Oxygenation Catalysis by All-Inorganic, Oxidation-Resistant, Dawson-Type Polyoxoanion-Supported Transition Metal Precatalysts, [(CH₃CN)xM]n⁺Plus P₂W₁₅Nb₃O₆₂⁹⁻(M = MnII, FeII, CoII, NiII, CuI, CuII, ZnII)

Eleven new polyoxoanion-supported transition metal acetonitrile compositions have been synthesized in 1:1, 1:2, and even a few 1:3 M n + to polyoxoanion ratios; these new precatalysts were then tested for their catalytic efficacy for norbornene and cyclohexene oxygenation using [PhIO] n as the oxidant. The catalytic results identify {(CH 3 CN) x Mn 2+ /P 2 W 15 Nb 3 O 62 9 - } ( 1 ) and {2(CH 3 CN) x Mn 2+ /P 2 W 15 Nb 3 O 62 9 - } ( 2 ) as the best precatalysts within this new subclass of polyoxoanion-supported catalysts. The results reveal a modest ca. 14-fold rate increase for either 1 or 2 in norbornene or cyclohexene epoxidation compared to the polyoxoanion-free [Mn II (CH 3 CN) 4 ](BF 4 ) 2 solvate, kinetic results which require the presence of the P 2 W 15 Nb 3 O 62 9 - polyoxoanion in the rate-determining step of the active catalyst. Catalyst reisolation, then IR, UV−visible, and ion-exchange resin studies (and in comparison to authentic 2 that has not undergone catalysis) provide compelling evidence that 2 is, in fact, the true catalyst. Also compared to 1 and 2 is the polyoxoanion-framework-incorporated P 2 W 17 Mn III O 61 7 -, the first such comparison of a polyoxoanion- supported and - incorporated catalyst; the results reveal, for example, a distinctive catalytic epoxidation stereochemistry for the polyoxoanion-supported vs the polyoxoanion-incorporated Mn catalysts. These experiments, only the second test of the concept of polyoxoanion-supported catalysis, provide further evidence for the conceptual distinctiveness of polyoxoanion-supported transition metals as a new subclass of all-inorganic, oxidation-resistant, polyoxoanion-based catalysts.