Nucleophilic displacement versus electron transfer in the reactions of alkyl chlorosilanes with electrogenerated aromatic anion radicals

摘要: Abstract Anion radicals of a series aromatic compounds (C 6 H 5 CN, C COOEt, anthracene, 9,10-dimethyl-, 9,10-diphenyl- and 9-phenylanthracene, pyrene naphthalene) react with trialkyl chlorosilanes R 1 2 3 SiCl (R 1-3  = Me, Et; 1,2  =  t -Bu) in multiple ways, following classical bimolecular schemes. The ratio one-electron transfer (ET) to two-electron process (S N 2-like nucleophilic attack the reduced form mediator on chlorosilane, k  ≅ 10 -10 8  M −1  s ) is inversely related steric availability Si for displacement reactions. substitution pathway mainly results mono- disilylated products. Paralleling electrochemical data DFT calculations, role silicophilic solvent (DMF) S was shown be quite complex because its involvement into coordination extension at silicon, dynamically modifying energetics along reaction coordinate. Although 2,2'-bipyridine also forms delocalized persistent anion radicals, they do not induce neither ET nor reactions same manner as mediators. Silicophilicity being superior that DMF, SiCl·bipy hypercoordinated silicon electroactive ligand formed instead, whose reduction requires about 1 V less negative potentials than bipyridine itself.