Highly efficient hydrosilylation of alkenes by organoyttrium catalysts with sterically demanding amidinate and guanidinate ligands

The sterically demanding guanidine ArNHC(Me(2))NAr (Ar = 2,6-diisopropylphenyl, HL) reacts with Y(CH(2)SiMe(3))(3)(THF)(2) to give the yttrium dialkyl complex (L)Y(CH(2)SiMe(3))(2)(THF) (1), which was structurally characterized. Electronic interaction of the -NMe(2) 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(CH(2)SiMe(3))(2)(THF) (2) are highly active and selective catalysts for alkene hydrosilylation with PhSiH(3) (tof > 600 h(-1) at 23 degrees 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.