19392-93-9Relevant academic research and scientific papers
Elucidating Dramatic Ligand Effects on SET Processes: Iron Hydride versus Iron Borohydride Catalyzed Reductive Radical Cyclization of Unsaturated Organic Halides
Kyne, Sara H.,Clémancey, Martin,Blondin, Geneviève,Derat, Etienne,Fensterbank, Louis,Jutand, Anny,Lefèvre, Guillaume,Ollivier, Cyril
, p. 761 - 771 (2018)
An iron(II) borohydride complex ([(η1-H3BH)FeCl(NCCH3)4]) is employed as the precatalyst in iron-catalyzed radical cyclizations of unsaturated organic halides in the presence of NaBH4. Mechanistic investigations have established that the ligand bound to the metal center (acetonitrile versus ethylenebis(diphenylphosphine) (dppe)) plays a crucial role in the structure and reactivity of the active anionic iron(I) hydride ([HFeCl(dppe)2]-) and borohydride ([(η1-H3BH)FeCl(NCCH3)4]-) with unsaturated haloacetals. This work provides new insights into iron(I) hydride and borohydride species and their potential implication in single-electron processes.
Iron(II) catalyzed reductive radical cyclization reactions of bromoacetals in the presence of NaBH4: optimization studies and mechanistic insights
Kyne, Sara H.,Lévêque, Christophe,Zheng, Shiwen,Fensterbank, Louis,Jutand, Anny,Ollivier, Cyril
, p. 7727 - 7737 (2016)
5-Exo-trig radical reductive cyclization reactions of bromoacetals are catalyzed by iron in the presence of the reducing agent NaBH4. Both iron(II) and iron(III) were found to effectively mediate these reactions. As shown by cyclic voltammetry, iron(III) can be reduced to an iron(II) precatalyst before passing through an identical reaction mechanism in which monoelectronic activation of the substrate would occur by an anionic hydridoiron(I) complex. Further studies have established that both the substrate (iodo- vs bromo-derivative) and the precatalytic mixture are decisive in determining the reaction outcome.
Substitutional lability of diphosphine ligands in tetrahedral iron(II) chloro complexes
Langer, Robert,B?nisch, Friedrich,Maser, Leon,Pietzonka, Clemens,Vondung, Lisa,Zimmermann, Thomas Philipp
, p. 141 - 148 (2015)
A series of iron(II) dihalogenide complexes with two different bisphosphinoethane ligands is reported. In the case of 1,2-bis(diphenylphosphanyl)ethane (dppe), depending on the stoichiometry, the tetrahedral [(μ-dppe)FeCl2]n and octahedral trans-[(dppe)2FeCl2] complexes are formed. The polymeric complex [(μ-dppe)FeCl2]n, with iron in a tetrahedral environment, preferentially reacts with chelating amines to give the octahedral diphosphine complex, trans-[(dppe)2FeCl2], and different octahedral amine complexes. With the sterically more demanding 1,2-bis(diisopropylphosphanyl)ethane (dippe), the monomeric and tetrahedral halogen complexes [(dippe)FeX2] are exclusively obtained (X = Cl, Br). These complexes react with chelating amines in a similar manner, to give free ligand and the corresponding octahedral amine complex. The present results suggest that the diphosphines in the investigated iron(II) complexes are bound too weakly to form productive catalyst precursors.
Mechanistic Studies on Iron Phosphine Complexes. Part 1. Protonation and Substitution of trans- (X=Cl or Br, diphosphine=Et2PCH2CH2PEt2 or Ph2PCH2CH2PPh2)
Henderson, Richard A.
, p. 509 - 514 (2007/10/02)
The mechanisms of protonation and substitution of trans- have been investigated in tetrahydrofuran at I=0.1 mol dm-3(n4>) and 25 deg C.In the presence of acid, HX, loss of phosphine and formation of occurs by a variety of pathways dependent upon the nature of the phosphine.When diphosphine=dppe rapid ring opening of the chelate from trans- allows protonation of the pendant phosphorus atom.Subsequent dissociation of the phosphine ligand, and protonation of the metal, with release of dihydrogen, results in the formation of .When diphosphine=depe a further pathway involving initial protonation of the metal is identifiable.In contrast, substitution of trans- by L=CO, MeCN, or PhCN to yield trans-+ has to await the slow dissociation of halide.
