Thermally Stable Rare-Earth Metal Complexes Supported by Chelating Silylene Ligands

The use of N-heterocyclic silylenes (NHSi) as ligands is a rapidly developing field. However, only a handful of f-element silylene complexes have been disclosed so far. Herein, we report the synthesis and characterization of a series of thermally stable divalent and trivalent rare-earth metal complexes bearing the bis(silylene) LSiFcSiL (L = PhC(NtBu)2, Fc = ferrocenediyl) and the mono(silylene) LNSi (N = 2-(methylamido)pyridine). For the bis(silylene) LSiFcSiL ligand, the divalent complexes [Ln{N(SiMe3)2}2(LSiFcSiL)] (Ln = Eu, Yb) were obtained, while for the mono(silylene) LNSi, divalent [Ln{N(SiMe3)2}2(LNSi)] (Ln = Eu, Yb) and the trivalent compounds [Ln{N(SiHMe2)2}3(LNSi)] (Ln = Y, La, Lu) were isolated. The thermal stability of these complexes differs considerably from that of the bis(silylene) complexes reported in our previous study, for which reduction-induced Si(II)-N bond cleavage of the bis(silylene) ligand was observed.