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Heteroleptic lanthanide amide complexes bearing carbon-bridged bis(phenolate) ligands: synthesis, structure and their application in the polymerization of ε-caprolactone
A convenient method for the synthesis of anionic lanthanide amide complexes bearing carbon-bridged bis(phenolate) ligands H 2 L [L = ( o -CH 3 )PhCH(C 6 H 2 -3- t Bu-5-R-2-O) 2 ; R = Me, L = L 1 and R = t Bu, L = L 2 ] is described. The bis(phenolato)lanthanide complexes LLnN(SiMe 3 ) [L = L 1 , Ln...
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| Published in: | RSC advances 2016, Vol.6 (27), p.22269-22276 |
|---|---|
| Main Authors: | , , , , , |
| Format: | Article |
| Language: | English |
| Citations: | Items that this one cites Items that cite this one |
| Online Access: | Get full text |
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| Summary: | A convenient method for the synthesis of anionic lanthanide amide complexes bearing carbon-bridged bis(phenolate) ligands H
2
L [L = (
o
-CH
3
)PhCH(C
6
H
2
-3-
t
Bu-5-R-2-O)
2
; R = Me, L = L
1
and R =
t
Bu, L = L
2
] is described. The bis(phenolato)lanthanide complexes LLnN(SiMe
3
) [L = L
1
, Ln = La (
1
), Ln = Gd (
2
) and L = L
2
, Ln = La (
3
), Ln = Gd (
4
)] were synthesized in nearly quantitative yields by the reaction of Ln[N(SiMe
3
)
2
]
3
(Ln = La or Gd) with H
2
L in a 1 : 1 molar ratio in THF at 60 °C. The bis(phenolato)lanthanide pyrazolato complexes LLnPzMe
2
(THF)
3
[L = L
1
, Ln = La (
5
), Ln = Gd (
6
) and L = L
2
, Ln = La (
7
), Ln = Gd (
8
)] were obtained in high yields by further reacting the obtained LLnN(SiMe
3
) with another 1 equiv. of 3,5-dimethylpyrazole (Me
2
PzH). Meanwhile, the complexes LLnPzMe
2
can also be synthesized by the direct reaction of Ln[N(SiMe
3
)
2
]
3
with H
2
L and Me
2
PzH in 1 : 1 : 1 molar ratio
in situ
in THF. Complexes
5–8
have been characterized by X-ray crystal structural analysis. The central lanthanide metal atom is seven-coordinated by one bis(phenolate) ligand, one pyrazole ligand and three THF molecules in a distorted pentagonal bipyramid. The catalytic activity of compounds
1–8
in the ring-opening polymerization of ε-caprolactone was studied. The catalytic mechanism was studied and discussed as well. |
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| ISSN: | 2046-2069 2046-2069 |
| DOI: | 10.1039/C5RA23520K |