Reactivity of Neutral Nitrogen Donors in Planar d8 Metal Complexes. Part 2. The System chloroplatinum(II) with Pyridines and Amines in Methanol. Effect of Basicity, ?-Acceptor Capacity and Steric Hindrance

Article abstract of DOI:10.1039/DT9940003539

The kinetics of the forward and reverse steps of the process Cl>(1+) + am -->/<-- (am)>(2+) + Cl(1-) a number of pyridines and some heterocyclic and aromatic amines covering a wide range of basicity> has been studied in methanol at 25 deg C.Both forward and reverse reactions obey the usual two-term rate law observed in square-planar substitution.The second-order rate constants for the forward reactions, k₂^f, show only a slight dependence upon the basicity of the entering am, and steric hindrance markedly decreases the reactivity.The second-order rate constants for the reverse reactions, k₂^r, are very sensitive to the nature of the leaving group and plots of log k₂^r against the pK_a of the conjugate acids of unhindered pyridines with different ? systems are linear with a slope of -0.45.A comparison among the different pyridines and sp³ nitrogen donor bases indicates an appreciable ? contribution to the stability of the Pt-N(sp²) bond.The equilibrium constants for the reactions have been determined in a number of cases from the ratio of the rate constants and a plot of log K against the pK_a is linear with a slope of 0.66.The results are compared with data from the literature.

Full text of DOI:10.1039/DT9940003539

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