New publication in IC online
Triflate vs Acetonitrile: Understanding the Iron(II)-Based Coordination Chemistry of Tri(quinolin-8-yl)amine
Metal complexes with labile coligands are important precursor species for catalytically active biomimetic complexes. Due to the lability of the coligands, the solid state structure and the main species in solution can differ significantly. Structural characterisation of the complexes is typically performed by X-ray single crystal structure analysis in the solid state, but the catalytic experiments take place in solution. The challenge is to characterise both species.
In this publication, iron(II) complexes with the tetradentate tripodal ligands tri(quinolin-8-yl)amine were studied in the solid state and in solution. For the co-ligands triflate and acetonitrile, which are in competition to each other, all three variants – bis(acetonitrile)-, bis(triflato)- and a mixed species – could be characterised for the first time under the same synthesis conditions in the solid state as single crystal structures. In solution, however, there are clearer preferences. In the non-coordinating solvent dichloromethane, the bis(triflato) species is mainly present, while in coordinating acetonitrile the bis(acetonitrile) species dominates. The latter shows a temperature-dependent spin-crossover behaviour in solution.
In the synthesis of the iron(II) complexes, both the solvent and the anion were varied. The obtained species were characterised as X-ray single crystal structures. Species with a pure N-donor environment on the iron are low-spin while all heterogeneous donor environments are high-spin species. The spin state is also reflected in the spatial arrangement of the quinoline donors around the metal centre: low-spin species show a T-shaped arrangement while high-spin species show a geometry reminiscent of a distorted windmill.
The Full article “ Triflate vs Acetonitrile: Understanding the Iron(II)-Based Coordination Chemistry of Tri(quinolin-8-yl)amine ” is available on the publishers website.