Reactivity of homodinuclear rare-earth metal complexes with an indol-2-yl based pincer ligand toward nitrogen- and oxygen-containing compounds

Abstract

Diverse reactivity of homodinuclear rare-earth metal alkyl complexes with an indol-2-yl based pincer ligand (rare-earth metals = Gd, Dy, Y, Er, Yb, Lu) with nitrogen- and oxygen-containing organic compounds has been explored, resulting in isolation and characterization of a range of dinuclear rare-earth metal complexes with different functional groups. Donor substrates such as tBuCN, DMAP, or Ph₃P=O simply displaced the coordinated THF molecules in the complexes, while 1,2-dimethoxyethane (DME) resulted in the formation of a cis-dialkyl complex. The C–H activation of Ph2CHCN (α-C−H bond of nitrile), N-substituted imidazoles, o-carborane and the N−H bond activation of amines afford rare metal complexes featuring aza-allenyl moieties, unique amido-enolate dianions, o-carboryne-bridged species and a cis-configured bulky 2,6-diisopropylanilido moiety, respectively. Moreover, redox reactions between the metal complexes and Ph2X2 (X = S, Se) yield the corresponding dinuclear complexes bearing trans-configured phenylchalcogenolate groups. Notably, insertion of Ph₂CO or PhNCO into both the RE−CH₂SiMe₃ and RE–Cind bonds generates dinuclear complexes with distinct coordination environments. Novel imidazole- and bipyridine-indole functionalized groups were unpercedently obtained from the reactions of the metal complexes with N-phenyl imidazole and bipyridine. As a result, the indol-2-yl imido/amido pincer ligand provides a direct route to dinuclear complexes for probing bimetallic synergistic effects in catalysis.