Cycloaddition with Diphenyl Hydrazone - American Chemical Society

Oct 27, 2009 - intermediates of diimine and hydrazine) results in the clea- vage of the NrN bond.3,4 In the literature the cleavage of the. NrN bond o...
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Organometallics 2009, 28, 6574–6577 DOI: 10.1021/om9007086

Insertion Reaction of a Silylene into a N-H Bond of Hydrazine and a [1þ4] Cycloaddition with Diphenyl Hydrazone§ Anukul Jana,† Herbert W. Roesky,*,† Carola Schulzke,‡ and Prinson P. Samuel† †

Institut f€ ur Anorganische Chemie der Universit€ at G€ ottingen, Tammannstrasse 4, 37077 G€ ottingen, Germany, and ‡School of Chemistry, Trinity College Dublin, Dublin 2, Ireland Received August 10, 2009

The reaction of a stable six-membered N-heterocyclic silylene, LSi (1) [L = CH{(CdCH2)(CMe)(2,6-iPr2C6H3N)2}], with hydrazine and its derivatives is described. 1 reacts with hydrazine to form LSi(H)NHNH2 (2) under N-H bond insertion of the silylene. The reaction of 1 and N-methyl hydrazine results exclusively in the formation of LSi(H)NHNHMe (3). Treatment of 1 with an equimolar amount of diphenyl hydrazone in toluene yields the dearomatized siloxy-indolin-1-amine 4 in almost quantitative yield rather than the insertion product at the N-H bond of the NH2 group. Compounds 2-4 were characterized by microanalysis, multinuclear NMR, and IR spectroscopy. Compounds 2 and 4 are confirmed by X-ray structural analysis with the result that 2 and 4 are both monomeric and the silicon center of each resides in a distorted tetrahedral environment.

Introduction Hydrazine and its derivatives are important molecules in the field of organic and inorganic chemistry since the discovery of a new indole synthesis in 1883 by Emil Fischer.1 Hydrazine is also very well known as an intermediate of nitrogenase in the field of biochemistry.2 The conversion of N2 to ammonia by enzymatic or chemical methods (via the intermediates of diimine and hydrazine) results in the cleavage of the N-N bond.3,4 In the literature the cleavage of the N-N bond of hydrazine is well documented by a variety of model systems, while the N-H bond cleavage of hydrazine is rare.5 On the metal surface the N-H bond cleavage of hydrazine is reported,6 and substitution reactions of the §

Dedicated to Professor L. Kolditz on the occasion of his 80th birthday. *To whom correspondence should be addressed. Fax: þ49-551393373. E-mail: [email protected]. (1) (a) Fischer, E.; Jourdan, F. Ber. 1883, 16, 2241–2245. (b) Fischer, E.; Hess, O. Ber. 1884, 17, 559–568. (c) van Orden, R. B.; Lindwell, H. G. Chem. Rev. 1942, 30, 69–96. (2) (a) Thorneley, R. N. F.; Eady, R. E.; Lowe, D. J. Nature 1978, 272, 557–558. (b) Barney, B. M.; Yang, T.-C.; Igarashi, R. Y.; Dos Santos, P. C.; Laryukhin, M.; Lee, H. -I.; Hoffman, B. M.; Dean, D. R.; Seefeldt, L. C. J. Am. Chem. Soc. 2005, 127, 14960–14961. (3) (a) Howard, J. B.; Ress, D. C. Chem. Rev. 1996, 96, 2965–2982. (b) Burgess, B. K.; Lowe, D. J. Chem. Rev. 1996, 96, 2983–3011. (4) (a) Pool, J. A.; Lobkovsky, E.; Chirik, P. J. Nature 2004, 427, 527– 530. (b) Avenier, P.; Taoufik, M.; Lesage, A.; Solans-Monfort, X.; Baudouin, A.; de Mallmann, A.; Veyre, L.; Basset, J.-M.; Eisenstein, O.; Emsley, L.; Uqadrelli, E. A. Science 2007, 317, 1056–1060. (5) Chu, W.-C.; Wu, C.-C.; Hsu, H.-F. Inorg. Chem. 2006, 45, 3164– 3166, and references therein. (6) (a) Alberas, D. J.; Kiss, J.; Liu, Z.-M.; White, J. M. Surf. Sci. 1992, 278, 51–61. (b) Lim, C.; Choi, C. H. J. Chem. Phys. 2004, 120, 979–987. (7) (a) Wiberg, N.; Veith, M. Chem. Ber. 1971, 104, 3176–3190. (b) Clegg, W.; Haase, M.; Hluchy, H.; Klingebiel, U.; Sheldrick, G. M. Chem. Ber. 1983, 116, 290–298. (c) Drost, C.; Klingebiel, U. Chem. Ber. 1993, 126, 1413–1416. (d) Gellermann, E.; Klingebiel, U.; Pape, T.; Antonia, F. D.; Schneider, T. R.; Schumatz, S. Z. Anorg. Allg. Chem. 2001, 627, 2581–2588. pubs.acs.org/Organometallics

Published on Web 10/27/2009

hydrogen atoms of hydrazine are well known.7 To the best of our knowledge no insertion reactions at the N-H bond of hydrazine have been mentioned. Recently we reported on the oxidative N-H bond cleavage of ammonia at the silicon(II) center.8 Herein we describe the reaction of silylene LSi (1)9 [L = CH{(CdCH2)(CMe)(2,6-iPr2C6H3N)2}] with hydrazine, N-methyl hydrazine, and diphenyl hydrazone, respectively.

Results and Discussion The addition of hydrazine to a yellow solution of 1 in toluene leads to a rapid vanishing of the yellow color (Scheme 1). From the colorless solution the volatiles were removed under vacuum, and the residue was extracted with n-hexane. Concentration of the solution yielded colorless crystals of LSi(H)NHNH2 (2) in 85% yield. Single crystals of 2 were obtained from a saturated n-hexane solution at -32 °C after two days. Compound 2 crystallizes in the monoclinic space group P21/n, with one monomer in the asymmetric unit. X-ray crystal structure analysis afforded a monomeric structure as illustrated in Figure 1. Surprisingly, 2 is monomeric in the solid state, and what is even more striking, the NHNH2 group is not involved in any kind of hydrogen bonding, as shown by X-ray structural analysis. Compound 2 is stable in the solid state as well as in solution for a longer period of time without any decomposition under inert atmosphere. The coordination polyhedron around the silicon atom features a distorted tetrahedral geometry. The silicon is attached to two nitrogen atoms from the backbone of the chelating ligand, the NHNH2 group, and a hydrogen atom. (8) Jana, A.; Schulzke, C.; Roesky, H. W. J. Am. Chem. Soc. 2009, 131, 4600–4601. (9) Driess, M.; Yao, S.; Brym, M.; W€ ullen, C.van; Lentz, D. J. Am. Chem. Soc. 2006, 128, 9628–9629. r 2009 American Chemical Society

Article

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Table 1. Crystallographic Data for the Structural Analyses of Compounds 2 and 4 2

4

empirical formula C29H44N4Si CCDC No. 740333 T [K] 133(2) cryst syst monoclinic space group P21/n a [A˚] 11.574(2) b [A˚] 20.188(4) c [A˚] 12.598(3) R [deg] 90 β [deg] 97.53(3) γ [deg] 90 2918.3(10) V [A˚3] Z 4 -3 1.085 Dcalcd [g cm ] -1 0.103 μ [mm ] F(000) 1040 θ range [deg] 1.92-25.94 data/restraints/params 5679/0/323 reflns collected/unique 24 687/5679 [R(int) = 0.0704] 0.0614, 0.1333 R1, wR2 [I > 2σ(I)]a 0.1036, 0.1479 R1, wR2 (all data) a GoF 1.043 -3 0.381, -0.392 ΔF(max), ΔF(min) [e A˚ ] P P P a 2 2 2 P R1 = ||Fo| - |Fc||/ |Fo|. wR2 = [ w(Fo - Fc ) / w(Fo2)2]0.5.

C42H52N4Si 740334 133(2) triclinic P1 9.2397(18) 12.543(3) 16.134(3) 78.93(3) 84.21(3) 77.19(3) 1786.1(6) 2 1.192 0.101 692 1.69-026.96 7665/0/632 15 866/7665 [R(int) = 0.0358] 0.0390, 0.1031 0.0441, 0.1063 1.026 0.399, -0.342

Scheme 1. Preparation of Compounds 2 and 3

Scheme 2. Preparation of Compound 4

The composition of 2 was proven by multinuclear NMR spectroscopy, mass spectrometry, and elemental (C, H, N) analysis. The 1H and 29Si NMR spectra revealed that 2 has a Si(H)NHNH2 moiety. The Si-H proton shows a doublet (δ 5.05 ppm) with a coupling constant of 3J(H-H) = 4.34 Hz. The 29Si NMR spectrum exhibits a doublet resonance (δ -42.33 and -44.95 ppm) with a coupling constant of 2 J(Si-H) = 260.5 Hz. Each doublet further splits into a doublet with the coupling constant of 3J(Si-H) = 12.73 Hz due to the NH proton. In addition the 1H NMR spectrum exhibits a singlet and doublet for the γ-CH and NH2 protons at δ 5.30 and 1.85 ppm, respectively. The most intense peak in the EI mass spectrum appeared at m/z = 461 [Mþ - CH3], and the signal at m/z = 476 (10%) was assigned to the molecular ion [Mþ]. The addition product of ammonia and SiH2 was theoretically studied by Walsh et al.10 Comparing our results with those of the theoretical calculations we are only able to confirm the oxidative addition rather than the reductive elimination of hydrogen. Furthermore we were interested in the selective N-H bond cleavage of the nonsymmetric hydrazine derivative. (10) Becerra, R.; Cannady, J. P.; Walsh, R. Silicon Chem. 2005, 3, 131–138.

Figure 1. Thermal ellipsoids (50%) drawing of 2. Isopropyl groups of the phenyl rings and hydrogen atoms, except those at silicon and at nitrogen, which were found and refined freely, are not shown for clarity. Selected bond lengths [A˚] and angles [deg]: Si1-N1 1.679(2), N1-N2 1.435(3), Si1-N3 1.730(2); Si1-N1-N2 120.20(19), N1-Si1-N3 114.58(11).

Therefore we selected MeNHNH2. Compound 1 reacts with N-methyl hydrazine in toluene at room temperature to form exclusively LSi(H)NHNHMe (3). This was confirmed by 1H NMR in solution. The 1H NMR spectrum shows a doublet and quartet resonance (δ 2.25 and 1.73 ppm), which corresponds to the two different N-H protons of 3. In addition there are no signals corresponding to the NH2 protons; therefore we excluded the formation of another isomer of 3. Also the 29Si NMR spectrum exhibits a doublet resonance (δ -42.31 and -44.97 ppm) with a coupling constant of 2 J(Si-H) = 263.8 Hz. Each doublet again is split into a doublet with the coupling constant 3J(Si-H) = 13.17 Hz. This coupling constant is similar to that in compound 2. Furthermore each doublet again splits into a doublet due to its neighboring proton of the NHMe group, with the coupling constant 4J(Si-H) = 2.34 Hz. The most intense peak in the EI mass spectrum appeared at m/z = 475 [Mþ - CH3]þ, and the signal at m/z = 490 (25%) was assigned to the molecular ion [Mþ].

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Jana et al.

the supporting ligand, one carbon atom from the dearomatized phenyl group, and one nitrogen atom of the hydrazone moiety, featuring a distorted tetrahedral geometry. Compound 4 represents a spirocyclic compound with the silicon atom at the spiro center comprising a six-membered SiN2C3 ring and a five-membered SiNC3 ring, which are orthogonally arranged to each other. A noteworthy feature of compounds 2 and 4 is the Si-N-NH2 moiety (Si1-N1 1.679(2) A˚ for 2 and Si1-N1 1.7480(12) A˚ for 4); these Si1-N1 bond lengths can be compared with that in LSi(H)NH2 (1.653(3) A˚)8 and those in RSi(NH2)3 (R = 2,4,6-Ph3C6H2 av 1.709(7) A˚,12 R = 2,6iPr2C6H3NSiMe3 av 1.709(2) A˚, and R = 2,4,6-tBu3C6H2O av 1.692(6) A˚).13 The N-N bond lengths in 2 and 4 (N1-N2; 1.435(3) and 1.4322(15) A˚) are comparable with that in LGeN(CO2Et)NHCO2Et (1.418(14) A˚).14 Figure 2. Thermal ellipsoids (50%) drawing of 4. Isopropyl groups of the phenyl rings and hydrogen atoms, except those at N2, C26, and C30 and nonaromatics, which were found and refined freely, are not shown for clarity. Selected bond lengths [A˚] and angles [deg]: Si1-N1 1.7480(12), N1-N2 1.4322(15), Si1-C1 1.8786(13), C1-C6 1.5260(16), C6-C7 1.3596(17); Si1-N1-N2 117.46(8), Si1-C1-C6 103.70(8), N3-Si1-N4 103.44(9).

The reaction of 1 with an equimolar amount of diphenyl hydrazone in toluene proceeds rapidly even in a broad temperature range (-78 °C, ambient temperature) under the formation of the remarkably dearomatized siloxy-indolin1-amine 4 in almost quantitative yield. To our surprise we observed no insertion of the silicon(II) center into the N-H bond of the NH2 group during the reaction. Even after a longer period of time 4 is not converted into an aromatized silyl amine tautomer or any other product. Very recently Driess et al. reported that 1 reacts with benzophenone under formation of a dearomatized product at low temperatures.11 However this product converted to the tautomeric aromatic silyl ether. The reported result is in contrast to the formation of compound 4. 4 is a yellow solid soluble in benzene, THF, n-hexane, and n-pentane, respectively, and shows no decomposition on exposure to dry air. 4 was characterized by multinuclear spectroscopy, EI mass spectrometry, elemental analysis, and X-ray structural analysis. The 1H NMR spectrum of 4 exhibits a singlet (δ 2.97 ppm) that can be assigned to the NH2 protons. The 29Si NMR spectrum exhibits a doublet resonance (δ -19.87 and -20.07 ppm) with a coupling constant of 3J(Si-H) = 20.4 Hz. In the EI mass spectrum at m/z = 625 [Mþ - CH3] (100 %) was the most intense peak, and the molecular ion arises at m/z = 640 [Mþ] (10%) albeit in low intensity. Suitable crystals for X-ray structural analysis are obtained from a hot saturated n-hexane solution of 4 after keeping this solution overnight at room temperature. 4 crystallizes in the triclinic space group P1, with one molecule of 4 in the asymmetric unit. 4 exists as a monomer in the solid state (Figure 2). There are no intermolecular hydrogen bonds observed in the crystal lattice. The coordination polyhedron around the silicon atom comprises two nitrogen atoms from (11) Xiong, Y.; Yao, S.; Driess, M. Chem.;Eur. J. 2009, 15, 5545– 5551.

Summary and Conclusion In summary we have shown that the silylene inserts into one of the N-H bonds of hydrazine and its nonsymmetric Nmethyl derivative, affording the silane-substituted hydrazines 2 and 3. In contrast to these observations diphenyl hydrazone reacts with silylene to form the nonaromatic siloxy-indolin-1-amine derivative 4.

Experimental Section General Considerations. All manipulations were performed under a dry and oxygen-free atmosphere (N2) using standard Schlenk techniques or inside a MBraun MB 150-GI glovebox maintained at or below 1 ppm of O2 and H2O. Solvents were purified with the M-Braun solvent drying system. The starting material 1 was prepared using literature procedures.9 Other chemicals were purchased and used as received. 1H and 29Si NMR spectra were recorded on a Bruker Avance DRX 500 MHz instrument and referenced to the deuterated solvent in the case of the 1H NMR and SiMe4 for the 29Si NMR spectra. Elemental analyses were performed by the Analytisches Labor des Instituts f€ ur Anorganische Chemie der Universit€ at G€ ottingen. Infrared spectral data were recorded on a PerkinElmer PE-1430 instrument. EI-MS were measured on a Finnigan Mat 8230 or a Varian Mat CH5 instrument. Melting points were measured in sealed glass tubes with a B€ uchi melting point B 540 instrument and are not corrected. Synthesis of 2. NH2NH2 (1 mL, 1 M in THF) was added to a yellow solution of 1 (0.45 g, 1 mmol) in toluene (20 mL) at 0 °C. Then the reaction mixture was allowed to come to room temperature. After that, the reaction mixture was stirred for an additional 30 min. All the volatiles were removed under vacuum from the solution, and the residue was extracted with n-hexane (30 mL). The solution was reduced to half of its volume. Storage of the solution at -32 °C in a freezer for two days yielded 2 as colorless crystals suitable for single-crystal X-ray diffraction studies. Yield: 0.40 g (85%); mp 177 °C. 1H NMR (500 MHz, C6D6): δ 7.03-7.19 (m, 6H, Ar-H), 5.30 (s, 1H, γ-CH), 5.05 (d, 1H, Si-H), 3.94 (s, 1H, CH2), 3.65 (sept, 2H, (12) Ruhlandt-Senge, K.; Bartlett, R. A.; Olmstead, M. M.; Power, P. P. Angew. Chem. 1993, 105, 459–461. Angew. Chem., Int. Ed. Engl. 1993, 32, 425-427. (13) Wraage, K.; K€ unzel, A.; Noltemeyer, M.; Schmidt, H.-G.; Roesky, H. W. Angew. Chem. 1995, 107, 2954–2956. Angew. Chem., Int. Ed. Engl. 1995, 34, 2645-2647. (14) Jana, A.; Sen, S. S.; Roesky, H. W.; Schulzke, C.; Dutta, S.; Pati, S. K. Angew. Chem. 2009, 121, 4310–4312. Angew. Chem., Int. Ed. 2009, 48, 4246-4248.

Article CH(CH3)2), 3.55 (sept, 2H, CH(CH3)2), 3.30 (s, 1H, CH2), 2.41 (br, 1H, NH), 1.85 (d, 2H, NH2), 1.47 (s, 3H, CH3), 1.39-1.17 (m, 24H, CH(CH3)2) ppm. 29Si NMR (99.35 Hz, C6D6): δ -43.63 (dd, 2J(Si-H) = 260.5 Hz, 3J(Si-H) = 12.73 Hz) ppm. EI-MS (70 eV): m/z (%) 476 (10) [Mþ], 461 (100) [Mþ - CH3]. Anal. Calcd for C29H44N4Si (476.33): C, 73.06; H, 9.30; N, 11.75. Found: C, 72.47; H, 9.14; N, 11.65. Synthesis of 3. MeNHNH2 (0.05 g, 1 mmol) was added to a yellow solution of 1 (0.45 g, 1 mmol) in toluene (20 mL) at room temperature. After that, the reaction mixture was stirred for an additional 30 min. All the volatiles were removed under vacuum from the solution and the residue was extracted with n-hexane (30 mL). Yield of 3: 0.39 g (80%); mp 73 °C. 1H NMR (500 MHz, C6D6): δ 7.04-7.22 (m, 6H, Ar-H), 5.34 (d, 1H, Si-H), 5.33 (s, 1H, γ-CH), 3.99 (s, 1H, CH2), 3.71 (sept, 1H, CH(CH3)2), 3.65 (sept, 1H, CH(CH3)2), 3.59 (sept, 1H, CH(CH3)2), 3.50 (sept, 1H, CH(CH3)2), 3.35 (s, 1H, CH2), 2.25 (d, 1H, SiNH), 1.73 (q, 1H, NHCH3), 1.66 (br, 3H, NCH3), 1.49 (s, 3H, CH3), 1.42 (d, 3H, CH(CH3)2), 1.38 (d, 3H, CH(CH3)2), 1.37 (d, 3H, CH(CH3)2), 1.13-1.31 (m, 15H, CH(CH3)2) ppm. 29 Si NMR (99.35 Hz, C6D6): δ -43.64 (ddd, 2J(Si-H) = 263.8 Hz, 3J(Si-H) = 13.17 Hz, 4J(Si-H) = 2.34 Hz) ppm. EI-MS (70 eV): m/z (%) 490 (25) [Mþ], 475 (100) [Mþ -CH3]. Anal. Calcd for C30H46N4Si (490.35): C, 73.42; H, 9.45; N, 11.42. Found: C, 73.74; H, 9.34; N, 10.48. Synthesis of 4. A solution of Ph2CdNNH2 (0.20 g, 1 mmol) in toluene (5 mL) was added to a yellow solution of 1 (0.57 g, 1 mmol) in toluene (20 mL) at room temperature. Then the reaction mixture was stirred for 1 h. All the volatiles from the solution were removed under vacuum, and the residue was extracted with n-hexane (30 mL). Suitable crystals for X-ray structural analysis were obtained from a hot saturated n-hexane solution of 4 after keeping the solution overnight at room temperature. Yield: 0.41 g (90%); mp 192 °C. 1H NMR

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(500 MHz, C6D6): δ 7.00-7.17 (m, 6H, Ar-H), 6.04 (d, 1H, CH), 5.67 (m, 1H, CH), 5.56 (s, 1H, γ-CH), 5.52 (m, 1H, CH), 5.41 (m, 1H, CH), 4.02 (s, 1H, CH2), 3.88 (sept, 1H, CH(CH3)2), 3.74 (sept, 1H, CH(CH3)2), 3.57 (sept, 2H, CH(CH3)2), 3.43 (s, 1H, CH2), 3.08 (m, 1H, SiCH), 2.97 (s, 2H, NH2), 1.54 (s, 3H, CH3), 1.42 (d, 3H, CH(CH3)2), 1.40 (d, 3H, CH(CH3)2), 1.38 (d, 3H, CH(CH3)2), 1.31 (d, 3H, CH(CH3)2), 1.30 (d, 3H, CH(CH3)2), 1.28 (d, 3H, CH(CH3)2), 1.23 (d, 3H, CH(CH3)2), 1.20 (d, 3H, CH(CH3)2) ppm. 29Si NMR (99.35 Hz, C6D6): δ -19.97 (d, 3J(Si-H) = 20.4 Hz) ppm. EI-MS (70 eV): m/z (%): 640 (10) [Mþ], 625 (100) [Mþ - CH3]. Anal. Calcd for C42H52N4Si (640.97): C, 78.70; H, 8.18; N, 8.74. Found: C, 78.47; H, 8.54; N, 8.52. Crystallographic Details for Compounds 2 and 4. Suitable crystals of 2 and 4 were mounted on a glass fiber, and data were collected on an IPDS II Stoe image-plate diffractometer (graphite-monochromated Mo KR radiation, λ = 0.71073 A˚) at 133(2) K. The data were integrated with X-area. The structures were solved by direct methods (SHELXS-97)15 and refined by full-matrix least-squares methods against F2 (SHELXL-97).15 All non-hydrogen atoms were refined with anisotropic displacement parameters. The hydrogen atoms were refined isotropically on calculated positions using a riding model, except H at silicon and at nitrogen, which were found.

Acknowledgment. This work was supported by the Deutsche Forschungsgemeinschaft. Supporting Information Available: X-ray data for 2 and 4 (CIF). This material is available free of charge via the Internet at http://pubs.acs.org. (15) Sheldrick, G. M. Acta Crystallogr., Sect. A 2008, 64, 112–122.