1,1′-Ferrocenylene-Bridged Bis(N-Heterocyclic Olefin) Derivatives

The 1,1 '-ferrocenylene (fc)-bridged bis(N-heterocyclic olefin) compounds (IMes=CH)(2)fc (1, IMes=1,3-dimesitylimidazolin-2-ylidene) and (IPr=CH)(2)fc (2, IPr=1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene) were synthesised from (ICH2)(2)fc (3) and the respective N-heterocyclic carbene IMes or IPr. Ligand substitution reactions of 1 and 2 with [BH3(THF)] afforded the complexes [1(BH3)(2)] and [2(BH3)(2)] as mixtures of the rac- and meso-diastereomers. The new ferrocene derivatives 1-3 and the complexes meso-[1(BH3)(2)], rac-[1(BH3)(2)] and rac-[2(BH3)(2)] were structurally characterised by single-crystal X-ray diffraction. 1 and 2 represent a new class of ferrocene-based, and hence redox-active, bidentate ligands. The presence of three redox-active moieties, viz. the ferrocene unit and the two NHO units, is reflected by three consecutive oxidations according to an electrochemical investigation exemplarily performed with 2 by cyclic voltammetry.

Automated summary

In this study, new ferrocene derivatives and complexes were synthesized and structurally characterized by single-crystal X-ray diffraction. Compounds 1 and 2 represent a new class of ferrocene-based bidentate ligands. Electrochemical investigation revealed the presence of three redox-active moieties in these compounds.