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

Summary: 9,1O-Dimethyl-9,lO-disilaanthracene dimer (2) was prepared by treatment of 9,1O-dihydro-9,10- disilaanthracene (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-9,10- dimethyl-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 con- verted into the corresponding cyclic compounds 6-9, respectively.

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,lO- dimethyl-9,lO-disilaanthracene dimer, a silicon analog to the anthracene dimer.

Although the Wurtz coupling reaction of 9,lO-dichloro- 9,10-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-disilaan- thracene (la) with lithium.

Reaction of a cidtrans mixture (=45/55)4 of 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 bridged dimer 2 was obtained in 61% yield (Scheme 1). The structure of dimer 2 has been confirmed by spectral data5 and an X-ray analysis (Figure 1).6 Although the

@ Abstract published in Advance ACS Abstracts, July 15, 1995. (1) (a) Jutzi, P. Chem. Ber. 1971, 104, 1455. (b) Jutzi, P. Angew.

Chem., Int. Ed. Engl. 1975, 14, 232. (2) (a) van den Winkel, Y.; van Baar, B. L. M.; Bickelhaupt, F.; Kulik,

W.; Sierakowski, C.; Maier, G. Chem. Ber. 1991,124,185. (b) van den Winkel, Y.; van Baar, B. L. M.; Bastiaans, M. M.; Bickelhaupt, F. Tetrahedron 1990,46, 1009. (c) Bickelhaupt, F.; van Mourik, G. L. J . Organomet. Chem. 1974,67,389.

(3) (a) McCarthy, W. Z.; Corey, J. Y.; Corey, E. R. Organometallics 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"; lFo21 I 3alFO21) were measured on an Enraf-Nonius CAD4 diffracto- meter using Mo Ka irradiation and an (0-8 scan. An empirical absorption correction based on a series of I ~ J 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.

0276-7333/95/2314-3625$09.00/0 3

12, 1995@

H2 1 If

H23

H24

H I 3

OH411

Figure 1. ORTEP drawings of 9,lO-disilaanthracene dimer 2 showing the thermal ellipsoids at the 50% prob- ability level. Important bond distances (A) and angles (deg): Si(l)-Si(4) = 2.3710(9), Si( l)-C(l) = 1.867(3), Si- (1)-C(16) = 1.884(2), Si(2)-Si(3) = 2.377(1), Si(2)-C(2) = 1.870(3), Si(2)-C(21) = 1.882(2); Si(4)-Si( 1)-C( 1) = 110.9- (l), Si(4)-Si(l)-C(l6) = 106.48(8), C(l)-Si(l)-C(l6) = 111.8(1), C(16)-Si(l)-C(46) = 107.9(2), Si(3)-Si(2)-C(2) = 111.7(1), Si(3)-Si(2)-C(21) = 106.29, C(2)-Si(2)-C(21) = 111.7(1), C(21)-Si(2)-C(36) = 108.1(1).

exact nature of the intermediate produced from the dihydrodilsilanaanthracene remains uncertain, we ten- tatively suggest that is the silicon-centered 9,lO-disi- laanthracene 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,lO- dihydro-9,9,10-trimethyl-9,10-disilaanthracene was also obtained in 32% yield along with IC.

1995 American Chemical Society

3626 Organometallics, Vol. 14, No. 8, 1995 Communications

Scheme 1. Preparations of 9,lO-Disilaanthracene Dimer 2

l a 2 l b

Scheme 2. Generation of Bis(9,lO-dimethyl-9,10-disilaanthracen-9-yl) Dianion 3

2 3 5 67%

Scheme 3. Syntheses of lc,d and 9,lO-Bridged Polysila-9,lO-disilaanthracenes 6-9

Me db Me' 'Me

I C (M = Li : 13010) (M = K : 80%)

2

THF 24hr

1

Me

9 500.

solution.8 After removal of unreacted lithium and treatment with an excess of methyl iodide, 9,lO-dihydro- 9,9,10,10-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). 29Si NMR chemical shifts for 4a,b in THF-ds were

Me, ,Me si

6 12%

2 M+

7 18%

observed at -45.4 and at -42.8 ppm, respectively, a large upfield shift compared to other silyl anions (Pha- SiM, -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. Chem. SOC. 1985, 107, 303. ( c ) Edlund, U.; Buncel, E. In Progress in Physical Organic Chemistry; Taft, R. W., Ed.; Wiley: New York, 1993; Vol. 19, p 254.

Communications Organometallics, Vol. 14, No. 8, 1995 3627

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 alkox- ide,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-dimethyl- lo-( 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 silicon- silicon 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,@-dichloropolysilanes as 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. (l l)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,

135.17, 142.22, 143.54; 29Si NMR (60 MHz, CDCl3) r> -33.70, -33.55, -18.50; MS mlz (relative intensity) 622 (M+, 261,550 (37). Anal. Calcd

(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 I 21.7'; lFo21 2 3rrlFO21) were measured on an Enraf-Nonius CAD4 diffractometer using Mo Ka irradiation and an ro-8 scan. The structure was solved by direct methods, and hydrogen atoms were located and their positions and isotropic thermal parameters were refined.

7.39 ( d d , J = 3.3,5.4 Hz,4H), 7.56 ( d d , J = 3.3,5.4 Hz,4H); 13C NMR (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); 13C NMR (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); 13C NMR (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);13C NMR (75 MHz, CDCl3) 0 -10.21, -7.33, 127.85, 132.33, 144.68; 29Si NMR (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

-6.58, 127.66, 133.03, 143.86; 29Si NMR (60 MHz, CDCl3) 0 -46.39, -39.60, -30.98; MS mlz (relative intensity) 412 (M+, 471, 339 (61).

4H); 13C NMR (75 MHz, CDCl3) d -1.40, -0.71, -0.53, 127.55, 134.60,

for Cl8Hl8Si4: c , 65.52: H, 7.44. Found: c , 65.49; H, 7.48.

(16) Id: 'H NMR (300 MHz, CDCl3) i, 0.07 (s, 18H), 0.62 (s, 6H),

(dd, J = 3.3, 5.4 Hz, 4H); 13C NMR (75 MHz, CDCl3) (3 -7.21, -6.74,

Figure 2. ORTEP drawings of opened dimer 5 showing the thermal ellipsoids at the 50% probability level. Im- portant 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-dichlorotetramethyldisilane and 1,3-dichloro- hexamethyltrisilane, respectively,18 without formation of dimeric products. The formation of 6-9 clearly reveals that the generated dipotassium disilaanthra- cenide (4b) has a cis configuration.

It is clear that dipotassium 9,10-dimethyl-9,10-disi- laanthracenide (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 crystallographic procedures and tables of crystallographic data, 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.

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