Organometallics 1983,2,453-454
453
Communications Organoslllcon Rotanes: Synthesis and an Unexpected Rearrangement
Table I. Yields and NMR Data for Tetramethylenesilicon Rotanee
Corey W. Carlson, Xing-Hua Zhang, and Robert West' Department of Chemistry, University of Wisconsin Madison, Wisconsin 53706 Received October 4, 1982
Summary: Reaction of 2.0 equiv of Li with (CH,),SiCI, yields [(CH,),Si],, n = 5-12; similarly, reaction of (CH2&3iCI2with 2.2 equiv of potassium gives [(CH,),Si], , n = 5 and 6. If an excess of Li or potassium is used in the condensation of (CH,),SiCI,, [(CH,),SiIe and a novel rearrangement product, 4, are formed.
Recent reports have shown that cyclic polysilanes with a variety of alkyl substituenb can be synthesized by alkali-metal condensation of the corresponding dialkyldichlorosilanes.' We have extended this approach to tetramethylenedichlorosilane [(CH2)4SiC12]and pentamethylenedichlorosilane [ (CH2),SiC12]and now describe the synthesis and initial characterization of several novel polyspirocyclopolysilanes (eq 1). These compounds are (CH2),SiC12 + M [(CH,),Si], + MCl (1) x=4,5 x = 4, n = 5-12 x = 5, n = 5 and 6 M=K,L
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silicon analogues to the carbocyclic r o b e s 2 such as 1 and provide the first examples of rotane structures based on a central ring of silicon atoms.
1
To prepare the tetramethylenesilicon rotanes, (CH,)4SiClZ3in dry THF was added dropwise to 2.0 equiv of lithium in dry THF at 0 OC.4 After 16 h, lithium chloride was removed by several cycles of concentration of the solution, addition of hexane, and filtration under argon. Evaporation of the solvent then left a waxy solid mixture that was separated by HPLC? yielding the rotanes (1) (a) (i-PrzSi)4: Watanabe, H.; Muraoka, T.; Kageyama, M.; Nagai, Y. J. Organomet. Chem. 1981, 216, C45-57. (b) (MezSi)6 West, R.; Brough, L. F.; Wojnowski, W. Inorg. Synth. 1979, 19, 265-268. (c) (Me@),: Brough, L. F.; West, R. J. Am. Chem. SOC. 1981, 103, 3049-3056. (d) (Et&),: Carlson, C. W.; Matsumura, K.; West, R. J. Organomet. Chem. 1980,194, C5-6. (e) (EtMeSi),: Katti, A.; Carlson, C. W.; West, R. unpublished studies. (0( M i l 5 : Watanabe, H.; Muraoka, T.; Kohara, Y.; Nagai, Y. Chem. Lett. 1980, 735-736. (2) Prange, T.; Pascod, C.; de Meijere, A.; Behreens, U.; Barnier, J.; Conia, J. Nouu. J. Chim. 1980,5,321-327. Fitjer, L. Angew. Chem., Int. Ed. Engl. 1976,15,763-4; Proksch, E.; de Meijere, A. Tetrahedron Lett. 1976,52,4851-4854. Ripoll, J. L.; Limasset, J. C.; Conia, J. M. Tetrahedron 1971,27,2431-2452. (3) West, R. J. Am. Chem. Soc. 1964, 76, 6012-6014. (4) This reaction requires degassed, peroxide-free THF and the exclusion of air since one of the products, [(CH&3i],, is moderately oxygen sensitive. (5) MeOH/THF on a Whatman M-9 column containing Partisil-10 ODS was used.
0276-7333/83/2302-0453$01.50/0
5 6
7 8 9 10 11 12
20 = 3ga 14 7.3b 5.5b 2.6 2.9
1.4b
9.50, 29.70 10.43, 29.81 11.17, 29.86 11.93, 29.91 12.52, 29.84 12.70, 29.84 12.70, 29.86 12.77, 29.91
GLC analysis. HPLC analysis. Intensity ratio for each pair is 1:1.
a
-29.85 -29.37 -29.85 -28.68 -26.50 -23.91 -24.58 -24.80
In benzene-d,.
[(CH&3i],, where n = 5-12 (Table I)! The HPLC results suggest that smaller amounts of additional rotanes, up to at least n = 25, are also present. This result closely resembles those from the analogous condensations of Me2SiC1p and EtMeSiCl,,le where reaction with exactly 2 equiv of lithium produces mixtures containing large-ring compounds. Condensation of (CH2)5SiC123 was best effected by using 2.2 equiv of potassium in refluxing THF. The reaction mixture contained only two volatile products, [ (CH2),Si], and [(CH,),Si], (in 40% and 11% yields, respectively, by GLC analysis). After 18 h, workup was carried out by the usual procedure,lb and the crystalline rotanes were separated by successive recrystallization from ethanol-THF. In contrast to the facile reaction of lithium with other dialkyldichlorosilanes, the reaction of (CH2),SiC1, with lithium proceeded slowly and gave mostly insoluble polymeric products. The condensation of dialkyldichlorosilanesusing excess lithium or potassium typically results in equilibration among the different rings and leads to high yields of the thermodynamically favored cyclosilane. Thus, the reaction of MePSiC12with excess Na/K gives mainly (Mez.%),, and the reaction of EtSiCl, with excess potassium gives predominantly (Et2Si),. For (CH2)4SiC12, the products are quite different. When (CHJ4SiC12was condensed with 2.2 equiv of lithium in THF at 0 "C and stirred for 12 h, the only products isolated were [(CH,),Si], (2, 28%) and a mixture consisting of [(CH,),Si], (3, 1%) and an isomer of [(CH,),Si], (12%), to which we assign structure 4. Analogous results were obtained by using 2.2 equiv of potassium in refluxing THF. A mixture of 2 (45%), 3 (3%),and 4 (40%) was also obtained when 2 was stirred in THF solution with (triphenylsily1)lithium for 48-72 h.
2
4
(6) All of the rotanes gave molecular weights by high-resolution mass spectrometry in agreement with the formulas assigned.
0 1983 American Chemical Society
Organometallics 1983,2,454-457
454
Table I1 chem shifts, ppm Si, Sih Si, Sin Me2 Me2
Si,
-9.4 -38.8 -40.9 -42.3 -82.2
Registry No. 2, 84098-37-3; 3, 84098-38-4; 4, 84081-96-9; [(CH,),SiI5, 84081-92-5;[ (CH2)4Si]8, 84081-93-6;[ (CH2)4Si]9, 84098-39-5;[(CH2),Sill0, 84098-40-8;[(CH2),Si],,, 84098-41-9; [(CH2),SiI12, 84098-42-0;(CH2)4SiC12,2406-33-9;(CH2),SiC1,, 2406-34-0; [(CH2),SiI5,84081-94-7; [ (CH2),SiI6,84081-95-8; (triphenylsilyl)lithium, 791-30-0.
S,--s, b C\d Me3gi-4Me
~ikle:,
e'j,-d
"e2 \'e2
-0.2 -27.1 -28.2 -29.4 -81.8
Sllacrowns: Phase-Transfer Catalysts Barry Arkles,' Kevln Klng, Roy Anderson, and Willlam Peterson
Reference 7 ; in CDCI,. In benzene-d, using Cr(acac), as a paramagnetic relaxation agent. The intensities of the five lines were observed t o be 1:2:2:1:1. Also contains a [(CH,),Si], resonance at -29.85 ppm.
Isomers 3 and 4 could not be separated by either HPLC or GLC and were isolated as a mixture by HPLC., The identification of compound 4 was based primarily on its 29SiNMR, which closely resembles the known spectrum of (trimethylsilyl)undecamethylcyclohexasilane,' a permethyl compound with the same skeletal structure as 4 (Table 11). A resonance for 3 is also found, and measurement of peak intensities establishes the 12:l ratio of 4:3 in the mixture. Other spectral properties of 4 are in agreement with the assigned structure. The mass spectrum shows a base peak at mle 588 corresponding to the parent molecular ion and fragments similar to those obtained from other cyclotetramethylenesilicon rotanes. The UV of the isomeric mixture [270 nm (sh, t 4600), 245 (sh, 10500), 209 (sh, 44400)] closely matches 2 [275 nm (sh, t 1200),252 (5100), 208 (sh, 31 300)], but not 3 [260 nm (sh, t 5300), 236 (sh, lOOOO)]. The I3C NMR spectrum consists of 11 lines, falling into two groups from 10.4 to 17.7 ppm and from 27.1 to 29.5 ppm, assigned to carbons a and 0 to the silicon, respectively. The infrared spectrum shows only the C-H, C-C, and Si-C bands expected for 4. To see if the rearrangement leading to 4 would take place upon thermolysis, compound 2 was pyrolyzed neat, in an evacuated sealed tube, at 220 "C for 3 days. The only products were [(CH,),Si], (5,15%), 2 (80%), and 3 (5%). Similar pyrolysis of 3 led to 5 (2%), 2 (3%), and recovered 3 (95%). The resulta show that 4 is not formed under these thermal conditions but that thermal redistribution of the cyclopolysilanes to give different ring sizes does take place. This is the first example of such thermal redistribution that has been reported. The organosilicon rotanes are all colorless crystalline solids. Both [(CH,),Si], and [(CH2),SiI6are inert to air, but the cyclotetramethylene compounds, especially 5, tend to be mildly air sensitive. Although many of the chemical and physical properties of silicon rotanes resemble those of other peralkylcyclopolysilanes,some are rather different. A more complete account of our studies of these novel compounds will be published later.
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Acknowledgment. This work was supported by the Air Force Office of Scientific Research, Air Force System Command, USAF, under Grant No. AFOSR 82-0067. The United States Government is authorized to reproduce and distribute reprints for governmental purposes notwithstanding any copyright notation thereon. (7) Ishikawa, M.; Watanabe, M.; Iyoda, J.; Ikeda, H.; Kumada, M. Organometallics 1982, I, 317.
Research Laboratories, Petrarch Systems Incorporated Bristol, Pennsylvania 19007 Received September 30, 1982
Summary: The synthesis, solubility enhancement, and phase-transfer catalysis properties of cyclic poly(alky1eneoxy)silanes are described. The compounds have the I
I
general structure R'R2Si(OCH,CH,), 0 and are denoted silacrowns. Solubility enhancements of lithium, sodium, and potassium ions are a function of macrocycle and ion size. Phase-transfer catalysis of acetate, azide, cyanide, fluoride, and nitrite ions in displacement reactions are reported.
In the course of work on the immobilization of phasetransfer catalysts and in the transport of organic salts across liquid membranes, the ionophoric properties of silacrowns have been disclosed.'J Silacrowns have the generalized structure R1R2Si(OCH2CH2),0. Specific examples are dimethylsila-17-crown-6 (I), dimethylsila3,6,9-trimethyl-ll-crown-4 (II), and [3-(N-(2-aminoethy1)amino)propyllmethylsila-14-crown-5(111). We now I
I
""\ /Me Me\
\
/Me SI
I
I1 ,NHCHpCHzNHp
CH "C
H pC H2
\JMe
/ \ 0'
'0
L
O
J
I11
wish to report our preliminary findings on these materials. The silacrowns exhibit ionophoric properties that are (1) Arkles, B.;King, K.; Peterson, W. In "Chemically Modified Surfaces in Catalysis and Electrocatalysis"; Miller, J. S., Ed.; American Chemical Society: Washington, D.C., 1982; ACS Symp. Ser. No. 192. (2) Rico, E.; Pannell, K. H.; Arkles, B. "Transport of Na and K Picrates Across a Liquid Membrane Using New Silacrowns as Ionophores", presented 38th Southwest American Chemical Society, Meeting Dec 2, 1982.
0276-7333/83/2302-0454$01.50/00 1983 American Chemical Society
