Uncatalysed cis–trans isomerization of chloro-(o-tolyl)bis(triethylphosphine)platinum(II) in protic solvents
- 1 January 1971
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in J. Chem. Soc. A
- p. 1877-1881
- https://doi.org/10.1039/j19710001877
Abstract
The rates of the spontaneous conversion of cis-[Pt(PEt3)2(o-tolyl)Cl] into its trans-isomer have been examined for methanol and ethanol solutions at different temperatures and compared with the rates at which chloride is replaced by iodide and cyanide. The substitution reactions obey the typical two-term rate law, kobs=k1+k2[Y]; k1 is ca. 100 times ki although the entropy of activation is very much less than that of the isomerization path. The isomerization suffers mass-law retardation by chloride ions. A nonsynchronous mechanism is suggested in which the rate-determining step is the breaking of the bond between the metal and the chloride ion to yield a three-co-ordinate intermediate. The reaction profile contains two minima, corresponding to the presence of two labile intermediates having a ‘cis-like’ and a ‘trans-like’ structure. This is the first kinetic study of an uncatalysed isomerization of a platinum(II) complex and the first example of a dissociative path being characterized in the presence of a much more favourable bimolecular path for substitution.Keywords
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