Synthesis and characterization of 2-t-butylimino-functionalized indolyl rare-earth metal amido complexes for the catalytic addition of terminal alkynes to carbodiimides: the dimeric complexes with the alkynide species in the mu-eta(1):eta(2) bonding modes

摘要

A series of new rare-earth metal amido complexes bearing a 2-t-butylimino-functionalized indolyl ligand were synthesized via dehydrogenation of a secondary amine, and their reactivities and catalytic performances were investigated. The reactions of 2-((BuNHCH2)-Bu-t)C8H5NH (1) with rare-earth metal amides [(Me3Si)(2)N](3)RE(mu-Cl)Li(THF)(3) afforded the complexes [2-((BuN)-Bu-t & xe001;CH)C8H5N]RE[N(SiMe3)(2)](2) (RE = Er (2), Y (3), Dy (4), Sm (5), Nd (6)) containing the bidentate ligand via dehydrogenation of the amine to the imine group. Complexes 2-6 exhibited an excellent catalytic activity for the addition of terminal alkynes to carbodiimides affording a series of corresponding N,N '-dialkyl-propiolamidines. The catalysts can also be efficiently used for the preparation of the sterically bulky N,N '-diaryl-propiolamidine. Furthermore, the dimeric complexes {(mu-eta(1):eta(2)-RC & xe002;C)RE[2-((BuN)-Bu-t & xe001;CH)C8H5N](2)}(2) (11: RE = Y, R = Ph; 12: RE = Yb, R = SiMe3), with the alkynyl ligand in the mu-eta(1):eta(2) haptic modes, were isolated in attempts to study the catalytic mechanism.