The "innocent" role of Sc(3+) on a non-heme Fe catalyst in an O2 environment

Density functional theory calculations have been used to investigate the reaction mechanism proposed for the formation of an oxoiron(iv) complex [Fe(IV)(TMC)O](2+) (P) (TMC = 1,4,8,11-tetramethylcyclam) starting from a non-heme reactant complex [Fe(II)(TMC)](2+) (R) and O2 in the presence of acid H(+) and reductant BPh4(-). We also addressed the possible role of redox-inactive Sc(3+) as a replacement for H(+) acid in this reaction to trigger the formation of P. Our computational results substantially confirm the proposed mechanism and, more importantly, support that Sc(3+) could trigger the O2 activation, mainly dictated by the availability of two electrons from BPh4(-), by forming a thermodynamically stable Sc(3+)-peroxo-Fe(3+) core that facilitates O-O bond cleavage to generate P by reducing the energy barrier. These insights may pave the way to improve the catalytic reactivity of metal-oxo complexes in O2 activation at non-heme centers.