µ-Dialkyl inner transition metal(III) tetra-alkylaluminates; the crystal and molecular structure of di-µ-methyl-(dimethylaluminium)biscyclopentadienylyttrium and -ytterbium

Abstract

The crystalline title compounds, [M(C₅H₅-η)₂R₂AlR₂](R = Me and M = Sc, Gd, Dy, Ho, Er, Tm, or Yb; R = Et and M = Sc or Y), were obtained by reaction of [M(C₅H₅-η)₂Cl]₂ and Li[AlR₄] in toluene; the presence of the double alkyl bridge between M and Al was established by ¹H and ¹³C n.m.r. spectra of the Sc and Y compounds {[Y(C₅H₅-η)₂Et₂AlEt₂], unlike the Sc analogue, is fluxional at room temperature showing rapid bridge and terminal Et exchange}, and single-crystal X-ray analysis for the Y and Yb tetramethylaluminates.