The behavior of pyrrolyl ligands within the rare-earth metal alkyl complexes. Insertion of C=N and C=O double bonds into Ln-sigma-C bonds

作者:Yang, Y,Cui, DM,Chen, XS
关键字:beta-diketiminato ligands; lactide polymerization; ethylene polymerization; structural-characterization; yttrium complexes; enantioselective hydroamination/cyclization; isospecific polymerization


This paper presents some unusual reactions of lanthanide tris(alkyl)s or lanthanide mono-Cp′ (Cp′ = (C5Me4)SiMe3) bis(alkyl)s with pyrrolyl ligands, and the η5- or η1-coordination mode of the pyrrolyl ring, as well as C[double bond, length as m-dash]N and C[double bond, length as m-dash]O double bonds insertion into Ln–σ-C moities. N,N,O-tridentate ligand HL1, 2-(2-CH3OC6H3N[double bond, length as m-dash]CH)–C4H3NH, was prepared. Treatment of HL1 with rare-earth metal tris(alkyl)s, Ln(CH2SiMe3)3(THF)2, generated centrosymmetric bimetallic (pyrrolylaldiminato)lanthanide mono(alkyl) complexes [{2-(2-CH3OC6H3NC(H)R)–C4H3N}LnR]2 (1a: Ln = Y; 1b: Ln = Lu) (R = CH2SiMe3). In this process, HL1 was deprotonated by the metal alkyl and its imino C[double bond, length as m-dash]N group was deactivated by the intramolecular alkylation, generating dianionic species that bridged the two metal alkyl units in η5/η1:κ1 modes. When the reaction was carried out in dimethoxyethane (DME), asymmetric complex [2-(2-CH3OC6H3NC(H)R)–C4H3N]2Y2R2(DME) (2) was given. Furthermore, the reaction of alkyl complex 1b and benzophenone (Ph2C[double bond, length as m-dash]O) afforded alkyl-insertion product [{2-(2-CH3OC6H3NC(H)R)–C4H3N}LuOC(R)Ph2]2 (3). Both the intermolecular alkylation and the pyrrole''s behavior as the hetero-cyclopentadienyl ligand were also observed in complexes 2 and 3. HL1reacted with (η5-Cp′)Y(CH2SiMe3)2(THF) (E) to form a mixed ligands supported alkyl complex [(η5-Cp′)(L1)]Y(CH2SiMe3)(THF) (4), whilst complex E was treated with 2-(2,6-iPr2C6H3N[double bond, length as m-dash]CH)–C4H3NH (HL2) to yield [(η5-Cp′)(L2)]Y(CH2SiMe3)(THF) (5). However, reaction of E and 2-(Me2NCH2)–C4H3NH (HL3) afforded Y[(η5-Cp′)(L3)2] (6), and ligand redistribution was found in this process. The molecular structures of complexes 5 and 6 were confirmed by X-ray diffraction, which indicated that the C[double bond, length as m-dash]N double bond survived and the pyrrolyl ring coordinated to the metal center in η1-mode.