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Issue 32, 2017
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Characterization of secondary phosphine oxide ligands on the surface of iridium nanoparticles

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Abstract

The synthesis of iridium nanoparticles (IrNPs) ligated by various secondary phosphine oxides (SPOs) is described. This highly reproducible and simple method via H2 reduction produces well dispersed, small nanoparticles (NPs), which were characterized by the state-of-the-art techniques, such as TEM, HRTEM, WAXS and ATR FT-IR spectroscopy. In particular, multinuclear solid state MAS-NMR spectroscopy with and without cross polarization (CP) enabled us to investigate the different binding modes adopted by the ligand at the nanoparticle surface, suggesting the presence of three possible types of coordination: as a purely anionic ligand Ir–P(O)R2, as a neutral acid R2P–O–H and as a monoanionic bidentate H-bonded dimer R2P–O–H⋯O[double bond, length as m-dash]PR2. Specifically, the higher basicity of the dicyclohexyl system leads to the formation of IrNPs in which the bidentate binding mode is most abundant. Such cyclohexyl groups are bent towards the edges, as is suggested by the study of 13CO coordination on the NP surface. This study also showed that the number of surface sites on faces available for bridging CO molecules is higher than the number of sites for terminal CO species on edges and apices, which is unexpected taking into account the small size of the nanoparticles. In addition, the IrNPs present a high chemoselectivity in the hydrogenation of cinnamaldehyde to the unsaturated alcohol.

Graphical abstract: Characterization of secondary phosphine oxide ligands on the surface of iridium nanoparticles

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Publication details

The article was received on 22 May 2017, accepted on 27 Jul 2017 and first published on 28 Jul 2017


Article type: Paper
DOI: 10.1039/C7CP03439C
Citation: Phys. Chem. Chem. Phys., 2017,19, 21655-21662
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    Characterization of secondary phosphine oxide ligands on the surface of iridium nanoparticles

    I. Cano, L. M. Martínez-Prieto, P. F. Fazzini, Y. Coppel, B. Chaudret and P. W. N. M. van Leeuwen, Phys. Chem. Chem. Phys., 2017, 19, 21655
    DOI: 10.1039/C7CP03439C

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