Synthesis and Characterization of Homoleptic Rare Earth Nitrato Complexes with the Quaternary Ammonium Cations Et4N+ and nPr4N+

Abstract

AbstractTwo periodic series of homoleptic rare earth nitrato complexes, [R4N]x[M(NO3)y] (M=La−Nd, Sm−Lu, Y); R=Et, Pr; x=2‐3; y=5‐6) have been synthesized, and characterized by single crystal X‐ray diffraction, IR and Raman spectroscopy, comparing the solid state speciation of the nitrate ions as a function of lanthanide ion and quaternary ammonium cation. The series of the form [Et4N]3[Ln(NO3)6] crystallizes in the rhombohedral space group R , as a twelve‐coordinate hexanitrato complex [Et4N]3[Ln(NO3)6] with cocrystallized HNO3 for La, Pr, and Nd. For Ce, a distinct orthorhombic phase retaining the same formula, [Et4N]3[Ce(NO3)6] is isolated in the absence of HNO3 to prevent oxidation of the Ce(III) to Ce(IV) in nitric acid. A ten‐coordinate pentanitrato complex, [Et4N]2[Ln(NO3)5], in monoclinic symmetry forms for the remainder of the series, and for Y(III). The entire series crystallized in the presence of [nPr4N]+ counterions forms a pentanitrato complex [nPr4N]2[M(NO3)5] in the orthorhombic space group, Pccn. Analysis of trends in the structural and spectroscopic characteristics of these series reveal insight into the structure‐directing influences of both the lanthanide contraction and the quaternary ammonium cations.