Tris(trimethylsilyl)germyl radicals, (TMS)(3)Ge(*), thermally or photochemically generated by means of suitable radical initiators, were reacted with a number of unsaturated compounds. The preparative scale reaction of (TMS)(3)GeH with a variety of alkynes proceeded stereo- and regioselectively affording exclusively 2-alkenylgermanes in excellent chemical yields. In the analogous reactions with alkenes, no addition products were obtained except in the case of 4-vinylpyridine. This behavior is explained in terms of the reversibility of germyl radical addition to olefines. The reaction with arylalkenes, ketones, quinones, azines, and nitroalkanes was instead carried out in the cavity of an EPR spectrometer. In most cases the corresponding radical adducts were observed; however, quite often the intensity of the spectra was lower than expected and with azines no EPR signals could be detected. These results have been interpreted as an indication that the addition reaction of tris(trimethylsilyl)germyl radicals to multiple bonds is less exothermic than that of trialkylgermyl radicals. With some of the investigated compounds, the addition of (TMS)(3)Ge(*) is thermoneutral or even endothermic and is therefore readily reversible.

Addition Reactions of Tris(trimethylsilyl)germyl Radicals to Unsaturated Compounds. An EPR and Product Study.-The preparative scale reactions of the germyl radical, generated from hydride (II), with a variety of alkenes and alkynes are studied. With alkenes like vinylcyclohexane, vinyltrimethylsilane, and 2,3-dihydrofuran no addition products are observed. Only pyridine (I) reacts with the radical yielding product (III), probably because of a resonance stabilized intermediate adduct, longliving enough to undergo subsequent hydrogen transfer from the germane. The reaction with alkynes (IV) proceeds regio-and stereoselectively with exclusive formation of (Z)-2-alkenylgermanes (V). EPR studies are made with the radical and arylalkenes, ketones, quinones, azines, and nitroalkanes. In most cases the corresponding adducts are detected, with azines no adducts are obtained. -(BERNARDONI, S.; LUCARINI, M.; PEDULLI, G. F.; VALGIMIGLI, L.; GEVORGYAN, V.; CHATGILIALOGLU, C.; J.