Structural and magnetic properties of one-dimensional coordination polymers {trans-[Ru(CN-tBu)4(CN)2]FeX3}n vs. molecular squares {cis-[Ru(CN-tBu)4(CN)2]FeX3}2 (X = NO3, Cl)

The reaction of cis- or trans-[Ru(CNtBu)4(CN)2] with Fe(III) compounds leads to the formation of molecular squares of the general formula cyc-[Ru(CN-tBu)4(CN)2FeX3]2 or one-dimensional coordination polymers [Ru(CN-tBu)4(CN)2FeX3]n, respectively. Temperature dependent susceptibility measurements indicate that the magnetic properties of the coordination compounds are determined by their molecular structure. Of particular importance is the local symmetry at the iron(III) center which is related to the coordinating anion. The magnetic properties are best described in terms of weak antiferromagnetic interactions between the iron centers for the molecular squares as well as the coordination polymer with X = NO3 and as weak ferromagnetic interactions in case of the linear coordination polymer with X = Cl. For all compounds zero field splitting at low temperatures has to be taken into account.