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

η6‐Arene(iodido‐/bromido‐aluminato)lanthanoid(III) complexes, [Ln(η6‐C6H5Me)(AlI4)3] [Ln=La (1), Ce (2), Nd (3), (Gd) (4); C6H5Me=toluene], [Ln(η6‐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(η6‐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 η6‐arene and three chelating κ(I, I′)‐tetraiodidoaluminato ligands. The tetrabromidoaluminate complexes have similar structures. The precatalyst 3 was treated with AlR3 (R=Me or iBu) to give [Nd(η6‐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. Lanthanoid (III) iodido‐/bromido‐aluminato η6‐arene complexes, [Ln(η6‐C6H5Me)(AlI4)3], [Ln(η6‐C6H3Me3‐1,3,5)(AlI4)3], and [Ln(η6‐C6H5Me)(AlBr4)3 were prepared and structurally characterized. The catalytic activity of [Nd(η6‐C6H5Me)(AlI4)3] towards isoprene polymerization has also been investigated.