Alkyl-bridged complexes of the d- and f-block elements. Part 2. Bis[bis(η-cyclopentadienyl)methylmetal(III)] complexes, and the crystal and molecular structure of the yttrium and ytterbium species

The reaction of [(η-C5H5)2MMe2AlMe2](M = Y, Dy, Ho, Er, Tm, or Yb) and pyridine in equimolar amounts gives a series of complexes [{M(η-C5H5)2Me}2] assigned a dimeric structure on the basis of 1H and 13C n.m.r. (M = Y) and i.r. data, and by crystal and molecular structural determinations of [{M(η-C5H5)2Me}2](M = Y or Yb). A similar reaction of [(η-C5H5)2ScMe2AlMe2] with a Lewis base L gives [Sc(η-C5H5)2Me(L)](L = pyridine or tetrahydrofuran). Other reactions described are of [{Y(η-C5H5)2Me}2] with Lewis bases (an amine, phosphine, or phosphine oxide) or with a Lewis acid [Al2MenCl6 –n](n= 2, 4, or 6). A single-crystal X-ray analysis of the isostructural [{M(η-C5H5)2Me}2] has been carried out to R 0.048 (Y) or 0.066 (Yb) and R′ 0.055 (Y) or 0.061 (Yb); the complexes have an approximately tetrahedral metal environment (space group P21/n) with the YMe2Y unit in the yttrium complex remarkably similar to AlMe2Al in [Al2Me6]. Important average bond lengths (Å) and angles for the yttrium complex (Yb in parentheses) are: Y–C (cyclopentadienyl) 2.655(18)[2.613(13)] and Y–Me 2.545(11)[2.511(35)]; Y–C–Y 87.7(3)[86.6(3)] and Me–Y–Me 92.3(3)[93.4(4)].