Model systems for methane monooxygenase - Synthesis, characterization and catalytic property of (mu-phenoxo)bis(mu-carboxylato)dimetal [Fe(III),Mn(III)] complexes

A methane monooxygenase (MMO) - like dinuclear metal (iron/manganese) compl ex which consists of a [(mu - phenoxo)bis(mu - carboxylato) dimetal] core a nd a chiral phenolic ligand bearing two chelating arms of L - histidine has been synthesized and characterized. Its catalytic properties in olefin epo xidations and in alkane hydroxylations were investigated with iodosylbenzen e as a terminal oxidant. It has been found that the Fe-2 complex nicely rep roduces some qualititive characteristics of electronic spectrum of MMO. It is able to catalyze the epoxidation of styrene giving styrene oxide in a 84 0% yield (based on the catalyst) and a 45.4% e.e. for the R - ( +) - enanti omer. Similarly, using the Mr? analogue complex, styrene gave corresponding epoxide in a 7080% yield and a 51.6% e.e. for the R-enantiomer and cyclohe xene gave epoxycyclohexane (3880%) as a major product together with cyclohe xenol(603%) and cyclohexenone (189%). In addition, the hint complex catalyz ed the hydroxylation of cyclohexane giving cyclohexanol (1053%) and cyclohe xanone (639%). EPR evidence suggested the presence of a high valent med-oxo intermediate in the reactions.