Reactivity of functionalized indoles with rare-earth metal amides. Synthesis, characterization and catalytic activity of rare-earth metal complexes incorporating indolyl ligands

摘要

The reactivity of several functionalized indoles 2-(RNHCH2)C8H5NH (R = C6H5 (1), Bu-t (2), 2,6-(Pr2C6H3)-Pr-i (3)) with rare-earth metal amides is described. Reactions of 1 or 2 with [(Me3Si)(2)N](3)RE(mu-Cl)Li(THF)(3) (RE = Eu, Yb) respectively produced the europium complexes [2-(C6H5N=CH)C8H5N](2)Eu[N(SiMe3)(2)] (4) and [2-((BuN)-Bu-t=CH)C8H5N]Eu[N(SiMe3)(2)](2) (5), and the ytterbium complex [2-((BuN)-Bu-t=CH)C8H5N](2)Yb[N(SiMe3)(2)] (6), containing bidentate anionic indolyl ligands via dehydrogenation of the amine to the imine. In contrast, reactions of the more sterically bulky indole 3 with [(Me3Si)(2)N](3)RE(mu-Cl)Li(THF)(3) afforded complexes [2-(2,6-(Pr2C6H3NCH2)-Pr-i)C8H5N]RE[N(SiMe3)(2)](THF)(2) (RE = Yb (7), Y (8), Er (9), Dy (10)) with the deprotonated indolyl ligand. While reactions of 3 with yttrium and ytterbium amides in refluxing toluene respectively gave the complexes [2-(2,6-(Pr2C6H3N)-Pr-i=CH)C8H5N](3)Y (11) and [2-(2,6-(Pr2C6H3N)-Pr-i=CH)C8H5N] Yb-2(II)(THF)(2) (12), along with transformation of the amino group to the imino group, and also with a reduction of Yb3+ to Yb2+ in the formation of 12. Reactions of 3 with samarium and neodymium amides provided novel dinuclear complexes {[mu-eta(5):eta(1):eta(1)-2-(2,6-(Pr2C6H3NCH2)-Pr-i)C8H5N]RE[N(SiMe3)(2)]}(2) (RE = Sm (13), Nd (14)) having indolyl ligands in mu-eta(5):eta(1):eta(1) hapticities. The pathway for the transformation of the amino group to the imino group is proposed on the basis of the experimental results. The new complexes displayed excellent activity in the intramolecular hydroamination of aminoalkenes.