NUCLEAR MAGNETIC RESONANCE STUDIES OF RATES OF ELECTRON EXCHANGE BETWEEN ISONITRILE COMPLEXES OF MANGANESE(1) AND MANGANESE-(2)

Manganese-isonitrile complex ions (RNC)6Mn+ and (RNC)6Mn2+ are useful for the study of simple electron-transfer reactions since these can occur without ligand transfers or other complications. The rates can be measured by 55Mn nmr line broadening. If R is ethyl the rate constant for electron exchange at 7˚ is 6.4 x 105, and if R is t-butyl the rate constant is 4.0 x 104 1. mol-1 sec-1. Thus, it appears that the bulky t-butyl group has an electrically insulating effect. If R is an electrical conductor such as phenyl or vinyl, more complicated phenomena appear. The Mn2+ complex exists as a diamagnetic dimer which is in rapid equilibrium with a paramagnetic species, as shown by paramagnetic contact shifts of the phenyl protons in the 60-MHz proton nmr spectrum. Electron exchange with the Mn+ complexes was shown to be rapid by the effect on the position of the shifted nmr peaks. © 1969, American Chemical Society. All rights reserved.