An Unprecedented FeIII(μ-OH)ZnII Complex that Mimics the Structural and Functional Properties of Purple Acid Phosphatases

This communication reports the synthesis and X-ray structure of the first mixed-valence Fe III Zn II complex containing the Fe III (μ-OH)Zn II structural unit. Based on the structure, physicochemical solution studies, and the catalytic properties toward the hydrolysis of the diester 2,4-bis(dinitrophenyl)phosphate (BDNPP), it is proposed that complex 1 employs a hydrolytic mechanism similar to that proposed for red kidney bean purple acid phosphatase, including a nucleophilic attack by the terminal, Fe III -bound hydroxide and the concomitant release of 2,4-dinitrophenolate. Furthermore, it is demonstrated that the μ-hydroxo group in the {Fe III (μ-OH)(μ-ROPO 3 )Zn II } intermediate is unable to hydrolyze the monoester 2,4-dinitrophenylphosphate (DNPP), which suggests that the μ-hydroxo group is a significantly poorer nucleophile than the terminally Fe III -bound OH - group.