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

Abstract

Intramolecular sp 3 -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 YCl 3 with a 2-fold molar excess of Ap‘K in THF afforded complex [Ap‘ 2 YCl(thf)] ( 1 ). Alkylation of 1 with an equimolar amount of LiCH 2 SiMe 3 in hexane allowed isolation of the alkylyttrium derivative [Ap‘ 2 YCH 2 SiMe 3 (thf)] ( 2 ) in 65% yield. Unexpectedly treatment of complex 2 with PhSiH 3 (toluene, 20 °C) afforded the product of intramolecular sp 3 -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 PhSiH 3 . Molecular structures of complexes 2 and 3 have been confirmed by X-ray crystal structure analysis.