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Bis(amido) rare-earth complexes coordinated by tridentate amidinate ligand: synthesis, structure and catalytic activity in the polymerization of isoprene and -lactide
A series of bis(amido) complexes of rare earth metals {2-[Ph 2 P(O)]C 6 H 4 NC( t Bu)N(2,6-Me 2 C 6 H 3 )}Ln(N(SiMe 3 ) 2 ) 2 , (Ln = Y ( 2 ), Nd ( 3 ), La ( 4 )) was synthesized using the amine elimination reaction of Ln[N(SiMe 3 ) 2 ] 3 (Ln = Y, Nd, La) and parent amidine 1 in THF, and the product...
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| Published in: | RSC advances 2016-02, Vol.6 (22), p.17913-1792 |
|---|---|
| Main Authors: | , , , , , |
| Format: | Article |
| Language: | |
| Online Access: | Get full text |
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| Summary: | A series of bis(amido) complexes of rare earth metals {2-[Ph
2
P(O)]C
6
H
4
NC(
t
Bu)N(2,6-Me
2
C
6
H
3
)}Ln(N(SiMe
3
)
2
)
2
, (Ln = Y (
2
), Nd (
3
), La (
4
)) was synthesized using the amine elimination reaction of Ln[N(SiMe
3
)
2
]
3
(Ln = Y, Nd, La) and parent amidine
1
in THF, and the products were isolated in 60 (
2
), 61 (
3
) and 72% (
4
) yields, respectively. The X-ray studies revealed that complexes
2-4
are solvent-free and feature intramolecular coordination of the Ph
2
P&z.dbd;O group to the Ln ion. Complexes
2-4
were investigated as precatalysts for isoprene polymerization. The ternary systems
2-4
/borate/AlR
3
(AlR
3
= AliBu
3
, AliBu
2
H; borate = [Ph
3
C][B(C
6
F
5
)
4
], [PhNHMe
2
][B(C
6
F
5
)
4
]) were found to be active in isoprene polymerization and enable complete conversion of 1000 equivalents of monomer into polymer at 25 °C within 1-24 h affording polyisoprenes with polydispersities
M
w
/
M
n
= 1.12-9.46. The effect of the organoaluminium component and [Ln]/[AlR
3
] ratio on the catalytic activity and selectivity of the ternary catalytic systems was investigated. Complexes
2-4
proved to be efficient catalysts for the ring-opening polymerization of
rac
-lactide, which allow conversion of up to 500 equivalents of monomer into a polymer at room temperature within 30 min and afford atactic polylactides with high molecular weights and moderate molecular-weight distributions (1.29-2.12). Complexes
2-4
appear to be well-suited for achieving immortal polymerization of lactide, through the introduction of large amounts of isopropanol as a chain-transfer agent.
Rare-earth bis(amides) {2-[Ph
2
Р(O)]C
6
H
4
NC(
t
Bu)N(2,6-Me
2
C
6
H
3
)}Ln(N(SiMe
3
)
2
)
2
(Ln = Y, Nd, La) coordinated by tridentate amidinate ligand were synthesized, structurally characterized and evaluated as catalysts for isoprene and
rac
-lactide polymerizations. |
|---|---|
| ISSN: | 2046-2069 |
| DOI: | 10.1039/c5ra27960g |