Synthesis, properties and crystal structures of iron-(II) and -(III) complexes of 2,2′:6′,2″:6″,2‴-quaterpyridine
Journal
Journal of the Chemical Society, Dalton Transactions
Journal Issue
18
Pages
2961-2966
Date Issued
1995
Author(s)
Abstract
Several iron complexes of 2,2′:6′,2″:6″,2‴-quaterpyridine (L) in di- and tri-valent oxidation states have been prepared, and the structures of [FeL(OH2)2][ClO4]21, [{FeL(ClO4)}2(µ-O)]·8.5H2O 2·8.5H2O and [{FeL(Cl)}2(µ-O)][ClO4]2·2H2O 3·2H2O, have been determined by X-ray crystal analyses. In each complex, the quaterpyridine ligand is planar. In 2, the FeII is seven-co-ordinate with the [ClO4]– acting as a bidentate ligand with Fe–O–Fe 155.2(4)°. In 3, the Fe–O–Fe unit is linear and the Fe–O distance of 1.779(1)Å is considerably shorter than the Fe–O(OH2) distance of 2.141(5)Å in 1. The results of molecular orbitals calculations revealed that the unoccupied molecular orbitals of 2 and 3 mainly comprise the π* orbital of L. In 2, bending of the Fe–O–Fe unit gives rise to a decrease in the antibonding interaction between Fe(dyz) and O(Py) orbitals. Complex 3 is less stable in the spin-paired (S= 0) than in open-shell (S= 1) state by 49.3 kcal mol–1. This coincides with magnetic susceptibility measurements which show that 3 is paramagnetic with µeff 1.75 µB per iron atom.
SDGs
Type
journal article