η6-Arene(halogenidoaluminato)lanthanoid(III) Complexes: Synthesis, Characterization and Catalytic Activity for Isoprene Polymerization

eta(6)-Arene(iodido-/bromido-aluminato)lanthanoid(III) complexes, [Ln(eta(6)-C6H5Me)(AlI4)(3)] [Ln=La (1), Ce (2), Nd (3), (Gd) (4); C6H5Me=toluene], [Ln(eta(6)-C6H3Me3-1,3,5)(AlI4)(3)] [Ln=La (5), Ce (6), Pr (7), Nd (8), Sm (9), Gd (10); C6H3Me3-1,3,5=mesitylene], and [Ln(eta(6)-C6H5Me)(AlBr4)(3)] [Ln=La (11), Nd (12), Sm (13)] were prepared by reactions of aluminium triiodide or aluminium tribromide with the corresponding lanthanoid metals and 1,2-diiodoethane or 1,2-dibromoethane in an arene (toluene or mesitylene) solution (molar ratio : 6 : 2 : 3). The first X-ray crystal structures of arene(iodidoaluminato)lanthanoid(III) complexes are reported. The lanthanoid atom is coordinated by an eta(6)-arene and three chelating kappa(I, I')-tetraiodidoaluminato ligands. The tetrabromidoaluminate complexes have similar structures. The precatalyst 3 was treated with AlR3 (R=Me or iBu) to give [Nd(eta(6)-C6H5Me)(AlI3R)(3)] species in situ, which were then tested for catalytic activity towards isoprene polymerization. Although the resulting polyisoprene had a desirable high cis-1,4 content, the catalyst performance was well below known best performing systems and indicates that iodidoaluminates are the least favorable of the halogenidoaluminatolanthanoid(III) complexes.

Automated summary

Eta(6)-arene(iodido-/bromido-aluminato)lanthanoid(III) complexes were prepared by reacting aluminium triiodide or aluminium tribromide with corresponding lanthanoid metals and halogenated ethanes in an arene solution. The first X-ray crystal structures of these complexes were reported. The lanthanoid atom in the complexes is coordinated by an eta(6)-arene and three chelating tetrahalidoaluminato ligands. However, the catalytic performance of these complexes towards isoprene polymerization was found to be lower compared to other halogenidoaluminatolanthanoid(III) complexes.