Axial Ligand Substitution Reaction Kinetics Of Pyrimidine-2-thionato Bridged Binuclear Platinum(iii) Complexes

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ABSTRACT


AXIAL LIGAND SUBSTITUTION REACTION KINETICS OF PYRIMIDINE-2-THIONATO BRIDGED BINUCLEAR PLATINUM(III) COMPLEXES




G&ouml / y, Aytun&ccedil / M. S. Department of Chemistry
Supervisor: Prof. Dr. H&uuml / seyin iS&ccedil / i
Co-supervisor: Assoc. Prof.Dr. Seniz &Ouml / zalp Yaman



September 2007, 89 pages



The kinetics of the ligand substitution reactions, which is represented by the equation,

[Pt2(C4H3N2S)4X2] + 2Y- Pt2(C4H3N2S)4Y2 + 2X-

where X- = Cl-, Br-, I- and Y- = Cl-, Br-, I- are studied in acetonitrile in the presence of excess Y- ion concentrations, under constant ionic strength. All reactions are reversible. The rate of the above reaction is dependent on binuclear complex and entering ligand concentrations. Thus general rate equation can be written as

Rate = k [Y-]a[Pt2(C4H3N2S)4X2]b

The reaction rates are first order with respect to the substrate complex (b=1). The experimentally determined values of the order of the reaction with
repect to entering ligand, &ldquo / a&rdquo / , are 0.96&plusmn / 0.057 (X=I-, Y=Cl-), -0.49&plusmn / 0.037 (X=Cl-, Y=I-), 0.28&plusmn / 0.023 (X=I-, Y=Br-), 0.48&plusmn / 0.044 (X=Br-, Y=I-), 0.53&plusmn / 0.042 (X=Br-, Y=Cl-), and -0.21&plusmn / 0.014 (X=Cl-, Y=Br-).
The rate constants are 12.1&plusmn / 2.05 M-1s-1 (X=I-, Y=Cl-), (5.7&plusmn / 1.6)x10-3 M1/2s-1 (X=Cl-, Y=I-), 0.3&plusmn / 0.27 M-0.3s-1 (X=I-, Y=Br-), 0.53&plusmn / 0.11 M-1/2s-1 (X=Br-, Y=I-), 1.74&plusmn / 0.16 M-1/2s-1 (X=Br-, Y=Cl-), and 1.71&plusmn / 0.37x10-2 M0.2s-1 (X=Cl-, Y=Br-).
To obtain information about the energetics of the reactions, the temperature dependence of the rate constants is determined and the activation parameters &amp / #916 / H* and &amp / #916 / S* are calculated. The values &amp / #916 / S* are negative and, in the range of -81 and -236 J K-1 mol-1. These results support an associative-interchange, Ia, mechanism. All data obtained in this work are used to propose a mechanism which will be consistent with the experimentally determined rate law.

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QD Inorganic Chemistry 146-197

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Identifer	oai:union.ndltd.org:METU/oai:etd.lib.metu.edu.tr:http://etd.lib.metu.edu.tr/upload/2/12608684/index.pdf
Date	01 August 2007
Creators	Goy, Aytunc
Contributors	Isci, Huseyin
Publisher	METU
Source Sets	Middle East Technical Univ.
Language	English
Detected Language	English
Type	M.S. Thesis
Format	text/pdf
Rights	To liberate the content for METU campus