Square pyramidal geometry around the metal and tridentate coordination mode of the tripod in the [6-(3′-cyanophenyl)-2-pyridylmethyl]bis(2-pyridylmethyl)amine FeCl2 complex: a solid state effect

Metalation of the cyanophenyl mono α-substituted TPA ligand by ferrous chloride affords a stable neutral compound with spectroscopic properties in solution (molecular conductivity, UV-visible and paramagnetic 1H NMR) indicating that the ligand coordinates in the tetradentate mode providing a distorted octahedral geometry around the metal. In the solid state however, the tripod acts as a tridentate ligand, and crystal structure analysis reveals a square pyramidal geometry around the metal. The substituted pyridyl arm is the dangling one, and the cyanide group seems to interact with the metal center of a neighboring molecule. Increasing the ionic strength of a solution of the compound leads to dissociation of the chloride ions from the metal, affording the bis (μ-chloro) diferrous dication, the structure of which is also reported.