The synthesis of 4fn Ln3+ complexes of the tris(aryloxide) mesitylene ligand, ((Ad,MeArO)3mes)3-, with Ln = La, Ce, Pr, Sm, and Yb, and their reduction with potassium have revealed that this ligand system can be redox active with some metals. Protonolysis of [Ln(N(SiMe3)2)3] (Ln = La, Ce, Pr, Sm, Yb) with the tris(phenol) (Ad,MeArOH)3mes yielded the Ln3+ complexes [((Ad,MeArO)3mes)Ln] (Ln = La, Ce, Pr, Sm, Yb), 1-Ln. Single electron reduction of each 4fn complex, 1-Ln, using potassium yielded the reduced products, [K(2.2.2-cryptand)][((Ad,MeArO)3mes)Ln] (Ln = La, Ce, Pr, Sm, Yb), 2-Ln. The Sm and Yb complexes have properties consistent with the presence of Ln2+ ions with traditional 4fn+1 electron configurations. However, the La, Ce, and Pr complexes appear to formally contain Ln3+ ions and ((Ad,MeArO)3mes)4- ligands. Structural comparisons of the [((Ad,MeArO)3mes)Ln] and [((Ad,MeOAr)3mes)Ln]1- complexes along with UV-vis absorption and EPR spectroscopy as well as density functional theory calculations support these ground state assignments.
Bibliographical noteFunding Information:
We thank the U.S. National Science Foundation for support of the theoretical studies (CHE-1464828 to F.F.) and the experimental studies (CHE-1565776 to W.J.E.). We also thank Professor Arnold Rheingold, Dr. Milan Gembicky, Dr. Jason R. Jones, and Dr. Jordan F. Corbey for assistance with X-ray crystallography and Professor A. S. Borovik for spectroscopic assistance. We also thank the NSF for providing graduate fellowship support for C.T.P. (DGE-1321846). D.P.H. acknowledges the Graduate School Molecular Science (GSMS) of FAU Erlangen-Nürnberg for generous support. The Bundesministerium für Bildung und Forschung (BMBF, support codes 02NUK012C and 02NUK020C), the FAU Erlangen-Nürnberg, the Deutsche Forschungsgemeinschaft (DFG) and the Cluster of Excellence EXC 315 “Engineering of Advanced Materials” (www.eam.uni-erlangen.de), and COST Action CM1006 are acknowledged for funding.