Development of Synthetic Methods for Novel Species on the bases of Concept of Steric Protection

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In this project, we arc studying the synthesis and isolation of novel, highly reactive species stabilized by steric protection and the elucidation of their properties by taking advantage of the spectrometry, X-ray crystallographic analysis, and theoretical calculations. Although we have not synthesized a silicon-silicon triple-bond compound, which is one of the most important target molecules of this project, we have succeeded in the synthesis of 1) novel, strained ring compounds containing a heavier group 14 element, metallacyclopropabenzenes, and 2) new type of heteraaromatic compounds containing a heavier group 14 element, 9-silaanthracene and 2-germanaphthalene, tris [bis (trimethylsilyl) methyl] phenyl (Tbt) group, which is useful reactive compounds. S by for taking advantage of 2,4,6-stabilization of various highly reactive compounds.1) Reactions of dilithiometallanes [Tbt(Dip)Mli_2 : M = Si, Ge] with o-dibromobenzene gave the corresponding metallacyclopropabenzenes [Tbt(Dip)MC_6H_4 : M = Si, Ge] (1). The X-ray structural analysis of 1 indicated that the structural parameters of the metallacyclopropabenzene rings are nearly consistent with the calculated parameters for the parent metallacyclopropabenzenes. The metallacyclopropabenzene rings are completely planar and the strain of 1 is smaller than that of cyclopolrpabenzenes.2) We succeeded in the synthesis and isolation of the first stable 9-silaanthracene and 2-germanaphthalene by taking advantage of Tbt group. The spectroscopic data. X-ray structural analyzes, and theoretical calculations indicated that the 9-silaanthracene and 2-germanaphthalene rings are completely planar, and that they are aromatic compounds. In addition, it was elucidated that 9-silaanthracene and 2-germanaphthalene showed the reactivities as Si=C and Ge=C double-bond compounds, respectively.