Heterotrimetallic M−M′−M′′ Transition Metal Complexes Based on 1,3,5-Triethynylbenzene: Synthesis, Solid State Structure, and Electrochemical and UV−Vis Characterization. EPR Analysis of the in Situ Generated Associated Radical Cations

The synthesis of a series of complexes with different organometallic building blocks unsymmetrically arranged around the periphery of a 1,3,5-triethynylbenzene core is discussed. They are accessible by diverse consecutive reaction sequences, which allow the introduction of transition metal units such as Fc, [(^tBu₂bpy)(CO)₃Re], [(η⁵-C₅H₅)(Ph₃P)₂Ru], [(η⁵-C₅H₅)(Ph₃P)₂Os], and trans-[(Ph₃P)₂(Cl)Pt] (Fc = (η⁵-C₅H₅)(η⁵-C₅H₄)Fe; ^tBu₂bpy = 4,4′-di-tert-butyl-2,2′-bipyridyl). The solid state structures of five complexes have been determined. The electrochemical behavior of the newly synthesized mono-, heterobi-, and heterotrimetallic assemblies have been studied, showing that there is no significant electronic interaction between the respective metal atoms. UV−vis spectroscopic measurements suggest a weak interaction between the appropriate metal atoms. The associated radical cations were in situ generated by stepwise chemical oxidation and characterized by continuous wave electron paramagnetic resonance (EPR) investigations in X-band performed at low temperatures.