Complexes of Group 3 Metals and Lanthanides That Contain Siloxane-Bridged Bisaminopyridinato Ligands: Synthesis, Structure, and Application in the Ring-Opening Polymerization of Lactones
✍ Scribed by Henrik Noss; Markus Oberthür; Christine Fischer; Winfried P. Kretschmer; Rhett Kempe
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 272 KB
- Volume
- 1999
- Category
- Article
- ISSN
- 1434-1948
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✦ Synopsis
The reaction of one equivalent of dilithiated O(SiMe 2 -Ap-H) 2 Cl(THF) Bu 4 N (5), O(SiMe 2 -Ap) 2 Y(BH 4 ) 2 Na(THF) 2 (6) and O(SiMe 2 -Ap) 2 Y(CH(TMS) 2 ) 2 Li(THF) 3 ( ), respectively. The [Ap-H = -N(2-amino-4-methylpyridine)] (1), generated in situ, with LnCl 3 (Ln = Y, Sm) in THF affords O(SiMe 2 -steric demand of the O(SiMe 2 -Ap) 2-ligand is not large enough to stabilize monoalkyl or monoborohydride Ap) 2 YCl(THF) 2 (2) or O(SiMe 2 -Ap) 2 SmCl(THF) 3 (3). In contrast, the reaction of one or two equivalents of dilithiated complexes. Complex 4 has been used as an initiator for the ring-opening polymerization of ε-caprolactone or δ-1, again generated in situ, with LaBr 3 in THF affords O(SiMe 2 -Ap) 2 ) 2 LaLi(THF) 3 ( ). An X-ray structural analysis valerolactone. In both cases an almost linear relation between the monomer-to-initiator ratio and the molecular of 2 and 3 reveal the O(SiMe 2 -Ap) 2-ligand to bind in a planar tetradentate manner. Equivalent Sm-N distances in 3 weight of the obtained polyester is observed. By conducting the polymerization in neat ε-caprolactone at room indicate a delocalized binding mode. Compound 2 reacts with Bu 4 NBH 4 , NaBH 4 or LiCH(SiMe 3 ) 2 to give the temperature a solid polyester block is formed after 3 min (300000 g•mol -1 , M w /M n 2.3). corresponding "ate" complexes O(SiMe 2 -Ap) 2 Y(BH 4 )vent the formation of "ate" complexes. Recently, "ate" com- [a] Institut für Organische Katalyseforschung (IfOK), Buchbinderstr. 5Ϫ6, D-18055 Rostock, Germany ent with C 2v monomeric structures in which the nuclei [b] Center for Catalytic Olefin Polymerization, Department of Chemeasured show a single set of signals. Single crystal X-ray