Benzyllanthanide Chemistry: Revival of Manzer’s ortho‐Me₂N‐Benzyl Ligand

Abstract

The Manzer benzyl ligand, ortho-Me 2 N-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 La 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 Me 2 N-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.

Physical Properties of Superbulky Lanthanide Metallocenes: Synthesis and Extraordinary Luminescence of [EuII(CpBIG)2] (CpBIG=(4‐nBu‐C6H4)5‐Cyclopentadienyl)

“…Therefore we set out to prepare [Eu(dma) 3 ] (DMA=2‐dimethylaminobenzyl) by reaction of three equivalents of the potassium salt of DMA with water‐free EuCl 3 in THF. Whereas this salt metathesis route proved to be convenient for a large variety of Ln metals (Ln=Sc, Y, La, Pr, Nd, Sm, Gd, Dy, Ho, Er, Tm, Yb, Lu),17–18 we were unable to obtain a hydrocarbon‐soluble product in this case. Instead we got an insoluble orange precipitate that, after quenching with CD 3 OD, gave the deuterated product 1‐Me 2 N‐2‐CH 2 D‐benzene.…”

Exploiting σ/π Coordination Isomerism to Prepare Homologous Organoalkali Metal (Li, Na, K) Monomers with Identical Ligand Sets

“…The chemical shift of the para C À H is also highly indicative of charge delocalization, [31] since as the metal migrates away from the CH 2 group and towards the aromatic ring, the interaction between the metal and the aromatic system increases. This is clearly the case in this series as Table 2 shows, with a considerable upfield shift occurring for the para C and H resonances on going from 1 to 3.…”

Electronic, Steric, and Ligand Influence on the Solid‐State Structures of Substituted Sodium and Potassium Anilides

“…Phenylamides (anilides) and benzyl anions are isoelectronic, and they are expected to exert a similar influence on the negative charge delocalization on the NMR parameters. [28] The degree of charge delocalization strongly de-pends on the hybridization of the amido nitrogen atom: the negative charge is mainly located on sp 3 -hybridized N atoms, whereas an effective charge backdonation is realized with sp 2 -hybridized amido functionalities. In agreement with this concept, the δ( 1 H) values of the para-CH fragments of the amides show significant high-field shifts due to backdonation of negative charge from the amido functionalities compared to the free amines.…”