Differentiating between Trivalent Lanthanides and Actinides

*S Supporting Information ABSTRACT: The reactions of LnCl3 with molten boric acid result in the formation of Ln[B4O6(OH)2Cl] (Ln = La−Nd), Ln4[B18O25(OH)13Cl3] (Ln = Sm, Eu), or Ln[B6O9(OH)3] (Ln = Y, Eu−Lu). The reactions of AnCl3 (An = Pu, Am, Cm) with molten boric acid under the same conditions yield Pu[B4O6(OH)2Cl] and Pu2[B13O19(OH)5Cl2(H2O)3], Am-[B9O13(OH)4]·H2O, or Cm2[B14O20(OH)7(H2O)2Cl]. These compounds possess three-dimensional network structures where rare earth borate layers are joined together by BO3 and/or BO4 groups. There is a shift from 10-coordinate Ln 3+ and An3+ cations with capped triangular cupola geometries for the early members of both series to 9-coordinate hula-hoop geometries for the later elements. Cm3+ is anomalous in that it contains both 9- and 10-coordinate metal ions. Despite these materials being synthesized under identical conditions, the tw