Synthesis and reactivity of a cerium(III) scorpionate complex containing a redox non-innocent 2,2'-bipyridine ligand

Abstract

The Ce(III) hydrotris(3,5-dimethylpyrazolyl)borate complex [Ce(TpMe2)2(κ2-dmpz)] (1) (TpMe2 = (HB(dmpz)3)-; dmpz = 3,5-dimethylpyrazolide) was isolated in fair yield from the reaction of [Ce(I)3(THF)4] with two equivalents of [K(TpMe2)] via the facile decomposition of TpMe2. [Ce(TpMe2)2(bipy)] (2) was synthesized in poor yield by the "onepot" reaction of [Ce(I)3(THF)4], bipy (bipy = 2,2'-bipyridine), KC8 and two equivalents of [K(TpMe2)] in tetrahydrofuran (THF). The reaction of 2 with N-methylmorpholine-N-oxide produced the known decomposition product [Ce(TpMe2)(μ-BOpMe2)]2 (3) (BOpMe2 = (HBO(dmpz)2)2-) in poor yield, presumably by N-O and B-N bond cleavage of a reactive intermediate. The reaction of 2 with trimethylsilylazide gave [Ce(TpMe2)2(N3)] (4) in poor yield; the fate of bipy and the trimethylsilyl group is unknown. Complexes 1-4 were characterized by single crystal XRD, NMR and FTIR spectroscopy and elemental analysis. Complex 2 was additionally probed by UV/Vis/NIR and Electron Paramagnetic Resonance (EPR) spectroscopies, Cyclic Voltammetry (CV) and magnetometry, which together indicate a formal 4f1 Ce(III) center coordinated by a bipy.- radical anion in this system.