Low-Coordinate Organoyttrium Complexes Supported by β-Diketiminato Ligands

Several organoyttrium complexes stabilized by β-diketiminato ligands (Ar)NC(R)CHC(R)N(Ar) (Ar = 2,6-ⁱPr₂C₆H₃; R = CH₃ (ligand a), R = ⁱBu (ligand b)) have been prepared. Ligand-supported yttrium diiodides LYI₂(THF)_n were alkylated with organolithium or potassium reagents, yielding low-coordinate bis-alkyl derivatives. Several of these compounds have been characterized by X-ray crystallography, and a discussion of these structures in comparison to similar scandium complexes is presented. An out-of-plane bonding mode is observed in the solid state, analogous to that seen in scandium bis-alkyls, and spectroscopic studies reveal that fluxional behavior in solution is also comparable to that observed for the scandium species. The bis-alkyls LYR₂ are susceptible to metalative alkane elimination at room temperature in solution. Activation of (Liga)YR₂ with [HNMe₂Ph][B(C₆F₅)₄] generates alkyl cations stabilized with η⁶-arene-bound NMe₂Ph. This unique coordination mode was studied via 1D ¹H, ¹³C, and ¹⁵N NMR and 2D ROESY spectroscopy and appears to stabilize the alkyl cations against metalative alkane elimination.