Metalloligands containing aminofulvene-aldiminate (AFA) ligands and their bimetallic complexes

Abstract

A simple and convenient route to η⁵-coordinated Ru and Rh aminofulvene-aldiminate (AFA) complexes is described. The metalloligands [Cp*Ru{η⁵-(Ph₂AFAH)}][BF₄] (3), [Cp*Ru{η⁵-(benzyl₂AFAH)}][OTf] (7), [Cp*Rh{η⁵-(Cy₂AFA)H}][BF₄]₂ (8) and [Cp*Rh{η⁵-(Cy₂AFA)}][BF₄] (9) have been synthesised and characterised. The basicity of 9 has been found to be significantly less than its neutral analogue and thus eliminates the need for a deprotonation step to ligate to a second metal in the κ²-N,N′-coordination mode. The reaction of 9 with a palladium precursor provides a mixed-metal complex [Cp*Rh(η⁵/κ²-Cy₂AFA)PdCl₂][BF₄] (12). Cyclic voltammetry studies of the Ph₂AFAH ligand shows an irreversible one electron oxidation peak at +1.0 V (vs. Fc/Fc⁺). Complex 3 shows an irreversible oxidation at +1.5 V and a reduction peak at −1.0 V. The oxidation of 3 occurs on the AFA ligand backbone whereas the structurally analogous neutral 1,2-bis(imidoyl)pentamethyl-ruthenocene shows reversible oxidation at the Ru center.