Exploring allostery in oxidative catalysis with first-row metal complexes of a pentadentate phosphine oxide scaffold.

An extended family of complexes have been synthesized from the new mononuclear, pentadentate ligand Py5P2O2. This ligand contains 5 chelating pyridyl groups and a uniquely Lewis basic phosphine-oxide backbone. The first-row transition metals from Mn-Zn have been coordinated and fully characterized, including X-ray crystallographic studies. An Fe-complex has catalysed both the lactonization of a 1,4-diol and the oxidative cleavage of a family of p-substituted-benzylaniline substrates using H2O2 as an environmentally friendly oxidant. The Lewis-basic nature of this ligand design has been exploited by the inclusion of 2 equivalents of the hard Lewis acid Sc(OTf)3 to the reaction pot which resulted in an increase in kinetic rates for both reactions.