Journal ArticleReaction Pathway for the Aerobic Oxidation of Phosphines Catalyzed by Oxomolybdenum Salen ComplexesRusmore, Theo A; Lander, Chance; Nicholas, Kenneth M<title>Abstract</title> <p>Catalysis of<italic>O</italic>‐atom transfer (OAT) reactions is a characteristic of both natural (enzymatic) and synthetic molybdenum‐oxo and ‐peroxo complexes. These reactions can employ a variety of terminal oxidants, e. g. DMSO,<italic>N</italic>‐oxides, and peroxides, etc., but rarely molecular oxygen. Here we demonstrate the ability of a set of Schiff‐base‐MoO₂complexes (cy‐salen)MoO₂(cy‐salen=<italic>N,N’</italic>‐cyclohexyl‐1,2‐bis‐salicylimine) to catalyze the aerobic oxidation of PPh₃. We also report the results of a DFT computational investigation of the catalytic pathway, including the identification of energetically accessible intermediates and transition states, for the aerobic oxidation of PMe₃. Starting from the dioxo species, (cy‐salen)Mo(VI)O₂(<bold>1</bold>), key reaction steps include: 1) associative addition of PMe₃to an oxo‐O to give LMo(IV)(O)(OPMe₃) (<bold>2</bold>); 2) OPMe₃dissociation from<bold>2</bold>to produce mono‐oxo complex (cy‐salen)Mo(IV)O (<bold>3</bold>); 3) stepwise O₂association with<bold>3</bold>via superoxo species (cy‐salen)Mo(V)(O)(η¹‐O₂) (<bold>4</bold>) to form the oxo‐peroxo intermediate (cy‐salen)Mo(VI)(O)(η²‐O₂) (<bold>5</bold>); 4) the<italic>O</italic>‐transfer reaction of PMe₃with oxo‐peroxo species<bold>5</bold>at the oxo‐group, rather than the peroxo unit leading, after OPMe₃dissociation, to a monoperoxo species, (cy‐salen)Mo(IV)(η²‐O₂) (<bold>7</bold>); and 5) regeneration of the dioxo complex (cy‐salen)Mo(VI)O₂(<bold>1</bold>) from the monoperoxo triplet^{<bold>3</bold>}<bold>7</bold>or singlet^{<bold>1</bold>}<bold>7</bold>by a concerted, asynchronous electronic isomerization. An alternative pathway for recycling of the oxo‐peroxo species<bold>5</bold>to the dioxo‐Mo<bold>1</bold>via a bimetallic peroxo complex LMo(O)‐O−O‐Mo(O)L<bold>8</bold>is determined to be energetically viable, but is unlikely to be competitive with the primary pathway for aerobic phosphine oxidation catalyzed by<bold>1</bold>.</p>Wiley2024-02-0110539102European Journal of Inorganic Chemistry2741434-1948https://doi.org/10.1002/ejic.2023005062102071National Science Foundation