Unusual selective reactivity of the rare-earth metal complexes bearing a ligand with multiple functionalities

International audience; Ligands play a key role in controlling activity of organometallic complexes so that development of new ligands to overcome the challenge is the main topic of modern chemistry. The first example of 1,1-hydride migratory insertion and intramolecular redox reaction has been realized in this work by applying a new ligand in rare-earth metal chemistry. The novel rare-earth metal complexes LMesRECH2TMS(THF) (RE = Y (1a), Dy (1b), Er (1c), Yb (1d), LMes = 1-(3-(2,6-iPr2C6H3N=CH)C8H4N)-CH2CH2-3-(2-CH2—4,6-Me2C6H2)-(N(CH)2NC), THF = tetrahydrofuran) bearing a ligand with imino, indolyl, NHC (N-heterocyclic carbene) multiple functionalities were synthesized and characterized. Treatment of complexes 1 with silanes (PhSiH3 or PhSiH2Me or PhSiD3) selectively produced the unprecedented 1,1-hydride (or deuterated H) migratory insertion of the indolyl moiety of the novel unsymmetrical dinuclear rare-earth metal complexes 2. The complex 2a reacts with Ph2C-O to give the selective C-O double bond insertion to the RE-Co-methylene-Mes bond product 3a which further reacts with another Ph2C-O (or DMAP, 4-N, N-dimethylaminopyridine) affording the novel μ-η2:η3-dianionic 3-iminoindolyl dinuclear rare-earth metal complex 4a. The latter is formed through an unusual intramolecular redox reaction (through electron migration from the 2-carbanion of the indolyl ring to the imino motif) resulting in the re-aromatization of the indolyl ring.