RESUMO
The first isolated genuine germenyl lithiums (R3 Si)(1-Ad)C=Ge(SiMetBu2 )(Liâ 2 L) (R3 Si=tBu2 MeSi, L=THF (1 a), or L=12-crown-4 (1 b) and R3 Si=tBuMe2 Si, L=THF (2 a), or L=12-crown-4 (2 b)), were synthesized by reaction of the corresponding acyl germanes 3 and 4, respectively, with tBu2 MeSiLi in THF at 70 °C. The novel 1 a and 2 b were characterized by NMR and UV/Vis spectroscopy, and also by X-ray crystallography (r(C=Ge)=1.865â Å for 1 a and 1.877â Å for 2 b). Nucleophilic addition reaction of 1 a with MeI and a C-H insertion reactions to the C=Ge bond of 1 a, 2 a and 2 b, are reported. Oxidation of 1 a and 2 b (toluene, 230â K) produces the first persistent germenyl radicals (R3 Si)(1-Ad)C=Geâ -(SiMetBu2 ) (R3 Si=tBu2 MeSi (13 a), R3 Si=tBuMe2 Si (13 b)), which were characterized by EPR spectroscopy (t1/2 ≈30â min at 230â K, g=2.029, aav (73 Ge) is 55.0G for 13 a and 60.2G for 13 b). The experimental EPR parameters and DFT calculations indicate that 13 a and 13 b have a strongly bent structure at Ge (calc. â¡(C=Ge-Si)=136.7° (13 a), 135.9° (13 b)), and that the unpaired electron has a substantial s-character.