Addition of silyl and germyl radicals to 1,3,5-tricyanobenzene. ESR detection of 6,silyl- and 6,germyl-1,3,5-tricyanocyclohexadienyl radicals

The radical adducts between triethylsilyl, triphenylsilyl, and triphenylgermyl radicals and 1,3,5-tricyanobenzene have been detected by ESR spectroscopy. The values of the a(H6) hyperfine coupling constant in these species are discussed in terms of distortion of the cyclohexadienyl ring, the deviation angles from palanarity having been estimated as ca, 15, 17 and 19 degrees for the three adducts, respectively. The detection of the 1,3,5-tricyano-6-triphenylgermyl cyclohexadienyl radical is berlieved to represent the first direct evidence of the addition of germyl radicals to arenes.