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

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 L Mes RECH 2 TMS(THF) (RE = Y ( 1a ), Dy ( 1b ), Er ( 1c ), Yb ( 1d ), L Mes = 1-(3-(2,6- i Pr 2 C 6 H 3 N=CH)C 8 H 4 N)-CH 2 CH 2 -3-(2-CH 2 —4,6-Me 2 C 6 H 2 )-(N(CH) 2 NC), THF = tetrahydrofuran) bearing a ligand with imino, indolyl, NHC ( N -heterocyclic carbene) multiple functionalities were synthesized and characterized. Treatment of complexes 1 with silanes (PhSiH 3 or PhSiH 2 Me or PhSiD 3 ) 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 Ph 2 C-O to give the selective C-O double bond insertion to the RE-C o -methylene-Mes bond product 3a which further reacts with another Ph 2 C-O (or DMAP, 4- N, N -dimethylaminopyridine) affording the novel μ-η 2 : η 3 -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.