期刊
INORGANIC CHEMISTRY
卷 47, 期 21, 页码 10000-10008出版社
AMER CHEMICAL SOC
DOI: 10.1021/ic801231p
关键词
-
资金
- National Science Foundation [CHE-0543133]
- Robert A. Welch Foundation [A-0923]
The most active and robust current catalysts for the copolymerization of carbon dioxide and epoxides or oxetanes, (salen)CrX in conjunction with PPNX (PPN+ = (Ph3P)(2)N+) or n-Bu4NX (X = Cl, N-3, CN, NCO), are characterized both in solution by infrared spectroscopy and in the solid-state by X-ray crystallography. All anions (X) afford six-coordinate chromium(III) PPN+ or n-Bu4N+ salts composed of trans-(salen)CrX2- species. Of the X groups investigated in (salen)CrX, chloride is easily displaced by the others, that is, the reaction of (salen)CrCl with 2 equiv of N-3(-), CN-, or NCO- quantitatively provide (salen)Cr(N-3)(2)(-), (salen)Cr(CN)(2)(-), and (salen)Cr(NCO)(2)(-), respectively. On the other hand, addition of less than 2 equiv of azide to (salen)CrCl leads to a Schlenk (ligand redistribution) equilibrium of the three possible anions both in solution and in the solid-state as shown by X-ray crystallography and electrospray ionization mass spectrometry. It was further demonstrated that all trans- (salen)CrX2- anions react with the epoxide or oxetane monomers in TCE (tetrachloroethane) solution to afford an equilibrium mixture containing (salen)CrX center dot monomer, with the oxetane adduct being thermodynamically more favored. The ring-opening steps of the bound cyclic ether monomers by X- were examined, revealing the rate of ring-opening of the epoxides (cyclohexene oxide and propylene oxide) to be much faster than of oxetane, with propylene oxide faster than cyclohexene oxide. Furthermore, both X anions in (salen)CrX2- were shown to be directly involved in monomer ring-opening.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据