Role of chelate substituents and cis sigma-effect on the rate of ligand substitution at Pt(N-N-N) and Pt(N-N-C) centres

Dalton Transactions : an International Journal of Inorganic Chemistry
Deogratius JaganyiRudi van Eldik

Abstract

Four complexes of the type [Pt(N-N-X)Cl](X = N or C) were tailor synthesized for mechanistic studies in methanol. The terdentate ligands included terpy, 4'-Ph-terpy, 4'-(2"-CF(3)-Ph)-terpy, and 4'-(2"'-CF(3)-Ph)-6-Ph-2,2'-bipy. The rate of substitution of the chloro ligand by thiourea, N,N'-dimethylthiourea, and N,N,N',N'-tetramethylthiourea was studied as a function of nucleophile concentration, temperature and pressure by using a stopped-flow technique. The observed pseudo-first-order rate constants for the substitution reactions obeyed the simple rate law k(obs) = k(2)[Nu]. Second-order kinetics and negative activation entropies and volumes support an associative substitution mechanism. At 298 K, the values of the second-order rate constant show a slight dependence on the nature of the moiety attached to the terpy ligand. Changing from a nitrogen sigma-donor to a carbon sigma-donor in the cis position, results in a deceleration of the substitution rate. The results suggest that the Pt-C bond in the cis position activates the metal centre in a different way than in the trans position.

Citations

Jun 14, 2006·Dalton Transactions : an International Journal of Inorganic Chemistry·Deogaratius JaganyiZivadin D Bugarcić
Sep 14, 2018·Dalton Transactions : an International Journal of Inorganic Chemistry·SneŽana RadisavljevićAna Rilak Simović
Jan 21, 2009·Dalton Transactions : an International Journal of Inorganic Chemistry·D Reddy, D Jaganyi
Jun 14, 2006·Dalton Transactions : an International Journal of Inorganic Chemistry·Zivadin D BugarcićRudi van Eldik
Mar 27, 2009·Dalton Transactions : an International Journal of Inorganic Chemistry·Luca RigamontiAlessandro Pasini
Aug 1, 2012·Dalton Transactions : an International Journal of Inorganic Chemistry·Peter Ongoma, Deogratius Jaganyi
Dec 7, 2013·Dalton Transactions : an International Journal of Inorganic Chemistry·Isaac M Wekesa, Deogratius Jaganyi
Dec 12, 2012·Dalton Transactions : an International Journal of Inorganic Chemistry·Peter O Ongoma, Deogratius Jaganyi
Apr 27, 2013·Dalton Transactions : an International Journal of Inorganic Chemistry·A ShairaD Jaganyi
Nov 19, 2011·Dalton Transactions : an International Journal of Inorganic Chemistry·Allen Mambanda, Deogratius Jaganyi
Nov 19, 2010·Dalton Transactions : an International Journal of Inorganic Chemistry·Allen Mambanda, Deogratius Jaganyi

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