Rare-earth metal bis(alkyl) amidopyridinate complexes in dehydrocoupling of anisole with hydrosilanes

Abstract

The reaction of equimolar amounts of Gd(CH₂SiMe₃)₃(THF)₂ and 2,6-Pr₂ⁱC₆H₃N(H)-CH₂C(CH₂Ph)₂-2-C₅H₄N (ApH) afforded the new bis(alkyl) complex ApGd-(CH₂SiMe₃)₂(THF) coordinated by the amidopyridinate ligand. The structure of the complex was determined by X-ray diffraction. The new compound and its Y- and Lu-containing analogs were studied as catalysts for the dehydrocoupling of alkoxyarenes with hydrosilanes (2: 1 molar ratio, toluene, 90 °C). The bis(alkyl) complexes ApLn(CH₂SiMe₃)₂(THF) (Ln = Y (1), Lu (2), Gd (3)) exhibited low catalytic activity in the dehydrocoupling of anisole with hydrosilanes, providing a conversion of 14–31% within 24 h. However, the use of cationic alkyl complexes, which were generated in situ from [Ph₃C][B(C₆F₅)₄] and complexes 1–3 (1: 1 molar ratio), as catalysts made it possible to significantly increase the reaction rate and the yield of dehydrocoupling products (78% within 24 h) under similar conditions. In all cases, the selective silylation of the arene substrates was observed, resulting in the formation of a new Si—C bond exclusively in the ortho position with respect to the alkoxy substituent on the aromatic ring.