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Kinetics and Mechanism of the Reaction of Chloroplatinum(II) Complexes with Alkyl Radicals
Author(s) -
Chen WenJang,
Espenson James H.,
Bakac Andreja
Publication year - 1993
Publication title -
journal of the chinese chemical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.329
H-Index - 45
eISSN - 2192-6549
pISSN - 0009-4536
DOI - 10.1002/jccs.199300051
Subject(s) - chemistry , radical , flash photolysis , reaction rate constant , medicinal chemistry , kinetic isotope effect , kinetics , reductive elimination , platinum , aqueous solution , alkyl , hydrolysis , hydride , photochemistry , hydrogen , organic chemistry , deuterium , catalysis , physics , quantum mechanics
The reaction between certain platinum(II) complexes and alky radicals produces an unstable organoplatinum(III) intermediate, {Pt III ‐R}. The kinetics of this step were evaluated by laser flash photolysis with ABTS 2 (2,2′‐azinobis(3‐ethylbenzothiazoline‐6‐sulfonate) ion) and TMPD (tetramethylphenylenediamine) as kinetic probes. The rate constants for PtCl 4 2− are: k Pt /10 8 L mol −1 s −1 = 5.2, 2.8 and 0.27 for CH 3, C 2 H 5 , and CH 2 Cl in aqueous solution at pH 1. Those with cis‐Pt(NH 3 ) 2 Cl 2 are somewhat smaller, and those for Pt(NH 3 ) 4 2+ too small to measure will) this technique. The product analysis indicates that the decomposition of organoplatinum takes place by hydrolysis and (for R = C 2 H 5 only) by β‐elimination, The kinetic isotope effect on die β‐elimination of DCH 2 CH 2 PtC 4 , 2− is k H /k D = 1.2. The β‐elimination step produces a Pt III ‐hydride that releases hydrogen gas and forms {Pt III ‐OH}. The short‐lived Pt(III) intermediate may disproportionate or oxidize the Co II complex that is produced in the radical‐generating step.