Synthesis and Properties of para-Substituted NCN-Pincer Palladium and Platinum Complexes

Authors

  • Martijn Q. Slagt Dr.,

    1. Debye Institute, Department of Metal-Mediated Synthesis, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands, Fax: (+31) 30-2523615
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  • Gema Rodríguez Dr.,

    1. Debye Institute, Department of Metal-Mediated Synthesis, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands, Fax: (+31) 30-2523615
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  • Michiel M. P. Grutters Drs.,

    1. Debye Institute, Department of Metal-Mediated Synthesis, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands, Fax: (+31) 30-2523615
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  • Robertus J. M. Klein Gebbink Dr.,

    1. Debye Institute, Department of Metal-Mediated Synthesis, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands, Fax: (+31) 30-2523615
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  • Wim Klopper Dr.,

    1. Debye Institute, Department of Theoretical Chemistry, Utrecht University, Padualaan 14, 3584 CH Utrecht, The Netherlands
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  • Leonardus W. Jenneskens Prof. Dr.,

    1. Debye Institute, Department of Physical Organic Chemistry, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
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  • Martin Lutz Dr.,

    1. Bijvoet Centre for Biomolecular Research, Department of Crystal and Structural Chemistry, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
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  • Anthony L. Spek Prof. Dr.,

    1. Bijvoet Centre for Biomolecular Research, Department of Crystal and Structural Chemistry, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
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  • Gerard van Koten Prof. Dr.

    1. Debye Institute, Department of Metal-Mediated Synthesis, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands, Fax: (+31) 30-2523615
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Abstract

A variety of para-substituted NCN-pincer palladium(II) and platinum(II) complexes [MX(NCN-Z)] (M=PdII, PtII; X=Cl, Br, I; NCN-Z=[2,6-(CH2NMe2)2C6H2-4-Z]; Z=NO2, COOH, SO3H, PO(OEt)2, PO(OH)(OEt), PO(OH)2, CH2OH, SMe, NH2) were synthesised by routes involving substitution reactions, either prior to or, notably, after metalation of the ligand. The solubility of the pincer complexes is dominated by the nature of the para substituent Z, which renders several complexes water-soluble. The influence of the para substituent on the electronic properties of the metal centre was studied by 195Pt NMR spectroscopy and DFT calculations. Both the 195Pt chemical shift and the calculated natural population charge on platinum correlate linearly with the σp Hammett substituent constants, and thus the electronic properties of predesigned pincer complexes can be predicted. The σp value for the para-PtI group itself was determined to be −1.18 in methanol and −0.72 in water/methanol (1/1). Complexes substituted with protic functional groups (CH2OH, COOH) exist as dimers in the solid state due to intermolecular hydrogen-bonding interactions.

Abstract

Een verscheidenheid aan para-gesubstitueerde NCN-pincer-palladium(II) en -platina(II) complexen [MX(NCN-Z)] (M=PdII, PtII; X=Cl, Br, I; NCN-Z=[2,6-(CH2NMe2)C6H2-4-Z]; Z=NO2, COOH, SO3H, PO(OEt)2, PO(OH)(OEt), PO(OH)2, CH2OH, SMe, NH2) is gesynthetiseerd via substitutiereacties zowel voor, en hoogst opmerkelijk, ook na de metallering van het ligand. De oplosbaarheid van de pincer-complexen wordt gedomineerd door de aard van de para-substituent Z, waardoor enkele van de complexen wateroplosbaar zijn. De invloed van de para-substituent op de elektronische eigenschappen van het metaalcentrum is bestudeerd met behulp van195Pt-NMR en DFT-berekeningen. Zowel de chemische verschuiving van de195Pt-kern, als de berekende ′natural population′ lading op platina vertonen een lineaire correlatie met de σpHammett-substituentconstante, hetgeen het voorspellen van de elektronische eigenschappen van nieuwe pincercomplexen mogelijk maakt. De σp-waarde van de para-PtI eenheid blijkt respectievelijk −1.18 in methanol en −0.72 in waterige methanol (1/1, v/v) te zijn. Door de aanwezigheid van intermoleculaire waterstofbruggen komen de complexen met protische functionele groepen (CH2OH, COOH) in de vaste stof voor als dimeren.

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