Mechanistic studies of the reaction of hydrosiloles with nucleophiles. Crystal structures of the enantiomers of 1-methyl-2-(dimethylsilyl)-2,3,4,5-tetraphenyl-1- silacyclo-3-pentene and 1-(bis(trimethylsilyl)amino)-5-methyl-2,3,4,5-tetraphenyl-1-silacyclo-3-pentene

The X-ray crystal structure determination of the trapping products of 1-met hyl-1,1-dihydrido-5-potassio-2,3,4,5-tetraphenyl-1-silacyclopentadiene sili cate, [Ph4C4SiMeH2-].[K+] (2), with excess dimethylchlorosilane shows enant iomers of 1-methyl-2-(dimethylsilyl)-2,3,4,5-tetraphenyl-1-silacyclo-3-pent ene (5a1, 5a2) in a ratio of 1:1. The trans orientation of the H-Si-C-H lin kage is confirmed by torsional angles of two hydrogens (angle HSiCH = 140.7 degrees). Structural characterization of the enantiomers of 1-(bis(trimeth ylsilyl)amino)-5-sodio-2,3,4,5-tetraphenyl-1-silacyclo-3-pentene (9) (10a, 10b), obtained as major products from the reaction of 1-(bis(trimethylsilyl )amino)-5-sodio-2,3,4,5-tetraphenyl-1-silacyclo-3-pentene (9) with excess M el indicate the cis arrangement of the H-Si-C-H linkage (angle HSiCH = 29.8 degrees). All of the reaction products can be envisioned as resulting from a pathway involving pentacoordinate anionic intermediates that undergo pse udorotation, 1,2-hydride migration from silicon to carbon, and quenching wi th RX (RX = Me2HSiCl, MeI).