Kinetic Study of the Insertion of Norbornadiene into Palladium-Carbon Bonds of Complexes Containing the Rigid Bidentate Nitrogen Ligand Bis(arylimino)acenaphthene
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- 作者：Johannes H. Groen ; Johannes G. P. Delis ; Piet W. N. M. van Leeuwen ; and Kees Vrieze
- 刊名：Organometallics
- 出版年：1997
- 出版时间：January 7, 1997
- 年：1997
- 卷：16
- 期：1
- 页码：68 - 77
- 全文大小：367K
- 年卷期：v.16,no.1(January 7, 1997)
- ISSN：1520-6041
文摘
The ionic[Pd(C7H8C(O)R)(Ar-BIAN)]X (R= Me, Et, iPr, Ph; X = Cl, Br, I; Ar =p-An,p-FC6H4,p-BrC6H4, p-Tol, Ph,o,o'-Me2C6H3,o,o'-iPr2C6H3)complexes (1b-12b), bearing thebidentate nitrogen ligand bis(arylimino)acenaphthene(Ar-BIAN), have been synthesized viareaction of the corresponding neutral acylpalladium complexesPd(C(O)R)X(Ar-BIAN) (1a-12a) with norbornadiene (nbd). For the first time, anextensive kinetic study of this migratoryalkene insertion into acyl-palladium bonds of neutral complexescontaining 
chars/alpha.gif" BORDER=0>-diimine ligandshas been carried out. It has been found that underpseudo-first-order circumstances thesereactions follow the rate law kobsd =k1 + k2[nbd],which shows that these reactions proceedvia a pathway independent of alkene concentration(k1 pathway) and a pathwaydependenton alkene concentration (k2 pathway). Thedramatic decrease of the rate constants k1andk2 upon increasing the steric bulk of the BIANligand and the large negative entropy ofactivation and low enthalpy of activation for both pathways indicatethat the k1 andk2pathways are closely related and involve associative processes.From the influence of solvent,X and C(O)R ligand, steric and electronic properties of the BIANligand, the presence offree halide and free BIAN, and the parameters of activation, mechanismshave been proposedfor both pathways. The k1 pathway mayproceed via a rate-determining solvent-assistedhalide or nitrogen dissociation, followed by alkene association andmigratory insertion, whilethe k2 pathway may occur via a rate-determiningmigratory alkene insertion in a contaction pair intermediate. This species may be formed via alkeneassociation followed by eitherhalide or nitrogen dissociation.
chars/alpha.gif" BORDER=0>-diimine ligandshas been carried out. It has been found that underpseudo-first-order circumstances thesereactions follow the rate law kobsd =k1 + k2[nbd],which shows that these reactions proceedvia a pathway independent of alkene concentration(k1 pathway) and a pathwaydependenton alkene concentration (k2 pathway). Thedramatic decrease of the rate constants k1andk2 upon increasing the steric bulk of the BIANligand and the large negative entropy ofactivation and low enthalpy of activation for both pathways indicatethat the k1 andk2pathways are closely related and involve associative processes.From the influence of solvent,X and C(O)R ligand, steric and electronic properties of the BIANligand, the presence offree halide and free BIAN, and the parameters of activation, mechanismshave been proposedfor both pathways. The k1 pathway mayproceed via a rate-determining solvent-assistedhalide or nitrogen dissociation, followed by alkene association andmigratory insertion, whilethe k2 pathway may occur via a rate-determiningmigratory alkene insertion in a contaction pair intermediate. This species may be formed via alkeneassociation followed by eitherhalide or nitrogen dissociation.