Mechanisms of organometallic reactions. Part II. Kinetics of the reaction of acetonitrile with tricarbonyl-(cycloheptatriene) and -(arene) complexes of metals in Group VI
- 1 January 1974
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in J. Chem. Soc., Dalton Trans.
- No. 4,p. 428-432
- https://doi.org/10.1039/dt9740000428
Abstract
Kinetic studies of the reaction of acetonitrile with [(C7H8)M(CO)3](M = Cr, Mo, or W) complexes show the third-order rate law, Rate =k[Complex][MeCN]2. This order is explained in terms of a mechanism involving pre-equilibrium association between the complex and acetonitrile, followed by rate-determining addition of a second molecule of MeCN. The ease of cycloheptatriene displacement varies with the nature of the metal in the order Mo > W > Cr. In contrast, similar studies of the reaction of acetonitrile with the complex [(C6H3Me3)Mo(CO)3] indicate the second-order rate law, Rate =k[Complex][MeCN]. The change in mechanism is rationalised in steric terms. Comparison with previous data for the corresponding reaction of acetonitrile with the cation [(C7H7)Mo(CO)3]+ suggest the order C7H8 > C6H3Me3 > C7H7 for ease of displacement of π-bonding organic ligands from [LMo(CO)3]n+(n= 0 or 1) species.Keywords
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