C 2 O 4 ) 2 и H 2 O with Ln ϭ La, . . ., Gd, M ϭ Li, n ϭ 1, and Two new families of lanthanide complexes associating the M ϭ Na, n ϭ 2, may be prepared by pseudo-hydrothermal ligands oxalate and carbonate or oxalate and formate have synthesis around 150Њ-200ЊC for 3 days (8).
been prepared under autogenous pressure at 200؇C using a
We have continued the preceding study by varying pseudo-hydrothermal method. The two families have been exthe time of treatment or by adding oxalic acid in the tended to some lanthanides (Ln): oxalate-carbonate Ln ؍ Ce, suspension of cerium oxalate. Thus, we have isolated two Pr, Nd, and Eu; oxalate-formate Ln ؍ La, Ce, and Sm. The new phases, lanthanide oxalate-carbonate and lanthanide starting suspension contains either oxalate or a mixture of oxalate-formate, which will be respectively referred to oxalate and oxalic acid. The structures have been solved for as 1 and 2.
the element cerium. In both cases, the structure is built up from Complexes associating oxalate and carbonate may be cerium atoms sharing all their oxygen atoms with oxalate and of particular interest for oceanography and geochemistry.
carbonate or oxalate and formate ligands, thus forming a three-Light rare-earth elements are present in seawater as dimensional network. The cerium polyhedra share either faces or edges or corners. The coordination scheme of the oxalate carbonate complexes (9). However, these latter phases ligands is variable: bischelating, bischelating and monodenevolve toward the formation of mixed complexes tate, or bischelating and bismonodentate. The carbonate group Ln(CO 3 ) x (C 2 O 4 ) zϪ y through their leaching by natural waacts as a bischelating and bismonodentate ligand while the ters which are rich in oxalate (10). Up to the present, there formate group is chelating and monodentate. The characterizahas been only one structural report on complexes of mixed tion of these two original families by infrared spectra and theroxalate-carbonate ligands, K 4 [Zr(C 2 O 4 )(CO 3 )F 2 ] и 4H 2 O mal behavior is presented for some pure phases. A tentative (11). The complexes K 5 [Sm(CO 3 ) 2 (C 2 O 4 ) 2 ] и H 2 O and explanation of the synthesis of these two phases will be (CN 3 H 6 ) 5 [Ln(CO 3 ) 2 (C 2 O 4 ) 2 ] и H 2 O have been studied as emphasized.