Hydrosilylation of dienes by yttrium hydrido complexes containing a linked amido-cyclopentadienyl ligand

Abstract

The dimeric hydrido complex [Y(L)(THF)(μ-H)]₂ (2) containing the CH₂SiMe₂-linked amido-cyclopentadienyl ligand L = C₅Me₄CH₂SiMe₂NCMe₃²⁻ catalyzed the hydrosilylation of 1,5-hexadiene, 1,7-octadiene and vinylcyclohexene by PhSiH₃. As demonstrated for 1,7-octadiene, the product distribution of the hydrosilylation strongly depends on the molar ratio of the reagents. In the absence of PhSiH₃, the stoichiometric reaction of 2 with 1,5-hexadiene gave the isolable crystalline cyclopentylmethyl complex [Y(L){CH₂CH(CH₂)₄}(THF)] (3). Internal olefins such as trans-stilbene and alkynes such as tert-butylacetylene were not hydrosilylated by 2. trans-Stilbene was inserted into the yttrium–hydride bond of 2 to give the 1,2-diphenylethyl complex [Y(L){CH(CH₂Ph)Ph}(THF)] (4). tert-Butylacetylene reacted with 2 to give the dimeric acetylide [Y(L)(CCCMe₃)]₂ (5). In an attempt to detect the monomeric hydrido species as a DME adduct [Y(L)H(DME)], complex 2 was reacted with DME to form the sparingly soluble, dimeric 2-methoxyethoxy complex [Y(L)(μ-OCH₂CH₂OMe-κO)]₂ (6) under C–O splitting.