LANGLEBIGE α-METALLIERTE METHYLRADIKALE UND DEREN DIMERE

Article abstract of DOI:10.1016/S0022-328X(00)92576-2

Persistent radicals R'2C<*>-MR3 (I), R'C<*>(MR3)2 (II) and RC<*>(MR3)OMR3 (III), R'=mostly Ph but also t-Bu, H, R'2=also 9-fluorenyl or 9-xanthenyl, M=Si, Ge, Sn, have been generated from the corresponding C-H or C-Hal compounds or by addition of R3M<*> to ketones.Radicals I, II and III are investigated by ESR spectroscopy.A temperature-dependent equilibrium has been found between these radicals and their dimers (IV), of, as far as investigated, quinonoid structure.Dimers IV rearrange with acids giving diaryl methanes.Autoxidation of radicals I at 80 deg C gives thebenzpinacol derivatives, whose radicals are oxidized again, undergoing different fragmentations.At room temperature, however, the dimers IV are attacked by O2 forming the metalated benzophenone derivatives via fragmentation, which are split by UV light into the radicals R3M<*> (M=Si, Ge, Sn) and the oxyl radicals, which are highly stabilised by mesomerism.