Intramolecular (sp³-hybridized) C−H Activation: Yttrium Alkyls versus Transient Yttrium Hydrides

Abstract

Intramolecular sp3-hybridized C−H activation of novel yttrium alkyl and hydrido complexes supported by bulky aminopyridinato ligands derived from deprotonated 2,6-(diisopropylphenyl)-[6-(2,6-dimethylphenyl)pyridin-2-yl]amine (Ap‘-H) is reported. Reaction of YCl3 with a 2-fold molar excess of Ap‘K in THF afforded complex [Ap‘2YCl(thf)] (1). Alkylation of 1 with an equimolar amount of LiCH2SiMe3 in hexane allowed isolation of the alkylyttrium derivative [Ap‘2YCH2SiMe3(thf)] (2) in 65% yield. Unexpectedly treatment of complex 2 with PhSiH3 (toluene, 20 °C) afforded the product of intramolecular sp3-hybridized C−H bond activation, Ap‘(Ap‘-H)Y(THF) (3). Most likely a hydrid species is formed in the course of this reaction, which undergoes rapid C−H activation since 3 is formed from 2 directly about 500 times slower than in the presence of 1 equiv of PhSiH3. Molecular structures of complexes 2 and 3 have been confirmed by X-ray crystal structure analysis.