Molecular and Crystal Structures of Mononuclear trans‐[Fe(CN)₂(^tOcNC)₄] and trans‐[Mn(CN)(CO)(^tOcNC)₄] as well as of Cyanide Bridged Coordination Polymers Derived from trans‐[M(CN)₂(^tOcNC)₄] (M = Fe, Ru)

Abstract

The octahedral complexes trans‐[Fe(CN)2(tOcNC)4] and trans‐[Mn(CN)(CO)(tOcNC)4] are produced by the reaction of 2‐isocyano‐2,4,4‐trimethyl‐pentane (tert. octyl‐isocyanide) with the corresponding transition metal carbonyls Fe2(CO)9 and Mn2(CO)10. In contrast to isostructural compounds with less bulky tert.‐butylisocyanide ligands the cyanide groups in trans‐[Fe(CN)2(tOcNC)4] and trans‐[Mn(CN)(CO)(tOcNC)4] do not act as hydrogen bond acceptors towards solvent molecules in the crystal structures. In addition, the corresponding cis‐isomers are configurationally unstable. The reaction of trans‐[Fe(CN)2(tOcNC)4] and trans‐[Ru(CN)2(tOcNC)4] with MnCl2, NiCl2 and Co(NO3)2 ends up in the formation of cyanide bridged coordination polymers. X‐ray structure determinations of the cobalt compounds reveal different molecular structures. Whereas the former produces highly distorted infinite polymeric chains with the nitrate anions still coordinated to the cobalt centers, the latter forms polymers with the cobalt atoms being coordinated by four ethanol molecules to which the anions are bound via hydrogen bond interactions. The coordination geometries around ruthenium and cobalt in this coordination polymer are therefore nearly perfectly octahedral and tetrahedral, respectively. Measurements of the magnetic susceptibility of the coordination polymers at different temperatures are indicative of weak antiferromagnetic coupling of the paramagnetic centers along the polymeric chains.