Mechanistic Study of Hydrogen Transfer to Imines from a Hydroxycyclopentadienyl Ruthenium Hydride. Experimental Support for a Mechanism Involving Coordination of Imine to Ruthenium Prior to Hydrogen T
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- 作者：Joseph S. M. Samec ; Alida H. É ; ll ; Jenny B. Å ; berg ; Timofei Privalov ; Lars Eriksson ; Jan-E. Bä ; ckvall
- 刊名：Journal of the American Chemical Society
- 出版年：2006
- 出版时间：November 8, 2006
- 年：2006
- 卷：128
- 期：44
- 页码：14293 - 14305
- 全文大小：295K
- 年卷期：v.128,no.44(November 8, 2006)
- ISSN：1520-5126
文摘
Reaction of [2,3,4,5-Ph4(
hars/eta.gif" BORDER=0 >5-C4COH)Ru(CO)2H] (2) with different imines afforded ruthenium aminecomplexes at low temperatures. At higher temperatures in the presence of 2, the complexes decomposedto give [Ru2(CO)4(
-H)(C4Ph4COHOCC4Ph4)] (1) and free amine. Electron-rich imines gave ruthenium aminecomplexes with 2 at a lower temperature than did electron-deficient imines. The negligible deuterium isotopeeffect (kRuHOH/kRuDOD = 1.05) observed in the reaction of 2 with N-phenyl[1-(4-methoxyphenyl)ethylidene]amine (12) shows that neither hydride (RuH) nor proton (OH) is transferred to the imine in therate-determining step. In the dehydrogenation of N-phenyl-1-phenylethylamine (4) to the correspondingimine 8 by [2,3,4,5-Ph4(hars/eta.gif" BORDER=0 >4-C4CO)Ru(CO)2] (A), the kinetic isotope effects observed support a stepwisehydrogen transfer where the isotope effect for C-H cleavage (kCHNH/kCDNH = 3.24) is equal to the combined(C-H, N-H) isotope effect (kCHNH/kCDND = 3.26). Hydrogenation of N-methyl(1-phenylethylidene)amine(14) by 2 in the presence of the external amine trap N-methyl-1-(4-methoxyphenyl)ethylamine (16) afforded90-100% of complex [2,3,4,5-Ph4(hars/eta.gif" BORDER=0 >4-C4CO)]Ru(CO)2NH(CH3)(CHPhCH3) (15), which is the complexbetween ruthenium and the amine newly generated from the imine. At -80 
C the reaction of hydride 2with 4-BnNH-C6H9=NPh (18), with an internal amine trap, only afforded [2,3,4,5-Ph4(hars/eta.gif" BORDER=0 >4-C4CO)](CO)2RuNH(Ph)(C6H10-4-NHBn) (19), where the ruthenium binds to the amine originating from the imine, showing thatneither complex A nor the diamine is formed. Above -8 C complex 19 rearranged to the thermodynamicallymore stable [Ph4(hars/eta.gif" BORDER=0 >4-C4CO)](CO)2RuNH(Bn)(C6H10-4-NHPh) (20). These results are consistent with an innersphere mechanism in which the substrate coordinates to ruthenium prior to hydrogen transfer and aredifficult to explain with the outer sphere pathway previously proposed.
hars/eta.gif" BORDER=0 >5-C4COH)Ru(CO)2H] (2) with different imines afforded ruthenium aminecomplexes at low temperatures. At higher temperatures in the presence of 2, the complexes decomposedto give [Ru2(CO)4(-H)(C4Ph4COHOCC4Ph4)] (1) and free amine. Electron-rich imines gave ruthenium aminecomplexes with 2 at a lower temperature than did electron-deficient imines. The negligible deuterium isotopeeffect (kRuHOH/kRuDOD = 1.05) observed in the reaction of 2 with N-phenyl[1-(4-methoxyphenyl)ethylidene]amine (12) shows that neither hydride (RuH) nor proton (OH) is transferred to the imine in therate-determining step. In the dehydrogenation of N-phenyl-1-phenylethylamine (4) to the correspondingimine 8 by [2,3,4,5-Ph4(hars/eta.gif" BORDER=0 >4-C4CO)Ru(CO)2] (A), the kinetic isotope effects observed support a stepwisehydrogen transfer where the isotope effect for C-H cleavage (kCHNH/kCDNH = 3.24) is equal to the combined(C-H, N-H) isotope effect (kCHNH/kCDND = 3.26). Hydrogenation of N-methyl(1-phenylethylidene)amine(14) by 2 in the presence of the external amine trap N-methyl-1-(4-methoxyphenyl)ethylamine (16) afforded90-100% of complex [2,3,4,5-Ph4(hars/eta.gif" BORDER=0 >4-C4CO)]Ru(CO)2NH(CH3)(CHPhCH3) (15), which is the complexbetween ruthenium and the amine newly generated from the imine. At -80 C the reaction of hydride 2with 4-BnNH-C6H9=NPh (18), with an internal amine trap, only afforded [2,3,4,5-Ph4(hars/eta.gif" BORDER=0 >4-C4CO)](CO)2RuNH(Ph)(C6H10-4-NHBn) (19), where the ruthenium binds to the amine originating from the imine, showing thatneither complex A nor the diamine is formed. Above -8 C complex 19 rearranged to the thermodynamicallymore stable [Ph4(hars/eta.gif" BORDER=0 >4-C4CO)](CO)2RuNH(Bn)(C6H10-4-NHPh) (20). These results are consistent with an innersphere mechanism in which the substrate coordinates to ruthenium prior to hydrogen transfer and aredifficult to explain with the outer sphere pathway previously proposed.