Tuning Reactivity of Platinum(II) Complexes

ppm. These spectra are indicative of the formation of other minor transient intermediate
products. ............................................................................................................................. 22
Figure 4.9: 195 Pt NMR spectra of the reaction mixture of pzn–Cl with six mole equivalents
TU, showing pure dinuclear Pt(II) complex pzn–Cl (A, δ = -2302.2 ppm)before the
reaction and the final degradation product (E, δ = -4045.0 ppm) corresponding to
[Pt(TU)4] 4+, 24.0 h after the reaction. Proposed minor transient products (B, C and D, at
δ = -2962.0, -3125.0, and -3276.0 ppm, correspond to -- respectively). ........................... 23
Figure 4. 10: First order plot for the reaction of cis-[{PtCl(NH3)2}2-μ-pzn] +2 (0.221
mM) with excess TU (1.323 mM) (in the molar ratio complex:ligand = 1:6) in D2O at 30°
C, using 1H NMR spectroscopy. The equation used in calculation is: ln[ML]t = -kobs1 +
ln[ML]0 , where [ML]0 = [free pyrazine ligand] = [L]infinite time, and [ML]t = [L]infinite – [L]t
using the area of the signals for released pyrazine ligand. ................................................ 24
Figure 4.11: Plots of ln(k2/ T) versus 1/T for the first reaction step of 2,5pzn with a
series nucleophiles in the temperature range 15-35 °C. ................................................... 26
Figure 4.12: Plots of ln(k2 /T) versus 1/T for the substitution reaction of second step of
2,5pzn with thiourea nucleophiles in the temperature range 15-35 °C. ........................... 26
Figure 4.13: Plots of ln(k2 / T) versus 1/T for the substitution reaction of third step of
2,5pzn with thiourea nucleophiles in the temperature range 15-35 °C. ........................... 27
Figure 4.14: DFT-calculated electron density distribution plots for the investigated
complexes illustrating steric hindrance by the bridging pyrazine ligand and the coordinated
thiourea nucleophiles. The blue (arrows indicate the least sterically hindered pathway for
the incoming thiourea nucleophiles, while the red arrows indicate pathways that are
subject to increased axial steric hindrance by the methyl groups present on the linker
and the already attached thiourea ligand. .......................................................................... 31
List of Tables
Table 4.1: A summary of the DFT calculated data for the investigated
[{cis–Pt(OH2)(NH3)2}2–µ–pzn]
iii
4+ complexes at B3LYP/LACVP ** level of theory ............. 12