A novel alpha,omega silyl dianionic salt. The synthesis and characterization of remotely connected benzannulated silole monoanions

The novel dilithium salt of 1,2-bis((BPSI)(2))ethane (BPSI = 3-butyl-2-phen yl-1-silaindenyl) 4 was prepared from the reaction of 2 with 1,2-bis(chloro -BPSI) ethane 3 and characterized by NMR spectroscopy and by X-ray crystall ography. It is demonstrated that dianions of silicon not only can perform s tepwise reactions but also that, when a quenching reagent possesses two rem ote electrophilic centers, they can be attacked separately and maintain sin gle charges on the silicon centers. The two lithium ions in 4 are eta(1)-co ordinated to two remote silyl anions. NMR and X-ray data are consistent wit h a low degree of pi-electron delocalization in the C4Si ring.