Iron vs. ruthenium: syntheses, structures and IR spectroelectrochemical characterisation of half-sandwich Group 8 acetylide complexes

Abstract

A convenient modification to the established synthetic routes for the preparation of complexes [M(CCR)(dppe)Cp′] (M = Fe, Ru; Cp′ = η⁵-C₅H₅ (Cp), η⁵-C₅Me₅ (Cp*); R = C₆H₅, C₆H₄-p-OMe, C₆H₄-p-NO₂, ^tBu) and [Ru(CCR)(PPh₃)₂Cp] from the corresponding [MCl(PP)Cp′] complex and the alkyne HCCR via an intermediate vinylidene is described. The complexes are generally obtained as high quality crystalline samples directly from the reaction mixture. In agreement with previous studies, the iron complexes undergo a predominantly metal-centred oxidation, whilst there is greater involvement of the acetylide ligand in the oxidation processes associated with the ruthenium analogues. Analysis of the redox properties and spectroelectrochemical investigations reveal limited differences in the gross electronic structures of the Cp vs. Cp* derivatives in each of the Fe and Ru series.