Supporting Information N N Bond Cleavage of Hydrazines with a Multiproton-Responsive Pincer-Type Iron Complex Kazuki Umehara, Shigeki Kuwata,* and Takao Ikariya* Department of Applied Chemistry, Graduate School of Science and Engineering, Tokyo Institute of Technology O-okayama, Meguro-ku, Tokyo 152-8552, Japan skuwata@apc.tiech.ac.jp (S.K.); tikariya@apc.titech.ac.jp (T.I.) Table of Contents Experimental Details S2 Table S1. Yield of Ammonia in Catalytic Disproportionation of Hydrazine S12 Table S2. Yield of Dinitrogen in Catalytic Disproportionation of Hydrazine S13 Figure S1. Structure of 1 S14 Figure S2. Structure of 5 S14 S1
Experimental Details General. All manipulations were performed under an atmosphere of argon using standard Schlenk technique unless otherwise specified. Solvents were dried by refluxing over sodium benzophenone ketyl (THF, toluene, diethyl ether, and hexane), CaH 2 (dichloromethane and acetonitrile), and Mg(OMe) 2 (methanol) and distilled before use. Aniline- 15 N and sodium nitrite- 15 N were purchased from ISOTEC. The 15 N-enriched phenylhydrazine- 15 N 2 was prepared by diazotization of aniline- 15 N with sodium nitrite- 15 N and following reduction with tin(ii) chloride. 1 2,6-Bis(5-tert-buthyl-1H- pyrazol-3-yl)puridine (LH 2 ) was synthesized according to the literature. 2 1 H (399.8 MHz), 15 N (40.5 MHz), and 31 P (161.8 MHz) NMR spectra were obtained on a JEOL JNM-ECX-400 spectrometer. 1 H NMR shifts are relative to the residual CHDCl 2 (δ 5.32), while 15 N and 31 P shifts are referenced to nitromethane and phosphoric acid (δ 0.0), respectively. Infrared spectra were recorded on a JASCO FT/IR-6100 spectrometer. Elemental analyses were performed on a Perkin-Elmer 2400II CHN analyzer. Magnetic susceptibility was measured on a Sherwood Scientific MSB-AUTO at room temperature. The diamagnetic correction was estimated from Pascal s constants. 3 UV-vis spectra and absorbance were measured on a JASCO V-630. Nitrogen gas evolved in disproportionation of hydrazine was determined by GLC analysis using a Shimadzu GC-2010 Plus gas chromatograph equipped with a Molecular Sieve 5A column. S2
Synthesis of [FeCl 2 (MeOH)(LH 2 )] (1). A mixture of FeCl 2 4H 2 O (26.3 mg, 0.132 mmol) and LH 2 (42.9 mg, 0.133 mmol) in methanol (2 ml) was stirred for 2 h at room temperature. Slow addition of diethyl ether (20 ml) to the concentrated reaction mixture (ca. 0.5 ml) afforded 1 as orange crystals (39.4 mg, 0.0817 mmol, 62%). µ eff = 5.0 µ B. IR(ATR, cm 1 ): 3063, 3090, 3114, 3150 (NH), 3263 (OH). Anal. Calcd for C 20 H 29 Cl 2 FeN 5 O: C, 49.81; H, 6.06; N, 14.52. Found: C, 49.68; H, 6.07; N, 14.66. Synthesis of [Fe(MeCN)(PMe 3 ) 2 (LH 2 )](OTf) 2 (2a). To a solution of 1 (109.5 mg, 0.227 mmol) and sodium trifluoromethansulfonate (312.9 mg, 1.819 mmol) in acetonitrile (5 ml) was added a toluene solution of trimethylphosphine (1 M, 0.5 ml, 0.5 mmol), and the mixture was stirred for 18 h at room temperature. After removal of the solvent in vacuo, the residue was extracted with dichloromethane (3 ml 3). Slow addition of hexane (15 ml) to the concentrated extract (ca. 6 ml) afforded 2a (169.7 mg, 0.195 mmol, 86%). 1 H NMR (CD 2 Cl 2 ): δ 0.74 (t, 18H, J PH = 3.9 Hz, 18H, PMe 3 ), 1.39 (s, 18H, t-bu), 3.04 (t, 5 J PH = 1.8 Hz, 3H, MeCN), 6.68 (s, 2H, pyrazole CH), 7.70 (d, 3 J HH = 7.8 Hz, 2H, aryl), 7.95 (t, 3 J HH = 7.8 Hz, 1H, aryl), 12.40 (s, 2H, NH). 31 P{ 1 H} NMR (CD 2 Cl 2 ): δ 17.9 (s). IR(ATR, cm 1 ): 3081, 2170 (NH). Anal. Calcd for C 29 H 46 F 6 FeN 6 O 6 P 2 S 2 : C, 40.01; H, 5.33; N, 9.65. Found: C, 39.99; H, 5.10; N, 9.54. Crystals suitable for X-ray analysis were obtained by recrystallization from acetonitrile diethyl ether. Synthesis of [Fe(NH 3 )(PMe 3 ) 2 (LH 2 )](OTf) 2 (3). To a solution of 2a (29.8 mg, S3
0.0342 mmol) in dichloromethane (2 ml) was added a methanol solution of ammonia (2 M, 0.5 ml, 1.0 mmol), and the mixture was stirred for 20 h at room temperature. Slow addition of hexane (15 ml) to the reaction mixture afforded 3 as brown crystals (24.0 mg, 0.0283 mmol, 83%). 1 H NMR (CD 2 Cl 2 ): δ 0.66 (t, 18H, J PH = 3.2 Hz, PMe 3 ), 1.38 (s, 18H, t-bu), 3.09 (s, 3H, NH 3 ), 6.68 (s, 2H, pyrazole CH), 7.67 (d, 3 J HH = 7.6 Hz, 2H, aryl), 7.89 (t, 3 J HH = 7.6 Hz, 1H, aryl), 12.57 (s, 2H, NH). 31 P{ 1 H} NMR (CD 2 Cl 2 ): δ 16.9 (s). Anal. Calcd for C 27 H 46 F 6 FeN 6 O 6 P 2 S 2 : C, 38.30; H, 5.48; N, 9.93. Found: C, 38.24; H, 5.14; N, 9.78. The 15 N-labeled complex 3-15 N was observed in the reaction of 2a with phenylhydrazine- 15 N 2 (vide infra). (CD 2 Cl 2 ): δ 305.5 (s). Synthesis of L Me H. 31 P{ 1 H} NMR (CD 2 Cl 2 ): δ 16.9 (s). A 15 N{ 1 H} NMR mixture of LH 2 (620.8 mg, 1.919 Bu t H N N N N NMe Bu t Bu t N Me N N N NMe Bu t mmol) and sodium hydride (60% wt% L Me H L Me2 in mineral oil, 71.4 mg, 1.785 mmol) in THF (15 ml) was stirred for 1 h at room temperature. To the mixture a THF (10 ml) solution of methyl iodide (111 µl, 1.78 mmol) was added dropwise at 0 C, and the mixture was warmed slowly to room temperature with stirring. After 19 h, the mixture was evaporated to dryness and subjected to the column chromatography on alumina under air. The first band eluted with dichloromethane contained L Me2. The second band was collected and evaporated, giving S4
L Me H as a white solid (191.8 mg, 0.568 mmol, 32%). 1 H NMR (CDCl 3 ): δ 1.38, 1.44 (s, 9H each, t-bu), 4.05 (s, 3H, NMe), 6.65, 6.72 (s, 1H each, pyrazole CH), 7.56 (d, 1H, 3 J HH = 7.7 Hz, aryl), 7.70 (t, 1H, 3 J HH = 7.7 Hz, aryl), 7.79 (d, 1H, 3 J HH = 7.7 Hz, aryl). Anal. Calcd for C 20 H 27 N 5 : C, 71.18; H, 8.06; N, 20.75. Found: C, 71.14; H, 8.08; N, 20.46. Synthesis of L Me2. A mixture of LH 2 (279.2 mg, 0.863 mmol), potassium t-butoxide (193.7 mg, 1.726 mmol), and methyl iodide (0.11 ml, 1.77 mmol) in THF (5 ml) was allowed to reflux for 15 h. After removal of the solvent in vacuo, the resulting solid was chromatographed on a column of alumina under air with dichloromethane as eluent. 41%). Evaporation of the solvent afforded L Me2 as a white solid (125.8 mg, 0.358 mmol, 1 H NMR (CDCl 3 ): δ 1.47 (s, 18H, t-bu), 4.17 (s, 6H, NMe), 7.18 (s, 2H, pyrazole CH), 8.01 (t, 1H, 3 J HH = 7.7 Hz, aryl), 8.11 (d, 2H, 3 J HH = 7.7 Hz, aryl). Anal. Calcd for C 21 H 29 N 5 : C, 71.76; H, 8.32; N, 19.92. Found: C, 71.73; H, 8.36; N, 19.66. Synthesis of [Fe(MeCN)(PMe 3 ) 2 (L Me H)](OTf) 2 (2b). A mixture of FeCl 2 4H 2 O (33.8 mg, 0.170 mmol) and L Me H (65.3 mg, 0.194 mmol) in methanol (3 ml) was stirred for 2 h at room temperature. The mixture was concentrated to ca. 1 ml, and diethyl ether (15 ml) was layered. The resultant orange crystals, tentatively assigned as [FeCl 2 (L Me H)], were filtered off and dried in vacuo. The crystals were dissolved in acetonitrile (2 ml) and to the solution was added sodium trifluoromethanesulfonate (121.2 mg, 0.704 mmol) and a toluene solution of trimethylphosphine (1M, 0.3 ml, 0.3 mmol). The mixture was stirred for 18 h at room temperature and evaporated to dryness. S5
Recrystallization from dichloromethane diehyl ether (2 ml/15 ml) afforded 2b as brown crystals (65.4 mg, 0.0739 mmol, 77%). 1 H NMR (CD 2 Cl 2 ): δ 0.78 (t, 18H, J PH = 3.9 Hz, PMe 3 ), 1.39, 1.42 (s, 9H each, t-bu), 3.06 (t, 3H, 5 J PH = 2.5 Hz, MeCN), 3.86 (s, 3H, NMe), 6.74, 6.83 (s, 1H each, pyrazole CH), 7.81, 7.84 (d, 1H each, 3 J HH = 7.8 Hz, aryl), 8.07 (t, 1H, 3 J HH = 7.8 Hz, aryl), 12.28 (s, 1H, NH). 31 P{ 1 H} NMR (CD 2 Cl 2 ): δ 17.34 (s). Anal. Calcd for C 30 H 48 F 6 FeN 6 O 6 P 2 S 2 : C, 40.73, H, 5.47; N, 9.50. Found: C, 40.82; H, 5.67; N, 9.44. Synthesis of [Fe(MeCN)(PMe 3 ) 2 (L Me2 )](OTf) 2 (2c). This compound was obtained by essentially the same procedure as that described for 2b, except using L Me2 instead of L Me H. Yield: 94%. 1 H NMR (CD 2 Cl 2 ): δ 0.86 (t, 18H, J PH = 4.0 Hz, PMe 3 ), 1.40 (s, 18H, t-bu), 3.15 (s, 3H, MeCN), 3.85 (s, 6H, NMe), 6.81 (s, 2H, pyrazole CH), 7.88 (d, 2H, 3 J HH = 8.0 Hz, aryl), 8.14 (t, 1H, 3 J HH = 8.0 Hz, aryl). 31 P{ 1 H} NMR (CD 2 Cl 2 ): δ 16.03 (s). Anal. Calcd for C 31 H 50 F 6 FeN 6 O 6 P 2 S 2 : C, 41.43, H, 5.61; N, 9.35. Found: C, 41.07; H, 5.35; N, 8.99. Reaction of 2a with Hydrazine. To a dichloromethane methanol (1 ml/1 ml) solution of 2a (33.5 mg, 0.0385 mmol) in a Schlenk tube (inside volume: ca. 35 ml) was added anhydrous hydrazine (6.1 µl, 0.19 mmol), and the mixture was stirred for 2 h at room temperature. An aliquot (0.100 ml) of the gas phase was subjected to GLC analysis. In a separate run, all volatile material inside was distilled into a 1N H 2 SO 4 aqueous solution after the reaction, and the residue was further extracted with an additional amount of S6
distilled water. The collected ammonia and unreacted hydrazine were quantified by indophenol 4 and p-(dimethylamino)benzaldehyde method, 5 respectively. The results are summarized in Tables S1 and S2. The complex that formed was also determined in a separate reaction. To a dichloromethane methanol (1 ml/1 ml) solution of 2a (33.5 mg, 0.0385 mmol) in a Schlenk tube was added anhydrous hydrazine (6.1 µl, 0.19 mmol), and the mixture was stirred for 2 h at room temperature. The 1 H NMR spectrum of the crude product, with 1,3,5-trimethoxybenzene as an internal standard, revealed that the ammine complex 3 was formed in 67% yield. Subsequent recrystallization from dichloromethane hexane (0.5 ml/15 ml) affored 3 (16.3 mg, 0.0193 mmol, 50%). Synthesis of [Fe(HN=NPh)(PMe 3 ) 2 (LH 2 )](OTf) 2 (4a). To a solution of 2a (44.3 mg, 0.0509 mmol) in dichloromethane (2 ml) was added phenylhydrazine (49 µl, 0.50 mmol), and the mixture was immediately depressurized with a vacuum line. After stirring the mixture under a reduced pressure for 14 h at room temperature, the mixture was evaporated to dryness. The resulting solid was washed with diethyl ether (3 ml 3) and recrystallized from dichloromethane hexane (3 ml/15 ml) to afford 4a as deep violet crystals (30.0 mg, 0.0321 mmol, 63%). 1 H NMR (CD 2 Cl 2 ): δ 0.72 (t, 18H, J PH = 4.3 Hz, PMe 3 ), 1.41 (s, 18H, t-bu), 6.90 (s, 2H, pyrazole CH), 7.71 (br s, 3H, aryl), 7.95 (br s, 2H, aryl), 8.06 (d, 2H, 3 J HH = 7.9 Hz, aryl), 8.29 (t, 1H, 3 J HH = 7.9 Hz, aryl), 12.27 (s, 2H, pyrazole NH), 17.46 (s, 1H, =NH). 31 P{ 1 H} NMR (CD 2 Cl 2 ): δ 18.27 (s). IR(ATR, S7
cm 1 ): 3092, 2139, 3205 (NH). UV-vis (CH 2 Cl 2 ) λ max, nm (ε, L mol 1 cm 1 ): 253 (34780), 551 (15910). Anal. Calc for C 33 H 49 F 6 FeN 7 O 6 P 2 S 2 : C, 42.36; H, 5.28; N, 10.48. Found: C, 42.54; H, 4.93; N, 10.23. The 15 N-labeled complex 4a- 15 N 2 was prepared in a similar manner with phenylhydrazine- 15 N 2. 1 H NMR (CD 2 Cl 2 ): δ 0.72 (t, 18H, J PH = 4.1 Hz, PMe 3 ), 1.41 (s, 18H, t-bu), 6.90 (s, 2H, pyrazole CH), 7.71 (br s, 3H, aryl), 7.95 (br s, 2H, aryl), 8.06 (d, 2H, 3 J HH = 7.9 Hz, aryl), 8.30 (t, 1H, 3 J HH = 7.9 Hz, aryl), 12.26 (s, 2H, pyrazole NH), 17.46 (d, 1H, 1 J NH = 67.0 Hz, =NH). 31 P{ 1 H} NMR (CD 2 Cl 2 ): δ 18.31 (d, 2 J PN = 7.4 Hz). 15 N{ 1 H} NMR (CD 2 Cl 2 ): δ 414.1, 466.3 (m, 1N each). Tube Reaction of 2a with Phenylhydrazine. In an NMR tube equipped with a J-Young valve, a mixture of 2a (8.9 mg, 0.010 mmol) and phenylhydrazine (4.9 µl, 0.050 mmol) were dissolved in CD 2 Cl 2 (0.45 ml) and kept for 18 h at room temperature. The 1 H NMR spectrum using 1,3,5-trimethoxybenzene as an internal standard revealed the formation of the phenyldiazene complex 4a (0.0045 mmol, 45% per 2a), aniline (0.0036 mmol, 36% per 2a), and the ammine complex 3 (0.0037 mmol, 37% per 2a). Synthesis of [Me 3 PNHNPh 2 ]OTf (5). This compound was synthesized by using a procedure similar to that for the triphenylphosphonium analogues. 6 A mixture of [Me 3 PI]I (114.9 mg, 0.348 mmol), 7 triethylamine (49 µl, 0.35 mmol), and 1,1-diphenylhydrazine (58 µl, 0.35 mmol) in toluene (2 ml) was stirred for 6 h at room temperature. The white precipitate that formed was filtered off, washed with diethyl ether S8
(5 ml 2), and dried in vacuo. To the resultant iodide was added silver trifluoromethanesulfonate (200.0 mg, 0.778 mmol) and dichloromethane (3 ml). The mixture was stirred for 15 min at room temperature and filtered off. The filtrate was evaporated to dryness, washed with cold water (1 ml 2), and dried in vacuo. Recrystallization from dichloromethane hexane (2 ml/15 ml) afforded 5 as colorless crystals (40.9 mg, 0.100 mmol, 29%). 1 H NMR (CDCl 3 ): δ 1.99 (d, 9H, 2 J PH = 13.3 Hz, PMe 3 ), 7.17 (m, 6H, aryl), 7.36 (m, 4H, aryl), 7.99 (d, 1H, 2 J PH = 31.6 Hz, NH). 31 P{ 1 H} NMR (CD 2 Cl 2 ): δ 57.40 (s). Anal. Calcd for C 16 H 20 F 3 N 2 O 3 PS: C, 47.06; H, 4.94; N, 6.86. Found: C, 47.09; H, 5.14; N, 6.87. Reaction of 2a with 1,1-Diphenylhydrazine. In an NMR tube equipped with a J-Young valve, a mixture of 2a (7.8 mg, 0.009 mmol) and 1,1-diphenylhydrazine (7.4 µl, 0.045 mmol) was dissolved in CD 2 Cl 2 (0.45 ml) and kept at 40 C for 18 h. The 1 H NMR spectrum using 1,3,5-trimethoxybenzene as an internal standard revealed the formation of diphenylamine (0.0047 mmol, 52% per 2a), 5 (0.0045 mmol, 50% per 2a), and uncharacterized iron complexes. X-ray Diffraction Studies. Single crystals suitable for X-ray analyses were mounted on a fiber loop. Diffraction experiments were performed on a Rigaku Saturn CCD area detector with graphite monochromated Mo-Kα radiation (λ = 0.710 70 Å). Intensity data were corrected for Lorentz polarization effects and for absorption. Structure solution and refinements were carried out by using the CrystalStructure S9
program package. 8 The heavy-atom positions were determined by a direct methods program (SIR92; 9 for 1, 4a and 5) or a Patterson method program (PATTY; 10 for 2a) and remaining non-hydrogen atoms were found by subsequent Fourier syntheses. 11 All non-hydrogen atoms were refined anisopropically by full-matrix least-squares techniques based on F 2. The methanol hydrogen atom in 1 and diazene hydrogen atom in 4a was found in the final difference Fourier map and refined isotropically. The rest hydrogen atoms were placed at calculated positions and included in the refinements with a riding model. The absolute structure of 5 was determined on the basis of the Flack absolute structure parameter. 12 References (1) Zhang, P.; Zhang, Y.; Xue, X.; Wang, C.; Wang, Z.; Huang, L. Anal. Biochem. 2011, 418, 1. (2) Yoshinari, A.; Tazawa, A.; Kuwata, S.; Ikariya, T. Chem. Asian J. 2012, 7, 1417. (3) Bain, G. A.; Berry, J. F. J. Chem. Educ. 2008, 85, 532. (4) Weatherburn, M. W. Anal. Chem. 1967, 39, 971. (5) Watt, G. W.; Chrisp, J. D. Anal. Chem.1952, 24, 2006. (6) Zimmer, H.; Singh, G. J. Org. Chem. 1964, 29, 1579. (7) Bellachioma, G.; Cardaci, G.; Macchioni, A.; Venturi, C.; Zuccaccia, C. J. Organomet. Chem. 2006, 691, 3881. S10
(8) CrystalStructure 4.0: Crystal Structure Analysis Package, Rigaku and Rigaku/MSC, The Woodlands TX 77381 USA, 2000 2010. (9) Altomare, A.; Cascarano, G.; Giacovazzo, C.; Guagliardi, A.; Burla, M.; Polidori, G.; Camalli, M. J. Appl. Cryst. 1994, 27, 435. (10) Beurskens, P. T.; Admiraal, G.; Behm, H.; Beurskens, G.; Bosman, W. P.; García-Granda, S.; Gould, R. O.; Smits, J. M. M.; Smykalla, C. Z. Kristallogr., Suppl. 1991, 4, 99. (11) Beurskens, P. T.; Admiraal, G.; Behm, H.; Beurskens, G.; Smits, J. M. M.; Smykalla, C. Z. f. Kristallogr. Suppl. 4 1991, p.99. The DIRDIF-99 program system, Technical Report of the Crystallography Laboratory, University of Nijmegen, The Netherlands, 1999. (12) Flack, H. D. Acta Crystallogr. Sect. A 1983, 29, 876. S11
Table S1. Yield of Ammonia in Catalytic Disproportionation of Hydrazine a yield of NH 3 run cat. cat., mmol N 2 H 4 charged, mmol S/C b remaining conv. of N 2 H 4, mmol c N 2 H 4, % d free, mmol c per Fe cat. e + coord.f % g 1 2a 0.048 0.243 5.06 <0.003 >98 0.267 5.56 (5.49) 2 2a 0.037 0.200 5.41 <0.003 >98 0.218 5.89 (5.44) 3 2a 0.038 0.190 5.00 <0.003 >98 0.206 5.42 (5.42) average of runs 1 3 5.62 (5.45) 6.29 (6.12) 92 4 2b 0.033 0.164 4.96 0.075 54 0.093 5 2c 0.032 0.161 5.03 0.011 37 0.011 2.82 (2.84) 0.34 (0.34) h 43 h 5 6 3 0.037 0.187 5.05 <0.003 >98 0.249 6.73 (6.66) 7.62 (7.54) 113 (100) a b Reaction conditions: CH 2 Cl 2 MeOH, 1 ml/1 ml; rt; 18 h, under Ar. (Moles of N 2 H 4 charged)/(moles of Fe cat). c Determined by colorimetry. d (Moles of N 2 H 4 consumed)/(moles of N 2 H 4 charged). e (Moles of free NH 3 )/(moles of Fe cat). The value normalized by dividing by (S/C)/5 is in parentheses. f Including the amount of ammine complex 3 determined by 1 H NMR. The value based on the amount of the normalized free NH 3 is in parentheses. g (Moles of NH 3 produced)/(mols of N 2 H 4 charged)/(4/3) 100. The value after excluding the amount of recovered 3 is in parenthesis. h The ammine complex was not characterized. S12
Table S2. Yield of Dinitrogen in Catalytic Disproportionation of Hydrazine a yield of N 2 run cat. cat., mmol N 2 H 4 charged, mmol S/C b N 2, mmol c per Fe cat. d %e 1 2a 0.037 0.197 5.32 0.061 2 2a 0.038 0.200 5.26 0.060 3 2a 0.036 0.190 5.28 0.058 average of runs 1 3 4 2b 0.035 0.178 5.09 0.028 5 2c 0.034 0.172 5.06 0.018 1.65 (1.55) 1.58 (1.50) 1.61 (1.53) 1.61 (1.53) 0.80 (0.79) 0.53 (0.52) 92 47 31 6 3 0.034 0.172 5.06 0.047 1.38 (1.36) a Reaction conditions: CH 2 Cl 2 MeOH, 1 ml/1 ml; rt; 18 h, under Ar. b (Moles of N 2 H 4 charged)/(moles of Fe cat). c Determined by GC. d (Moles of produced N 2 )/(moles of Fe cat). The value normalized by dividing by (S/C)/5 is in parentheses. e (Moles of N 2 produced)/(mols of N 2 H 4 charged)/(1/3) 100. 82 S13
Figure S1. Crystal structure of 1. C(19) C(16) C(10) C(7) C(17) C(11) C(6) C(8) C(9) C(5) N(5) N(4) N(3) C(4) Cl(1) C(2) C(3) Fe(1) Cl(2) N(2) C(13) C(15) C(1) C(12) N(1) H(1) C(14) H(29) O(1) C(20) C(18) Figure S2. Crystal structure of 5. C(2) C(12) C(13) C(1) C(11) N(1) C(10) N(2) C(14) C(15) C(4) P(1) H(1) O(1) C(3) F(3) O(2) S(1) O(3) C(16) F(1) C(9) C(8) C(7) C(5) C(6) F(2) S14