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TY - JOUR AU - Kinunda , Grace A. PY - 2018/07/31 Y2 - 2025/07/26 TI - A trans influence and π-conjugation effects on ligand substitution reactions of Pt(II) complexes with tridentate pendant N/S-donor ligands JF - Tanzania Journal of Science JA - Tanz. J. Sci. VL - 44 IS - 2 SE - Articles DO - UR - http://www.tjs.udsm.ac.tz/index.php/tjs/article/view/242 SP - 45-63 AB - <p><em>The rate of displacement of the chloride ligands by three neutral nucleophiles (Nu) of different steric demands, namely thiourea (TU), N,N’-dimethylthiourea (DMTU) and N,N,N,’N-tetramethylthiourea (TMTU) in the complexes viz; </em><em>[Pt(II)(bis(2-pyridylmethyl)amine)Cl]ClO₄, (<strong>Pt1</strong>), [Pt(II){N-(2-pyridinylmethyl)-8-quinolinamine}Cl]Cl, (<strong>Pt2</strong>), [Pt(II)(bis(2-pyridylmethyl)sulfide)Cl]Cl, (<strong>Pt3</strong>) and [Pt(II){8-((2-pyridylmethyl)thiol)quinoline}Cl]Cl, (<strong>Pt4</strong>)</em><em> was studied under pseudo first-order conditions as a function of concentration and temperature using a stopped-flow technique and UV-Visible spectrophotometry. The observed pseudo first-order rate constants for substitution reactions obeyed the simple rate law</em><em>. The results have shown that </em><em>the chloro ligand in <strong>Pt(N^S^N)</strong> complexes is more labile by two orders of magnitude than <strong>Pt(N^N^N)</strong> complexes due to the high trans labilizing effect brought by the S-donor atom</em><em>. The quinoline based Pt(II) complexes (<strong>Pt2</strong> and <strong>Pt4</strong>) have been found to be slow than their pyridine counterparts <strong>Pt1</strong> and <strong>Pt3</strong> due to poor π-acceptor ability of quinoline. Second-order kinetics and large negative activation entropies support an associative mode of activation. </em></p> ER -