Unraveling the Origin of Regioselectivity in Rhodium Diphosphine Catalyzed Hydroformylation. A DFT QM/MM Study

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• 作者：Jorge J. Carbó ; Feliu Maseras ; Carles Bo ; and Piet W. N. M. van Leeuwen
• 刊名：Journal of the American Chemical Society
• 出版年：2001
• 出版时间：August 8, 2001
• 年：2001
• 卷：123
• 期：31
• 页码：7630 - 7637
• 全文大小：94K
• 年卷期：v.123,no.31(August 8, 2001)
• ISSN：1520-5126

文摘

The origin of regioselectivity in rhodium diphosphine catalyzed hydroformilation was investigatedby means of hybrid QM/MM calculations using the IMOMM method. The roles of the diphosphine bite angleand of the nonbonding interactions were analyzed in detail by considering rhodium systems containing xantphos-type ligands, for which a correlation between the natural bite angle and regioselectivity has been recentlyreported. From the pentacoordinated equatorial-equatorial HRh(CO)(alkene)(diphosphine) key intermediate,eight possible reaction paths were defined and characterized through their respective transition states (TS).We succeeded in reproducing the experimentally observed trends for the studied diphosphines. By performingadditional calculations on model systems, in which the steric effects induced by the phenyl substituents ofxantphos ligands were canceled, we were able to separate, identify, and evaluate the different contributions toregioselectivity. These additional calculations showed that regioselectivity is governed by the nonbondinginteractions between the diphenylphosphino substituents and the substrate, whereas the effects directly associatedto the bite angle, what we call orbital effects, seem to have a smaller influence.