Activation of C-H Bond in the Coordination Sphere of Platinum(II)

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Abstract

[Pt(N-N)Cl(h1-CH2CH2OR)] complexes were generally considered to be indefinitely stable, both in solution and in the solid state. In a previous work we unexpectedly found that complex [Pt(Me2phen)Cl(1-CH2CH2OR)], 1, Me2phen = 2,9-dimethyl-1,10-phenanthroline, in solution, undergoes spontaneous decomposition to give vinyl-ether together with a Pt(II) hydride species. We demonstrated that this decomposition pathway is mediated by a H- b-shift process promoted by the unbearable steric hindrance introduced by Me2phen in the Pt(II) coordination plane. In this work we found that [Pt(Me2phen)Cl(h1-CH2CH2OR)] complexes can undergo H-D exchange on Me2phen Me’s, when dissolved in protic basic deuterated solvents. Moreover, we observed by 1H NMR that this exchange is considerably slowed down in the analogous complex [Pt(Me2bpy)Cl(h1-CH2CH2OR)], Me2bpy = 6,6’-dimethyl-2,2’-bipyridil, demonstrating the relevant effect of ligand flexibility. Increased acidity of the metal core in the formed T-shaped species reported in the Figure, could be responsible for the observed H-D exchange. An analogous H-D exchange process was observed and investigated by 1H NMR and LC-MS spectroscopy in the related complex [Pt(Me2phen)Cl2]. Further studies demonstrated that this phenomenon is considerably slowed down in the less sterically demanding complexes [Pt(Me2phen)(OR)2] and [Pt(Me2bpy)(OR)2], R = H, Me. It cannot be excluded a role of the H- b-shift process also in the catalysis of the observed H-D exchange process.

Autore Pugliese

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  • M. Benedetti , C. R. Barone , C. R. Girelli , F. P. Fanizzi , G. Natile , L. Maresca

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2013

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