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Tuning Reactivity of Platinum(II) Complexes

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Figure 2.9: Rates <strong>of</strong> Pt(<strong>II</strong>) complexes correlated with trans-[Pt(py)2Cl2] as reference,<br />

for different entering nucleophiles: • = trans-[Pt(PEt3)2Cl2] in methanol at<br />

30 °C; ▲ = [Pt(en)Cl2] in water at 35 °C. 18<br />

The free energy linear relationship (LFER) obtained is given as: 18<br />

logkY = S. n o pt + C (2.43)<br />

where, S is the nucleophilic discrimination factor and depends on the complex.<br />

C is the intrinsic reactivity.<br />

The value <strong>of</strong> S reflects the electrophilicity and steric properties at the site <strong>of</strong> substitution<br />

felt by the entering nucleophiles. A value <strong>of</strong> S equal to 1 is given to the reference<br />

complex, trans-[Pt(py)2Cl2]. 15,26 Values <strong>of</strong> S > 1 show increased reactivity <strong>of</strong> a particular<br />

complex toward the range <strong>of</strong> nucleophiles used relative to reference complex. The<br />

intercept, C, estimates the reactivity <strong>of</strong> the weakest nucleophile at the metal site and its<br />

effect can be likened to that <strong>of</strong> a solvent. Since the complex is more discriminating in a<br />

27

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