title: Si3C2-rings: from a nonconjugated trisilacyclopentadiene to an aromatic trisilacyclopentadienide and cyclic disilenide.
abstract: 1,2,3-Trisilacyclopenta-1,4-diene 2, featuring three skeletal Si atoms in the five-membered ring, was synthesized by the thermolysis of the 1,2,3-trisilabicyclo[1.1.0]butane derivative 1 at 130 degrees C in the presence of hex-3-yne. Possessing the properties of nonconjugated cyclopentadiene, 2 readily underwent reduction with KC(8), which was followed by treatment with LiBr to form the lithium salt of 1,2,3-trisilacyclopentadienide 3(-)*[Li(+)(thf)], from which the ketone-coordinated derivative 3(-)*[Li(+)(O=C(t)Bu(2))] was prepared. Both 3(-)*[Li(+)(L)] (L = thf, O=C(t)Bu(2)) are classified as novel 6pi-electron aromatic systems based on their characteristic X-ray crystal and NMR spectral data. Addition of 12-crown-4 to 3(-)*[Li(+)(thf)] resulted in the unexpected formation of 4(-)*[Li(+)(12-crown-4)(2)], featuring the unprecedented cyclic disilenide ion 4(-).
authors.affiliation: Department of Chemistry, Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Yasuda
authors.forename: Vladimir Ya
authors.initials: VY
authors.lastname: Lee
authors.forename: Akira
authors.initials: A
authors.lastname: Sekiguchi