Strong Evidence of a Phosphanoxyl Complex: Formation, Bonding, and Reactivity of Ligated Phosphorus Analogues of Nitroxides

Facile access to [W(CO)5(Ph2P‐OTEMP)] is used to initiate a study on the generation, properties, and reactions of transient phosphanoxyl complexes [MLn(R2PO)], the first example of which could be trapped via heterocoupling with the trityl radical. It is also demonstrated that the phosphorus nitroxyl complex acts as radical initiator in the polymerization of styrene. The quest for P−O versus O−N bond homolysis, as well as the initial steps of the polymerization were studied by DFT methods. Build up to break: P‐OTEMP phosphane metal complex I preferentially undergoes homolytic O−N bond cleavage forming the transient phosphanoxyl complex II. DFT calculations provide insight into the formation of I as well as into the homolysis processes of I and the trapping reactions of II.