期刊
INORGANIC CHEMISTRY
卷 48, 期 9, 页码 4258-4266出版社
AMER CHEMICAL SOC
DOI: 10.1021/ic802427f
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资金
- Russian Foundation for Basic Research [08-03-00391-a, 06-03-32728]
- Program of the Presidium of the Russian Academy of Science (RAS)
- RAS Chemistry and Material Science Division
- Institut Universitaire de France (IUF)
A series of new yttrium complexes supported by the bulky enediamido dianionic ligand DAB(2-) (DAB(2-) = (2,6-C(6)H(3)iPr(2))NC(Me)=C(Me)N(2,6-C6H3Pr2)(2-)), that is, {DAB}Y(THF)(2)(mu-Cl)(2)Li(THF)(2) (1), {DAB}Y(OtBu)(THF)(DME) (2), and {{DAB}Y(BH4)(2)}{Li(DME)(3)} (3), was synthesized by salt metathesis. The complexes were isolated after recrystallization in 73, 66, and 52% yield, respectively, and characterized in solution by NMR and in the solid state by single-crystal X-ray diffraction studies. In complex 1, the DAB 2- ligand is bonded to the metal center via two covalent Y-N bonds, while in complexes 2 and 3 additional eta(2)-coordination of the C=C bond to the metal atom is observed, both in solution and in the solid state. The tert-butoxide and borohydride complexes 2 and 3 act as monoinitiators for the room temperature ring-opening polymerization of racemic lactide and beta-butyrolactone, providing atactic polymers with controlled molecular weights and relatively narrow polydispersities (M-w/M-n = 1.15-1.82). Effectively immortal ROP of lactide with as many as 50 equiv of isopropanol per metal center was performed using complex 2 as the catalyst.
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