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Issue 6, 2014
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Metal control of selectivity in acetate-assisted C–H bond activation: an experimental and computational study of heterocyclic, vinylic and phenylic C(sp2)–H bonds at Ir and Rh

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Abstract

Acetate-assisted C(sp2)–H bond activation at [MCl2Cp*]2 (M = Ir, Rh) has been studied for a series of N-alkyl imines, iPrN[double bond, length as m-dash]CHR, (R = N-methyl-2-pyrrolyl, H-L1; 2-furanyl, H-L2; 2-thiophenyl, H-L3a; C2H2Ph, H-L4; and Ph, H-L5) as well as phenylpyridine (H-L6) by both experimental and computational means. Competition experiments reveal significant variation in the relative reactivity of these substrates and highlight changes in selectivity between Ir (H-L4H-L2 < H-L3aH-L5 < H-L1H-L6) and Rh (H-L2H-L1 < H-L3aH-L4 < H-L5 < H-L6). Comparison of H-L3a with its N-xylyl analogue, H-L3b, gives a further case of metal-based selectivity, H-L3a being more reactive at Ir, while H-L3b is preferred at Rh. H/D exchange experiments suggest that the selectivity of C–H activation at Ir is determined by kinetic factors while that at Rh is determined by the product thermodynamic stability. This is confirmed by computational studies which also successfully model the order of substrate reactivity seen experimentally at each metal. To achieve the good level of agreement between experiment and computation required the inclusion of dispersion effects, use of large basis sets and an appropriate solvent correction.

Graphical abstract: Metal control of selectivity in acetate-assisted C–H bond activation: an experimental and computational study of heterocyclic, vinylic and phenylic C(sp2)–H bonds at Ir and Rh

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Publication details

The article was received on 11 Mar 2014, accepted on 22 Mar 2014 and first published on 24 Mar 2014


Article type: Edge Article
DOI: 10.1039/C4SC00738G
Citation: Chem. Sci., 2014,5, 2340-2346
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    Metal control of selectivity in acetate-assisted C–H bond activation: an experimental and computational study of heterocyclic, vinylic and phenylic C(sp2)–H bonds at Ir and Rh

    K. J. T. Carr, D. L. Davies, S. A. Macgregor, K. Singh and B. Villa-Marcos, Chem. Sci., 2014, 5, 2340
    DOI: 10.1039/C4SC00738G

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