Synthesis and Properties of the First Stable Neutral Germaaromatic Compound, 2-{2,4,6-Tris- [bis-(trimethylsilyl)methyl]phenyl}-2-germanaphthalene

Abstract

The first stable neutral germaaromatic compound, 2-germanaphthalene 1a, was synthesized by taking advantage of an extremely bulky and efficient steric protection group, 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl (Tbt). The molecular structure and aromaticity of 1a were discussed on the basis of its NMR, UV−vis, and Raman spectra, X-ray crystallographic analysis, and theoretical calculations. All the 1H and 13C NMR chemical shifts of the 2-germanaphthalene ring of 1a were in good agreement with the calculated values for 2-germanaphthalene and 2-phenyl-2-germanaphthalene. The patterns of UV−vis and Raman spectra of 1a were similar to those of naphthalene, although the shift to longer wavelength (in the UV−vis spectrum) and smaller wavenumber (in the Raman spectrum) resulting from the replacement of carbon with germanium were observed. X-ray crystallographic analysis of 1a revealed that the 2-germanaphthalene ring was almost planar and perpendicular to the benzene ring of the Tbt group. These experimental r...