Selective Crystallization for Green Separations of Lanthanides Using 5-(Pyrimidyl)Tetrazolate

Abstract

In an effort to develop facile, low-cost, and environmentally benign separations of lanthanides, the coordination chemistry and selective crystallization of Ln3+ cations with the water-soluble ligand 5-(pyrimidyl)­tetrazolate (pmtz) have been investigated. The wide range of coordination modes of pmtz allows for discrimination between these cations, and five distinct compound types can be prepared that are dependent on the lanthanide employed. La3+ leads to the formation of [La­(pmtz)2(H2O)6]Cl (S1). [Ln­(pmtz)3(H2O)3]·(3+n)­H2O is obtained with Ce3+and Pr3+ (S2). Ce3+ can also form [(Ce­(pmtz)2(H2O)3)2(μ-pmtz)]­(pmtz)·11H2O (S3). [(Ln­(pmtz)2(H2O)3)2(μ-pmtz)]2(pmtz)2·14H2O (S4) is formed with Nd3+ and Sm3+. The smaller Ln3+ cations, Dy3+ to Lu3+, all yield [Ln­(H2O)8]­(pmtz)3·3H2O (S5). This selective crystallization of Ln3+ cations based primarily on ionic radii provides a simple method for achieving group separations.

Transformation of Mononuclear Plutonium(III) Tetrazolate Complexes into Dinuclear Complexes in the Solid State

“…The solution was then agitated, causing immediate crystallization of NdCl 3 ·6H 2 O. Sodium 5-(pyrimidyl)­tetrazolate monohydrate [Na­(pmtz)·H 2 O] and {[Nd­(pmtz) 2 (H 2 O) 3 ] 2 (μ-pmtz)} 2 (pmtz) 2 ·14H 2 O ( Nd2 ) were synthesized according to literature procedures. , 239,240 Pu ( ca . 96% 239 Pu, 4% 240 Pu) was supplied by the Radiochemical Engineering Development Center (REDC) at ORNL.…”

“…Nd1 and Pu1 crystallize isotypically with the respective Ce(III) and Pr(III) compounds. 39 They crystallize in the monoclinic space group C2/c and contain the neutral complex [M(pmtz) 3 (H 2 O) 3 ], (M = Ce−Nd and Pu; Figure 1). The metal ion is coordinated by six nitrogen atoms from three bidentate pmtz − ligands (κ 2 N,N′ coordination) and three water molecules in a distorted tricapped trigonal-prismatic fashion (site symmetry 1/C 1 for the M atom).…”

“…9 Pu2 is isotypic with Nd(III) and Sm(III) analogs. 39 They crystallize in monoclinic space group C2/c (#15). The asymmetric unit contains two symmetry independent {[M-(pmtz) 2 (H 2 O) 3 ] 2 (μ-pmtz)} + (M = Nd, Sm, and Pu) cations and two noncoordinated pmtz − anions for charge balance, as well as 14 cocrystallized water molecules (Figure 1).…”

“…Based on parallels between the ionic radii of nine-coordinate Pu III (1.165 ± 0.002 Å) and Nd III (1.163 Å) that are within error of one another, , one could use tetrazoles to delineate potential bonding differences between these cations. − To this end, we compare the solid-state chemistry and spectroscopy of two Pu III tetrazolate compounds with their isotypic Nd III complexes, as well to the other reported isotypic Ln III tetrazolate complexes, such as [Nd­(H 2 ibt)­(H 2 O) 7 ]­(H 2 ibt) 2 ·4­(H 2 O), [H 3 ibt = 4,5-bis­(tetrazol-5-yl)­imidazole], and [Nd­(hqt) 3 ]­K 3 [H 2 hqt = 2-(1H-tetrazol-5-yl)­quinoline-8-ol (8-hydroxyquinoline-2-tetrazole)] …”

“…Interatomic Distances d in Ce1,39 Pr1,39 Nd1, and Pu1 at 100 K and Effective Ionic Radii R ionic of Nine-Coordinated MIII9,38 …”