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

摘要

This paper presents some unusual reactions of lanthanDEe tris(alkyl)s or lanthanDEe mono-Cp' (Cp' = (C5Me4)SiMe3)bis(alkyl)s with pyrrolyl ligands, and the eta(5)- or eta(1)-coordination mode of the pyrrolyl ring, as well as C=N and C=O double bonds insertion into Ln-sigma-C moities. N, N, O-trDEentate ligand HL1, 2-(2-CH3OC6H3N=CH)-C4H3NH, was prepared. Treatment of HL1 with rare-earth metal tris(alkyl)s, Ln(CH2SiMe3)(3)(THF)(2), generated centrosymmetric bimetallic (pyrrolylaldiminato)lanthanDEe 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=N group was deactivated by the intramolecular alkylation, generating dianionic species that brDEged the two metal alkyl units in eta(5)/eta(1):kappa(1) modes. When the reaction was carried out in dimethoxyethane (DME), asymmetric complex [2-(2-CH3OC6H3NC(H)R)-C4H3N](2)Y2R2(DME) (2) was given. Furthermore, the reaction of alkyl complex 1b and benzophenone (Ph2C=O) afforded alkyl-insertion product [{2-(2-CH3OC6H3NC(H)R)-C4H3N}LuOC(R)Ph-2](2) (3). Both the intermolecular alkylation and the pyrrole's behavior as the hetero-cyclopentadienyl ligand were also observed in complexes 2 and 3. HL1 reacted with (eta(5)-Cp')Y(CH2SiMe3)(2)(THF) (E) to form a mixed ligands supported alkyl complex [(eta(5)-Cp')(L-1)]Y(CH2SiMe3)(THF) (4), whilst complex E was treated with 2-(2,6-iPr(2)C(6)H(3)N=CH)-C4H3NH (HL2) to yield [(eta(5)-Cp')(L-2)]Y(CH2SiMe3)(THF) (5). However, reaction of E and 2-(Me2NCH2)-C4H3NH (HL3) afforded Y[(eta(5)-Cp')(L-3)(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=N double bond survived and the pyrrolyl ring coordinated to the metal center in eta(1)-mode.