113Cd NMR Determination of the Binding Parameters of Alicyclic Epoxides to [Hydrotris(3-phenylpyrazol-1-yl)borate]Cd(II) Acetate
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- 作者：Donald J. Darensbourg ; Damon R. Billodeaux ; and Lisa M. Perez
- 刊名：Organometallics
- 出版年：2004
- 出版时间：October 25, 2004
- 年：2004
- 卷：23
- 期：22
- 页码：5286 - 5290
- 全文大小：103K
- 年卷期：v.23,no.22(October 25, 2004)
- ISSN：1520-6041
文摘
The thermodynamic parameters for the binding of a series of epoxides to the complex[hydrotris(3-phenylpyrazol-1-yl)borate]Cd(II) acetate have been determined via 113Cd NMRspectroscopy. As the activation of an epoxide by interaction with a metal center is a keystep in the copolymerization of carbon dioxide and epoxides to produce polycarbonates, thetendency for epoxides to bind to metal centers may play a role in the propensity for epoxidesto ring-open. The epoxides examined include (+)-limonene oxide, 1,4-dihydronaphthaleneoxide, [2-(3,4-epoxycyclohexyl)ethyl]trimethoxysilane, exo-norbornene oxide, and 
hars/alpha.gif" BORDER=0>-pineneoxide. DFT calculations were performed to give optimized geometries of the epoxide adductsof the cadmium complex. Our investigations show that the binding abilities of these alicyclicepoxides vary over the range -22.1 to -38.7 kJ mol-1 for hars/Delta.gif" BORDER=0 >H
and do not differ significantlyfrom the corresponding values previously determined for the easily ring-opened epoxides(cyclohexene oxide and propylene oxide). The optimized geometries give a metal center-epoxide (Cd-O) bond distance range of 2.401-2.448 Å, which is in good agreement withvalues obtained experimentally for selected derivatives. In addition, comparative studiesinvolving the more strongly binding phosphine and amine ligands are reported. From theseobservations we conclude that the binding of the epoxide by the metal complex is notnecessarily the determining factor in the ability of the epoxide to be ring-opened by anucleophile.
hars/alpha.gif" BORDER=0>-pineneoxide. DFT calculations were performed to give optimized geometries of the epoxide adductsof the cadmium complex. Our investigations show that the binding abilities of these alicyclicepoxides vary over the range -22.1 to -38.7 kJ mol-1 for hars/Delta.gif" BORDER=0 >H and do not differ significantlyfrom the corresponding values previously determined for the easily ring-opened epoxides(cyclohexene oxide and propylene oxide). The optimized geometries give a metal center-epoxide (Cd-O) bond distance range of 2.401-2.448 Å, which is in good agreement withvalues obtained experimentally for selected derivatives. In addition, comparative studiesinvolving the more strongly binding phosphine and amine ligands are reported. From theseobservations we conclude that the binding of the epoxide by the metal complex is notnecessarily the determining factor in the ability of the epoxide to be ring-opened by anucleophile.