Biomimetic Oxidation Studies. 8. Structure of a New MMO Active Site Model, [Fe2O(H2O)2(tris((1-methylimidazol-2-yl)methyl)amine)2]4+, and Role of the Aqua Ligand in Alkane Functionalization Reactions

In this communication, we report on an X-ray crystallographicstudy of a new MMO active site analogue, [ Fe20(H20)2(tmima),]-(Cl04)4, 2, and on important mechanistic aspects of the C-Hbond functionalization reaction of several hydrocarbons with 2as the catalyst using anhydrous TBHP in the presence of oxygengas (02) and acetonitrile (CH3CN) as the solvent. We willdemonstrate that, by removing the p-OAc group and replacingit with terminal H20 ligands, complex 2 enhances the numberof turnovers/h for the alkane functionalization reaction, whileUV-vis and 1H NMR spectroscopic data suggest that 2 retains its integrity upon reaction with TBHP. In addition, we have further verified the previously found free radical mechanism for alkane functionalization with 2 by the use of a radical clock substrate, trans-2-phenylmethylcyclopropane to show only ring openedproducts that must emanate from a cyclopropylcarbinyl radical rearrangement.