Synthesis and Reactivity of the Rare-Earth Metal Complexes Bearing the Indol-2-yl-Based NCN Pincer Ligand.

The pincer rare-earth dialkyl complexes [ κ 3 - L RE(CH 2 SiMe 3 ) 2 (RE = Lu( 1a ), Yb( 1b ), Er( 1c ), Y( 1d ), Dy( 1e ))] with the indol-2-yl-based NCN pincer ligand were synthesized by the reactions of the proligand HL ( L = 1-Me 2 NCH 2 CH 2 -3-(2- i PrC 6 H 5 N═CH)C 8 H 4 N) with RE(CH 2 SiMe 3 ) 3 (THF) 2 . These complexes exhibited a variety of reactivities toward organic compounds such as amines, triphenylphosphine ylide, N -phenylimidazole, pyridine derivatives, and o -carborane leading to σ -bond metathesis, migration insertion, and redox reaction products. The reactions of the dialkyl rare-earth metal complexes with o -carborane afforded the novel NCN pincer-ligated carboryne-based metallacyclopropanes which reacted with diphenyl ketone to give insertion products of the RE-C 2-ind and one of the RE-C cage bonds, while the reaction of the carboryne-based metallacyclopropanes with diphenyldiazomethane produced the di- aza -metallacyclopentanes via the insertions of the N═N bond of the diphenyldiazomethane into two RE-C cage bonds and the RE-C 2-ind bond. The reactions of the dialkyl complexes with 2 equiv of 2,2'-bipyridine afforded the pincer-ligated bis(2,2'-bipyridyl monoanionic radical) complexes via the homolytic redox reaction.