Crystal structures of the chiral lithiosilanes [(Lis)-PhMe2SiLi x THF x (-)-sparteine] and [Ph2(NEt2)SiLi x (-)-sparteine].

The (-)-sparteine-coordinated lithiosilanes (Lis)-4 and 5 crystallize as monomers with coordination numbers of 4 and 3 on lithium and represent the first structurally characterized enantiopure lithiosilanes. Both systems are also monomeric in solution with Si-Li contacts detected by 29Si-7Li couplings in the 29Si NMR spectrum (for 5 even at room temperature).

Selective Si--C bond cleavage as synthetic entry to a functionalized lithiosilane.

Treatment of the phenyl-substituted silane 4 with lithium metal afforded the functionalized lithiosilane rac-2 by selective cleavage of one Si-C bond between silicon and a phenyl group. The resulting lithiosilane rac-2 crystallizes as the dimer (2.THF)2, which represents the first example of a dimeric organyl-substituted lithiosilane in the presence of THF.

Synthesis of a highly enantiomerically enriched silyllithium compound.

The highly enantiomerically enriched silyllithium compound lithiomethylphenyl(1-piperidinylmethyl)silane (4) reacts stereospecifically with chlorosilanes, but over a period of several hours slow racemization in solution at room temperature occurs, which can be suppressed by a transmetalation reaction with MgBr2(thf)4.