Ligand effects on the redox behavior of bimetallic tungsten(0)/ferrocene(II) complexes

This work presents a synthesis of bimetallic tungsten(0)/ferrocene(II) complex dppf[W(CO)(3)PMe3] and detailed comparisons of the redox behavior of dppf[W(C0)(3)PMe3], dppflW(C0)(4)], and dppflW(CO)(3)CH3CN]. Reaction of PMe3 with dppf[W(C0)(3)CH3CN] in dichloromethane under an inert atmosphere yields dppf[W(CO)(3)PMe3]. Slow cooling of the column purified product yields yellow blocks suitable for X-ray diffraction analysis. Structural, spectroscopic, electrochemical, and computational studies show that all three complexes have multiple redox events corresponding to tungsten and ferrocene oxidation. The complexes' distal tungsten ligands tune the first redox event over a broad range, from 37 to 200 meV versus ferrocene. Computational studies suggest that the ligand tunes the tungsten moiety's redox potential, changing the first redox event from ferrocene(II) oxidation to tungsten(0) oxidation. This bimetallic complex is thus an interesting candidate for redox-based sensing architectures. (C) 2014 Elsevier Ltd. All rights reserved.