Tris(triorganosilyl)methyl derivatives of potassium and lithium bearing dimethylamino or methoxy substituents at silicon.: Crystal structures of KC(SiMe3)2(SiMe2NMe2), KC(SiMe2NMe2)3 and [LiC(SiMe3)(SiMe2OMe)2]2

The compounds HC(SiMe3)(SiMe2X)(2), X = NMe2 or OMe, have been synthesized in several steps from the phenyl derivative HC(SiMe3)(SiMe2Ph)(2) and metallated to give organometallic compounds of the type MC(SiMe3)(SiMe2X)(2), M = K or Li. The structures of the compounds KC(SiMe3)(2)(SiMe2NMe2) and KC(SiMe2NMe2)(3) consist of infinite chains in which cations are co-ordinated to both nitrogen and carbon centres, whereas the lithium compound [LiC(SiMe3)(SiMe2OMe)(2)](2) crystallises in a lattice of dimeric cage molecules. Structural trends in the series MC(SiMe3)(n)(SiMe2X)(3-n), n = 0-3, M = K or Li, X = NMe2 or OMe, are discussed.