Nuclear Magnetic Resonance Studies of Electron Transfer between Tris (2,2′-dipyridyl) osmium (II) and (III) Ions, between Bis(cyclopentadienyl)iron(II) and (III) Ions, and between Tris(1,10-phenanthroline)iron(II) and (III) Ions

Abstract

Changes in linewidths and positions of the proton NMR absorption peaks for the diamagnetic species on addition of the corresponding paramagnetic species are interpreted as being due to very rapid electron transfer between the two species. On the assumption that the rates of electron transfer are first‐order with respect to each reactant, the following lower limits on the rate constants are obtained: Os ( dipy ) 3 2+ − Os ( dipy ) 3 3+ : k>5×10 4 mole −1 sec −1 (6° C and 26° C , D 2 O ,5×10 −3 M D + , 0.14 mole Cl − ), Fe ( C 5 H 5 ) 2 − Fe ( C 5 H 5 ) 2 + : k>1×10 5 mole −1 sec −1 (26° C , CD 3 COCD 3 ), Fe ( phen ) 3 2+ − Fe ( phen ) 3 3+ : k>1×10 5 mole −1 sec −1 (26° C , D 2 O ,3 F D 2 SO 4 ). The reactions could not be studied by the electron spin resonance method because the ESR spectra of the paramagnetic species showed no observable absorption peaks, presumably because the peaks are very broad.