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Title: C-H bond activation by a hydrotris(pyrazolyl)borato ruthenium hydridle complex
Authors: Ng, SM
Lam, WH
Mak, CC
Tsang, CW
Jia, GC
Lin, ZY
Lau, CP
Issue Date: 2003
Publisher: American Chemical Society
Source: Organometallics, 2003, v. 22, no. 4, p. 641-651 How to cite?
Journal: Organometallics 
Abstract: The ruthenium complex TpRu(PPh(3))(CH(3)CN)H (Tp = hydrotris(pyrazolyl)borate) catalyzes H/D exchange between CH(4) and some deuterated organic solvents-benzene-d(6), tetrahydrofuran-d(8), diethyl ether-d(10), and dioxane-d(8). Preferential cleavage of the alpha-C-D and the beta-C-D bonds of THF-d(8) and diethyl ether-d(10), respectively, is observed. The H/D exchange processes have been investigated by density functional theory calculations at the B3LYP level. Theoretical study on the reaction mechanism suggests that or-complexes TpRu(PPh(3))(eta(2)-H-R)H are active species in the exchange processes. During the exchange processes, the reversible transformations of TpRu(PPh(3))(eta(2)-H-R)H to TpRu(PPh(3))(eta(2)-H(2))R are the crucial steps. 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(PPh(3))-(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 (eta(2)-H-R) species to the (eta(2)-H(2)) species followed by H-H rotation in the latter. The rotation barriers are calculated to be in the range 2-4 kcal/mol. The exchange process having an aromatic R group is found to be most favorable due to the strong Ru-C(sp(2)) bonding, which stabilizes the (eta(2)-H(2)) species and lowers the transformation barrier. The complex TpRu(PPh(3))(CH(3)CN)H catalyzes H/D exchange between H(2) and the deuterated solvents too.
ISSN: 0276-7333
EISSN: 1520-6041
DOI: 10.1021/om0209024
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