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Tuning Reactivity of Platinum(II) Complexes

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H a<br />

H`a<br />

Equivalnt to that <strong>of</strong><br />

free ligand<br />

9.6 9.4 9.2 9.0 8.8 8.6 8.4 8.2 8.0 7.8 7.6 7.4 7.2 7.0 6.8 6.6 6.4 6.2<br />

ppm<br />

Hb<br />

H`b<br />

19<br />

t = 45. 0 min<br />

t = 0.0 h<br />

( + 20 fold TU)<br />

( 0 fold TU)<br />

Figure 5.4: 1H NMR spectra <strong>of</strong> the reaction <strong>of</strong> cis-[{Pt(OH2)(NH3)2}2-μ-pdn] +2 and 20<br />

NH 3<br />

NH 3<br />

Ha<br />

fold excess thiourea (TU).<br />

Hb<br />

N<br />

Pt N H2O H O 2 Pt<br />

NH3 NH3 +4<br />

Excess TU<br />

Ha'<br />

N N<br />

Hb'<br />

+ 2H 2 O + 2[Pt(TU) 4 ] +2<br />

+ undefined products<br />

Scheme 5.3: Structure and proton labels Ha, Hb, Ha’ and Hb’ for coordinated and<br />

un-coordinated pyridazine ligand after dissociation <strong>of</strong> the bridging ligand.<br />

Examination <strong>of</strong> the reaction products <strong>of</strong> the metal complexes pzn and pdn with<br />

thiourea, using 1 H and 195 Pt NMR, reveals the formation <strong>of</strong> free linker ligand-pyrazine<br />

and pyridazine, and a [Pt(TU)4] 2+ unit yielding a 195Pt resonance at around -4145 ppm,<br />

which is consistent with value <strong>of</strong> -3999 ppm reported by van Eldik, et.al. 15 This is<br />

attributed to release <strong>of</strong> the linker and the ammine ligands from the Pt(<strong>II</strong>) centre in the

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