THE SILOLYL ANION C4H4SIH- IS AROMATIC AND THE LITHIUM SILOLIDE C4H4SIHLI EVEN MORE SO

The eta(5) coordination of Li+ in lithium silolide Li+(CH)(4)SiH- (4), increases the delocalization and aromaticity relative to C4H4SiH- (1a ) strongly: 4 exhibits 80% of the stabilization energy of Li+C5H5-, de creased pyramidality of the silicon center, and increased CC bond leng th equalization. In addition, delta(Si-29) in 4 is shifted downfield, delta(C-13) is shifted upfield, and the diamagnetic susceptibility is exalted (A). Likewise, experimental X-ray data on. pRu(H)[eta(5)-Me(4 )C(4)SiSi(SiMe(3))(3)]}[BPh(4)] (2) and NMR studies on lithium 1-tertb utyl-2,3,4,5-tetraphenylsilolide (3) suggest delocalized silole rings.