Multiple C-H bond activation in group 3 chemistry: synthesis and structural characterization of an yttrium-aluminum-methine cluster.

Complete donor-induced alkylaluminate cleavage of halfmetallocene complex CpY(AlMe4)2, that is, treatment of CpY(AlMe4)2 with 2 equiv of diethyl ether, produces [CpY(mu2-Me)2]3 in high yield (95%). In contrast, the equimolar reaction of CpY(AlMe4)2 with diethyl ether reproducibly formed complex [Cp4Y4(mu2-CH3)2{(CH3)Al(mu2-CH3)2}4(mu4-CH)2] in low yield (10-30%) via a multiple C-H bond activation. The synthesis of the heterooctametallic yttrium-aluminum-methine cluster was also accomplished in moderate yield (47%) by the equimolar reaction of discrete CpY(AlMe4)2 and [CpY(mu2-Me)2]3 in the absence of any donor solvent and "free" AlMe3. This gives strong evidence that preformed heterometal-bridged Y-CH3-Al moieties are prone to multiple hydrogen abstraction in the presence of a highly basic reagent such as [CpY(mu2-Me)2]3. The monocylopentadienyl complexes [CpY(mu2-Me)2]3 and [Cp4Y4(mu2-CH3)2{(CH3)Al(mu2-CH3)2}4(mu4-CH)2] were structurally characterized.