectra were recorded on 400 Mz, 500 Mz, and 600 Mz Varian MR spectrometers. 1 and 13 C MR chemical shifts were determined relative to the residual solvent signals (dmso-d 6 ) or internal standard (TMB). The gas mixtures were analyzed using a Thermo gas chromatograph (column: Supelco, Carboxen 1010 plot, 30 mx0.53 mm) equipped with a TCD detector (CO detection limit: v/v%). 2 (Gilmore, ultra-high pure grade) was used without further purification. Caution: Reactions are associated with 2 gas. They should be carefully handled inside proper fume hoods without any flame or spark sources nearby. h h Ru C-1 CO B 3 h h h h Ru Cl C-2 CO h h Me Ru h h Cl C-3 CO h h Et Ru Et C-4 t Bu t Bu CO Ru ir ir Cl C-5 CO ir ir Fe ir ir Br C-6 CO ir ir h O Ts Ru h C-7 Cl xyl xyl xyl xyl 3 CO Cl Ru C OMe Figure S1. Catalysts screened in this study 2. Standard procedure for dehydrogenation reactions In a nitrogen-filled chamber, amine (1-7) (1 mmol), catalyst C-1 C-8 (10 µmol), K 3 O 4 ( mmol), methanol (2-4 mmol) and solvent (1.5 or 3 ml) (toluene or 1,4-Dioxane) were added to a 134 ml Monel arr reactor equipped with a magnetic stir bar, thermocouple and piezoelectric pressure transducer (Figure S2). The reaction mixture was then placed in a preheated oil bath and was stirred at 800 rpm. The internal temperature of the reaction mixture ( C), and pressure generated in the reactor were monitored through the LabVIEW 8.6 software. After heating for a given amount of time (24 h), the reactor was cooled down to room temperature. The gas generated was collected in an airtight bag, and was analyzed by GC (Figure S4). A homogeneous solution (white solids in case of benzylamine, m-xylylenediamine, S2

3 and p-xylylenediamine) was obtained upon opening the reaction vessel. DMSO-d 6 was added to the reaction mixture and then a known amount of TMB was added as an internal standard. The reaction mixture was then analyzed by 1 and 13 C MR. The 2 yield was calculated indirectly from the amount of CO (from 7a + 7b) formed, which was determined by 1 MR. The above mixture was concentrated by rotavap to get the seperate yields of 7a and 7b (Figure S5-7) Standard procedure for hydrogenation reaction Dehydrogenation reaction was performed before subsequent hydrogenation of the reaction mixture. Upon completion of dehydrogenation reaction, reaction vessel was cooled down to room temperature and the generated pressure was slowly released. Subsequently it was filled with 2 to desired internal pressure (40-60 bar) and was placed in a preheated oil bath (120 C) with stirring (800 rpm). After the desired time (24 h), vessel was cooled down to room temperature and was further cooled in a liquid 2 bath for 10 min (to avoid the loss of methanol during the release of 2 ). The internal 2 gas was then slowly released. Reaction vessel was warmed up to room temperature and then opened. A known amount of TMB was added as an internal standard to the reaction mixture. The reaction mixture was then analyzed by 1 and 13 C MR in DMSO-d 6. Yields of 7 and C 3 O were calculated by 1 MR. The above mixture was concentrated on a rotavap to obtain the unreacted 7a and 7b. S3

4 Figure S2. Image of an autoclave used in this study. S4

5 Reservoir Modified burette Leveling U-tube Figure S3. Image of a gas burette used in this study. 4. Gas volume measurement An oil-filled modified gas burette with a reservoir was connected to the autoclave through a pressure leveling U-tube (Figure S3). The leveling U-tube contained a methanol solution of methylorange as a clear visual aid. After completion of the reaction, the accumulated gas in the autoclave was slowly released, collected in the burette and the reservoir was adjusted accordingly so that the U-tube is leveled to the atmospheric pressure. The total volume of the gas in the burette was measured and then the gas mixture in the burette was analyzed by gas chromatography. S5

6 Figure S4. GC spectra of collected gas after dehydrogenation of methanol in presence of 7 with (a) C-1 as catalyst (b) C-5 as catalyst. Reaction condition: 7 (1 mmol), methanol (4 mmol), C- 1/C-5 (10 µmol), K 3 O 4 (0.05 mmol), Toluene (1.5 ml), 120 C, 24 h. Figure S5. 1 MR of pure 7a in dmso-d 6. S6

7 Figure S6. 1 MR spectra of the formyl region after dehydrogenative coupling of 7 and C 3 O. Reaction conditions: 7 (1 mmol), C 3 O (4 mmol), C-5 (1 mol%), toluene (1.5 ml), time (24 h), K 3 O 4 (5 mol%), T=120 C. Figure S7. 1 MR spectra of the dehydrogenative coupling product of 7 and C 3 O after concentration of the reaction mixture. Reaction conditions: 7 (1 mmol), C 3 O (4 mmol), C-5 (1 mol%), toluene (1.5 ml), time (24 h), K 3 O 4 (5 mol%), T=120 C. S7

8 Figure S8. 1 MR showing hydrogenation of in-situ formed 1a (in DMSO-d 6 ). Reaction conditions: 1 (2 mmol), C 3 O (2 mmol), C-1 (0.5 mol%), toluene (3 ml). (A) Dehydrogenation: The reaction mixture was heated to 140 C for 24 h. (B) ydrogenation: after releasing the 2 pressure, the reaction mixture A was heated again to 145 C for 24h under 60 bar 2. S8

9 Figure S9. 1 MR showing hydrogenation of in-situ formed 7a/7b (in DMSO-d 6 ). Reaction conditions: 7 (1 mmol), C 3 O (4 mmol), C-5 (1 mol%), toluene (1.5 ml) and K 3 O 4 (5 mol%). (A) Before heating the reaction mixture. (B) Dehydrogenation: Reaction mixture A was heated to 120 C for 24 h. (C) After concentration of the reaction mixture B. (D) ydrogenation: after releasing the 2 pressure, the reaction mixture B was heated again to 120 C for 24h under 60 bar Reaction Condition for the neat reaction Standard procedure for the hydrogenation and dehydrogenation that are given above were followed. 7 (5 mmol), C 3 O (20 mmol), C-5 (1 mol%) and K 3 O 4 (5 mol%). 185 ml of 2 was collected after 2 h of dehydrogenation at 120 C. Then the autoclave was reheated to 120 C for 22 more hours to get an additional 180 ml of hydrogen. This two-stage heating process was carried out to prevent buildup of 2 pressure (in the closed reactor), which could prevent the completion of dehydrogenation process due to the reversibility of the reaction. Thus, a total of 365 ml (76% yield, 15.2 mmol) of 2 was obtained after dehydrogenation at 120 C with no detectable amount of CO in the gas mixture. S9

10 ydrogenation: The reverse reaction (hydrogenation) was performed under 60 bar 2 at 120 C for 24 h. 3.5 mmol of 7 was obtained back after hydrogenation from original 5 mmol of 7. 10% (0.5 mmol) 7a and 7b remained unreacted after hydrogenation. Further investigation is needed to understand this lower conversion. 6. MR Study of the Reaction Mixture In the absence of K 3 O 4, when the amine (7, 0.1 mmol) and C 3 O were heated to 120 C for 3 h with catalyst C-5 (7 : C-5 ratio = 5:1; 7 : C 3 O ratio = 1:4) in toluene-d 8, most of the C-5 remained unchanged and no trace of product was observed. On the other hand, in the presence of K 3 O 4, under the same reaction conditions, the products (7a/7b) were observed with a large amount of starting materials and C-5 remaining unreacted. In addition, a new hydride signal (C- 9) in the 1 MR at ppm (broad triplet) with the corresponding 13 C signal (of CO) at ppm and 31 signals at 80.3 ppm (singlet) was observed. When the 7 (1 mmol) to C-5 ratio was increased to 50:1 with the corresponding amount of C 3 O (C 3 O:7 = 4:1) in the presence of K 3 O 4, only traces of C-5 remained after 24h, and the monohydride (C-9) was the main species, in what appears to be a resting state of the catalyst. In addition, several new hydride peaks were observed in the 1 MR, which we were unable to identify due to the low concentration of the newly formed species (Figure S10 and S11) Standard procedure for MR study of reaction mixture In a nitrogen chamber, diamine 7 (0.1 mmol or 1 mmol), catalyst C-5 (20 µmol), K 3 O 4 (0.02 mmol or 0.05 mmol), methanol (0.4 mmol or 4 mmol) and 1 ml toluene-d 8 were added to a 134 ml Monel arr reactor equipped with a magnetic stir bar, thermocouple and piezoelectric pressure transducer. The reaction mixture was then placed in a preheated oil bath and was stirred at 800 rpm. The internal temperature of the reaction mixture (120 º C), and pressure generated in the reactor were monitored through the LabVIEW 8.6 software. After heating for a given time, the reactor was cooled to room temperature. Then autoclave was opened in 2 -filled chamber and the reaction mixture was analyzed through 1, 31, and 13 C MR (Figure S10 and S11). S10

11 Figure S10. 1 MR of the reaction mixture after the dehydrogenation of 7 in the presence of C-5. Reaction condition: 7 (1 mmol), methanol (4 mmol), C-5 (20 µmol), K 3 O 4 (0.05 mmol), toluene-d8 (1 ml), 120 C, 24 h. S11

12 Figure S MR of the reaction mixture after the dehydrogenation of 7 in the presence of C-5. Reaction condition: 7 (1 mmol), methanol (4 mmol), C-5 (20 µmol), K 3 O 4 (0.05 mmol), toluene-d8 (1 ml), 120 C, 24 h. S12

13 Figure S12. Recycling studies. Reaction conditions: 7 (1 mmol), C 3 O (4 mmol), C-5 (1 mol%), toluene (1.5 ml) and K 3 O 4 (5 mol%). 7. Experimental details for the recycling studies: Dehydrogenation: In a nitrogen-filled chamber, amine (7) (1 mmol), catalyst C-5 (1 mol%), K 3 O 4 (5 mol%), methanol (4 mmol) and toluene (1.5 ml) were added to a 134 ml Monel arr reactor equipped with a magnetic stir bar, thermocouple and piezoelectric pressure transducer. The reaction mixture was then placed in a preheated oil bath and was stirred at 800 rpm. The internal temperature of the reaction mixture (120 C), and pressure generated in the reactor were monitored through the LabVIEW 8.6 software. After heating for a given amount of time (24 h), the reactor was cooled to room temperature. The gas generated was collected in a gas burette. After measuring the volume of the evolved gas, the gas mixture was analyzed by GC. ydrogenation: The above mixture after dehydrogenation was pressurized with 60 bar 2 pressure and was placed in a preheated oil bath (120 C) with stirring (800 rpm). After 24 h, the vessel was cooled down to room temperature and was placed in a liq. 2 bath (due to the loss of methanol). When the internal 2 gas is slowly released and passed through a liq. 2 cooled trap, methanol, toluene and some 7 condensed in the trap. Before the next cycle, 1.5 mmol of methanol was added to the reaction mixture in a 2 filled chamber to compensate the loss of methanol during the hydrogen release. The reaction mixture was then placed in a preheated oil bath and the internal temperature of the autoclave was kept at S13

14 120 C. The same procedure as in cycle 1 was followed for subsequent cycles 2 and 3. The amount of evolved 2 gas after the dehydrogenation of each cycle is shown in Figure S12. REFERECES 1) an, Z.; Rong, L.; Wu, J.; Zhang, L.; Wang, Z.; Ding, K. Angew. Chem. Int. Ed. 2012, 51, ) Bertoli, M.; Choualeb, A.; Lough, A. J.; Moore, B.; Spasyek, D.; Gusev, D. G. Organometallics 2011, 30, ) Chakraborty, S; Dai,.; Bhattacharya,.; Fairweather,. T.; Gibson, M.S.; Krause, J. A.; Guan,. J. Am. Chem. Soc. 2014, 136, ) Barham, J..; Coulthard, G.; Emery, K. J.; Doni, E.; Cumine, F.; ocera, G.; John, M..; Berlouis, L. E. A.; McGuire, T.; Tuttle, T.; Murphy, J. A. J. Am. Chem. Soc. 2016, 138, S14