Accessing the +IV Oxidation State in Molecular Complexes of Praseodymium

Out of the 14 lanthanide (Ln) ions, molecular complexes of Ln­(IV) were known only for cerium and more recently terbium. Here we demonstrate that the +IV oxidation state is also accessible for the large praseodymium (Pr) cation. The oxidation of the tetrakis­(triphenysiloxide) Pr­(III) ate complex, [KPr­(OSiPh3)4(THF)3], 1-PrPh, with [N­(C6H4Br)3]­[SbCl6], affords the Pr­(IV) complex [Pr­(OSiPh3)4(MeCN)2], 2-PrPh, which is stable once isolated. The solid state structure, UV–visible spectroscopy, magnetometry, and cyclic voltammetry data along with the DFT computations of the 2-PrPh complex unambiguously confirm the presence of Pr­(IV).