Insertion Reactions Involving Palladium Complexes with Nitrogen Ligands. 2. Carbon monoxide and Alkene Insertion Reactions with Novel Palladium Compounds Containing Terdentate Ligands
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- 作者：Richard E. Rü ; lke ; Vincent E. Kaasjager ; Dave Kliphuis ; Cornelis J. Elsevier ; Piet W. N. M. van Leeuwen ; Kees Vrieze ; and Kees Goubitz
- 刊名：Organometallics
- 出版年：1996
- 出版时间：January 23, 1996
- 年：1996
- 卷：15
- 期：2
- 页码：668 - 677
- 全文大小：381K
- 年卷期：v.15,no.2(January 23, 1996)
- ISSN：1520-6041
文摘
Neutral and ionic methylpalladium compounds containingtrinitrogen ligands (N-N-N)Pd(Me)(Y) (N-N-N = trinitrogen ligand; Y =Cl-, CF3SO3-,4-Me-C6H4SO3-)have beensynthesized and characterized by spectroscopic methods. Thecoordination mode of thetrinitrogen ligand depends not only on the rigidity of the ligand butalso on the solvent andon the anion Y. With the weakly coordinating ligandsCF3SO3- andBF4- the trinitrogenligands readily adopt a terdentate coordination mode, resulting incomplexes of the type[(
chars/sigma.gif" BORDER=0 >3-N-N-N)Pd(Me)]Y. Inmethylchloropalladium compounds, the flexible trinitrogenligandsadopt a bidentate coordination mode, resulting in the complexes(chars/sigma.gif" BORDER=0 >2-N-N-N)Pd(Me)(Cl),whereas the terdentate coordination mode has been found for rigidligands, resulting in theionic complexes [(chars/sigma.gif" BORDER=0 >3-N-N-N)Pd(Me]Cl.Polar solvents, such as acetonitrile, stabilize theformation of ionic complexes. The methylpalladium compoundsreadily insert carbonmonoxide, resulting in the facile formation of the acetylpalladiumcompounds (chars/sigma.gif" BORDER=0 >2-N-N-N)Pd(C(O)Me)(Cl) and[(chars/sigma.gif" BORDER=0 >3-N-N-N)Pd(C(O)Me)]Y (Y =Cl-, OTf-), in which thecoordinationmode of the ligands remains unchanged. CO insertion half-lives ofthe methylpalladiumcompounds show that substituents adjacent to one nitrogen donor atomaccelerate theinsertion for both the neutral and the ionic complexes.Interestingly, the CO insertion half-life is not correlated to the rigidity of the trinitrogen ligand, sincethe compound [(terpy)Pd(Me)]Cl, which contains the rigid ligand terpy, undergoes afaster carbon monoxideinsertion than analogous complexes with the flexible ligandsC5H4N-2-C(H)=N(CH2)2C5H4N.Alkene insertion has been tested by reacting the acetylpalladiumcompounds with norbornadiene (NBD). The NBD-inserted compounds contain theC7H8C(O)CH3 moietycoordinatingin an unprecedented monodentate chars/sigma.gif" BORDER=0 >-C fashion. Peculiarly,[(terpy)Pd(C(O)Me)]Cl not onlyundergoes NBD insertion but does so at a very high rate. On thebasis of these findings atentative mechanism is suggested.
chars/sigma.gif" BORDER=0 >3-N-N-N)Pd(Me)]Y. Inmethylchloropalladium compounds, the flexible trinitrogenligandsadopt a bidentate coordination mode, resulting in the complexes(chars/sigma.gif" BORDER=0 >2-N-N-N)Pd(Me)(Cl),whereas the terdentate coordination mode has been found for rigidligands, resulting in theionic complexes [(chars/sigma.gif" BORDER=0 >3-N-N-N)Pd(Me]Cl.Polar solvents, such as acetonitrile, stabilize theformation of ionic complexes. The methylpalladium compoundsreadily insert carbonmonoxide, resulting in the facile formation of the acetylpalladiumcompounds (chars/sigma.gif" BORDER=0 >2-N-N-N)Pd(C(O)Me)(Cl) and[(chars/sigma.gif" BORDER=0 >3-N-N-N)Pd(C(O)Me)]Y (Y =Cl-, OTf-), in which thecoordinationmode of the ligands remains unchanged. CO insertion half-lives ofthe methylpalladiumcompounds show that substituents adjacent to one nitrogen donor atomaccelerate theinsertion for both the neutral and the ionic complexes.Interestingly, the CO insertion half-life is not correlated to the rigidity of the trinitrogen ligand, sincethe compound [(terpy)Pd(Me)]Cl, which contains the rigid ligand terpy, undergoes afaster carbon monoxideinsertion than analogous complexes with the flexible ligandsC5H4N-2-C(H)=N(CH2)2C5H4N.Alkene insertion has been tested by reacting the acetylpalladiumcompounds with norbornadiene (NBD). The NBD-inserted compounds contain theC7H8C(O)CH3 moietycoordinatingin an unprecedented monodentate chars/sigma.gif" BORDER=0 >-C fashion. Peculiarly,[(terpy)Pd(C(O)Me)]Cl not onlyundergoes NBD insertion but does so at a very high rate. On thebasis of these findings atentative mechanism is suggested.