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Displacement of Neutral Nitrogen Donors by Chloride in AuCl 3 (3R‐py) (3R‐py = meta ‐Substituted Pyridine): Comparison between meta ‐ and para ‐Substituted Pyridines by Kinetics and DFT Calculations
Author(s) -
Pitteri Bruno,
Bortoluzzi Marco
Publication year - 2007
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.200700597
Subject(s) - chemistry , pyridine , nucleophile , reactivity (psychology) , medicinal chemistry , nitro , reaction rate constant , substitution reaction , stereochemistry , conjugate , kinetics , organic chemistry , catalysis , medicine , alkyl , alternative medicine , physics , pathology , quantum mechanics , mathematical analysis , mathematics
Abstract The kinetics of the process AuCl 3 (3R‐py) + Cl – → AuCl 4 – + 3R‐py (3R‐py = one of a number of meta ‐substituted pyridines covering a wide range of basicity) have been studied in methanol at 25 °C. The reactions obey the usual two‐term rate law observed in the substitution reactions of square‐planar complexes. The second‐order rate constants, k 2 , are very sensitive to the nature of the leaving group and plots of log k 2 against the p K a of the conjugate acids are linear with the same slope of ca. –0.6 already found for para ‐substituted pyridines (4R‐py). Until now the two groups of bases have been considered to behave in the same manner in their displacement from Au III and Pt II by various nucleophiles but, on the contrary, the reactivity of the two classes of N donors is slightly different and follows the order: 4R‐py > 3R‐py. This kinetic result is explained on the basis of an energetic difference between the frontier orbitals of the AuCl 3 (3R‐py) and AuCl 3 (4R‐py) derivatives.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)