| Abstract;The chemistry of unsaturated cyclic compound consisting of heavier Group 14 elements has been developed recently. We have succeeded synthesis and structure determination of cyclotrisilene, cyclotrigermene, disilagermirenes, which are analogues to cyclopropene having an unsaturated three-membered ring skeleton. We have also succeeded the transformation of cyclotrisilene and cyclotrigermene into cyclotetrasilenylium ion and cyclotrigermenylium ion, respectively. Crystallographic and NMR analysis revealed that (1) both cyclic cations are "free" silyl or germyl cation which have no interaction with counter-anion and solvent molecules in condensed phase, (2) cyclotetrasilenylium ion is homoaromatic species with 1,3-orbital interaction between Si1 and Si3, and (3) cyclotrigermenylium ion is a 2.PI.-electron aromatic system. Furthermore, we have succeeded to isolate stable silyl radical, cyclotetrasilenyl, by the one electron reduction of cyclotetrasilenylium ion. (author abst.) |
