The (aminoferrocenyl)phosphine ligand 1-diphenylphosphino-2,1‘-(1-dimethylaminopropanediyl)ferrocene, 1, was used to synthesize new palladium(0) and -(II) complexes. The reaction of Pd2(dba)3·CHCl3 with 1 in the presence of the electron-withdrawing olefins dimethylfumarate (DMFU) and maleic anhydride (MA) gave the new complexes Pd(1)(DMFU) (2) and Pd(1)(MA) (3). The allyl complex [Pd(η3-2-Me-C3H4)(1)]Tf (4) was obtained from the reaction of 1 with [Pd(η3-2-Me-C3H4)(Cl)]2 in the presence of AgTf. In solution all these compounds exist as mixtures of two diastereomers, with either the alkene or the allyl group differently oriented with respect to the aminophosphine ligand. The orientation of these ligands in the major isomers has been determined by means of NOEs. Alkene rotation takes place in complexes 2 and 3 with free energies of activation ΔG 340 ⧧ = 73.1 kJ mol-1 (2) and ΔG 368 ⧧ = 79.9 kJ mol-1 (3), respectively. These barriers are compared with those of some analogous ferrocenyl aminophosphine ligands, PPFA (2-(1-dimethylaminoethyl)-1-diphenylphosphinoferrocene) and PTFA (1-diphenylphosphino-2,3-endo-(α-dimethylamino)tetramethyleneferrocene) complexes. For 3, the alkene rotation leads to isomer interconversion, while the observed isomerization of 2 must proceed via an olefin face exchange. Some experiments in relation to the nature of this process are discussed. Starting from PdRR‘L‘ precursors and 1 or PPFA, other Pd(II) derivatives of formulas PdRR‘(1), R = Cl, R‘ = Me, L‘ = cod, 5; R = R‘ = Me, L‘ = tmeda, 6; R = R‘ = C6F5, L‘ = cod, 7, or PdClMe(PPFA), 8, were prepared. For 5 and 8, only the isomers with the methyl group trans to nitrogen were obtained. The Pd−N bond rupture in the new complexes of 1 and in similar derivatives of PPFA and PTFA has been analyzed by variable-temperature 1H NMR studies, and in some cases a line shape analysis has been carried out. The influence of the ferrocenyl aminophosphine and ancillary ligands as well as of the oxidation state of the palladium center on this process is discussed. The molecular structures of both rotamers of 3, present in the same crystal, were determined by X-ray structure analysis.

Four new enantiopure homo- and heteroannularly bridged ferrocenyl diphosphine ligands have been synthesized, characterized, and tested in enantioselective hydrogenations of olefins [methyl-(Z)-(α)-(acetamido)cinnamate, (Z)-(α)-methylcinnamic acid and dimethyl itaconate], ketones (ethyl pyruvate, methyl phenylglyoxylate, and ketopantolactone), and the imine 2-ethyl-N-(2-methoxy-1-methylethylidene)-6-methylbenzeneamine (MEAI). Generally, the homoannularly bridged ligand (S c ,R p )-[η 5 -cyclopentadienyl][η 5 -4-dicyclohexylphosphino-3-diphenylphosphino-4,5,6,7-tetrahydro-1H-indenyl]iron(II) performed best, giving up to 90.6% ee in the rhodium-catalyzed hydrogenation of dimethyl itaconate and 73% ee in the iridium-catalyzed hydrogenation of MEAI. The molecular structures of all new ligands in the solid state have been determined by X-ray diffraction. A structural comparison of the four new diphosphines with Josiphos-type ligands revealed that the stiffness of the ligand backbone strongly influences the enantioselectivity observed.

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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 Pd 2 (dba) 3 ‚ CHCl 3 in the presence of electron-withdrawing alkenes to give palladium(0) complexes Pd(BPPFA)(alkene), where alkene ) dimethyl fumarate (2), maleic anhydride (3). Displacement of weak donor ligands from the appropriate palladium(II) precursors leads to the derivatives [Pd(η 3 -2-Me-C 3 H 4 )(BPPFA)]TfO (4), Pd(C 6 F 5 ) 2 (BPPFA) (5), Pd(C 6 F 5 ) 2 (BPPFMe) (6), PdMe 2 (BPPFA) (7), and PdClMe(BPPFA) (8). Complexes 2-4 and 8 each exist in solution as 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 (R C ,S P )-BPPFA in a Pd:L ratio higher than 1:1, polynuclear species are formed. A Pd:L ratio of 2:1 leads to the tetranuclear derivatives {cis-PdClX(µ-κ 3 -BPPFA)} 2 -{PdX(µ-Cl) 2 PdX} (X ) Me (9), Cl (10)), while a ratio of 1.5:1 gives the trinuclear complexes {cis-PdClX(µ-κ 3 -BPPFA)} 2 (trans-PdClX) (X ) Me (11), Cl ( 12)) along with the corresponding tetra-and mononuclear derivatives. Mechanistic studies concerning the formation of the tetranuclear complexes have shown that a P,P to P,N coordination shift and Pd-P bond rupture are feasible processes. Variable-temperature 1 H NMR studies have provided evidence of Pd-N interactions in complexes 2, 5, 7, and 8 that involve an unprecedented terdentate κ 3 N,P,P chelate coordination of BPPFA to palladium. The pentafluorophenyl complexes 5 and 6 each exist in solution as two conformers that are interconvertible by torsional twisting of the Cp rings. In the case of complex 5 this interconversion process is slowed at low temperature to such an extent that both conformers can be observed separately by NMR spectroscopy. This phenomenon is presumably due to the Pd-N interaction. The molecular structures of 2M and 8M (M ) major isomer) have been determined by X-ray diffraction.

A comparative study of the synthesis, stereochemical characterization and reactivity of new chiral ruthenium(II) complexes with (aminoferrocenyl)phosphine ligands. X-Ray crystal structure of RuClH(cod)(PTFA) and Ru( 3 -C 8 H 13 )Cl(PPFA) [PTFA ‫؍‬ 1diphenylphosphino-2,3-endo-( -dimethylamino)tetramethyleneferrocene and PPFA ‫؍‬ 2-(1-dimethylaminoethyl)-1-diphenylphosphinoferrocene] †

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Chart 3. Prefered (a) and Less Stable (b) Conformation of Ligand 1; Numbering Scheme of 1 (a)