A new functional model complex of extradiol-cleaving catechol dioxygenases: properties and reactivity of [Fe^II(BLPA)DBCH]BPh₄

[Fe^II(BLPA)DBCH]BPli₄ (1), a new functional model for the extradiol-cleaving catechol dioxygenases, has been synthesized, where BLPA is bis(6-methyl-2-pyridylmethyl)(2-pyridylmethyl)amine and DBCH is 3,5-di/e/7-butylcatecholate monoanion. ¹H NMR and EPR studies confirm that 1 has a high-spin Fe(II) (S = 2) center. The electronic spectrum of 1 exhibits one absorption band at 386 nm, showing the yellow color of the typical [Fe^II(BLPA)J complex. Upon exposure to O₂, 1 is converted to an intense blue species within a minute. This blue species exhibits two intense bands at 586 and 960 nm and EPR signals at g = 5.5 and 8.0 corresponding to the high-spin Fe(III) complex (S = 5/2, E/D = 0.11 ). This blue complex further reacts with O₂ to be converted to (μ-oxo)Fe^III₂ complex within a few hours. Interestingly, 1 affords intradiol cleavage (65%) and extradiol cleavage (20%) products after the oxygénation. It can be suggested that 1 undergoes two different oxygenation pathways. The one takes the substrate activation mechanism proposed for the intradiol cleavage products after the oxidation of the Fe^II to Fe^III. The other involves the direct attack of O₂ to Fe^II center, forming the Fe^III-superoxp intermediate which can give rise to the extradiol cleavage products. 1 is the first functional Fe(II) complex for extradiol-cleaving dioxygenases giving extradiol cleavage products.