New Complexes of Actinides with Monobromoacetate Ions: Synthesis and Structures

Synthesis, FTIR spectral study, and X-ray diffraction analysis of single crystals of (CH₃)₄N­[UO₂(mba)₃] (I), (CH₃)₄N­[NpO₂(mba)₂(NO₃)] (II), (CH₃)₄N­[PuO₂(mba)₂(NO₃)] (III), and (CH₃)₄N­[NpO₂(mba)­(NO₃)₂] (IV), where mba is a monobromoacetate ion (CH₂BrCOO^–), were conducted. The main structural units of crystals I–IV are mononuclear anionic complexes of the [AnO₂(mba)₃]⁻, [AnO₂(mba)₂(NO₃)]⁻, or [AnO₂(mba)­(NO₃)₂]⁻ composition. All these complex units are characterized with the same crystal-chemical formula AB⁰¹₃ (A = AnO₂²⁺ and B⁰¹ = CH₂BrCOO^– or NO₃^–). Using the method of molecular Voronoi–Dirichlet polyhedra, the contributions of various types of noncovalent interactions into the formation of supramolecular structures of the obtained complexes were characterized. The analysis of coordination modes of all monobromoacetate-containing compounds from the Cambridge Structural Database was accomplished. Actinide contraction in the studied compounds is discussed.