Electron spin resonance studies of some aromatic ketyls complexed with the tricarbonylchromium group

Abstract

The e.s.r. spectra of some pivalophenone and benzophenone ketyl radicals complexed with the Cr(CO)₃ group have been obtained and compared with those of the uncomplexed compounds. The strong decrease of the hyperfine coupling constants of the complexed ring protons is explained in terms of substantial modification of the σ- rather than the π-electron density introduced by the inorganic system. For benzophenone ketyls a model is suggested in which the complexed ring is twisted out of the plane of the carbonyl and the uncomplexed ring. The variation of the coupling constants of the uncomplexed phenyl is explained in terms of the strong electron-withdrawing effect of the Cr(CO)₃ group.