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- Title
Bis(β-diketiminato) lanthanide amides: synthesis, structure and.
- Authors
Zheng, Yu; Jiao, Rui; Shen, Xiao ‐ dong; Xue, Ming ‐ qiang; Yao, Ying ‐ ming; Zhang, Yong; Shen, Qi
- Abstract
Treatment of the chlorides (L2,6-iPr2Ph)2LnCl (L2,6-iPr2Ph = [(2,6- iPr2C6H3)NC(Me)CHC(Me)N(C6H5)]−) with 1 equiv. of NaNH(2,6- iPr2C6H3) afforded the monoamides (L2,6-iPr2Ph)2LnNH(2,6- iPr2C6H3) (Ln = Y ( 1), Yb ( 2)) in good yields. Anhydrous LnCl3 reacted with 2 equiv. of NaL2,6-iPr2Ph in THF, followed by treatment with 1 equiv. of NaNH(2,6- iPr2C6H3), giving the analogues (L2,6-iPr2Ph)2LnNH(2,6- iPr2C6H3) (Ln = Sm ( 3), Nd ( 4)). Two monoamido complexes stabilized by two L2-Me ligands, (L2-Me)2LnNH(2,6- iPr2C6H3) (L2-Me = [N(2-MeC6H4)C(Me)]2CH)−; Ln = Y ( 5), Yb ( 6)), were also synthesized by the latter route. Complexes 1, 2, 3, 4, 5, 6 were fully characterized, including X-ray crystal structure analyses. Complexes 1, 2, 3, 4, 5, 6 are isostructural. The central metal in each complex is ligated by two β-diketiminato ligands and one amido group in a distorted trigonal bipyramid. All the complexes were found to be highly active in the ring-opening of L-lactide (L-LA) and ε-caprolactone (ε-CL) to give polymers with relatively narrow molar mass distributions. The activity depends on both the central metal and the ligand (Yb < Y < Sm ≈ Nd and L2-Me < L2,6-iPr2Ph). Remarkably, the binary 3/benzyl alcohol (BnOH) system exhibited a striking 'immortal' nature and proved able to quantitatively convert 5000 equiv. of L-LA with up to 100 equiv. of BnOH per metal initiator. All the resulting PLAs showed monomodal, narrow distributions ( Mw/ Mn = 1.06 − 1.08), with molar mass ( Mn) decreasing proportionally with an increasing amount of BnOH. The binary 4/BnOH system also exhibited an 'immortal' nature in the of ε-CL in toluene. Copyright © 2014 John Wiley & Sons, Ltd.
- Subjects
RARE earth metals; AMIDE synthesis; LACTIDES; CAPROLACTONES; ORGANIC synthesis research; LIVING polymerization; ADDITION polymerization; POLYMERIZATION research
- Publication
Applied Organometallic Chemistry, 2014, Vol 28, Issue 6, p461
- ISSN
0268-2605
- Publication type
Article
- DOI
10.1002/aoc.3150