From M(BH4)3(M = La, Ce) Borohydride Frameworks to Controllable Synthesis of Porous Hydrides and Ion Conductors.
Rare earth metal borohydrides show a number of interesting properties, e.g., Li ion conductivity and luminescence, and the series of materials is well explored. However, previous attempts to obtain M(BH4)3(M = La, Ce) by reacting MCl3and LiBH4yielded LiM(BH4)3Cl. Here, a synthetic approach is presented, which allows the isolation of M(BH4)3(M = La, Ce) via formation of intermediate complexes with dimethyl sulfide. The cubic c-Ce(BH4)3(Fm3̅c) is isostructural to high-temperature polymorphs of A(BH4)3(A = Y, Sm, Er, Yb) borohydrides. The larger size of the Ce3+ion makes the empty void in the open ReO3-type framework structure potentially accessible to small guest molecules like H2. Another new rhombohedral polymorph, r-M(BH4)3(M = La, Ce), is a closed form of the framework, prone to stacking faults. The new compounds M(BH4)3(M = La, Ce) can be combined with LiCl in an addition reaction to form LiM(BH4)3Cl also known as Li4[M4(BH4)12Cl4]; the latter contains the unique tetranuclear cluster [M4(BH4)12Cl4]4-and shows high Li-ion conductivity. This reaction pathway opens a way to synthesize a series of A4[M4(BH4)12X4] (M = La, Ce) compounds with different anions (X) and metal ions (A) and potentially high ion conductivity.
Center for Materials Crystallography (CMC), Interdisciplinary Nanoscience Center (iNANO) and Department of Chemistry, University of Aarhus , Langelandsgade 140, DK-8000 Århus C, Denmark.|Max-Planck-Institut für Kohlenforschung , Kaiser-Wilhelm-Platz 1, 45470 Mülheim an der Ruhr, Germany.
Morten Brix
MB
Ley
Center for Materials Crystallography (CMC), Interdisciplinary Nanoscience Center (iNANO) and Department of Chemistry, University of Aarhus , Langelandsgade 140, DK-8000 Århus C, Denmark.
Mathias
M
Jørgensen
Laboratory of Crystallography, DQMP, University of Geneva , Quai Ernest-Ansermet 24, CH-1211 Geneva, Switzerland.
Radovan
R
Černý
Institute of Condensed Matter and Nanosciences, Université catholique de Louvain , Place L. Pasteur 1, 1348 Louvain-la-Neuve, Belgium.
Yaroslav
Y
Filinchuk
Center for Materials Crystallography (CMC), Interdisciplinary Nanoscience Center (iNANO) and Department of Chemistry, University of Aarhus , Langelandsgade 140, DK-8000 Århus C, Denmark.
Torben R
TR
Jensen