Organolanthanide Thermolysis Generates Ln/Al Tuck-Over Complexes and a 9,10-Dialumina-9,10-dihydroanthracenide Derivative

High Resolution Image Download MS PowerPoint Slide The synthesis of two new organoaluminum stabilized rare-earth-metal phenyl motifs is reported, featuring heterobimetallic Ln/Al tuck-over complexes Cp*Ln[C 5 Me 4 (CH 2 Al(μ–Ph)Ph 2 )] (Cp* = C 5 Me 5, Ln = Y, La, Lu) and 9,10-dialumina-9,10-dihydroanthracenido derivatives Cp*Ln[(μ-C 6 H 4 ) 2 Al 2 (μ–Ph)Ph 3 ] (Ln = Y, Lu). Prolonged thermal treatment of Cp* 2 Ln(AlMe 4 ) (Ln = Y, La, Lu) in benzene leads to stepwise methyl/phenyl exchange and then metalation of a Cp* methyl group and concomitant elimination of benzene to yield Ln/Al tuck-overcomplexes Cp*Ln[C 5 Me 4 (CH 2 Al(μ-Ph)Ph 2 )]. Isolated Cp* 2 Ln(AlPh 4 ) (Ln = Y, La) also reacts to Cp*Ln[C 5 Me 4 (CH 2 Al(μ-Ph)Ph 2 )] at elevated temperatures. Treatment of Cp*Ln[C 5 Me 4 (CH 2 Al(μ-Ph)Ph 2 )] (Ln = Y, Lu) with AlMe 3 results in a reverse phenyl/methyl exchange. THF breaks the Y–C(phenyl) bond in Cp*Y[C 5 Me 4 (CH 2 Al(μ-Ph)Ph 2 )] yielding zwitterionic complex Cp*Y(thf) 2 [C 5 Me 4 (CH 2 AlPh 3 )]. The 9,9,10,10-tetraphenyl-9,10-dialumina-9,10-dihydroanthracenido derivatives Cp*Ln[(μ-C 6 H 4 ) 2 Al 2 (μ–Ph)Ph 3 ] (Ln = Y, Lu) are either formed as very minor byproducts in the reaction of Cp* 2 Ln(AlMe 4 ) with benzene or upon treatment of the benzyl compounds Cp*Ln(CH 2 C 6 H 4 NMe 2 - o ) 2 with 5–6 equiv AlPh 3 . Mixed methyl/phenyl complexes Cp* 2 Lu(Me 2 AlPh 2 ), Cp* 2 La(MeAlPh 3 ), and phenyl complex Cp* 2 La(AlPh 4 ) were isolated from the methyl/phenyl exchange sequence when heating Cp* 2 Ln(AlMe 4 ) in benzene. Such thermally controlled benzene elimination from phenylaluminate complexes as highlighted by new structural motifs does not only extend rare-earth-metal phenyl chemistry but might inspire future investigations into inert bond activation with organolanthanide moieties at elevated temperatures.