Organometallics 1996,14, 4449-4451
4449
Synthesis of Dumbbell-ShapedOrganometallics: Synthesis of a Peralkynylated Dinuclear Cyclobutadiene Complex Jutta E. C. Wiegelmann-Kreiter and Uwe H. F. Bunz* Max-Planck-Institut fur Polymerforschung, Ackermannweg 10, 55021 Mainz, FRG Received June 16, 1995@ Summary: With a tricarbonyl(diethyny1cyclobutadiene)iron complex as starting material, 7 is prepared in a stepwise fashion by a repetitive deprotonation liodination lcoupling sequence; 7 is aprecursor to the dumbbellshaped peralkynylated organometallics 8, which are obtained by coupling of 7 with a ditin alkyne or butadiyne. Interest in the synthesis of carbon-rich compounds has risen considerably during the last few y e a r ~ . l -In~ particular, highly ethynylated compound^^-^ have attracted much attention, because they are viable monomers for the preparation of high carbon polymers, fullerene precursors, or fullerenyne segments. The synthesis of all-carbon mole~ulesl-~ and two-dimensional carbon nets is now an established (but not yet mastered) subfield of organic chemistry. To perform the controlled assembly of carbon molecules and all-carbon nets, it will be necessary to construct them from small units t o form consecutively larger and more complex segments. We have identified an organometallic all-carbon net consisting of organometallic (CpCo, (CO)sFe)-stabilized cyclobutadiene and alkyne or butadiyne bridges as targets and are involved in a program aiming at the
* To whom correspondence should be addressed. E-mail:
[email protected]. Abstract published in Advance ACS Abstracts, September 15,1995. (1) Bunz, U. H. F. Angew. Chem., Znt. Ed. Engl. 1994,33, 1073. (2) (a) Diederich, F.; Rubin, Y. Angew. Chem., Znt. Ed. Engl. 1992, 31, 1101. Diederich, F. Nature 1994, 369, 199 and references cited therein. (b) Anthony, J.; Knobler, C. B.; Diederich, F. Angew. Chem., Znt. Ed. Engl. 1993, 32, 406. Anderson, H. L.; Faust, R.; Rubin, Y.; Diederich, F. Angew. Chem., Znt. Ed. Engl. 1994, 33, 1366. ( c ) An, Y.-Z.; Rubin, Y.; Schaller, C.; McElvany, S. W. J . Org. Chem. 1994, 59, 2927. (d) Xu, Z.; Moore, J. S. Angew. Chem., Int. Ed. Engl. 1993, 32, 1354 and references cited therein. (e) Fritch, J. R.; Vollhardt, K. P. C. Organometallics 1982, 1, 590. (3) (a) Beck, W.; Niemer, B.; Wieser, M. Angew. Chem., Int. Ed. Engl. 1993, 32, 923 and references cited therein. (b) Weng, W.; Bartik, T.; Gladysz, J. A. Angew. Chem., Znt. Ed. Engl. 1994, 33, 2199. ( c ) Gloaguen, B.; Astruc, D. J . Am. Chem. SOC.1990,112,4607. Moulines, F.; Djakovitch, L.; Boese, R.; Gloaguen, B.; Thiel, W.; Fillaut, J.-L.; Delville, M.-H.; Astruc, D. Angew. Chem., Znt. Ed. Engl. 1993,32,1075 and references cited therein. (4) (a) Hexaethynylbenzene: Diercks, R.; Armstrong, J . C.; Boese, R.; Vollhardt, K. P. C. Angew. Chem., Znt. Ed. Engl. 1986, 25, 268. Hexabutadiynylbenzene: Boese, R.; Green, J. R.; Mittendorf, J.; Mohler, D. L.; Vollhardt, K. P. C. Angew. Chem., Int. Ed. Engl. 1992, 31, 1643. (b) Other examples of polyethynylated arenes: Neenan, T. X.; Whitesides, G. M. J. Org. Chem. 1988, 53, 2489. Rutherford, D. R.; Stille, J. K. Macromolecules 1988,21,3530. Hyatt, J. A. Org. Prep. Proced. Int. 1992,23, 460. Prafcke, K.; Kohne, B.; Singer, D. Angew. Chem., Znt. Ed. Engl. 1990,29, 177. Laschewsky, A. Angew. Chem., Znt. Ed. Engl. 1989,28, 1745. ( 5 ) Hashmi, A. S. K.; Vollmer, A.; Szeimies, G. Liebigs Ann. Chem. 1995,471. Hashmi, A. S. K.; Szeimies, G. Chem. Ber. 1994,127,1075. (6) (a) Kozhushkov, S. I.; Haumann, T.; Boese, R.; De Meijere, A. Angew. Chem., Znt. Ed. Engl. 1993, 32, 401. (b) Hopf, H.; Kreutzer, M.; Jones, P. G. Chem. Ber. 1991, 124, 1471. ( c ) Vollhardt, K. P. C.; Winn, L. S. Tetrahedron Lett. 1986, 709. (7) Pericyclynes: Scott, L. T. In Modern Acetylene Chemistry; Stang, P. J., Diederich, F., Eds.; VCH: Weinheim, Germany in press. @
synthesis of fragments of this netas Linear: star-shaped (such as 3),8and ortho diethynylatedlO segments have been synthesized in our laboratory in addition to multiply alkynylated derivatives of cymantrene (2) which can be considered as parts of metal-complexed fullerenynes.ll
1
2
3
To date the only known perethynylated organic moieties are Vollhardt's he~aethynylbenzene~ ( 1) and tetraethynylethylene6 and componds further derived therefrom by Diederich;2 they also represent the only known oligomers of peralkynylated moieties. Surprisingly, dimeric or oligomeric species of 1-3 have been hitherto unknown, even though they represent structurally unusual and attractive synthetic goals. We here wish to report the synthesis of the peralkynylated dumbbell-shaped complex 8 , which represents a persilylated dimer of 3. Reaction of 410J5J6with sec-BuLi (THF, -78 "C) for 15 min led t o the formation of the desired lithiated species. Quenching by addition of 1,2-diiodoethaneand subsequent flash chromatography (silica gel; pentane) gave 5 in 89% yield. Due t o the stereochemical equivalence of the cyclobutadiene protons in 4, the usual precautions needed for selective ortho lithiation (very slow addition of sec-BuLi, careful control of the temper(8) (a)Bunz, U. H. F.; Enkelmann, V. Angew. Chem., Int. Ed. Engl. 1993, 32, 1653. (b) Bunz, U. H. F.; Enkelmann, V. Organometallics 1994,13, 3823. (9)(a)Wienelmann. J. E. C.: Bunz. U. H. F. 0rPanometallic.s 1993. 12,'3792. ( b l k t m a n n , M.; Bunz, U.'H. F. Makrgmol. Chem., Rapid: Commun. 1994, 15, 785.
(10)Wiegelmann, J. E. C.; Bunz, U. H. F.; Schiel, P. Organometallics
1994, 13, 4349. (11) (a)Bunz, U. H. F.; Enkelmann, V.; Rader, J. Organometallics 1993, 12, 4745. (b) Bunz, U. H. F.; Enkelmann, V.; Beer, F. Organometallics 1995,14,2490. ( c ) Bunz, U. H. F. J . Organomet. Chem. 1996, 494, C8. (12) (a) Lo Sterzo, C.; Stille, J. K. Organometallics 1990,9,687 and
references cited therein. (b) Viola, E.; Lo Sterzo, C.; Crescenzi, R.; Frachey, G. J . Organomet. Chem. 1995,493, 55. Viola, E.; Lo Sterzo, C.; Crescenzi, R.; Frachey, G. J . Organomet. Chem. 1995,493. C9. (13) Beletskaya, I. P. J. Organomet. Chem. 1983, 250, 551 and references cited therein. (14)Farina, V.; Krishnan, B. J . A m . Chem. SOC.1991, 113, 9585 and references cited therein.
0276-7333/95/2314-4449$Q9.00/Q0 1995 American Chemical Society
Communications
4450 Organometallics, Vol. 14, No. 10, 1995 Scheme 1"
p'
ps
-
b
a
be(COh
SMS
6
4
I""
jy,
II
SiMq
SiMq
8a (n = l), 8b (n = 2) a Legend: ( a )sec-BuLi, THF, 15 min, -78 "C, 1,2-diiodoethane; (b) Me3SiCWSnMe3 (9),5 mol % PdCl2(CHsCN)2, DMF, 18 h; ( c ) MesSnCX!SnMes, 5 mol % PdC12(CH3CN)2, DMF, 18 h; ( d )MesSnC=CC=CSnMea (lo),Pdddbah, AsPhs, THF, 5 h.
7
aturelO)were not necessary. At 21 "C 5 showed a pronounced tendency toward decomposition; it was stable for longer periods of time only a t temperatures (-30 "C but could be characterized by NMR, IR, and mass spectro~copy.'~J~ Immediate coupling of 5 with (trimethylsilyl)(trimethylstannyl)ethyne in DMF (catalyst PdC12(CH3CN)214)afforded the t r i p e 6 in 53%yield after aqueous workup and flash chromatography (silica gel; pentane). Use of Beletskaya's catalyst14 proved more successful than that of the Farina system,13since complete removal of catalyst residues containing triphenylarsine and decomposition products of Pdddba)~ (dba = dibenzylideneacetone) by chromatography was impossible in the latter case. The lemon yellow, crystalline t r i p e 615J6was stable under laboratory conditions for several days and showed no signs of decomposition when stored in the freezer for extended periods of time. Performance of the deprotonatiodiodination reaction ~
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(15) Experimental procedures are as follows. (a) Iodides 5 and 7: Alkyne 4 (1.00 g, 2.60 mmol) is dissolved in dry THF (-78 "C, 70 mL). sec-BuLi (2.0 mL, 2.8 mmol; 1.4 M in cyclohexane) is added to the solution. M e r 15 min a considerable darkening of the reaction mixture from yellow to dark amber is observed and l,2-diiodoethane (806 mg, 2.86 mmol) is introduced. Removal of the cooling bath and continued stirring (1h) is followed by workup with aqueous sodium thiosulfate solution. Flash chromatography (silica gel; pentane) affords 1.16 g (87%)of 5. Reaction of 6 (300 mg, 0.624 mmol) with sec-BuLi (0.7 mL, 0.98 mmol, 1.5 equiv), l,2-diiodoethane (265 mg, 0.940 mmol) under the conditions described above yields 7 (153 mg, 40%). (b) Alkynes 6 and 8: Iodide 5 (790 mg, 1.55 mmol), (trimethylsilyl)(trimethylstannyl)ethyne (499 mg, 1.91 mmol), and [PdC12(CH3CN)2],(12 mg, 46 mmol) are dissolved in DMF (15 mL) and stirred. After 12 h the same amount of catalyst is added again and the reaction mixture is stirred for another 12 h. Flash chromatography (silica gel; pentane) affords 395 mg (53%) of 6. Iodide 7 (240 mg, 0.396 mmol), bis(trimethylstanny1)ethyne (68.6 mg, 0.195 mmol), Pdz(dba)a (18.3 mg, 20 mmol), and Ph3As (24.5 mg, 80 mmol) are dissolved in DMF (2 mL) and stirred for 18 h. Aqueous workup and repeated flash chromatography (silica gel; 80:20 pentane/dichloromethane) yields 147 mg (76%) of 8a. To obtain highly pure 8a,7 (300 mg, 0.495 mmol), bis(trimethylstanny1)ethyne (87.0 mg, 0.247 mmol), and [PdC12(CH3CN)21(2times 9.1 mg, 35 pmol) are reacted for 24 h to obtain 47 mg (19%) of highly pure 8a after workup (uide supra). Iodide 7 (220 mg, 0.363 mmol), bidtrimethylstanny1)butadiyne (73 mg, 0.194 mmol), P d d d b a ) ~ (31.2 mg, 34 mmol), and triphenylarsine (43.2 mg, 141 mmol) are dissolved in DMF (2 mL) and stirred for 18 h. Aqueous workup and flash chromatography (silica gel; 80:20 pentane/dichloromethane) yields 8b (121 mg, 66%).
with 6 produced the iodide 7 after chromatography in 41% yield. In contrast to iodide 5, 7 was stable to air and temperature under ambient conditions over several days. It was fully characterized by NMR, IR, and mass spectroscopy.15J6 The final stage of the synthesis involved coupling of compound 7 with bis(trimethylstanny1)ethyne or -butadiyne using catalytic palladium to obtain the dumbbell-shaped complexes 8a,b in yields of 76 and 66%, respectively, after aqueous workup and flash chromatography (silica gel; 80:20 pentane/dichloromethane).15J6 The lemon-colored dinuclear species 8 was readily soluble both in pentane and in dichloromethane. In the solid state 8a,b are only moderately sensitive under normal atmospheric conditions but are completely stable for extended periods of time in a freezer at -18 "C. Their structure was unequivocally assigned from recorded NMR, IR, and mass spectral data as well from the elemental composition (8b). (16) Physical data for the new compounds are as follows. 5: yellow oil; IR (KBr)3120,2962,2153,2056,1991,1451 cm-l; 'H NMR (CDCl3) 6 0.13 (s,9 H). 0.15 (s.9 H), 4.52 (s. 1. H): I3C NMR (CDCln) 6 -0.42. -o.32,2,29.73,64.~2,7o.34,7o.7i,94.~i,94.67,ioo.34,102.i0,211.85; MS (EI: m l z (relative intensitv)) M - CO. ",, 510 (M+. 4%). 482 i ., 14%). ~ , , 454 ( M - 2 CO, 5%),426 ( M - 3 CO, 67%);MS'iC17H;&Fe031 [M+l) calcd 507.9314, found 507.9327. 6: mp 88 "C; IR (KBr) 3058, 2993, 2310,2161,2054,2001, 1430 cm-'; 'H NMR (CDC13) 6 0.16 (s, 18 H), 0.19 (s, 9 H), 4.48 (SI; 13CNMR (CDC13) 6 -0.36, -0.25, 64.24, 68.14, 68.63, 94.70, 95.05, 100.03, 101.05, 211.56; MS (EI; m / z (relative intensity)) 480 (M+, 4%), 452 ( M - CO, ll%), 424 ( M - 2 CO, 3%), 396 ( M - 3 CO, 99%). Anal. Calcd: C, 54.99; H, 5.87. Found: C, 55.07; H, 5.89. 7: mp 92 "C dec; IR (KBr): 2970, 2152, 2064, 2002, 1260 cm-I; lH NMR (CDCL3) 6 0.20 (m, 27 H); 13C NMR (CDC13) 6 -0.33, -0.30, 33.96,69.26, 76.58, 93.55,93.92, 102.30, 102.97,211.15; MS (FD; m l z (relative intensity)) 606 ( M + ) ;MS (CzzH&i3FeO3 [ M + ] ) calcd 605.9662, found 605.9662. 8a: mp 117 "C dec; IR (KBr) 2964, 2930, 2158, 2063, 1997, 1463, 1252 cm-I; 'H NMR (CDC13) 6 0.19 (s, 18 H), 0.20 (s, 36 HI; I3C NMR (CDC13) 6 -0.22, 64.53, 67.44, 69.43, 84.19, 93.56, 93.64, 102.43, 102.68, 210.49; MS (FD; m l z (relative intensity)) 982 ( M + ) ;MS (C&&i6FezO6 [M+I)calcd 982.1235, found 982.1219. 8b: mp 172 "C dec; IR (KBr) 2960,2925,2150,2057,2008, 1999, 1954,910 cm-I; 'H NMR (CDC13) 6 0.18 (s, 18 H), 0.19 (s, 36 H); I3C NMR (CDC13) 6 -0.41, -0.39, 62.81, 67.79, 70.94, 74.22, 78.67, 93.18, 93.51, 103.06, 103.17, 210.31; MS (FD; m l z (relative intensity)) 1006.14 ( M + ) . Anal. Calcd: C, 57.24; H, 5.42. Found: C, 57.81; H, 5.50. ~
~
~~
Communications The complete functionalization of a cyclobutadiene complex in a merry-go-round fashion as achieved here should not only be applicable to the synthesis of peralkynylated species but may also serve as a starting point for the preparation of other fourfold-substituted tricarbonyl(cyc1obutadiene)irons. These compounds have not attracted much interest (an exception being tricarbonyl(tetramethylcyclobutadiene)iron, easily available by Criegee's routel'), probably due t o the absence of
Organometallics, Vol. 14, No. 10,1995 4451 simple synthetic pathways to these complexes. The future direction of our work will be t o use 7 as an endcapping agent in an attempt to build up a cyclobutadienylene-ethynylene copolymer decorated by alkyne groups. OM950460E (17)Criegee, R. Org. Synth. 1968,46, 34.
