623946-94-1Relevant academic research and scientific papers
A palladium-ferrocenyl tetraphosphine system as catalyst for suzuki cross-coupling and heck vinylation of aryl halides: Dynamic behavior of the palladium/phosphine species
Hierso, Jean-Cyrille,Fihri, Aziz,Amardeil, Regine,Meunier, Philippe,Doucet, Henri,Santelli, Maurice,Donnadieu, Bruno
, p. 4490 - 4499 (2003)
The system combining the new ferrocenyl tetraphosphine 1,1′,2,2′-tetrakis(diphenylphos-phino)-4,4′-di-tert-butylferro cene (called Fc(P)4tBu, 1) and [PdCl(η3-C3H5)]2 has been found to be an active catalyst for the cross-coupling of aryl halides with aryl boronic acids (i.e., Suzuki reaction) and for the vinylation of aryl halides with alkenes (Heck reaction). A variety of chlorides reacts in good yield with aryl boronic acids in the presence of 1-0.01% catalyst. The more reactive aryl bromides were reacted with aryl boronic acids or alkenes in the presence of 0.01-0.0001% catalyst. This system compares well with other catalytic systems that have been described for Suzuki or Heck reactions. 1H, 13C, and 31P NMR studies in solution were conducted with the view to obtain a better understanding of the interaction involving the palladium dimeric precursor and the tetraphosphine. The initial formation of kinetic and then different thermodynamic species was evidenced. A dynamic evolution from labile Pd(π-allyl)/tetraphosphine species toward the well-defined, stable, and nonfluxional complexes [PdCl2{Fc(P)4tBu}] (3) and [Pd2Cl4{Fc(P)4tBu}] (4) is observed. This behavior is different from the other known active tetraphosphine Tedicyp [cis,cis,cis-1,2,3,4-tetrakis-(diphenylphosphinomethyl)cyclopentane]. The palladium mononuclear 3 and dinuclear 4 complexes were isolated and fully characterized in the solid state by X-ray diffraction analysis and in solution by multinuclear NMR. The blocked conformation in solution of compounds 1, 3, and 4 respectively leads to original AA'BB', ABMX, and A2B2 31P NMR spin-systems for the four phosphorus atoms.
On the mechanistic behavior of highly efficient palladium-tetraphosphine catalytic systems for cross-coupling reactions: First spectroscopic and electrochemical studies of oxidative addition on Pd(0)/multidentate ferrocenylpolyphosphine complexes
Evrard,Lucas,Mugnier,Meunier,Hierso
, p. 2643 - 2653 (2009/02/02)
Electrochemical studies carried out in conjunction with 31P NMR spectroscopy on the palladium(II)/ palladium(O) halogeno complexes of the tetraphosphine 1,1′,2,2′-tetrakis(diphenylphosphino)-4,4′-di- tert-butylferrocene, termed Fc(P4)tBu, are reported. Fc(P4)1Bu was chosen with regard to its good performances in pallado-catalyzed cross-coupling reactions, which resulted in catalytic turnover numbers (TONs) up to 1 000 000 [Organometallics 2003, 22, 4490-4499]. The complexes [PdX2(Fc(P)4tBu}] (X = Cl, Br, I) are described with their X-ray molecular characterization in the solid state and multinuclear NMR in solution. The electrochemical behavior of Fc(P 4)tBu and [PdX2{Fc(P)4 tBu}] complexes was investigated by cyclic voltammetry and electrolysis: a formulation of the corresponding electro-generated Pd 0 species formed is proposed on the basis of their NMR characterization. The oxidative addition reaction of phenyl iodide on these zerovalent palladium/ferrocenyltetraphosphine complexes was also studied by combining electrochemistry and 31P NMR. The Pd(II) species that result from phenyl iodide oxidative addition are described, and their rate of formation under standard conditions is given; the halogeno phenyl products obtained are identified and characterized. These results are discussed in light of the knowledge existing for more classical systems combining Pd(II) halides or zerovalent palladium with n monodentate tertiary phosphines (n = 2-4). In this respect, me system using Fc(P4)tBu is relevant since its four triarylphosphine groups (Ph2PCp) are formally similar to a 4-fold excess of the triarylphosphine triphenylphosphine (PPh3) as ligand. However, the phosphorus atoms of the tetraphosphine ligand present a mutual spatial proximity that is absent in monophosphines, due to their implantation on the ferrocene platform. Therefore, the possible effects of multidentarity are discussed. Finally, the importance of palladium anionic species is confirmed in this study, and the rate value of Ph-I oxidative addition (130 ± 10 ms) on Pd(0) confirmed both the good reactivity and the enhanced stability provided to palladium species by the ferrocenyltet- raphosphine ligand.
1,1′,2,2′-Tetrakis(diphenylphosphino)-4,4′-di-tert-butylferrocene, a new cisoid arrangement of phosphino groups
Broussier, Roland,Bentabet, Emmanuelle,Amardeil, Régine,Richard, Philippe,Meunier, Philippe,Kalck, Philippe,Gautheron, Bernard
, p. 126 - 133 (2007/10/03)
The action of two equivalents of 1,2-bis(diphenylphosphino)-4-tert-butylcyclopentadienyllithium on FeCl2 led to the corresponding 1,1′,2,2′-tetraphosphinoferrocene. The X-ray structure of this bulky ferrocene is described. The spectroscopic results reveal a conformational chirality with a cisoid disposition of the phosphino groups. The first results about the complexation with representative elements of Group IX and X (Rh, Pd, Ir) are reported.
