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