Tuning Reactivity of Platinum(II) Complexes

trans-[Pt(py) 2 Cl 2 ] + Y n trans-[Pt(py) 2 (Y)Cl] (n+1) + Cl - (2.40)
When trans-[Pt(py)2Cl2] was used as the standard, the nucleophilicity constant of the
incoming ligand, n ° pt, is defined as: 26,35
log(
k y
k o s
) = n o Pt
where, kY = the measured second-order rate constant for the reaction of the
entering nucleophile, Y
25
(2.41)
k o S = the second-order rate constant for attack of the solvent (methanol)
in an associative mechanism and is equal to {ks/[MeOH]}
kS = the rate constant for attack of the solvent, MeOH, on the complex.
At 30 °C, the concentration of pure methanol is assumed to be 24.3 M and the equation
simplifies to:
n o pt = npt + 1.39 (2.42)
By definition the n o pt for methanol as the entering group is zero, while that for
triphenylphosphine ligand, {(Ph)3P}, is a high value of 8.99. The typical n o pt data
obtained for Equation 2.42 is summarised in Table 2.1 for different entering
nucleophiles (Y).