Electron‐Deficient Imidazolium Substituted Cp Ligands and their Ru Complexes

The synthesis of electron‐poor mono‐, di‐ and tri(imidazolium)‐substituted Cp‐ylides is presented and their electronic properties are discussed based on NMR spectroscopy, X‐ray structure analyses, electrochemical investigations and DFT calculations as well as by their reactivity toward [Ru(CH(3)CN)(3)Cp*](PF(6)). With mono‐ and di(imidazolium)‐substituted cyclopentadienides the respective monocationic and dicationic ruthenocences are formed (X‐ray), whereas tri(imidazolium) cyclopentadienides are too electron‐poor to form the ruthenocenes. Cyclic voltammetric analysis of the ruthenocenes shows reversible oxidation at a potential that increases with every additional electron‐withdrawing imidazolium substituent at the Cp ligand by 0.53–0.55 V in an electrolyte based on a weakly coordinating anion. A reversible oxidation can be observed for the free 1,3‐disubstituted ligand as well.