Accessing the + IV Oxidation State in Molecular Complexes of Praseodymium.

Out of the 14 lanthanide (Ln) ions, molecular com-plexes 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 spec-troscopy, magnetometry, and cyclic voltammetry data, along with the DFT computations of the 2-PrPh complex unambiguously confirm the presence of Pr(IV).