Redetermination of the crystal structure of bis(tri-2-pyridylamine)iron(II) bis(perchlorate), and a new refinement of the isotypic nickel(II) analogue: treatment of the perchlorate anion disorder

Abstract

The crystal structure of bis­(tri-2-pyridyl­amine)­iron(II) bis­(perchlorate) has been redetermined, and that of the isotypic bis­(tri-2-pyridyl­amine)­nickel(II) bis­(perchlorate) complex has been rerefined. In each case, the perchlorate anion is disordered over four sets of atomic sites, and the ions are linked by C—H⋯O hydrogen bonds to form a supra­molecular three-dimensional framework.

Importance of non-covalent interactions in a nitrile anion metal-complex based on pyridine ligands: A theoretical and experimental approach

“…Both types of Fe-N bond length are consistent with a high-spin state for the Fe atom, as Fe-N bond lengths are typically shorter for low-spin complexes. In a recent study of the structure of the low-spin salt FeL3(ClO4)2, 36 the Fe-N bond lengths averaged 1.98 Å, and in a similar Fe(II) thiocyanate crystal structure which contained both high-spin and low-spin molecules, 37 average Fe-N(pyr) bond lengths were reported as 1.96 Å for the low-spin complex and 2.13 Å for the high-spin complex, with corresponding Fe-N(NCS) bond lengths of 1.94 and 2.15 Å. Additionally, from the periodic DFT computations carried out over the experimental geometry, it was determined that the high-spin state is more stable by 28.6 kcal/mol. According to the Mulliken population analysis, 3.8 unpaired electrons are located in the Fe(II) metallic centre, which agrees with common expectation.…”

“…bidentate manner as in the present structure, and in all them except for one the central N atom has a geometry close to a trigonal planar, and the uncoordinated ligand has only a small torsional angle with the central NC3 plane. In contrast, in 12 structures where the ligand is tridentate, the central N atom adopts a flattened tetrahedral geometry, as in reference 36. The molecules are linked into chains along the a direction byC-H•••N hydrogen bonds, and the chains are linked into sheets in the ac plane by weak π-bonding interactions between the pyridine rings and by weak C-H•••S hydrogen bonds, which also link the sheets into a three-dimensional network.…”