Synthesis, crystal structure of diferrous complex and its reactivity with dioxygen

Abstract

The dinuclear complex of [Fe2L{O2P(OPh)2}](ClO4)2· Et2O(1) (where L represents the dinucleating ligand N-Et-HPTB, anion of N, N, N’, N’-tetrakis (N-ethyl-2-benzimidazolyemethyl)2-hydroxy-1, 3-diamino-propane) has been synthesized and crystallizes in the triclinic space group P1 with cell constants a = 1.526(3) nm, b = 1.259 8(3) nm, c = 1.563 0(3)° nm, α = 94.41(3)°, β = 115.31(3)°, γ = 99.90(3)°, V = 3.267(1) nm3, z = 2, R = 0.084 7 and Rw = 0.177 8. The Fe(II) sites are bridged by an alkoxide of the dinucleating ligand and a phosphate, affording a diiron core with an Fe-μ-O-Fe angle of 131.20(3)° and an Fe-Fe distance of 0.364 9 nm. Both Fe(II) centers have trigonal bipyramidal geometry. Dioxygen adduct (1/O2) forms upon exposure of the diferrous complex to O2 at low temperature (?60°C). The 1/O2 adduct is stable at ? 60°C but decomposes upon warming. The adduct exhibits visible absorption maximum near 606 nm and resonance Raman features at 478 cm-1 (γFe-O) and 897 cm-1 (γO-O), and the latter is the characteristic of a μ-1,2-peroxo species, indicating that dioxygen adducts can serve as models for the putative oxygenated intermediate of some non-heme diiron-oxo proteins.