81276-94-0Relevant academic research and scientific papers
A new class of (N,N′-bis(salicylideneamino)ethanato)iron(II) complexes: Five-coordinate [FeII(salen)L]-. Preparation, properties, and mechanism of electron-transfer reactions
Mukherjee,Abrahamson,Patterson,Stack,Holm
, p. 2137 - 2144 (2008/10/08)
The heterogeneous reaction of the Fe(II) complex Fe(salen) with ligands L- = F-, Cl-, OH-, NCS-, CN-, SH-, and SR- in acetonitrile afforded the purplish complexes [Fe(salen)L]-, isolated as sodium or Et4N+ salts. Also generated in situ was [Fe(Salen)(OC6H4-P-Me)]-. The complexes contain high-spin Fe(II) in a square-pyramidal coordination unit with an axial L- ligand, exhibit isotropically shifted 1H NMR spectra of good resolution, and are electrochemically oxidizable to Fe(salen)L in chemically reversible processes. Absorption and NMR spectra clearly indicate the similarity in structure of the complexes, and the isotropic shifts show that the S = 2 ground state, established for one complex in the solid and solution states, applies to all. (Et4N)[Fe(5-NO2salen)(SC6H4-p-Me)] crystallizes in triclinic space group P1 with a = 9.644 (2) ?, b = 12.115 (3) ?, c = 14.788 (3) ?, α = 98.33 (2)°, β = 105.84 (2)°, γ = 98.41 (2)°, and Z = 2. With use of 3483 unique data (Fo2 > 3σ(Fo2)), the structure was refined to R (Rw) = 4.5% (6.1%). The anion contains Fe(II) in a somewhat distorted-square-pyramidal geometry with the sulfur atom in the axial position. The Fe atom is displaced 0.49 ? above the O2N2 mean plane, with a Fe-S bond distance of 2.386 (2) ?. The structure is similar to those of [Fe(P)SR]- complexes (P = porphyrinate) and is assumed to apply to all members of the set. Selected reactions Fe(salen)L + [Fe(salen)L′]- in acetone result in electron transfer or ligand exchange and have been examined by 1H NMR spectroscopy. A mechanism involving a doubly bridged binuclear intermediate is proposed and provides fresh insight into how coordinatively unsaturated complexes of this type may undergo electron transfer and ligand exchange.
