A method is presented for the synthesis of tertiary, secondary, ether and a polysilanylpotassium compound. This route allows easy and flexible access to a number of novel polysila-and primary polysilylpotassium compounds. Reaction of potassium tert-butoxide, in either DME or THF, with a suitable nylpotassium compounds, avoiding the hitherto common use of poisonous mercury compounds. precursor molecule, proceeds by cleavage of a trimethylsilylΟͺ polysilanyl bond, and formation of trimethylsilyl tert-butyl
As is known from the pioneering work of Gilman and 1 coworkers tetrakis(trimethylsilyl)silane can react with methyllithium to form tetramethylsilane and tris(trimethylsilyl)-The results described in this paper show that this is not silyllithium. [2] a primary limitation, and that it can be easily overcome by the correct choice of the transmetalating agent.
(Me 3 Si) 4 Si Ο© MeLi Η (Me 3 Si)Me Ο© (Me 3 Si) 3 SiLi (1) 1
Results and Discussion
The latter compound has been rapidly accepted as a Our studies on the synthesis of dendritic and branched prototype of a bulky nucleophilic polysilyl anion and, only polysilanes [13] led to the investigation of some aspects of recently, has been referred to as "hypersilyl" group. [3] It has the chemistry of polysilyl anions. In reactions directed been used for the synthesis of transition metal silyl comtowards the formation of polysilanes with monosilyl anions pounds, [4] for the generation of silenes by means of silaand silyl halides we often found that the use of the potas-Peterson reaction, [5] and for a number of other purposes. [6] sium compound was superior to the use of lithium anions. However, it is noticeable that this reagent, although so So it was reasonable to also address the use of lithium vs. widely accepted, has rarely been the subject of variation.
potassium in the case of the "hypersilyl" anion. Although Only very recently have Klinkhammer [7] and Oehme [8] rethis compound was already known from the work of Klinkported on the synthesis of the potassium and magnesium hammer, [7] transmetalation from the corresponding bis-"hyanalogs, however the isotetrasilanyl moiety has almost persilyl" mercury, zinc, or cadmium compounds with ponever been varied. Nevertheless, Apeloig et al. have recently tassium did not seem to be a real alternative to the use of shown that variation of this moiety can be of some advanthe readily available "hypersilyllithium" 1. [2] We felt that a tage. They have been able to show that an increase in the really competitive synthesis must introduce the potassium size of ligand gives rise to the formation of stable siin as easy a fashion as the lithium. So the obvious reagent lenes. [9] [5g] of choice was potassium tert-butylate, which very effectively Although it would be interesting to have a set of bulky transforms dodecamethylcyclohexasilane into the correpolysilyl groups differing in reactivity and, especially, in sponding undecamethylcyclohexasilanylpotassium. [14] size, [10] in order to achieve different degrees of steric hin-Indeed initial experiments showed that the conversion of drance, this problem has not so far been systematically adtetrakis(trimethylsilyl)silane with tert-butylate in DME or dressed. The reason for this becomes obvious if one looks THF, in a clean and almost quantitative reaction, gives "hyat a fact that was first pointed out by Gilman, [11] and then persilylpotassium" 1a accompanied by the formation of trirecently studied in more detail by Apeloig et al., [12] namely methylsilyl tert-butyl ether (Eq. 3). that if polysilanes with "inner" SiΟͺSi bonds react with methyllithium there is a pronounced tendency for these "in-(Me 3 Si) 4 Si Ο© KOtBu Η (Me 3 Si) 3 SiK Ο© (Me 3 Si)OtBu
(3) ner" SiΟͺSi bonds to undergo scission. This means that, for 1a example, hexakis(trimethylsilyl)disilane yields 1 and tris(trimethylsilyl)methylsilane in the reaction with methyllithium Changing the solvent to toluene or pentane gives 1a as a crystalline compound, with one or two molecules of the (Eq. 2).