Tetravalent Cerium Alkyl and Benzyl Complexes

Abstract

High-valent cerium complexes of alkyl and benzyl ligands are unprecedented due to the incompatibility of the typically highly oxidizing Ce⁴⁺ ion and the reducing alkyl or benzyl ligand. Herein we report the synthesis and isolation of the first tetravalent cerium alkyl and benzyl complexes supported by the tri-<i>tert</i>-butyl imidophosphorane ligand, [NP(^tBu)₃]^1-. The Ce⁴⁺ monoiodide complex, [Ce⁴⁺I(NP(<i>tert</i>-butyl)₃)₃] (<b>1-CeI</b>), serves as a precursor to the alkyl and benzyl complexes, [Ce⁴⁺(Npt)(NP(<i>tert</i>-butyl)₃)₃] (<b>2-CeNpt</b>) (Npt = neopentyl, CH₂C(CH₃)₃) and [Ce⁴⁺(Bn)(NP(<i>tert</i>-butyl)₃)₃] (<b>2-CeBn</b>) (Bn = benzyl, CH₂Ph). The bonding and structure of these complexes are characterized by single-crystal XRD, NMR and UV-vis-NIR spectroscopy, cyclic voltammetry, and DFT studies.