Spectroscopic, Electrochemical, and DFT Studies of Oxo‐Centered Triruthenium Cluster Complexes with a Bis(tridentate) Triazine Ligand

Abstract

Oxo-centered triruthenium–acetate complexes with a tridentate or bis(tridentate) triazine ligand have been prepared by the reaction of [Ru3O(OAc)6(py)2(CH3OH)]+ ([1]+) with a triazine ligand [3-(2-pyridyl)-1,2,4-triazine (pytz), 3-(2-pyrimidinyl)-1,2,4-triazine (pmtz), or 5,5′,6,6′-tetramethyl-3,3′-bi-1,2,4-triazine (bdmt)]. The dimeric complex [{Ru3O(OAc)5(py)2}2(μ4-pmtz)]2+ ([5]2+), an intercluster mixed-valence complex ([Ru3III,III,II-pmtz-Ru3III,III,III]2+) containing an asymmetric bis(tridentate) pmtz ligands involved in both μ-η1(N),η2(N,N) and orthometalated μ-η1(C),η2(N,N) bonding modes, was prepared by substitution of a bridging acetate in the parent Ru3O(OAc)6 cluster core. Chemical or electrochemical reduction or oxidation of [5]2+ gave one-electron reduced product [5a]+ or oxidized species [5b]3+, respectively. It is demonstrated that substitution of the bridging acetate by a triazine ligand has a remarkable impact on the electronic and redox characteristics of the triruthenium cluster derivatives. Electrochemical, UV/Vis/NIR spectra, and DFT computational studies demonstrated that there is a distinct cluster–cluster interaction between the two triruthenium cluster moieties across an asymmetric bridging bis(tridentate) triazine in the dimeric triruthenium cluster complex [5]2+.