Benzyllanthanide Chemistry: Revival of Manzer's ortho-Me2N-Benzyl Ligand

The Manzer benzyl ligand, ortho-Me2N-benzyl (DMA), has been introduced in lanthanide (Ln) chemistry more than three decades ago with the syntheses of Sc(DMA)(3) and Er(DMA)(3) but no reaction chemistry or structures have been described. Only recently it was shown that a Ln(DMA)(3) complex can also be obtained for the largest Ln metal lanthanum and first crystal structures appeared. At present crystal structures of many Ln(DMA)(3) complexes throughout the series have been determined and were found to be isomorphous. This reports describes the improvement of synthetic methods for Ln(DMA)(3) complexes, a discussion on structures and trends and more important, the wide scope of Ln(DMA)(3) reagents as versatile building-blocks in lanthanide chemistry: the fast-growing number of complexes and catalysts that have been made starting from a Ln(DMA)(3) reagent are summarized. Despite the intramolecular chelating Me2N arm, half-sandwich catalysts containing the DMA fragment are still active in alkene polymerizations or other catalytic conversions. The main advantages of Ln(DMA)(3) complexes are: i) easy syntheses from commercially available starting materials, ii) convenient crystallization which warrants high purity, iii) high stability on account of intramolecular coordination while sufficient reactivity for further conversions is maintained and iv) availability of these reagents over the full Ln range which is advantageous for catalyst screening.