Boronic Acid Flux Synthesis and Crystal Growth of Uranium and Neptunium Boronates and Borates: A Low-Temperature Route to the First Neptunium(V) Borate

Molten methylboronic acid has been used as a reactive flux to prepare the first neptunium(V) borate, NpO2[B3O4(OH)2] (NpBO-1), and the first actinide boronate, UO2(CH3BO2)(H2O) (UCBO-1). NpBO-1 contains cation−cation interactions between the neptunyl units. In contrast, the presence of the methyl groups in the uranyl boronate leads to a one-dimensional structure.