Synthesis of Genuine Germenyl Lithiums and the First Persistent Germenyl Radicals

The first isolated genuine germenyl lithiums (R3Si)(1-Ad)C=Ge(SiMetBu(2))(Li center dot 2L) (R3Si=tBu(2)MeSi, L=THF (1a), or L=12-crown-4 (1b) and R3Si= tBuMe(2)Si, L=THF (2a), or L=12-crown-4 (2b)), were synthesized by reaction of the corresponding acyl germanes 3 and 4, respectively, with tBu(2)MeSiLi in THF at 70 degrees C. The novel la and 2b were characterized by NMR and UV/Vis spectroscopy, and also by X-ray crystallography (r(C=Ge) = 1.865 angstrom for 1a and 1.877 angstrom for 2b). Nucleophilic addition reaction of 1a with MeI and a C-H insertion reactions to the C=Ge bond of la, 2a and 2b, are reported. Oxidation of 1a and 2b (toluene, 230 K) produces the first persistent germenyl radicals (R3Si)(1-Ad)C=Ge*-(SiMetBu(2)) (R3Si=tBu(2)MeSi (13a), R3Si = (BuMe2Si (13b)), which were characterized by EPR spectroscopy (t(1/2)approximate to 30 min at 230 K, g = 2.029, a(av)(Ge-73) is 55.0G for 13a and 60.2G for 13b). The experimental EPR parameters and DFT calculations indicate that 13a and 13b have a strongly bent structure at Ge (calc. measured angle(C=Ge-Si) = 136.7 degrees (13a), 135.9 degrees (13b)), and that the unpaired electron has a substantial s-character.

Automated summary

This article reports the synthesis and characterization of the first isolated genuine germenyl lithiums. Several reactions and products of these compounds are described. Additionally, the structure and properties of the generated germenyl radicals are revealed through experiments and calculations.