Alkali metal complexes of sterically hindered mono- and di-carbanions containing Si–O bonds

Abstract

The oxygen-bridged, silicon-substituted alkane {(Me₃Si)₂CH(SiMe₂)}₂O (1) may be prepared by the reaction of {(Me₃Si)₂CH}Li with ClSiMe₂OSiMe₂Cl in refluxing THF. Similarly, the alkane {(Me₃Si)(Me₂MeOSi)CH(SiMe₂CH₂)}₂ (2) is readily accessible from the reaction between {(Me₃Si)(Me₂MeOSi)CH}Li and ClSiMe₂CH₂CH₂SiMe₂Cl under the same conditions. Compound 1 reacts with two equivalents of MeK to give the polymeric complex [[{(Me₃Si)₂C(SiMe₂)}₂O]K₂(OEt₂)]_∞ [5(OEt₂)] after recrystallisation. Treatment of 2 with two equivalents of either MeLi or MeK gives the corresponding complexes [{(Me₃Si)(Me₂MeOSi)C(SiMe₂CH₂)}₂Li][Li(DME)₃] [7(DME)₃] and [{(Me₃Si)(Me₂MeOSi)C(SiMe₂CH₂)}₂K₂]_n (8), respectively, after recrystallisation. Treatment of the alkane (Me₃Si)₂(Me₂MeOSi)CH with one equivalent of MeK gives the polymeric complex [{(Me₃Si)₂(Me₂MeOSi)C}K]_∞ (3). These compounds have been identified by ¹H and ¹³C{¹H} NMR spectroscopy and elemental analyses and compounds 5(OEt₂), 7(DME)₃ and 3 have been further characterised by X-ray crystallography. Compound 7(DME)₃ crystallises as a solvent-separated ion pair, whereas 5(OEt₂) and 3 adopt polymeric structures in the solid state.