μ-Diphenylacetylene-bis(tetracarbonylcobalt) undergoes two successive substitution reactions with tri-n-butylphosphine in decalin and the kinetics of these reactions have been studied. Each step shows pseudo-first-order behaviour with kobs = k1 + k2[PBu3] under an atmosphere of argon. Activation parameters have been obtained for each path in each step and the effect of carbon monoxide on the paths governed by k1 is consistent with a CO-dissociative mechanism. Relative rate constants for bimolecular attack on the co-ordinatively unsaturated intermediates by carbon monoxide and tributylphosphine have been obtained. The rate parameters for the two dissociative paths are quite similar but the second bimolecular path is governed by a much higher value of ΔH‡, and a much less negative value of ΔS‡, than the first.
Reaction mechanisms of metal-metal bonded carbonyls. Part IV. The substitution reaction of μ-diphenylacetylene-bis(tetracarbonylcobalt) with tri-n-butylphosphine
BASATO, MARINO;
1974
Abstract
μ-Diphenylacetylene-bis(tetracarbonylcobalt) undergoes two successive substitution reactions with tri-n-butylphosphine in decalin and the kinetics of these reactions have been studied. Each step shows pseudo-first-order behaviour with kobs = k1 + k2[PBu3] under an atmosphere of argon. Activation parameters have been obtained for each path in each step and the effect of carbon monoxide on the paths governed by k1 is consistent with a CO-dissociative mechanism. Relative rate constants for bimolecular attack on the co-ordinatively unsaturated intermediates by carbon monoxide and tributylphosphine have been obtained. The rate parameters for the two dissociative paths are quite similar but the second bimolecular path is governed by a much higher value of ΔH‡, and a much less negative value of ΔS‡, than the first.
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