Disilanyl anions

Treatment of the trisilane Me3SiSiMe2SiMe3 with TBAF in HMPA, however, does not proceed by formation of SiMe3 instead, the more stable disilanyl anion Me3SiMe2Si is formed in equilibrium, as was concluded from the products which were obtained when the reaction was performed in the presence of aldehydes16. 

The formation of Me3SiMe2SiLi as a by-product in the reaction of MesSi—SiMe3 with MeLi in HMPA/Et20 (which yields mostly Me3SiLi) has been mentioned earlier (Section IV.A). In a large-scale experiment the disilanyl anion has been reported to be... 

Similar results are observed in the reaction of a disilanyllithium with a chlorodisilane (28), as shown in Scheme 3. When a mixture of monosilyl and disilanyl anions is introduced to l-chloro-2-phenyltetramethyldisilane, the usual coupling products, 1,3-diphenyltrisilane and 1,4-diphenyltetra-silane, are formed. Alternatively, when the chlorosilane is added into a mixture of the anions, the scrambling processes via the Si-Si bond cleavage occur, to give a mixture of linear and cyclic oligosilanes. These results indicate that the scrambling processes are very fast, but much slower than the coupling of anions with chlorosilanes (see also Section VI-B). 

In this method, attack by an anionic initiator ( -BuLi, potassium alkoxides/cryptand[2.2.2],62 or silyl anions in benzene)63 occurs regioselectively on the less hindered silicon of 9, resulting in an anionically terminated disilanyl-lithium which then attacks another monomer at the less hindered silicon atom. The process continues rapidly (the reaction is usually complete within a few minutes) in a living polymerization fashion to yield 10 on alcohol workup. 

The Si-Si bond provided the first example of a a-bond donor in the formation of charge-transfer complexes with TCNE (tetracyanoethylene). Conversely, the Si-Si bond can act as an electron acceptor to form disilanyl radical anions. 

Also silyl anion chemistry was used to obtain cyclottisilanes as shown by Marschner and coworkers in the reaction of a 1,2-disilanyl dianirMi with -Pr2SiCl2 (3) [96],... 

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