Organometallics 1995,14, 3625-3627
3625
Synthesis and Reduction of the 9,lO-Disilaanthracene Dimer Wataru Ando,* Ken Hatano, and Rie Urisaka Department of Chemistry, University of Tsukuba, Tsukuba, Ibaraki 305, Japan Received April 12, 1995@ Summary: 9,1O-Dimethyl-9,lO-disilaanthracene dimer (2) was prepared by treatment of 9,1O-dihydro-9,10disilaanthracene (la) with 2 equiv of lithium. The reaction of 2 with excess lithium or potassium resulted in formation of 9,lO-dilithio- or 9,lO-dipotassio-9,10dimethyl-9,lO-disilaanthracene (4a,b), via the dianion 3, in which one Si-Si bond has been cleaved. On treatment with a,o-dichloropolysilanes, 4a was converted into the corresponding cyclic compounds 6-9, respectively.
H2 1If
H23
H24
The chemistry of 9,lO-dihydroanthracenes with the silicon in position 9 and/or 10 has been considerably developed by Jutzil and Bickelhaupt2 and modified by C ~ r e y .However, ~ the anthracene dimer analogs with bridgehead silicon atoms have not been reported. We report herein the synthesis and reduction of the 9,lOdimethyl-9,lO-disilaanthracenedimer, a silicon analog to the anthracene dimer. Although the Wurtz coupling reaction of 9,lO-dichloro9,10-dimethyl-9,10-disilaanthracene (lb) with sodium in toluene at 110 "C formed bridged dimer 2 in only 7% yield, increased yields of 2 have been achieved by direct reaction of 9,10-dihydro-9,10-dimethyl-9,lO-disilaanthracene (la)with lithium. Reaction of a cidtrans mixture (=45/55)4of la (4.80 g, 20.0 mmol) with 2 equiv of lithium (0.28 g, 40.0 m o l ) in THF (30 mL) containing 6 mL of TMEDA produces a yellow solution at room temperature over a reaction time of 48 h. After removal of unreacted lithium, the HI3 bridged dimer 2 was obtained in 61% yield (Scheme 1). The structure of dimer 2 has been confirmed by spectral OH411 data5 and an X-ray analysis (Figure 1).6Although the Figure 1. ORTEP drawings of 9,lO-disilaanthracene dimer 2 showing the thermal ellipsoids at the 50% probAbstract published in Advance ACS Abstracts, July 15, 1995. ability level. Important bond distances (A)and angles (1)(a) Jutzi, P. Chem. Ber. 1971, 104, 1455. (b) Jutzi, P. Angew. (deg): Si(l)-Si(4) = 2.3710(9),Si(l)-C(l) = 1.867(3),SiChem., Int. Ed. Engl. 1975, 14, 232. (1)-C(16) = 1.884(2),Si(2)-Si(3) = 2.377(1),Si(2)-C(2) = (2)(a)van den Winkel, Y.; van Baar, B. L. M.; Bickelhaupt, F.; Kulik, 1.870(3),Si(2)-C(21) = 1.882(2);Si(4)-Si( 1)-C( 1)= 110.9W.; Sierakowski, C.; Maier, G. Chem. Ber. 1991,124,185. (b) van den Winkel, Y.; van Baar, B. L. M.; Bastiaans, M. M.; Bickelhaupt, F. (l),Si(4)-Si(l)-C(l6) = 106.48(8), C(l)-Si(l)-C(l6) = Tetrahedron 1990,46, 1009. (c) Bickelhaupt, F.; van Mourik, G. L. J . 111.8(1),C(16)-Si(l)-C(46) = 107.9(2),Si(3)-Si(2)-C(2) Organomet. Chem. 1974,67,389. = 111.7(1), Si(3)-Si(2)-C(21) = 106.29, C(2)-Si(2)-C(21) (3) (a)McCarthy, W. Z.; Corey, J. Y.; Corey, E. R. Organometallics = 111.7(1),C(21)-Si(2)-C(36) = 108.1(1). 1984,3, 255. (b) Corey, J. Y.; McCarthy, W. Z. J. Organomet. Chem. @
1984,271, 319. (4)Welsh, K. M.; Corey, J. Y. Organometallics 1987,6, 1393. This compound was prepared by Corey's procedure. The &/trans ratio was determined by 'H NMR spectroscopy. (5)2: colorless crystals; mp '300 "C; 'H NMR (CDC13,300 MHz) 6 0.84(s,12H),7.03(dd,J=5.1,3.1Hz,8H),7.33(dd,J=5.1,3.1Hz, 8H); 13C NMR (CDC13, 75 MHz) 6 -7.18, 127.08, 131.89, 143.47; 29Si NMR (CDC13, 60 MHz) h -27.91; mass m/e (%) 476 (1001, 461 (561, 417 (67). Anal. Calcd for C28H28Sid: C, 70.52; H, 5.92. Found: C, 70.58: H, 5.88. (6) Crystallographic data for 2: fw 476.88, monoclinic, a = 14.157(1)A, b = 10.765(1)A,c = 18.469(2)A,/3 = 110.25(1)",V = 2640.6 A3, space group P21/a,2 = 4, p(Mo Ka)= 2.3 cm-l, @(calcd)= 1.20 g/cm3, R = 0.036 (R,= 0.036). The 3954 independent reflections (28 5 52.6"; lFo21I3alFO21)were measured on a n Enraf-Nonius CAD4 diffractometer using Mo K a irradiation and a n (0-8 scan. An empirical absorption correction based on a series of scans was applied to the data (0.925/0.999). The structure was solved by direct methods, and hydrogen atoms were located and added to the structure factor calculations, but their positions were not refined. I ~ J
0276-7333/95/2314-3625$09.00/0
exact nature of the intermediate produced from the dihydrodilsilanaanthracene remains uncertain, we tentatively suggest that is the silicon-centered 9,lO-disilaanthracene biradical or its equivalent intermediate via electron transfer reaction^.^ Further studies concerning these question are in progress. Stirring 2 (240 mg, 0.5 mmol) with an excess of lithium in THF at room temperature produced a green (7) Spectroscopic studies of the yellow solution appearing at A,, 349 nm did not support a clear assignment of the intermediate. ( 8 )The green compound probably is the 9,lO-disilaanthracene anion radical. As a support for the existence of the anion radical, 9,lOdihydro-9,9,10-trimethyl-9,10-disilaanthracene was also obtained in 32% yield along with IC.
31995 American Chemical Society
3626 Organometallics, Vol. 14, No. 8, 1995
Communications
Scheme 1. Preparations of 9,lO-Disilaanthracene Dimer 2
la
lb
2
Scheme 2. Generation of Bis(9,lO-dimethyl-9,10-disilaanthracen-9-yl) Dianion 3
2
5 67%
3
Scheme 3. Syntheses of lc,d and 9,lO-Bridged Polysila-9,lO-disilaanthracenes 6-9
db
2
Me
Me' IC
Me,
si
M ,e
THF 24hr
'Me
1
(M = Li : 13010) (M = K : 80%)
6 12%
7 18%
2 M+
Me
9
500.
solution.8 After removal of unreacted lithium and treatment with an excess of methyl iodide, 9,lO-dihydro9,9,10,10-tetramethyl-9,lO-disilaanthracene (IC) was obtained in 13%yield. In a similar reaction, potassium was employed for the silicon-silicon bond cleavage of the dimer 2. Treatment with methyl iodide followed; IC was produced in 80% yield (Scheme 3). It is noteworthy that the dimer 2 is easily reduced with potassium to afford dipotassium 9,lO-disilaanthracenide (4b). 29SiNMR chemical shifts for 4a,b in THF-ds were
observed a t -45.4 and at -42.8 ppm, respectively, a large upfield shift compared to other silyl anions (PhaSiM, -9.0 (M = Li), -7.5 (M = K) ppm; PhzMeSiM, -20.6 (M = Li), -18.5 (M = K) ppmLg The formation of these dianions 4 is strongly dependent upon the (9) (a) Olah, G.A,; Hunadi, R. J. J . Am. Chem. SOC.1980,102,6989. (b)Buncel, E.; Venkatachalam, T. K.; Eliasso, B.; Edlund, U. J . Am. 1985, 107, 303. ( c ) Edlund, U.; Buncel, E. In Progress in Chem. SOC. Physical Organic Chemistry;Taft, R. W., Ed.; Wiley: New York, 1993; Vol. 19, p 254.
Communications
solvent; it increased in THF and was suppressed in diethyl ether and dimethoxyethane(DME). In general, formation of silyl potassium reagents from disilanes has been accomplished by reaction with potassium alkoxide,1° potassium hydride,ll or Na-K alloy12 and by treatment with potassium metal in liquid ammonia.13 During the course of the reactions of 2 with an excess of lithium or potassium, the reaction mixture becomes a yellow suspension. Reaction of the yellow suspension with trimethylchlorosilane gave the bis(9,lO-dimethyllo-(trimethylsilyl)-9,lO-disilaanthracen-9-y1)(5)in 67% yield (Scheme 2).14 The molecular structure of the opened dimer 5 is shown in Figure 2.15 Two methyl groups on the disilaanthracene unit of 5 are substituted in a cis configuration, respectively. Thus, the siliconsilicon bond cleavage of bridged dimer 2 with alkali metal proceeds with retention of configuration around the silicon atom. It is logical from these results that these dianions 4 are generated via one silicon-silicon bond-cleaved dianion (3). The reactions of dipotassium disilaanthracenide (4b) with trimethylchlorosilane gave the expected adduct (ld)in 73%yield as one isomer.16 The dipotassium (4b) also was treated with a,@-dichloropolysilanesas shown in Scheme 3. The products were identified by means of lH, 13C, and 29Si NMR and mass spectra. The (10) Sakurai, H.; Kira, M.; Umino, H.Chem. Lett. 1977, 1265. (ll)Corriu, R. J. P.; Guerin, C. J. Chem. SOC.,Chem. Commun. 1980, 168. (12) (a)Benkeser, R. A.; Landesman, H.; Foster, D. J. J.Am. Chem. SOC.1951, 74,648. (b) Gilman, H.; Wu, T. C. J.Am. Chem. SOC.1951, 73, 4031. (13) Wiberg, E.; Stecher, 0.; Andrascheck, H. J.; Kreuzbichler, L.; Steude, E. Angew. Chem., Int. Ed. Engl. 1963,2, 507. (14) 5: colorless crystals; lH NMR (300 MHz, CDC13) d 0.02 (s, 18H), 0.51 (s, 6H), 0.53 (s, 6H), 7.20-7.39 (m, 12H), 7.50 (d, J = 7.35 Hz, 4H); 13CNMR (75 MHz, CDCl3) d -1.40, -0.71, -0.53, 127.55, 134.60, 135.17, 142.22, 143.54; 29SiNMR (60 MHz, CDCl3) r> -33.70, -33.55, -18.50; MS mlz (relative intensity) 622 (M+,261,550 (37). Anal. Calcd for Cl8Hl8Si4: c , 65.52: H, 7.44. Found: c , 65.49; H, 7.48. (15) Crystallographic data for 5: fw = 623.26, orthohombic, a = 13.051(1)A,b = 13.911(1)A,c = 20.697(4) A,V = 3757.4 A3, space group Pbca, 2 = 4, p(Mo Ka)= 2.4 em-', Q(calcd)= 1.10 g/cm3, R = 0.065 (R,= 0.067). The 1287 independent reflections (28 I21.7'; lFo21 2 3rrlFO21) were measured on a n Enraf-Nonius CAD4 diffractometer using Mo Ka irradiation and a n ro-8 scan. The structure was solved by direct methods, and hydrogen atoms were located and their positions and isotropic thermal parameters were refined. (16) Id: 'H NMR (300 MHz, CDCl3) i, 0.07 (s, 18H), 0.62 (s,6H), 7.39 ( d d , J = 3.3,5.4 Hz,4H), 7.56 ( d d , J = 3.3,5.4 Hz,4H); 13CNMR (75 MHz, CDC13) 0 -1.60, -1.47, 127.61, 134.49, 143.17; 29Si NMR (60 MHz, CDCl3) 0 -33.26, -18.31; MS mlz (relative intensity) 384 (M+,941, 311 (M+ - SiMe3, 82). (17)6: 'H NMR (300 MHz, C6D6) (3 0.04 (s,6H), 0.79 (s,6H), 7.17 (dd, J = 3.2, 5.3 Hz, 4H), 7.61 (dd, J = 3.2, 5.3 Hz, 4H); 13CNMR (75 MHz, C6Ds) (3 - 11.80, -7.12, 127.17, 131.59, 147.90; 29Si NMR (60 MHz, C6D6) i, -25.65, -15.94; MS mlz (relative intensity) 296 (M+ 15). 7: 'H NMR (300 MHz, CDC13)i,0.44 (s, 12H), 0.53 (s, 12H), 7.06 (dd, J = 3.3, 5.5 Hz, 8H), 7.56 (dd, J = 3.3,5.5 Hz, 8H); 13CNMR (75 MHz, CDC13) 0 -5.06, -1.72, 127.35, 134.20, 142.29; 29Si NMR (60 MHz, CDCl3) 6 -50.04, -33.60; MS mlz (relative intensity) 592 (M+, 25), 519 (11). (1818: 'H NMR (300 MHz, CDCl3) d 0.56 (s, 12H), 0.80 (s, 6H), 7.28 ( d d , J = 3.2,5.4 Hz,4H),7.56 ( d d , J = 3.2,5.4 Hz,4H);13CNMR (75 MHz, CDCl3) 0 -10.21, -7.33, 127.85, 132.33, 144.68; 29SiNMR (60 MHz, CDCl3) i, -58.33, -32.89; MS mlz (relative intensity) 354 (M+,76), 339 (M+ - Me, 43). Anal. Calcd for Cl8Hl8Si4: C, 62.36: H, 5.23. Found: C, 62.31; H,5.28. 9: lH NMR (300 MHz, CDCl3) i,0.39 (s, 6H), 0.01 (s, 12H), 0.75 (s, 6H), 7.32 (dd, J = 3.3, 5.4 Hz, 4H), 7.57 (dd, J = 3.3, 5.4 Hz, 4H); 13C NMR (75 MHz, CDCl3) (3 -7.21, -6.74, -6.58, 127.66, 133.03, 143.86; 29SiNMR (60 MHz, CDCl3) 0 -46.39, -39.60, -30.98; MS mlz (relative intensity) 412 (M+,471, 339 (61).
Organometallics, Vol. 14, No. 8, 1995 3627
Figure 2. ORTEP drawings of opened dimer 5 showing the thermal ellipsoids at the 50% probability level. Important bond distances (A) and angles (deg): Si(l)-Si(3) = 2.339(4), Si(l)-C(11) = 1.90(1),Si(1)-C(111) = 1.888(9),Si(2)-C(21) = 1.88(1),Si(2)-C(112) = 1.866(9),Si(3)C(31)= 1.85(1);Si(3)-Si(l)-C(ll) = 108.9(4),Si(3)-Si(l)C(111) = 112.3(3),C(ll)-Si(l)-C(lll) = 106.9(4),C(111)Si(l)-C(211) = 109.3(4),C(21)-Si(2)-C( 112) = 109.6(5), C(112)-Si(2)-C(212) = 109.9(3).
reaction of 4b with dimethyldichlorosilane gave the expected dimethylsilyl adduct 6 bonded to the 9- and 10-positions of the disilaanthracene and the dimeric compound 7 in 12%and 18%yields, re~pective1y.l~ The corresponding 9- and 10-position adduct was obtained in good yield when the dipotassium species 4b reacted with 1,2-dichlorotetramethyldisilaneand 1,3-dichlorohexamethyltrisilane, respectively,18 without formation of dimeric products. The formation of 6-9 clearly reveals that the generated dipotassium disilaanthracenide (4b)has a cis configuration. It is clear that dipotassium 9,10-dimethyl-9,10-disilaanthracenide (4b),generated from the dimer 2 with potassium metal, can be a valuable intermediate for the synthesis of a great variety of cis-9,lO-disilaanthracene derivatives. Acknowledgment. This work was supported by a Grant-in-Aid for Scientific Research from the Ministry of Education, Science and Culture of Japan. We thank Prof. K. Okamoto for useful discussions and Shin-Etsu Chemical Co. Ltd. for a gift of organosilicon reagents. Supporting Information Available: Text describing crystallographicprocedures and tables of crystallographicdata, atomic coordinates and thermal parameters, and bond lengths and angles for 2 and 5 (29 pages). Ordering information is given on any current masthead page. OM9502650
