Tuning Reactivity of Platinum(II) Complexes

The proton resonances for the coordinated aqua of pdn complex appeared within 45
min, while the reaction of chlorido–pzn took over 48 h to reach completion. The
substitution reactivity of the Pt–Cl bond in pzn was slower as expected compared with
the corresponding Pt–OH2 bond of the pdn complex because aqua ligand is more labile
and a better leaving group than the chloride ligand. 44 Only a section of the 1H NMR
spectra showing the first resonance for the unreacted complex and last resonance due
to the displaced pyrazine bridging ligand are presented in Figure 5.3, i.e. resonance at δ
= 9.04 ppm due to the symmetrically coordinated pyrazine ligand at the beginning of
the reaction, while a second singlet resonance at δ = 8.64 ppm, was observed after 48 h
and is assigned to free pyrazine ligand that resulted after release of the linker. 39,45
Similarly, the 195 Pt NMR spectra of the reaction of cis-[{PtCl (NH3)2}2-μ-pzn] +2 with TU
also revealed the presence of two main resonances: one peak at -2302 ppm consistent
with the N3Cl coordination sphere of unreacted pzn and at -4140 ppm for the
degradation product [Pt(TU)4] +215 as shown in Chapter 4 (Section4.3.4, Figure 4.9).
17