Redox Control of a Ring-Opening Polymerization Catalyst
摘要:
The activity of an yttrium alkoxide complex supported by a ferrocene-based ligand was controlled using redox reagents during the ring-opening polymerization of L-lactide. The oxidized complex was characterized by X-ray crystallography and H-1 NMR, XANES, and Mossbauer spectroscopy. Switching in situ between the oxidized and reduced yttrium complexes resulted in a change in the rate of polymerization of L-lactide. Synthesized polymers were analyzed by gel permeation chromatography. Polymerization of trimethylene carbonate was also performed with the reduced and oxidized forms of an indium alkoxide complex. The indium system showed the opposite behavior to that of yttrium, revealing a metal-based dependency on the rate of polymerization.
The coordination geometry about the In atom in trichlorobis(tetrahydrofuran)indium(III), [InCl3-(C4H8O)2], approximates a trigonal bipyramid, with three Cl atoms in equatorial positions and two axial tetrahydrofuran ligands. The molecule lies on a crystallographic twofold axis that is coincident with one of the In-Cl bonds.
作者:Gabbai, Francois P.、Schier, Annette、Riede, Juergen、Sladek, Alexander、Goerlitzer, Hans W.
DOI:——
日期:——
X-ray crystal structure of InCl3·2THF, a neutral five-coordinate bis-adduct of an indium(III) trihalide
作者:Mark F. Self、Andrew T. McPhail、Richard L. Wells
DOI:10.1016/s0277-5387(00)83393-8
日期:1993.3
The 2:1 mole ratio reaction of InCl3 and P(SiMe3)3 in a toluene/THF mixture was investigated. The reaction appears to occur in a 1:1 mole fashion, since the products obtained are unreacted InCl 3 (48.5 % recovered) as InCl3.2THF and a fine powder which appears to be [Cl2In3P3(SiMe3)2]n. The latter was characterized by melting point and partial elemental analysis. The X-ray crystal structure of InCl 3.2THF shows it to be a neutral penta-coordinated bis-adduct of an indium(III) trihalide. The crystal structure consists of discrete monomeric units with no abnormally short intermolecular separations. The geometry about the indium atom approximates to trigonal bipyramidal with oxygen atoms of each of the THF molecules occupying axial positions [In-O = 2.257(9) angstrom, O-In-O = 178.5(3)-degrees], while the three chlorine atoms (mean In-Cl = 2.321 angstrom) lie in the equatorial plane.