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Synthesis and characterization of dinuclear rare-earth complexes supported by amine-bridged bis(phenolate) ligands and their catalytic activity for the ring-opening polymerization of l-lactideCCDC 1471736-1471747. For crystallographic data in CIF see DOI: 10.1039/c6dt01486k
Erscheinungsjahr
2016-06
Quelle
Alma/SFX Local Collection
Beschreibungen/Notizen
Reactions of amine-bridged bis(phenolate) protio-ligands
N
,
N
-bis(3,5-di-
tert
-butyl-2-hydroxybenzyl)aminoacetic acid (L
1
-H
3
) and
N
,
N
-bis[3,5-bis(α,α′-dimethylbenzyl)-2-hydroxybenzyl]aminoacetic acid (L
2
-H
3
), with 1 equiv. M[N(SiMe
3
)
2
]
3
(M = La, Nd, Sm, Gd, Y) in THF at room temperature yielded the neutral rare-earth complexes [M
2
(L)
2
(THF)
4
] (L = L
1
, M = La (
1
), Nd (
2
), Sm (
3
), Gd (
4
), Y (
5
); L = L
2
, M = La (
6
), Nd (
7
), Sm (
8
), Gd (
9
), Y (
10
)). All of these complexes were characterized by single-crystal X-ray diffraction, elemental analysis and in the case of yttrium and lanthanum complexes,
1
H NMR spectroscopy. The molecular structure of
1
revealed dinuclear species in which the eight-coordinate lanthanum centers were bonded to two oxygen atoms of two THF molecules, to three oxygen atoms and one nitrogen atom of one L
1
ligand, and two oxygen atoms of the carboxyl group of another. Complexes
2-10
were also dinuclear species containing seven-coordinate metal centers similar to
1
, albeit with bonding to one rather than two carboxyl group oxygens of another ligand. Further treatment of
1
with excess benzyl alcohol provided dinuclear complex [La
2
(L
1
)
2
(BnOH)
6
] (
11
), in which each lanthanum ion is eight-coordinate, bonded to three oxygen atoms and one nitrogen atom of one ligand, three oxygen atoms of three BnOH molecules, as well as one oxygen atom of bridging carboxyl group of the other ligand. In the presence of BnOH, complexes
1-10
efficiently catalyzed the ring-opening polymerization of
l
-lactide in a controlled manner and gave polymers with relatively narrow molecular weight distributions. The kinetic and mechanistic studies associated with the ROP of
l
-lactide using
1
/BnOH initiating system have been performed.
Neutral rare-earth complexes [M
2
(L)
2
(THF)
4
] have been synthesized. Their activities toward the ring-opening polymerization of
l
-lactides will be presented.
Sprache
–
Identifikatoren
ISSN: 1477-9226
eISSN: 1477-9234
DOI: 10.1039/c6dt01486k
Titel-ID: cdi_rsc_primary_c6dt01486k
Format
–
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