ORGANOMETALLIC COMPOUNDS OF THE ALKALI-METALS WITH PHENYLSILYL SUBSTITUENTS AT THE CARBANIONIC CENTER - CRYSTAL-STRUCTURES OF LIC(SIME3)(2)(SIME2PH)CENTER-DOT-ET2O, NAC(SIME3)(2)(SIME2PH)CENTER-DOT-TMEDA, NAC(SIME3)(SIME2PH)(2)CENTER-DOT-TMEDA, (LICH(SIME2PH)(2))(2), RBC(SIME2PH)(3), AND CSC(SIME2PH)(3) (TMEDA = TETRAMETHYLETHYLENEDIAMINE)

The syntheses of a number of alkali metal compounds MC(SiMe3)(3-n)(Sil Me(2)Ph)(n), are described (n = 1, M = Li(TMEDA) (3a), Li(Et2O) (3b), or Na(TMEDA) (3c); n = 2, M = Li(THF)(2) (6a), Li(TMEDA) (6b), Na(TMED A) (6c), or K (6d); n = 3, M = Rb (7d) or Cs (7e); THF = tetrahydrofur an, TMEDA= tetramethylethylene diamine). The compounds 3b, 3c, and 6c adopt molecular structures with intramolecular metal-phenyl interactio ns. The lithium compound LiCH(SiMe2Ph)(2), 5, is dimeric with electron -deficient mu-Li bridges and intramolecular metal-phenyl interactions. The compounds MC(SiMe2Ph)(3), M = Na (7b), K (7c), Rb (7d), or Cs (7e ), form polymeric chains in the solid state with both intra-and interm olecular metal-phenyl interactions. For the lighter alkali metals the interaction is unsymmetrical and mainly with the ipso and ortho carbon atoms, but for the heavier metals there are almost equal metal-carbon distances to all six atoms of the phenyl ring. The long M-C and short Si-C bond lengths and the wide Si-C-Si angles indicate that the struc tures are highly ionic. The presence of ionic species in solution is r evealed by multinuclear NMR data, in particular by the low frequency s hifts associated with the central carbon atoms, by the high carbon-sil icon coupling constants, and by the low barriers to inversion compared with those in the trisilylmethanes from which the carbanions are deri ved.