Uranium(III)-Phosphorus(III) Synergistic Activation of White Phosphorus and Arsenic

The study of small-molecule activation by f-block elements still lags far behind that of transition metals. Although a few uranium complexes have been reported to activate dinitrogen, reports on the activation of heavier congeners, such as white phosphorus (P-4), by uranium species are extremely rare, and no example of uranium-mediated activation of elemental arsenic has appeared. Here, we report the first example of uranium-mediated elemental arsenic activation, leading to the formation of a uranium polyarsenide molecular chain with a Z-type As-4 unit. As a comparison, an analogous polyphosphide chain featuring an E-type P-4 unit was generated by the uranium-mediated activation of P-4. Computational studies show that the U(III)-P(III) synergistic effects allow a direct six-electron reduction of both elemental arsenic and P-4. The regioselectivity of these reactions is sterically controlled: the Z-isomer is the thermodynamically favored product, and the E-isomer is the kinetically favored product. The reactivity of both chains with silylene was also investigated. reduction of both elemental arsenic and P-4. The regioselectivity of these reactions is sterically controlled: the Z-isomer is the thermodynamically favored product, and the E-isomer is the kinetically favored product. The reactivity of both chains with silylene was also investigated. [GRAPHICS] .