Nucleophilic Attack on Cyclooctadiene Complexes of Palladium: Stereochemistry of the Resulting Cyclooctenylpalladium Derivatives
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- 作者：Gretchen R. Hoel ; Robert A. Stockland ; Jr. ; Gordon K. Anderson ; Folami T. Ladipo ; Janet Braddock-Wilking ; Nigam P. Rath ; and Juan C. Mareque-Rivas
- 刊名：Organometallics
- 出版年：1998
- 出版时间：March 16, 1998
- 年：1998
- 卷：17
- 期：6
- 页码：1155 - 1165
- 全文大小：155K
- 年卷期：v.17,no.6(March 16, 1998)
- ISSN：1520-6041
文摘
Reaction of [PdClMe(cod)] withMeO2CC
CCO2Me occurs in two steps,namely, insertionof the alkyne into the Pd-Me bond followed by migratory insertion ofone of the doublebonds of the coordinated cyclooctadiene into the Pd-alkenyl bond thusformed. The resultingchloride-bridged, cyclooctenyl complex was converted to[Pd(acac){
1,2-C8H12C(CO2Me)=CMe(CO2Me)}], 2a, which was characterizedcrystallographically. The molecular structurerevealed that each insertion took place in a cis manner. Reactionsof [PdCl2(cod)] with arange of nucleophiles were performed, which gave analogouschloride-bridged, cyclooctenylpalladium dimers, 1, which could be converted to theiracetylacetonate derivatives, 2.The solid-state structure of the methoxy complex[Pd(acac)(1,2-C8H12OMe)],2b, obtainedby reaction of [PdCl2(cod)] with NaOMe followed byAg(acac), was determined. This showedthat exo attack of the OMe group occurred. In contrast, thestructure of the phenyl derivative[Pd(acac)(1,2-C8H12Ph)],2e, produced by treatment of [PdCl2(cod)] withPh4Sn followed byAg(acac), indicated that the phenyl group added in an endofashion, presumably via a phenylpalladium intermediate of the type [PdClPh(cod)]. With thelarger mesityl group, the complex[PdCl(C6H2Me3)(cod)]could be isolated. Each of the complexes was fully characterizedby1H and 13C{1H} NMRspectroscopy, and the appearance of the CHPd signal was usedtodistinguish between the exo and endo isomers. On the basis of thecrystallographic andNMR data, it was deduced that the organometallic reagents ArMgX (Ar =Ph, 2-MeC6H4,2,4,6-Me3C6H2),Ph4Sn, and(4-MeC6H4)2Hg generate theendo products by initial attack atthe metal. In contrast, reactions with NaOR (R = Me, Et),NaCH(CO2Me)2, AgOAc, andEt2NH proceed by direct attack of the nucleophile atthe coordinated double bond to givethe exo products.
CCO2Me occurs in two steps,namely, insertionof the alkyne into the Pd-Me bond followed by migratory insertion ofone of the doublebonds of the coordinated cyclooctadiene into the Pd-alkenyl bond thusformed. The resultingchloride-bridged, cyclooctenyl complex was converted to[Pd(acac){1,2-C8H12C(CO2Me)=CMe(CO2Me)}], 2a, which was characterizedcrystallographically. The molecular structurerevealed that each insertion took place in a cis manner. Reactionsof [PdCl2(cod)] with arange of nucleophiles were performed, which gave analogouschloride-bridged, cyclooctenylpalladium dimers, 1, which could be converted to theiracetylacetonate derivatives, 2.The solid-state structure of the methoxy complex[Pd(acac)(1,2-C8H12OMe)],2b, obtainedby reaction of [PdCl2(cod)] with NaOMe followed byAg(acac), was determined. This showedthat exo attack of the OMe group occurred. In contrast, thestructure of the phenyl derivative[Pd(acac)(1,2-C8H12Ph)],2e, produced by treatment of [PdCl2(cod)] withPh4Sn followed byAg(acac), indicated that the phenyl group added in an endofashion, presumably via a phenylpalladium intermediate of the type [PdClPh(cod)]. With thelarger mesityl group, the complex[PdCl(C6H2Me3)(cod)]could be isolated. Each of the complexes was fully characterizedby1H and 13C{1H} NMRspectroscopy, and the appearance of the CHPd signal was usedtodistinguish between the exo and endo isomers. On the basis of thecrystallographic andNMR data, it was deduced that the organometallic reagents ArMgX (Ar =Ph, 2-MeC6H4,2,4,6-Me3C6H2),Ph4Sn, and(4-MeC6H4)2Hg generate theendo products by initial attack atthe metal. In contrast, reactions with NaOR (R = Me, Et),NaCH(CO2Me)2, AgOAc, andEt2NH proceed by direct attack of the nucleophile atthe coordinated double bond to givethe exo products.