Mixed valency in a neutral 1D Fe-chloranilate coordination polymer

Abstract

The syntheses and structures of a pair of neutral one-dimensional (1D) Fe-anilate based coordination polymers, Fe(Fan)(4,4′-bipy)₂ (Fanⁿ⁻ = deprotonated 3,6-difluoro-2,5-dihydroxy-1,4-benzoquinone; 4,4′-bipy = 4,4′-bipyridine) and Fe(Clan)(OPPh₃)₂ (Clanⁿ⁻ = deprotonated 3,6-dichloro-2,5-dihydroxy-1,4-benzoquinone; OPPh₃ = triphenylphosphine oxide), are reported. In the case of Fe(Fan)(4,4′-bipy)₂, the Fe centre is in the +2 oxidation state and the Fan ligand is present in its quinoidal, dianionic form. In contrast, the structurally similar Fe(Clan)(OPPh₃)₂ chain contains Fe centres and chloranilate ligands in oxidation states close to +3 and −3 respectively at low temperature. It is suggested that intrachain π–π interactions aid electron transfer from the Fe centres to the bridging ligands.