Controlled synthesis of mononuclear or binuclear aryloxo ytterbium complexes supported by β-diketiminate ligand and their activity for polymerization of ε-caprolactone and L-lactide

Abstract

The reaction of monomeric [(DIPPh)(2)nacnac]YbCl(2)(THF)(2) ((DIPPh)(2)nacnac = N,N-diisopropylphenyl-2,4-pentanediimineanion) with NaOAr (OAr = 2,6-diisopropylphenoxide) in THF afforded the mononuclear complexes [(DIPPh)(2)nacnac]Yb(OAr)Cl(THF) 1 and [(DIPPh)(2)nacnac]Yb(OAr)(2) 2 depending on the molar ratio of dichloride to sodium salt, while the same reaction with NaOAr' (OAr' = 2,6-dimethylphenoxide) in toluene yielded the binuclear complex [{(DIPPh)(2)nacnac}Yb(OAr')](2)(mu-Cl)(2) 3. Treatment of [(DIPPh)(2)nacnac]Yb(THF)(mu-Cl)(3)Yb(Cl)[(DIPPh)(2)nacnac] with NaOAr and NaOAr', respectively, in toluene yielded selectively the corresponding binuclear complexes {[(DIPPh)(2)nacnac]Yb(OAr)(mu-Cl)(3)Yb[(DIPPh)(2)nacnac](THF)} 4 and {[(DIPPh)(2)nacnac]Yb(OAr')(mu-Cl)(3)Yb[(DIPPh)(2)nacnac](THF)} 5 in high yields. All complexes were structurally characterized. Complex 2 was found to be a highly active initiator for both polymerizations of epsilon-caprolactone (epsilon-CL) and L-lactide. All monoaryloxide complexes can initiate the polymerization of epsilon-CL in a controlled manner giving polymers with narrow molecular weight distributions (M(w)/M(n) around 1.06) with relatively low activity relative to complex 2.

β‐Diketiminatoytterbium aryloxides: synthesis, structural characterization, and catalytic activity for addition of amines to carbodiimides

“…One nitrogen atom of the β‐diketiminato ligand (N(2)), the oxygen atom of aryloxido and the chlorine atom form the equatorial vertices (the sum of these bond angles is 359.5°), another nitrogen atom (N(1)) and the O(2) of the THF ligand occupy the apical positions with the angle of N(1)YbO(2) being 168.7(3)°. The coordination geometry of 1 is similar to those of the analogous Yb complexes reported . The average YbN distance of 2.302(8) Å is shorter than 2.323(4) Å in L'Yb(OAr 1 )Cl(THF) 67 and 2.319(2) Å in L'Yb(OAr 2 )Cl(THF).…”

“…β‐Diketiminato anions, as one of the most important non‐cyclopentadienyl ligands, have been widely used in organometallic and coordination chemistry of lanthanide metals due to their easily accessed and tunable steric and electronic effects . Several lanthanide aryloxides bearing a β‐diketiminato ligand, LYb[2,6‐ t Bu 2 C 6 H 3 O]Cl(THF) (L = [N(2,6‐Me 2 C 6 H 3 )C(Me)] 2 CH − ), L'Yb(OAr 2 )Cl(THF) (L' = [N(2,6‐ i Pr 2 C 6 H 3 )C(Me)] 2 CH − , Ar 2 = [2,6‐ i Pr 2 C 6 H 3 ]) and L'Yb(OAr 2 ) 2 have been prepared and found to serve as efficient initiators for ring‐opening polymerization of ε‐caprolactone and lactide in a living fashion. To explore their application as pre‐catalysts in organic synthesis, we investigated the syntheses and molecular structures of novel β‐diketiminato ytterbium aryloxides and tested their catalytic activity in the addition of amines to carbodiimides to guanidines.…”

β‐Diketiminato Rare‐Earth Metal Complexes: The Influence of Monoatomic Substituents in the N‐aryl Moieties on Structures and Properties

“…Cui's group successfully employed β‐diketiminato rare‐earth metal complexes as precursors for cis ‐1,4‐selective polymerization of isoprene and isoselective coordination polymerization of polar heteroatom‐substituted styrene derivatives . Yao and co‐workers exploited a variety of β ‐diketiminate rare‐earth metal complexes . Based on the studies in the past, tuning electronic and steric nature of β‐diketiminate ligands has been focused on variation of alkyl (Me, Et, i Pr) on the N‐aryl moieties, while halogen substituents on the N‐aryl moieties have not been utilized for the synthesis of rare‐earth metal complexes, to the best of our knowledge.…”

Synthesis and Characterization of β-Diketimine Schiff Base Complexes with Ni(II) and Zn(II) Ions: Experimental and Theoretical Study

“…Diimines, as 1,2-diimine (α-diimine) [9] or 1,3-diimine (β-diimine) [10,11], are applicable as ligands in the synthesis of a high variety of coordination complexes featuring diverse transition metals [1]. In this respect, for example, (α-diimine) ruthenium complexes can be applied in diverse areas such as solar energy conversion, sensor technology, homogeneous catalysis, biomedical research, supramolecular chemistry, and molecular electronics [12]. e β-diketiminate zinc complexes were used as catalysts for intramolecular hydroamination [13].…”