Synthesis, structure, and catalytic activity of novel trinuclear rare-earth metal amido complexes incorporating μ–η5:η1 bonding indolyl and μ3-oxo groups

Abstract

The reactions of different pyrrolyl-functionalized indoles with rare-earth metal(III) amides [(Me₃Si)₂N]₃RE^III(μ-Cl)Li(THF)₃ (RE = Yb, Er, Dy, Eu, Y) produced different kinds of rare-earth metal amido complexes. Reactions of N-((1H-pyrrol-2-yl)methylene)-2-(1H-indol-3-yl)ethanamine with rare-earth metal amides [(Me₃Si)₂N]₃RE^III(μ-Cl)Li(THF)₃ (RE = Yb, Er, Dy, Eu, Y) in toluene or THF at temperatures of 75–80 °C afforded the novel trinuclear rare-earth metal amido complexes incorporating the indolyl ligand in μ–η⁵:η¹ bonding modes and a μ₃-O group, which is believed to originate from cleavage of the THF ring based on experimental results. Reactions of 2-(1H-indol-3-yl)-N-((1-methyl-1H-pyrrol-2-yl)methylene)ethanamine with rare-earth metal(III) amides [(Me₃Si)₂N]₃RE^III(μ-Cl)Li(THF)₃ (RE = Yb, Dy) produced mononuclear ytterbium and dysprosium amides having the indolyl ligand in an η¹ bonding fashion. The results indicate that substituents not only have an influence on reactivity, but also have an influence on the bonding of the indolyl ligands with metals. The catalytic activities of the novel lanthanide amido complexes for the hydrophosphonylation of both aromatic and aliphatic aldehydes and ketones were explored. The results indicate that these complexes display a high catalytic activity for the C–P bond formation under mild conditions when using low catalyst loadings (0.1 mol% for aldehydes and ketones). Thus, it provides a potential way to prepare α-hydroxy phosphonates.