5708
Organometallics 2010, 29, 5708–5713 DOI: 10.1021/om100544f
Reactions of (Et2NCH2CH2NEt2) 3 H2SiCl2 with Selected Diorganometallic Reagents of Magnesium and Lithium† Joyce Y. Corey,* Kevin A. Trankler, Janet Braddock-Wilking, and Nigam P. Rath Department of Chemistry and Biochemistry, University of Missouri;St. Louis, St. Louis, Missouri 63121 Received June 2, 2010
Addition of the THF-insoluble di-Grignard reagent from 2,20 -dibromo-4,40 -tert-butylbiphenyl (1) to a solution of [(teeda) 3 H2SiCl2] in CH2Cl2/THF produced 2,7-di-tert-butyl-9H-9-silafluorene (3) in isolated, recrystallized yields of 300 °C whose 1H NMR spectra suggest a polymeric product that contains at least the skeleton from the starting 1 and 2, indicating another reaction pathway that diverts the diorganometallic from the formation of the monocycles or the spirocycles. The reaction of PhMgX (X = Cl, Br) with the teeda complex under solvent conditions different from those originally reported3 was also investigated. If only THF solvent is used in the reaction of PhMgCl with the teeda complex, the expected product Ph2SiH2 was formed in lower yields than in the original report. The reaction of PhMgBr with the teeda complex in CH2Cl2/THF gave Ph2SiH2 in yields somewhat lower than those reported for PhMgCl, and when Et2O replaced the THF, the yield of Ph2SiH2 was cut approximately in half.
Experimental Section General Procedures. All reactions, unless otherwise noted, were carried out under an argon atmosphere using standard Schlenk techniques. The solvents THF and Et2O were distilled from Na/9-fluorenone,8 and CH2Cl2 was distilled over P2O5 prior to use. Pentane was washed with H2SO4 prior to distillation from CaH2. The compounds 2,20 -dibromo-4,40 -di-tertbutylbiphenyl4 and bis(2-bromo-4-methylphenyl)methylamine6 were prepared by slightly modified literature methods (see the Supporting Information), and [(teeda) 3 H2SiCl2]3a was prepared by the literature method. The teeda complex was stored in a drybox, and portions were transferred when needed. Commercial MeLi (1.6 M in Et2O) and PhMgCl (1.8 M in THF) were (8) Kamaura, M.; Inanaga, J. Tetrahedron Lett. 1999, 40, 7347.
5711
used as supplied, and PhMgBr was prepared from PhBr and Mg turnings in diethyl ether. Low-resolution mass spectral data (EI, 70 eV) were collected on a Hewlett-Packard Model 5988A instrument and exact mass data on a JEOL-JMS-300 instrument (EI). Gas chromatographic analyses were performed on a Shimadzu Model GC14A gas chromatograph utilizing a 30 m DB-5 capillary column. The GC percentages are uncorrected. Melting point determinations were performed on a Mel-Temp electrothermal capillary melting point apparatus and are uncorrected. Proton, 13C{1H}, and 29Si{1H} nuclear magnetic resonance spectra were recorded using a Bruker ARX-500 spectrometer equipped with a 5 mm broadband probe or on an Avance300 instrument equipped with a 4 nucleus probe. Spectra are referenced internally to residual solvent peaks (CDCl3 or C6D6) or to external TMS. The DEPT sequence was utilized in collecting 29Si NMR data. Elemental analyses were performed by Atlantic Microlab, Inc. The X-ray crystal structure determination was performed on a Bruker SMART diffractometer equipped with a CCD area detector. Formation of the Grignard Reagent from 2,20 -Dibromo-4,40 -ditert-butylbiphenyl (1) and Mg Followed by Reaction with [(teeda) 3 H2SiCl2]. (a) A solution of 1 (2.01 g, 4.71 mmol) in THF (30 mL containing 0.4 mL of EDB) was added, dropwise, to a slurry of Mg turnings (0.567 g, 23.3 mmol) in THF (5 mL). The reaction was slightly exothermic. About 1/2 h after completion of the addition, an aliquot was removed and hydrolyzed with water. A GC/GCMS analysis indicated the presence of 4,40 -ditert-butylbiphenyl (57%; GC), 2-bromo-4,40 -di-tert-butylbiphenyl (14.5%; GC), and 1 (12%; GC) (all three verified by doping with authentic samples) in addition to a component (12%; GC) with m/e 282 tentatively assigned to 2-( p-tBuC6H4)-5-tBuC6H3OH. The mixture was heated at a gentle reflux for an additional 2 h. When the mixture was cooled to room temperature, a thick slurry formed. A solution of [(teeda) 3 H2SiCl2] (1.30 g, 4.72 mmol) in CH2Cl2 (8 mL) was cannulated into the THF slurry of the Grignard reagent, whereupon a clear solution formed. The mixture was stirred overnight before removing the solvent and adding diethyl ether (30 mL) and HCl (50 mL, 0.2 M). The ether layer was separated and dried over MgSO4. After removal of the ether the crude product was vacuum-distilled (Kugelrohr distillation). For the first fraction (0.547 g, bp 150-190 °C/0.2 mm), GC analysis showed that the sample contained silafluorene 3 (75%) and 4,40 -di-tert-butylbiphenyl (16%). The first fraction was dissolved in absolute EtOH and on cooling to -7 °C provided 0.269 g of 3 as a white solid (91% silafluorene 3 and 8.8% 4,40 -ditert-butylbiphenyl), mp 101-103 °C (lit.4 mp for 3 containing 3% 4,40 -di-tert-butylbiphenyl, 98-99 °C). A second 0.206 g fraction, with bp up to 250 °C/0.2 mm, was obtained. Recrystallization of this fraction from absolute EtOH gave 65 mg of a white solid, mp 253-255 °C, which proved to be the spirocycle 2,20 ,7,70 -tetra-tertbutyl-9,90 -spirobi[9H-9-silafluorene] (5). 1H NMR (CDCl3, 300 MHz): δ 1.27 (s, C(CH3)3, 36H), 7.42 (d, J = 2.0 Hz, Ar-H3, 4H), 7.54 (dd, J = 8.0, J = 2.0 Hz, Ar-H2, 4H), 7.82 (d, J = 8.0 Hz, ArH1, 4H). 1H NMR (C6D6, 300 MHz): δ 0.99 (s, C(CH3), 36H), 7.46 (dd, Ar-H2, 4H), 7.73 (d, Ar-H3, 4H), 7.92 (d, Ar-H1, 4H) (numbering of the Ar-H protons is the same as depicted in Figure 4). A second recrystallization from EtOH gave a few shiny crystals, mp 273-275 °C (as an ethanol solvate), that were used for the X-ray diffraction study. (b) A solution of 2,20 -dibromo-4,40 -di-tert-butylbiphenyl (7.8 g, 18 mmol) in dry THF (20 mL) was added slowly to a slurry of Mg (7.8 g, 320 mmol, 100 mesh) in THF (20 mL) to which a small amount of EDB had been added. The mixture was allowed to react at room temperature with stirring for 16 h and then cannulated into a pressure addition funnel. A slurry of [(teeda) 3 H2SiCl2] (5.0 g, 18 mmol) in THF (40 mL) was placed in a second addition funnel, and the two slurries were added to a 250 mL flask containing THF (40 mL). The mixture was allowed to react at room temperature for 2 days. After hydrolysis with saturated NH4Cl solution, the organic layer was dried over
5712
Organometallics, Vol. 29, No. 21, 2010
MgSO4 and the volatiles were removed to give a yellow oil. Kugelrohr distillation provided a forerun, bp up to 100 °C/0.2 mmHg, that contained 4,40 -di-tert-butylbiphenyl. Sublimation through the temperature range 100-250 °C/0.2 mmHg gave white, well-formed blocks of 2,20 ,7,70 -tetra-tert-butyl-9,90 spirobi[9H-9-silafluorene] (50 ): 3.7 g (74% based on the starting dibromide), mp 243-246 °C. 1H NMR (CDCl3, 500 MHz): δ 1.28 (s, C(CH3)3, 36H), 7.44 (d, J = 2.0 Hz, Ar-H3, 4H), 7.55 (dd, J = 8.2, 2.0 Hz, Ar-H2, 4H), 7.86 (d, J = 8.2 Hz, Ar-H1, 4H). 13C{1H} NMR (CDCl3, 125.8 MHz): δ 31.6, 35.0, 120.5, 128.4, 131.4, 133.6, 137.7, 150.5. 29Si{1H} NMR (CDCl3, 99.4 MHz): δ -6.52. Mass spectrum: m/e 556 (Mþ). Anal. Calcd for C40H48Si: C, 86.27; H, 8.69. Found: C, 86.22; H, 8.84. Reaction of nBuLi with Bis(2-bromo-4-methylphenyl)methylamine (2) Followed by Reaction with [(teeda) 3 H2SiCl2]. (a) A solution of 2 (0.496 g, 1.36 mmol) in diethyl ether was cooled in a dry ice/acetone bath (precipitation occurs), and nBuLi (1.1 mL, 2.5 M) was added. After addition was complete the flask was warmed to room temperature. An aliquot was withdrawn and hydrolyzed with D2O (99.96%), and the GC trace showed two major components (72% by GC, m/e 211-213, C15H17-nDnN; n = 2 (87%), 1 (7%), 0 (5.7%), and 15% by GC, m/e 227, C15H17NO (suggested structure, MeN(C6H4Me-p)(C6H3OH-o, Me-p)). The aryllithium solution was cannulated into a solution of [(teeda) 3 H2SiCl2] (0.39 g, 1.5 mmol) in CH2Cl2/Et2O (8 mL/9 mL), whereupon a precipitate formed. The mixture was stirred overnight before removing the solvents and adding diethyl ether (30 mL) and HCl (50 mL, 0.2 M). The ether layer was separated and dried over MgSO4. After removal of the ether, the crude product was vacuum-distilled (Kugelrohr distillation). The first fraction, bp up to 175 °C/0.01 mmHg, 0.154 g, contained three components >∼6% by GC: MeN(C6H4Me-p)2 (6.4%, m/e 211), phenazasiline 4 (69%, m/e 239), and a component with m/e 295 (5.5%) assigned to 2,5,8-trimethyl-10-butyl-5,10dihydrophenazasiline. The sample was recrystallized from absolute ethanol to give 4 (97% by GC): 0.051 g, mp 103-103.5 °C (lit.5 mp 103-104.5 °C). 1H NMR (C6D6, 300 MHz): δ 2.16 (s, C-CH3, 3H), 2.97 (s, N-CH3, 3H), 5.16 (s, SiH2, 2H), 6.71 (d, J = 8.4 Hz, Ar-H1, 2H), 7.06 (dd, J = 9.0, 2.0 Hz, Ar-H2, 2H), 7.33 (d, J = 2.0 Hz, Ar-H3, 2H) (chemical shift values and multiplicities correspond to the literature report5). (b) A solution of 2 (0.700 g, 1.90 mmol) in Et2O (10 mL) was cooled to -78 °C, at which point 2 begins to precipitate, and n BuLi (1.5 mL, 2.5 M) was added. The slurry was stirred for 1/2 h before it was slowly warmed to 0 °C, and the dry ice/acetone bath was replaced with an ice/water bath. An aliquot hydrolyzed with D2O (99.96%) showed two major components: C15H17-nDnN (m/e 211-213, n = 2 (69%), 1 (12%), 0 (18%); 71% by GC) and 2 (m/e 367, 369, 371; 17% by GC). After an additional 1/2 h, the lithium reagent was cannulated into a slurry of [(teeda) 3 H2SiCl2] (0.523 g, 1.92 mmol) in Et2O (20 mL) and the resultant mixture stirred overnight. The solvents were removed, and diethyl ether (30 mL) and HCl (50 mL, 0.2 M) were added. The ether layer was separated and dried over MgSO4. After removal of the ether from the crude product, distillation (Kugelrohr) provided a fraction, bp up to 130 °C/0.4 mmHg, 0.145 g, which solidified. A GC trace indicated that the only major component (84%) in the fraction was the starting dibromide 2. The nondistilled portion, 0.263 g, was dissolved in CH2Cl2; the CH2Cl2 was then replaced with boiling cyclohexane and the solution filtered while hot. The filtrate deposited a solid, 2,20 ,5,50 ,8,80 -hexamethyl-5,10-dihydro-10,10-spirobiphenazasiline (6): 0.104 g, mp 227-230 °C (lit.6 mp 230-233 °C after four recrystallizations). 1H NMR (C6D6, 300 MHz): δ 1.95 (s, CCH3, 12H), 3.23 (s, NCH3, 6H), 6.91 (d, J = 8.5 Hz, Ar-H1, 4H), 7.11 (dd, J = 8.5, 2.2 Hz, Ar-H2, 4H), 7.45 (d, J = 2.2 Hz, Ar-H3, 4H). 1H NMR (CDCl3, 300 MHz): δ 2.19 (s, CCH3, 12H), 3.65 (s, NCH3, 6H), 7.07 (d, Ar-H1, 4H), 7.11(d, Ar-H3, 4H), 7.22 (dd, Ar-H2, 4H). MS (EI, 70 eV): m/e found 446.2168, calcd 446.2178.
Corey et al. Reaction of PhMgX (X = Cl, Br) with [(teeda) 3 H2SiCl2] in THF. (a) To a slurry of [(teeda) 3 H2SiCl2] (1.00 g, 3.64 mmol) in THF (20 mL) was added, dropwise, a THF solution of PhMgCl (5 mL, 1.8 M), and the mixture was stirred overnight. After the usual workup, GC analysis of the crude product showed the presence of Ph2SiH2 (m/e 184, 60%), Ph3SiH (m/e 260, 14%) (both verified by doping with an authentic sample), and HPh2SiOSiPh2H (m/e 382, 14%). Kugelrohr distillation provided a fraction, bp 75-97 °C/0.4 mmHg, 0.285 g, that contained, from GC/GCMS analysis, Ph2SiH2 (76%) and HPh2SiOSiPh2H (9%). A second fraction, bp 100-190 °C/0.4 mmHg, 0.152 g, contained the following from GC analysis: Ph2SiH2 (16%), Ph3SiH (64%), and HPh2SiOSiPh2H (8%). The nondistilled portion, 0.133 g, contained HPh2SiOSiPh2H (60% by GC) and an unidentified component with a longer retention time (28% by GC). (b) A Grignard reagent was prepared from PhBr (0.80 mL, 1.19 g, 7.6 mmol) in THF (10 mL) that contained EDB (0.2 mL) and Mg turnings (0.182 g, 7.49 mmol). The PhMgBr was cannulated into a solution of [(teeda) 3 H2SiCl2] (1.07 g, 3.92 mmol) in a CH2Cl2/THF mixture (5 mL/12 mL), and the flask with the Grignard reagent was rinsed with additional THF (4 mL), added to the reaction mixture, and the resultant mixture was stirred overnight. After aqueous workup with dilute HCl (0.2 M) and extraction with ether, the ether layer was dried over MgSO4. The volatiles were removed, and distillation (Kugelrohr) of the remainder provided a fraction, 0.307 g, bp up to 85 °C/0.4 mmHg (nondistilled portion weighed 116 mg). Analysis of the distilled fraction by GC indicated the presence of teeda (12%), biphenyl (12%), and Ph2SiH2 (67%). Redistillation of this fraction gave a sample that contained biphenyl (10%), Ph2SiH2 (82%), and HPh2SiOSiPh2H (2.9%). (c) A similar reaction on half the scale described in (b) but with Et2O as solvent gave after workup a fraction, bp up to 85 °C/0.01 mmHg, 0.240 g, that contained the following by GC and GCMS: teeda (26%), biphenyl (9%), Ph2SiH2 (35%), Ph2Si(OEt)H (13%), and HPh2SiOSiPh2H (14%) with 0.128 g nondistilled material. X-ray Structure Determination for 2,20 ,7,70 -tetra-tert-butyl9,90 -spirobi[9H-9-silafluorene] (50 ) and Its Ethanol Solvate (5). Crystals of X-ray diffraction quality were obtained by recrystallization (2) of 5 from absolute ethanol, and crystals of 50 were obtained by sublimation. Crystals of appropriate dimension were used for the single-crystal X-ray structure determinations using Bruker Kappa ApexII and Bruker Smart 1K charge coupled device (CCD) detector systems. All data were collected using graphite-monochromated Mo KR radiation (λ = 0.710 73 A˚) from a fine-focus sealed-tube X-ray source. Preliminary unit cell constants were determined with a set of 36 narrow frame scans. Typical data sets consist of combinations of φ and φ scan frames with typical scan width of 0.5° and a counting time of 15-30 s/frame at a crystal to detector distance of 4.05.0 cm. The collected frames were integrated using an orientation matrix determined from the narrow frame scans. Apex II, SMART, and SAINT software packages9 were used for data collection and data integration. Analysis of the integrated data did not show any decay. Final cell constants were determined by global refinement of reflections from the complete data set. Collected data were corrected for systematic errors using SADABS10 on the basis of the Laue symmetry using equivalent reflections. Crystal data and intensity data collection parameters are given in Table 1. Structure solution and refinement were carried out using the SHELXTL-PLUS software package.11 The structures were solved by direct methods in monoclinic space groups C2/c and P21/n, respectively. The models were P refined with full-matrix least-squares refinement by minimizing w(Fo2 - Fc2)2. All nonhydrogen atoms were refined anisotropically to convergence. (9) SMART and SAINT; Bruker Analytical X-Ray, Madison, WI. (10) SADABS; Bruker Analytical X-Ray, Madison, WI, 2008. (11) Sheldrick, G. M. Bruker-SHELXTL. Acta Crystallogr. 2008, A64, 112.
Article One of the tBu groups is disordered over two positions for 50 . Disorder was resolved with 80%/20% occupancy atoms. Geometrical and displacement parameter restraints (SADI, ISOR, SIMU) were used for the disordered group in 50 , whereas the geometric restraint DFIX was used for the solvent molecule in 5. All H atoms were added in calculated positions and were refined using appropriate riding models (AFIX m3). The models were refined to convergence to the final residual values of R1 = 4.6% and 6.0% and wR2 = 13.1 and 15.9%, respectively. Complete listings of geometrical parameters, positional and isotropic displacement coefficients for hydrogen atoms, and anisotropic displacement coefficients for the non-hydrogen atoms are available as Supporting Information. Tables of calculated and observed structure factors are available from the authors in electronic format.
Organometallics, Vol. 29, No. 21, 2010
5713
Acknowledgment. J.Y.C. wishes to thank Teresa Bandrowsky and J. B. Carroll for assistance in collection of the NMR data and R. E. Winter and J. Kramer for collecting the mass spectral data. Funding from the National Science Foundation (MRI, No. CHE-0420497) for the purchase of the ApexII diffractometer is acknowledged. Supporting Information Available: Text giving experimental details for compounds 1 and 2 and tables, figures, and CIF files giving crystallographic data for 5 and 50 , including crystal data and structure refinement details, atomic coordinates, and bond distances and angles. This material is available free of charge via the Internet at http://pubs.acs.org.
