Electrochemically Induced Changes in Hapticity in Mixed-Sandwich Compounds of Iridium and Rhodium

Article abstract of DOI:10.1021/ja00306a011

The electrochemical reductions of two sandwich complexes, <(η⁵-C5Me5)M(η⁶-C6Me6)>²⁺ (M=Rh, Ir), are reported.The reduction of the rhodium complex occurs by two reversible one-electron transfer having E⁰ values separated by several hundred millivolts.The iridium complex reduces in a single two-electron step with cyclic voltammetric peak separations very dependent on electrode material.The neutral species of both metals have been isolated and the 1H NMR spectra indicate the structure <(η⁵-C5Me5)M(η⁴-C6Me6)>.Thus these complexes undergo reversible η⁶-><*><- η⁴ isomerization of the arene coordination with the transfer of two electrons.The relationship between the E⁰ values and the structure change is discussed, and a model is favored in which the slippage from η⁶- to η⁴-arene coordination occurs during the second electron transfer.