A Multifunctional Pincer Ligand for Cobalt‐Promoted Oxidation by N2O

The divalent cobalt complex of the diprotic pincer ligand bis‐pyrazolylpyridine, (H2L)CoCl2, is dehydrohalogenated twice by LiN(SiMe3)2 in the presence of PEt3 to give monomeric S=1/2 LCo(PEt3)2 (1), fully characterized in the solid‐state and solution as a square pyramidal monomer with a long axial Co−P bond. This 17‐electron species reacts in time of mixing with N2O to form L2Co2(μ‐OPEt3) (2)+3 OPEt3, the former the first example of phosphine oxide bridging two transition metals. The same products are formed from O2, and divalent cobalt persists even in the presence of excess oxidant. Species (2) catalyzes oxygen atom transfer (OAT) for generation of O=PEt3 from PEt3 from either N2O or O2. Bridging and terminal cobalt oxo intermediates are suggested, and the electron donor power, and potential redox activity of the dianionic pincer ligand is emphasized. A cobalt bis‐phosphine complex featuring a proton‐responsive pincer ligand is shown to be an active catalyst for oxygen atom transfer from N2O to substrate.