Versatile reactivities of rare-earth metal dialkyl complexes supported by a neutral pyrrolyl-functionalized β-diketiminato ligand

Abstract

Herein, rare-earth metal dialkyl complexes supported by a neutral pyrrolyl-functionalized β-diketiminato ligand with the formula LRE(CH₂SiMe₃)₂(thf) (RE = Y (1a), Dy (1b), Er (1c), Yb (1d); L = MeC(NDipp)CHC(Me)NCH₂CH₂NC₄H₂-2,5-Me₂, Dipp = 2,6-ⁱPr₂C₆H₃) were synthesized via the reactions of the β-diketimine HL with the rare-earth metal trialkyl complexes RE(CH₂SiMe₃)₃(thf)₂ in high yields. The reactivities of 1 with pyridine derivatives, unsaturated substrates, and elemental sulfur were investigated, and some interesting chemical transformations were observed. Ligand exchange and activation of sp² and sp³ C–H bonds occurred during the reactions with pyridine derivatives to afford different types of mononuclear rare-earth metal pyridyl complexes, namely, LEr(CH₂SiMe₃)₂(η¹-NC₅H₄) (2c), LRE(η³-CH₂-2-NC₅H₂-4,6-Me₂)₂ (RE = Y (3a), Er (3c)), and LRE(CH₂SiMe₃)(η²-(C,N)-2-(2-C₆H₄NC₅H₄)) (RE = Er (4c), Yb = (4d)). Similarly, activation of the sp C–H bond occurred during the reaction of phenylacetylene with 1c to produce the dinuclear erbium alkynyl complex [LEr(CH₂SiMe₃)(μ-CCPh)]₂ (5c). The mixed amidinate-β-diketiminato ytterbium complex LYb[(Dipp)NC(CH₂SiMe₃)N(Dipp)](CH₂SiMe₃) (6d) was obtained by the insertion of bis(2,6-diisopropylphenyl)carbodiimide into a Yb-alkyl bond, as well as via the direct alkane elimination of a CH₂SiMe₃ moiety with bis(2,6-diisopropylphenyl)formamidine to afford the erbium complex LEr(DippNCHNDipp)(CH₂SiMe₃) (7c). A rare sp² C–H bond oxidation of the β-diketiminato backbone with elemental sulfur insertion was detected to provide the unprecedented dinuclear rare-earth metal thiolate complexes (LRE)₂(μ-SCH₂SiMe₃)₂(μ-SCC(Me)(NDipp)C(Me)NCH₂CH₂NC₄H₂Me₂-2,5) (RE = Y (8a), Er (8c)) in the reactions of S₈ with 1a and 1c, respectively. The molecular structures of the complexes 1–8 were determined by single-crystal X-ray diffraction analyses.