INOR 737 |
| A number of reports on the nucleophilic behavior of N-donor heterocycles such as pyridines, thiazoles, oxazoles and imidazoles towards Pt(II) and Au(III) d8 transition metal complexes has been published [B. Pitteri et al., J. Chem. Soc. Dalton Trans. 1994, 3539; J. Chem. Soc. Dalton Trans. 1994, 1805; Polyhedron 2006, 25, 2698; Trans. Met. Chem. 2006, 31, 1028]. These studies, based on kinetic measurements, strongly support the idea that the ground-state π-interactions of five membered N-donors with Pt(II) and Au(III) metal centers are stronger than that of pyridines of the same basicity. Here we report a computational DFT approach for the comparison of the π-acceptor character of some N-donor heterocycles L {L = pyridines, imidazoles, pyrazoles and isooxazoles} in neutral AuCl3L complexes. The electronic properties of these ligands has been varied by considering various methyl- and trifluoromethyl-substituted derivatives. A linear relationship between the Mulliken charge of the AuCl3 fragment in AuCl3L and the computed proton affinity of L, intended as the energetic difference between L and its conjugated acid L-H, was found for all the considered ligands. The different angular coefficients can be considered as a representation of the π-acidity of these species once co-ordinated to AuCl3. The result of these calculations is the π-acidity scale:
pyridines << imidazoles < pyrazoles ≈ isooxazoles
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Theoretical and Computational Chemistry
7:00 PM-10:00 PM, Tuesday, August 21, 2007 BCEC -- Exhibit Hall - B2, Poster
Sci-Mix
Division of Inorganic Chemistry |
