The Chemistry of Germanium-Containing Heavy Ketones

The recent applications of an extremely bulky and efficient steric protection group, 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl (denoted as Tbt in this article), to the kinetic stabilization of a series of doubly bonded compounds between germanium and heavier chalcogen atoms (we coin the expression “germanium-containing heavy ketones” for this family of heavier congeners of germanone) are described. Combination of a Tbt group with some other bulky aromatic or alkyl substituent enabled us to synthesize the novel germanium-containing double-bond species [Tbt(R)Ge=X; R = 2,4,6-triisopropylphenyl (Tip) or bis(trimethylsilyl)methyl (Dis)] such as germanethiones (X = S), germaneselones (X = Se), and germanetellones (X = Te) as stable crystalline compounds, while the germanone [Tbt(Tip)Ge=O], the most reactive species among the germanium-containing heavy ketones, was found to be very difficult to isolate and was evidenced only by the trapping reactions. The X-ray crystallographic analysis of the isolated germanium-containing heavy ketones revealed a completely trigonal planar geometry around their germachalcogenocarbonyl units and their ideally doubly bonded character, which was also confirmed by their spectroscopic data.