Tuning the Electronic Communication in Heterobimetallic Mixed‐Valence Ions of (1‐Ferrocenyl)‐ and (2‐Ferrocenyl)indenyl Rhodium Isomers

A series of heterobimetallic complexes of general structure [RhL2{η5‐(2‐ferrocenyl)indenyl}] (L2=cod, nbd, L=CO; cod=cyclooctadiene; nbd=norbornadiene) has been synthesised with the aim of tuning the metal–metal interaction in their mixed‐valence ions generated both by chemical and electrochemical oxidation, and the results are compared with those obtained for [RhL2{η5‐(1‐ferrocenyl)indenyl}] isomers. Crystallographic studies and DFT calculations provide a detailed description of the structural and electronic features of these complexes evidencing a significant difference in the extent of planarity of the flexible bridging ligand between the 1‐ and 2‐ferrocenyl isomers. Independent experimental probes, in particular the potential splitting in the cyclic voltammograms and the IT bands in the near‐IR spectra, are rationalised in the framework of Marcus–Hush theory and at quantum chemistry level by DFT and TD‐DFT methods. These methods allow us to establish a trend based on the magnitude of iron–rhodium electronic coupling Habranging from valence trapped to almost delocalised ions. The quasi planar bridge and the olefin ancillary ligands make [Rh(nbd){η5‐(2‐ferrocenyl)indenyl}]+and [Rh(cod){η5‐(2‐ferrocenyl)indenyl}]+rare examples of heterobimetallic systems which can be classified as borderline Class II/Class III species.