Controlled ligand distortion and its consequences for structure, symmetry, conformation and spin-state preferences of iron(II) complexes
Nicole Kroll,a Kolja Theilacker,b Marc Schoknecht,a Dirk Baabe,c Dennis Wiedemann,a Martin Kaupp,*b Andreas Grohmann*a and Gerald Hörner*a a and b Technische Universität Berlin, Institut für Chemie, Germany. Dalton Trans . 2015 , 44 , 19232 Abstract The ligand-field strength in metal complexes of polydentate ligands depends critically on how the ligand backbone places the donor atoms in three-dimensional space. Distortions from regular coordination geo- metries are often observed. In this work, we study the isolated effect of ligand-sphere distortion by means of two structurally related pentadentate ligands of identical donor set, in the solid state (X-ray diffraction, 57Fe-Mössbauer spectroscopy), in solution (NMR spectroscopy, UV/Vis spectroscopy, conductometry), and with quantum-chemical methods. Crystal structures of hexacoordinate iron(II) and nickel(II) com- plexes derived from the cyclic ligand L1 (6-methyl-6-(pyridin-2-yl)-1,4-bis(pyridin-2-ylmethyl)-1,4-di- azepane) ...