ISSN:
1434-1948
Keywords:
N-ligands
;
Yttrium
;
Samarium
;
Ring-opening polymerization
;
Lactones
;
Chemistry
;
General Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The reaction of one equivalent of dilithiated O(SiMe2-Ap-H)2 [Ap-H = -N(2-amino-4-methylpyridine)] (1), generated in situ, with LnCl3 (Ln = Y, Sm) in THF affords O(SiMe2-Ap)2YCl(THF)2 (2) or O(SiMe2-Ap)2SmCl(THF)3 (3). In contrast, the reaction of one or two equivalents of dilithiated 1, again generated in situ, with LaBr3 in THF affords O(SiMe2-Ap)2)2LaLi(THF)3 (4). An X-ray structural analysis of 2 and 3 reveal the O(SiMe2-Ap)2- ligand to bind in a planar tetradentate manner. Equivalent Sm-N distances in 3 indicate a delocalized binding mode. Compound 2 reacts with Bu4NBH4, NaBH4 or LiCH(SiMe3)2 to give the corresponding “ate” complexes O(SiMe2-Ap)2Y(BH4)Cl(THF) Bu4N (5), O(SiMe2-Ap)2Y(BH4)2Na(THF)2 (6) and O(SiMe2-Ap)2Y(CH(TMS)2)2Li(THF)3 (7), respectively. The steric demand of the O(SiMe2-Ap)2- ligand is not large enough to stabilize monoalkyl or monoborohydride complexes. Complex 4 has been used as an initiator for the ring-opening polymerization of ε-caprolactone or δ-valerolactone. In both cases an almost linear relation between the monomer-to-initiator ratio and the molecular weight of the obtained polyester is observed. By conducting the polymerization in neat ε-caprolactone at room temperature a solid polyester block is formed after 3 min (300000 g·mol-1, Mw/Mn 2.3).
Additional Material:
2 Ill.
Type of Medium:
Electronic Resource
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