Generation and Decomposition of a Pentacoordinate Spirobis[1,2-oxasiletanide

Abstract

Sequential treatment of diphenylbis((phenylthio)methyl)silane with lithium naphthalenide, hexafluoroacetone, and then aqueous NH4Cl gave the (β-hydroxyalkyl)diphenyl((phenylthio)methyl)silane 8, Ph2Si(CH2SPh)CH2C(CF3)2OH, a hydroxyl group of which was protected with methoxymethyl to afford the corresponding methoxymethyl ether 9a. Similarly, the reaction of 9a with hexafluoroacetone followed by deprotection of the methoxymethyl group yielded the diphenylbis(β-hydroxyalkyl)silane 11, Ph2Si[CH2C(CF3)2OH]2. Sequential treatment of 11 with trifluorormethanesulfonic acid in CDCl3 and with 2 mol equiv of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) gave almost quantitatively [DBU·H]+, phenylbis[1,1,1-trifluoro-2-(trifluoromethyl)-2-propanolate(2−)-C3,O]silicate(−1) (6) along with [DBU·H]+ triflate at low temperature (−20 °C). The 29Si NMR, which showed a signal at δSi −61.75, as well as other NMR analyses indicate that 6 is a pentacoordinate silicate with two 1,2-oxasiletanide rings. Compound 6 decomposed at room t...