Oxidative Addition of Methyl Iodide to [RhI(CO){Ph2PCH2P(S)Ph2}]
5. Evidence for rhodium-methyl intermediate, 2.
This series of spectra were obtained from a reaction carried out at high methyl iodide concentration (8 M). This should favour a larger steady state concentration of the Rh-methyl intermediate, 2. The same approach was used successfully to detect a rhodium-methyl intermediate in the reaction of [RhI2(CO)2]- with methyl iodide [Ref. 5].
A weak band at 2062 cm-1 is shown expanded in red. The frequency of this band is in the expected region for the terminal n(CO) band of the oxidative addition product., 2. The band is shifted 75 cm-1 to high frequency compared with that of 1. Exactly the same shift has been reported for the product of oxidative addition of methyl iodide to [RhI(CO)(PPh3)2] [Ref. 6].
The weak absorption assigned to 2 decays at the same rate as the band due to 1, exactly the behaviour predicted by the steady state approximation for a reactive intermediate. We hope to obtain further evidence for the structure of this species by low temperature NMR spectroscopy.
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