Novel BPPFA Palladium Complexes. P,P to P,N Rearrangements Promoted by Chelating 3-N,P,P-BPPFA Inter
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- 作者：Blanca R. Manzano ; Fé ; lix A. Jaló ; n ; Felipe Gó ; mez-de la Torre ; Ana M. Ló ; pez-Agenjo ; Ana M. Rodrí ; guez ; Kurt Mereiter ; Walter Weissensteiner ; and Thomas Sturm
- 刊名：Organometallics
- 出版年：2002
- 出版时间：March 4, 2002
- 年：2002
- 卷：21
- 期：5
- 页码：789 - 802
- 全文大小：208K
- 年卷期：v.21,no.5(March 4, 2002)
- ISSN：1520-6041
文摘
Novel palladium complexes with BPPFA (N,N-dimethyl-1-[2,1'-bis(diphenylphosphino)ferrocenyl]ethylamine) and the newly prepared ligand 1,1'-bis(diphenylphosphino)-2-methylferrocene (BPPFMe, 1) have been synthesized. Racemic BPPFA reacts with Pd2(dba)3·CHCl3 in the presence of electron-withdrawing alkenes to give palladium(0) complexesPd(BPPFA)(alkene), where alkene = dimethyl fumarate (2), maleic anhydride (3). Displacement of weak donor ligands from the appropriate palladium(II) precursors leads to thederivatives [Pd(
3-2-Me-C3H4)(BPPFA)]TfO (4), Pd(C6F5)2(BPPFA) (5), Pd(C6F5)2(BPPFMe)(6), PdMe2(BPPFA) (7), and PdClMe(BPPFA) (8). Complexes 2-4 and 8 each exist in solutionas two diastereomers that do not interconvert at room temperature on the NMR time scale.In all mononuclear complexes BPPFA is P,P-coordinated to palladium. When PdClX(cod) (X= Cl, Me) is reacted with (RC,SP)-BPPFA in a Pd:L ratio higher than 1:1, polynuclear speciesare formed. A Pd:L ratio of 2:1 leads to the tetranuclear derivatives {cis-PdClX(
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3-BPPFA)}2{PdX(-Cl)2PdX} (X = Me (9), Cl (10)), while a ratio of 1.5:1 gives the trinuclear complexes{cis-PdClX(-3-BPPFA)}2(trans-PdClX) (X = Me (11), Cl (12)) along with the correspondingtetra- and mononuclear derivatives. Mechanistic studies concerning the formation of thetetranuclear complexes have shown that a P,P to P,N coordination shift and Pd-P bondrupture are feasible processes. Variable-temperature 1H NMR studies have provided evidenceof Pd-N interactions in complexes 2, 5, 7, and 8 that involve an unprecedented terdentate3N,P,P chelate coordination of BPPFA to palladium. The pentafluorophenyl complexes 5and 6 each exist in solution as two conformers that are interconvertible by torsional twistingof the Cp rings. In the case of complex 5 this interconversion process is slowed at lowtemperature to such an extent that both conformers can be observed separately by NMRspectroscopy. This phenomenon is presumably due to the Pd-N interaction. The molecularstructures of 2M and 8M (M = major isomer) have been determined by X-ray diffraction.
3-2-Me-C3H4)(BPPFA)]TfO (4), Pd(C6F5)2(BPPFA) (5), Pd(C6F5)2(BPPFMe)(6), PdMe2(BPPFA) (7), and PdClMe(BPPFA) (8). Complexes 2-4 and 8 each exist in solutionas two diastereomers that do not interconvert at room temperature on the NMR time scale.In all mononuclear complexes BPPFA is P,P-coordinated to palladium. When PdClX(cod) (X= Cl, Me) is reacted with (RC,SP)-BPPFA in a Pd:L ratio higher than 1:1, polynuclear speciesare formed. A Pd:L ratio of 2:1 leads to the tetranuclear derivatives {cis-PdClX(-3-BPPFA)}2{PdX(-Cl)2PdX} (X = Me (9), Cl (10)), while a ratio of 1.5:1 gives the trinuclear complexes{cis-PdClX(-3-BPPFA)}2(trans-PdClX) (X = Me (11), Cl (12)) along with the correspondingtetra- and mononuclear derivatives. Mechanistic studies concerning the formation of thetetranuclear complexes have shown that a P,P to P,N coordination shift and Pd-P bondrupture are feasible processes. Variable-temperature 1H NMR studies have provided evidenceof Pd-N interactions in complexes 2, 5, 7, and 8 that involve an unprecedented terdentate3N,P,P chelate coordination of BPPFA to palladium. The pentafluorophenyl complexes 5and 6 each exist in solution as two conformers that are interconvertible by torsional twistingof the Cp rings. In the case of complex 5 this interconversion process is slowed at lowtemperature to such an extent that both conformers can be observed separately by NMRspectroscopy. This phenomenon is presumably due to the Pd-N interaction. The molecularstructures of 2M and 8M (M = major isomer) have been determined by X-ray diffraction.