A Tris(alkyl)yttrium Compound Containing Six β-agostic Si-h Interactions

摘要

The new homoleptic rare earth compound [Y(C(SiHMe_2)_3)_3] (2) is prepared in 82% yield by salt metathesis of YCl_3 and 3 equivalents of [KC(SiHMe_2)_3] (1); two β-agostic Y …(H-Si) interactions are observed for each C(SiHMe_2)_3 ligand in 2, giving six agostic interactions per yttrium(III) center.rnβ-Agostic alkyl structures are intermediate between metal hydrido(olefin) and alkyl ligands, and their characteristic infrared (V_(CH) ～ 2250-2800 cm~(-1)) and NMR (~1J_(CH) ～ 50-100 Hz) spectroscopic features support this picture. More specifically, in d~0 agostic compounds, the interaction is better described by delocalization of the M-C_x bonding electrons to include the β-carbon. Several common features are observed in the bonding of β-agostic alkyl groups: the delocalized interactions are typically weak (< 10 kcal mol~ (-1)) and easily disrupted by the coordination of stronger donor ligands such as tetrahydro-furan. Usually only one metal-carbon(β) interaction occurs per alkyl ligand.