Ligand Topology Tuning of Iron-Catalyzed Hydrocarbon Oxidations We thank the National Institutes of Health for financial support (GM33162 to L.Q.) and Fundacio La Caixa for a postdoctoral fellowship (M.C.).

Quite unexpectedly, the topology of the tetradentate ligand in FeII(bpmcn)(OTf)2 (bpmcn=N,N′- bis-(2-pyridylmethyl)-N,N′-dimethyl-trans-1,2-diaminocyclohexane), whether cis-α or cis-β (see picture), determines the course of catalytic alkane hydroxylation and olefin oxidation reactions with H2O2, which afford products with varying stereoselectivity and dramatically different sources of incorporated oxygen. These results demonstrate the exquisite role ligands can play in the fine tuning of the reactivity of an iron catalyst.