Electron-Transfer Chain Catalysis of η2‑Arene, η2‑Alkene, and η2‑Ketone Exchange on Molybdenum

An oxidant-initiated, substitution process for dihapto-coordinated ligands is described for the {MoTp­(NO)­(DMAP)} system. Complexes of the form MoTp­(NO)­(DMAP)­(η2-alkene), MoTp­(NO)­(DMAP)­(η2-ketone), and MoTp­(NO)­(DMAP)­(η2-arene) (where Tp = hydridotris­(pyrazolyl)­borate and DMAP = 4-(dimethylamino)­pyridine) undergo an alkene-to-ketone exchange that is catalyzed by the addition of 2) and monocoordinated (κ-O) isomers and the differing redox characteristics of these two isomeric forms. This concept was then applied to the search of sodium-free reduction conditions for the conversion of MoTp­(NO)­(DMAP)­(I) to various molybdenum(0) complexes of unsaturated ligands, including MoTp­(NO)­(DMAP)­(η2-naphthalene) and MoTp­(NO)­(DMAP)­(α-pinene).