A new family of lanthanide borate halides with unusual coordination and a new neodymium-containing cationic framework

摘要

The reactions of Ln_2O_3/CeO_2/Pr _6O_(11) (Ln = La-Nd, Sm), molten boric acid, and concentrated HBr or HI result in the formation of La[B_7O_(10)(OH) _3(H_2O)Br], Ln[B_6O_9(OH) _2(H_2O)_2Br]·0.5H_2O (Ln = Ce, Pr), Nd2[B12O17.5(OH)5(H _2O)4Br1.5]Br_(0.5)·H _2O (NdBOBr), Sm4[B_(18)O_25(OH) 13Br_3], and Ln[B_7O_(11)(OH)(H _2O)_3I] (Ln = La-Nd, Sm). The lanthanide(Ⅲ) centers in these compounds are found with 9-coordinate hula hoop or 10-coordinate capped triangular cupola geometries, where there are six approximately coplanar oxygen donors provided by the polyborate sheet. The sheets are formed into three-dimensional frameworks via BO_3 triangles that are roughly perpendicular to the layers. Additionally, a new cationic framework, NdBOBr, has been isolated. NdBOBr is unusual in that not only is it a cationic framework, but it is also the first trivalent f-element borate to have terminal halides bound exclusively to the base site of the hula hoop. The Ln[B_7O _(11)(OH)(H_2O)_3I] (Ln = La-Nd, Sm) structures require two corner-shared BO_3 units in order to tether the layers together because of the large size of the capping iodine atom.