Group IVB organometal derivatives of pyridine. Part II. The reaction with bis(trimethylsilyl)mercury; organometal-substituted N-trimethylsilylpyridyl free radicals

Abstract

Bis(trimethylsilyl)mercury reacts with 3- and 4-trialkylmetal derivatives of pyridine (the metal can be silicon, germanium, tin, or lead) to give organometal-substituted NN′-bis(trimethylsilyl)tetra hydro-4,4′- or -2,2′-bipyridyls (I); no reaction occurs with 2-trialkylmetal derivatives of pyridine. The mechanism of the reaction is discussed. The bipyridyls (I) are either partially dissociated at room temperature or dissociate on warming to give stable pyridyl free radicals (II), the e.s.r. parameters of which are presented and discussed. The values of the metal hyperfine-splitting constants indicate that the trialkylmetal group stabilises the radicals merely by virtue of its bulk. No reaction was observed between the metallopyridines and bis(trimethylgermyl) mercury.