Highly Efficient Hydrosilylation of Alkenes by Organoyttrium Catalysts with Sterically Demanding Amidinate and Guanidinate Ligands

The sterically demanding guanidine ArNHC(NMe2)NAr (Ar = 2,6-diisopropylphenyl, HL) reacts with Y(CH2SiMe3)3(THF)2 to give the yttrium dialkyl complex (L)Y(CH2SiMe3)2(THF) (1), which was structurally characterized. Electronic interaction of the −NMe2 group with the conjugated ligand backbone can be inferred from structural and spectroscopic data. The new yttrium guanidinate complex 1 and its related amidinate analogue [PhC(NAr)2]Y(CH2SiMe3)2(THF) (2) are highly active and selective catalysts for alkene hydrosilylation with PhSiH3 (tof > 600 h−1 at 23 °C). For unfunctionalized olefins, full selectivity toward anti-Markovnikov products was obtained. The more electron donating guanidinate ligand affords the highest activities with heteroatom-functionalized substrates.