Oxo(triphenylphosphine)[bis(3,5-di-tert-butyl-2-phenoxo)amido]rhenium(V) [(ONOCat)ReO-(PPh3)] is prepared by the reaction of iododioxobis(triphenylphosphine)rhenium(V) [ReO2(PPh3)(2)I] with lead bis(3,5-di-tert-butyl-1,2-quinone-1-(2-oxy-3,5-di-tert-butylphenyl)imine) [Pb(ONOQ)(2)]. In this reaction, the ONO ligand undergoes a two-electron reduction, with concomitant oxidation of PPh3 to OPPh3 and transformation of the dioxorhenium(V) fragment into a monooxorhenium(V) fragment, constituting a net non-classical oxygen atom transfer. (ONOCat)ReO(PPh3) adopts a square pyramidal geometry with an apical oxo group [d(ReO) = 1.6873(14) angstrom] and a highly folded ONO ligand [O-Re-O = 129.55(6)degrees]. The fully reduced, trianionic oxidation state of the ONO ligand is confirmed by spectroscopic and metrical data.