Nucleophilic reactivity constants

Pearson, R.G., Sobel, H., and Songstad, J. (1968) Nucleophilic reactivity constants toward methyl iodide and trans-[Pt(py)2C12]./. Am. Chem. Soc. 90, 319-326. 

The term s is the nucleophile discrimination factor. The values of pt, the nucleophilic reactivity constant, is useful for correlating kinetic data for other Pt(II) complexes. 

You will notice in this case that the nucleophilic reactivity constants—these rate constants—vary roughly with the basicity. Hydroxide ion is almost the most powerful nucleophilic reagent because it is the strongest base that can exist in aqueous solution. Water is the weakest nucleophilic reagent, simply because anything weaker than water is not detectable in an aqueous solution. So this number is the lower limit for nucleophilic reactivity. 

Sacconi found a useful correlation between the spin state of five-coordinate complexes and the sum of the electronegativities and the nucleophilic reactivity constant of the donor groups.582... 

Table 16 Nucleophilicity Reactivity Constants ( pt) to trans-PtCl2(py)2...

TjPt = nucleophilic reactivity constant (for the entering ligand)... 

The rates of several substitution reactions at palladium(n) have been measured in methanol. For rra 5-[PdL2(N02)2] + Y ->-fra//j-[PdL2(N02)Y] + NO2-, where L = PPr"s, AsEtg, or piperidine and Y = Cl, N3-, Br, I, SCN, or (NH2)2CS, a set of nucleophilic reactivity constants npd = log ( alMeOHj/Ari) has been calculated, where and refer to rate constants for the solvolytic path and for direct nucleophilic attack on the complex rra/ij-[Pd(PPr 3)2(N02)2l. All the complexes studied obey the linear free-energy relation log kz = jnpd + log kx, where j is a nucleophilic discrimination factor. The npd sequence resembles that already found for platinum(n) complexes. 

Table 5. Relationship Between Cure Rate Constant and Relative Nucleophilic Reactivity Constant...

---