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Hydrogenation of phenyl-substituted C[triple bond, length as m-dash]N, C[double bond, length as m-dash]N,C[triple bond, length as m-dash]C, C[double bond, length as m-dash]C and C[double bond, length as m-dash]O functional groups by Cr, Mo and W PNP pincer complexes – a DFT study

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Abstract

The hydrogenation of phenyl-substituted C[triple bond, length as m-dash]N, C[double bond, length as m-dash]N, C[triple bond, length as m-dash]C, C[double bond, length as m-dash]C and C[double bond, length as m-dash]O functional groups catalyzed by PNP pincer amido M(NO)(CO)(PNP) and amino HM(NO)(CO)(PNHP) complexes [M = Cr, Mo and W; PNP = N(CH2CH2P(isopropyl)2)2] has been computed at the B3PW91 level of density functional theory. The computed structure and stability of the Mo and W complexes are in agreement with the experimental results. The hydrogenation of Ph–C[triple bond, length as m-dash]N, Ph–CH[double bond, length as m-dash]CH2 and Ph–CHO undergoes a stepwise mechanism, while that of Ph–C[triple bond, length as m-dash]CH, Ph–CH[double bond, length as m-dash]NH, Ph–CH[double bond, length as m-dash]NH–Ph, Ph–CH[double bond, length as m-dash]N–CH2–Ph and Ph–CO–CH3 follows a one-step mechanism. The computed barrier in the increasing order of Ph–C[triple bond, length as m-dash]N < Ph–CH[double bond, length as m-dash]NH < Ph–CH[double bond, length as m-dash]N–Ph < Ph–CH[double bond, length as m-dash]N–CH2–Ph is in agreement with the experimentally observed hydrogenation activity for the Mo and W complexes. In addition, the hydrogenation of Ph–C[triple bond, length as m-dash]N has a lower barrier than that of Ph–CH[double bond, length as m-dash]CH2, and this is also found for the hydrogenation of 4-vinylbenzonitrile catalyzed not only by the Mo complexes but also by the corresponding PNP Fe pincer complexes, in disagreement with the experiment. The finding that the hydrogenation of Ph–CHO has a lower barrier than those of Ph–CO–CH3 and Ph–CH[double bond, length as m-dash]NH–Ph is just opposite to the experimental results for the Mo complexes. It is found that the Mo complexes have higher catalytic activity than the W and Cr complexes. In contrast to the Mo and W complexes, the Cr complexes have not yet been reported experimentally.

Graphical abstract: Hydrogenation of phenyl-substituted C [[triple bond, length as m-dash]] N, C [[double bond, length as m-dash]] N,C [[triple bond, length as m-dash]] C, C [[double bond, length as m-dash]] C and C [[double bond, length as m-dash]] O functional groups by Cr, Mo and W PNP pincer complexes – a DFT study

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Publication details

The article was received on 31 Mar 2017, accepted on 24 Apr 2017 and first published on 25 Apr 2017


Article type: Paper
DOI: 10.1039/C7CY00629B
Citation: Catal. Sci. Technol., 2017, Advance Article
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    Hydrogenation of phenyl-substituted C[triple bond, length as m-dash]N, C[double bond, length as m-dash]N,C[triple bond, length as m-dash]C, C[double bond, length as m-dash]C and C[double bond, length as m-dash]O functional groups by Cr, Mo and W PNP pincer complexes – a DFT study

    Z. Wei, K. Junge, M. Beller and H. Jiao, Catal. Sci. Technol., 2017, Advance Article , DOI: 10.1039/C7CY00629B

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