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Ligand Self-Assembling through Complementary Hydrogen-Bonding in the Coordination Sphere of a Transition Metal Center : the 6-Diphenylphosphanylpyridin-2(1H)-one System

Gellrich, Urs and Huang, Jing and Seiche, Wolfgang and Keller, Manfred and Meuwly, Markus and Breit, Bernhard. (2011) Ligand Self-Assembling through Complementary Hydrogen-Bonding in the Coordination Sphere of a Transition Metal Center : the 6-Diphenylphosphanylpyridin-2(1H)-one System. Journal of the American Chemical Society, 133 (4). pp. 964-975.

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Official URL: http://edoc.unibas.ch/dok/A6002056

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Abstract

Motivated by previous findings which had shown that transition metal catalysts based on the 6-diphenylphosphanylpyridone ligand (6-DPPon, 2) display properties as a self-assembling bidentate ligand−metal complex, we have performed a thorough study on the bonding situation of this ligand, alone and in the coordination sphere of a late transition metal. Thus, combining a number of spectroscopic methods (UV−vis, IR, NMR, X-ray), we gained insights into the unique structural characteristics of 2. These experimental studies were corroborated by DFT calculations, which were in all cases in good agreement with the experimental results. The free ligand 2 prefers to exist as the pyridone tautomer 2A and dimerizes to the pyridone−pyridone dimer 4A in solution as well as in the crystal state. The corresponding hydroxypyridine tautomer 2B is energetically slightly disfavored (ca. 0.9 kcal/mol within the up-conformer relevant for metal coordination); hence, hydrogen bond formation within the complex may easily compensate this small energy penalty. Coordination properties of 2 were studied in the coordination sphere of a platinum(II) center. As a model complex, [Cl2Pt(6-DPPon)2] (11) was prepared and investigated. All experimental and theoretical methods used prove the existence of a hydrogen-bonding interligand network in solution as well as in the crystal state of 11 between one 6-DPPon ligand existing as the pyridone tautomer 2A and the other ligand occupying the complementary hydroxypyridine form 2B. Dynamic proton NMR allowed to determine the barrier for interligand hydrogen bond breaking and, in combination with theory, enabled us to determine the enthalpic stabilization through hydrogen-bonding to contribute 14−15 kcal/mol.
Faculties and Departments:05 Faculty of Science > Departement Chemie > Chemie > Physikalische Chemie (Meuwly)
UniBasel Contributors:Meuwly, Markus
Item Type:Article, refereed
Publisher:American Chemical Society
ISSN:0002-7863
Note:Publication type according to Uni Basel Research Database: Journal article
Identification Number:
Last Modified:07 Dec 2016 13:19
Deposited On:08 Nov 2012 16:10

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