Method embodiments for making lanthanide metal complexes from lanthanide metal oxides and separating the same from heavy lanthanide metal oxides, actinide oxides, and non-lanthanide rare earth element oxides

1. A method, comprising:

combining a lanthanide metal oxide, an oxygen scavenger, and a catalyst in a donor solvent to provide a reaction mixture, wherein the catalyst is selected from an aminopyridine catalyst, a urea-based catalyst, a phosphine chalcogenide catalyst, an N-heterocyclic carbene catalyst, or a sulfur-containing catalyst; and

heating the reaction mixture, or isolating a lanthanide complex from the reaction mixture, or any combination thereof.

2. The method of claim 1 , wherein the lanthanide metal oxide comprises a lanthanide selected from La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Ce, Sc, or Y, but wherein the lanthanide complex comprises a lanthanide selected from La, Pr, Nd, Sm, and Eu.

3. The method of claim 1 , wherein the lanthanide metal oxide comprises a lanthanide selected from La, Pr, Nd, Sm, Eu, the reaction mixture further comprises an actinide oxide comprising Th or U, and wherein the lanthanide complex comprises a lanthanide selected from La, Pr, Nd, Sm, and Eu.

4. The method of claim 1 , further comprising adding an anionic component source that is a different chemical species from the oxygen scavenger to the reaction mixture.

5. The method of claim 4 , wherein the anionic component source comprises a halogen selected from fluorine (F), chlorine (Cl), bromine (Br), iodine (I), or astatine (At); or a psuedohalogen.

6. The method of claim 4 , wherein the lanthanide metal oxide, the oxygen scavenger, the anionic component source, and the catalyst in the donor solvent are added simultaneously or sequentially in any order to a reaction vessel.

7. The method of claim 1 , wherein the reaction mixture is heated at a temperature ranging from greater than ambient temperature to 250° C.

8. The method of claim 1 , wherein the lanthanide metal oxide, the oxygen scavenger, and the catalyst in the donor solvent are added simultaneously or sequentially in any order to a reaction vessel.

9. The method of claim 1 , wherein the lanthanide metal oxide has a structure satisfying a formula Ln 2 O 3 , wherein Ln is a lanthanide selected from lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Ga), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), or lutetium (Lu); and the oxygen scavenger comprises a main group element selected from boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), tellurium (Te), or tin (Sn).

10. The method of claim 1 , wherein the oxygen scavenger also is an anionic component source and the oxygen scavenger comprises a metalloid, an organic functional group, and a halogen.

11. The method of claim 10 , wherein the oxygen scavenger is trimethylsilylchloride (Me 3 SiCl), trimethylsilyliodide (Me 3 SiI), trimethylsilylbromide (Me 3 SiBr), triethylsilylfluoride (Et 3 SiF), trimethylsilyltriflate (Me 3 SiSO 3 CF 3 ), trimethylsilylcyanide (Me 3 SiCN), or azidotrimethylsilane (Me 3 SiN 3 ).

12. The method of claim 1 , wherein the catalyst is an aminopyridine having a Formula I

wherein each of R and R′ independently is hydrogen, an aliphatic group, an alkoxy group, an aromatic group, an aryloxy group, a haloaliphatic group, a heteroaliphatic group, or any combination thereof.

13. The method of claim 1 , wherein the catalyst is a urea-based catalyst having a Formula II

wherein

X is oxygen (O), sulfur (S), or selenium (Se); and

each of R, R′, R″, and R″ independently is selected from hydrogen, an aliphatic group, an alkoxy group, an aromatic group, an aryloxy group, a haloaliphatic group, a heteroaliphatic group, or any combination thereof; or R″ and R′″ join together to provide a heterocyclic ring with the nitrogen atoms to which they are attached, wherein the heterocyclic ring is a 5, 6, or 7-membered ring.

14. The method of claim 1 , wherein the catalyst is a phosphine chalcogenide having a Formula III

wherein

X is oxygen (O), sulfur (S), or selenium (Se);

each of Z, Z′, and Z″ independently is selected from oxygen or nitrogen;

each of R a , R b , and R c independently is selected from hydrogen, an aliphatic group, an alkoxy group, an aromatic group, an aryloxy group, a haloaliphatic group, a heteroaliphatic group, or any combination thereof; and

q is an integer selected from 1 or 2.

15. The method of claim 1 , wherein the catalyst is an N-heterocyclic carbene having a Formula IV

wherein

each X independently is nitrogen, oxygen, or sulfur;

each of R and R′, if present, independently is selected from hydrogen, an aliphatic group, an alkoxy group, an aromatic group, an aryloxy group, a haloaliphatic group, a heteroaliphatic group, or any combination thereof;

each R″ independently is selected from hydrogen, an aliphatic group, an alkoxy group, an aromatic group, an aryloxy group, a haloaliphatic group, a heteroaliphatic group, halogen, or combinations thereof; or, if two R″ groups are present, they are either individually bonded to the five-membered ring and do not join together, or they are individually bonded to the five-membered ring and join together to form a fused ring system with the five-membered ring; and

p is an integer selected from 0, 1, or 2.

16. The method of claim 1 , wherein the catalyst is sulfur-containing catalyst having a Formula V

wherein

each of R and R′ independently is selected from hydrogen, an aliphatic group, an alkoxy group, an aromatic group, an aryloxy group, a haloaliphatic group, a heteroaliphatic group, or any combination thereof.

17. The method of claim 16 , wherein the sulfur-containing catalyst is a sulfoxide having a Formula VA or a sulfone having a Formula VB.

18. The method of claim 1 , wherein the catalyst is 4 dimethylaminopyridine (DMAP) and wherein the DMAP is used at a concentration ranging from 1 mol % to 15 mol %.

19. The method of claim 1 , wherein the donor solvent is selected from pyridine, dimethoxyethane, diglyme, triglyme, tetrahydrofuran (THF), tetrahydropyran (THP), or a combination thereof.

20. The method of claim 1 , wherein the lanthanide complex has the chemical formula LnX 3 (L) n , or LnX 2 (L) n , wherein Ln is a lanthanide selected from La, Pr, Nd, Sm, or Eu; X is a halide; and L is the donor solvent.

21. The method of claim 1 , wherein the catalyst is hexamethylphosphoramide (HMPA).