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

The dinuclear complex of [Fe2L{O2P(OPh)(2)}](ClO4)(2) . Et2O(1) (where L re presents 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 s ynthesized and crystallizes in the triclinic space group PI with cell const ants a = 1.526(3) nm, b = 1.259 8(3) nm, c = 1.563 0(3) nm, alpha = 94.41(3 )degrees, beta = 115.31(3)degrees, gamma = 99.90(3)degrees, V = 3.267(1) nm (3), z = 2, R = 0.084 7 and R-w = 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-mu-O-Fe angle of 131.20(3)degrees and an Fe-Fe distance of 0.364 9 nm. Both Fe(II) centers have trigonal bipyramidal geometry. Dioxyge n adduct (1/O-2) forms upon exposure of the diferrous complex to O-2 at low temperature (-60 degrees C). The 1/O-2 adduct is stable at -60 degrees C b ut decomposes upon warming. The adduct exhibits visible absorption maximum near 606 nm and resonance Raman features at 478 cm(-1) (gamma(Fe-O)) and 89 7 cm(-1) (gamma(O-O)), and the latter is the characteristic of a mu-1,2-per oxo species, indicating that dioxygen adducts can serve as models for the p utative oxygenated intermediate of some non-heme diiron-oxo proteins.