Ligand behavior of 2,6-pyridinediylbis(2-pyridinyl)methanone in solvent-controlled formation of iron(III) complexes: A novel asymmetric quasi-linear trinuclear core containing an eight-coordinate iron center

The crystal structures of two polymorphic forms of 2,6-pyridinediylbis(2-pyridinyl)methanone (1) crystallized from different solvents have been determined by X-ray crystallography. Solvent-controlled reaction between FeCl3 and 1 yielded four crystalline iron(III) complexes exhibiting two structural types: an asymmetric quasi-linear triiron core with a rarely observed eight-coordinate iron(III) center and three mononuclear moieties. Ligand 1 is solvolyzed at both carbonyl groups in the trinuclear complex but hydrolysis/solvolysis occurs at only one carbonyl site in its mononuclear complexes. The variable-temperature magnetic susceptibilities of 2 were also measured.