Tuning Reactivity of Platinum(II) Complexes

thiourea nucleophile is large enough to displace the bridging ligand to produce
[Pt(TU)4] 2+ and any other undefined products. This degradation process is 10 to 1000
times slower when compared to the first and the second substitution process
respectively. Similar results have been observed by Reedijk, et al., 32 where degradation
of the Pt-N(pht/pdn) bond occurred after initial substitution of the aqua ligands by 9EtG in
pdn and pht complexes. In all the cases, the rates of the successive substitution of the
aqua ligands and displacement of linker are influenced by the structure of the bridging
ligand.
5.3.5 Thermodynamic Parameters
To confirm that these complexes follow an associative mode of substitution,
characteristic of square-planar complexes, the enthalpy of activation (ΔH #) and entropy
of activation (ΔS # ) were determined in the temperature range 15-35 °C. The activation
enthalpies and entropies were calculated from the slope and y-intercept, respectively,
from the Eyring plots (Figure 5.9, 5.10 and 5.11) and these are summarised in Table 5.5.
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