C-H Bond Activation by a Hydrotris(pyrazolyl)borato Ruthenium Hydride Complex
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- 作者：Siu Man Ng ; Wai Han Lam ; Chi Chuen Mak ; Chun Wai Tsang ; Guochen Jia ; Zhenyang Lin ; and Chak Po Lau
- 刊名：Organometallics
- 出版年：2003
- 出版时间：February 17, 2003
- 年：2003
- 卷：22
- 期：4
- 页码：641 - 651
- 全文大小：309K
- 年卷期：v.22,no.4(February 17, 2003)
- ISSN：1520-6041
文摘
The ruthenium complex TpRu(PPh3)(CH3CN)H (Tp = hydrotris(pyrazolyl)borate) catalyzesH/D exchange between CH4 and some deuterated organic solvents-benzene-d6, tetrahydrofuran-d8, diethyl ether-d10, and dioxane-d8. Preferential cleavage of the 
hars/alpha.gif" BORDER=0>-C-D and the hars/beta2.gif" BORDER=0 ALIGN="middle">-C-Dbonds of THF-d8 and diethyl ether-d10, respectively, is observed. The H/D exchange processeshave been investigated by density functional theory calculations at the B3LYP level.Theoretical study on the reaction mechanism suggests that hars/sigma.gif" BORDER=0 >-complexes TpRu(PPh3)(hars/eta.gif" BORDER=0 >2-H-R)H are active species in the exchange processes. During the exchange processes, thereversible transformations of TpRu(PPh3)(hars/eta.gif" BORDER=0 >2-H-R)H to TpRu(PPh3)(hars/eta.gif" BORDER=0 >2-H2)R are the crucialsteps. The barriers for the transformations are in the range 10-13.4 kcal/mol. Interestingly,the transition states for the transformations correspond to the seven-coordinate TpRu(PPh3)(R)(H)(H), which are species derived from the oxidative addition of H-R to the metal center.The exchange processes involve transformations of the (hars/eta.gif" BORDER=0 >2-H-R) species to the (hars/eta.gif" BORDER=0 >2-H2) speciesfollowed by H-H rotation in the latter. The rotation barriers are calculated to be in therange 2-4 kcal/mol. The exchange process having an aromatic R group is found to be mostfavorable due to the strong Ru-C(sp2) bonding, which stabilizes the (hars/eta.gif" BORDER=0 >2-H2) species and lowersthe transformation barrier. The complex TpRu(PPh3)(CH3CN)H catalyzes H/D exchangebetween H2 and the deuterated solvents too.
hars/alpha.gif" BORDER=0>-C-D and the hars/beta2.gif" BORDER=0 ALIGN="middle">-C-Dbonds of THF-d8 and diethyl ether-d10, respectively, is observed. The H/D exchange processeshave been investigated by density functional theory calculations at the B3LYP level.Theoretical study on the reaction mechanism suggests that hars/sigma.gif" BORDER=0 >-complexes TpRu(PPh3)(hars/eta.gif" BORDER=0 >2-H-R)H are active species in the exchange processes. During the exchange processes, thereversible transformations of TpRu(PPh3)(hars/eta.gif" BORDER=0 >2-H-R)H to TpRu(PPh3)(hars/eta.gif" BORDER=0 >2-H2)R are the crucialsteps. The barriers for the transformations are in the range 10-13.4 kcal/mol. Interestingly,the transition states for the transformations correspond to the seven-coordinate TpRu(PPh3)(R)(H)(H), which are species derived from the oxidative addition of H-R to the metal center.The exchange processes involve transformations of the (hars/eta.gif" BORDER=0 >2-H-R) species to the (hars/eta.gif" BORDER=0 >2-H2) speciesfollowed by H-H rotation in the latter. The rotation barriers are calculated to be in therange 2-4 kcal/mol. The exchange process having an aromatic R group is found to be mostfavorable due to the strong Ru-C(sp2) bonding, which stabilizes the (hars/eta.gif" BORDER=0 >2-H2) species and lowersthe transformation barrier. The complex TpRu(PPh3)(CH3CN)H catalyzes H/D exchangebetween H2 and the deuterated solvents too.