4501-36-4Relevant articles and documents
Synthesis and characterization of Di- and tetracarbene iron(II) complexes with chelating N-heterocyclic carbene ligands and their application in aryl Grignard-Alkyl halide cross-coupling
Meyer, Steffen,Orben, Claudia Manuela,Demeshko, Serhiy,Dechert, Sebastian,Meyer, Franc
, p. 6692 - 6702 (2011)
A series of new and known bis(imidazolium) chloride and bromide salts bridged by either a methylene group (1-8, 10a,b) or an ethylene group (9a,b) and bearing different N substituents (Me, Et, Bn, tBu, Mes) have been reacted with [Fe{N(SiMe3)2}2]2 to yield the four-coordinate iron(II) complexes [LFeX2] (11-20; X = Cl, Br; L = chelating bis(imidazolylidene) ligand). Molecular structures of six of these complexes have been characterized by X-ray crystallography, and selected examples have been characterized by 1H NMR and UV-vis spectroscopy, cyclic voltammetry, Moessbauer spectroscopy, and SQUID magnetometry. In all cases the iron(II) is found in a distorted-tetrahedral environment; it is in the high-spin state and shows large quadrupole splittings in the range 3.67-4.03 mm?s-1 (δ = 0.73-0.81 mm?s-1). Subtleties of the metric parameters depend on the bridging unit between the two imidazolylidene groups, the peripheral N substituents, and the coligand (Cl or Br). In case of rather small (Me, Et) or flexible (Bn) N substituents the dicarbene species [LFeX2] are formed together with ferrous tetracarbene complexes [L2FeX2] (21-23), which are difficult to separate and could not be isolated in pure form. When the latter are dissolved in MeCN in the presence of residual [FeBr2(solv) x], however, they transform into the ionic complexes [L 2Fe(MeCN)2][FeBr4] (24-26), which have been characterized by single-crystal X-ray diffraction. They feature low-spin iron(II) (Moessbauer parameters δ ≈ 0.15 mm s-1, ΔEQ ≈ 1.36 mm s-1) and distorted-octahedral structures with the two MeCN ligands in a cis configuration. Selected examples of the new dicarbene complexes [LFeX2] have been tested as catalysts for the standard cross-coupling reaction between p-tolylmagnesium bromide and bromo- or chlorocyclohexane. They show moderate activity that appears to be generally lower than for related complexes with two monodentate NHC ligands, but the activities clearly depend on the peripheral N substituents and the linker between the two imidazolylidene groups; the best results are obtained for complex 19, which features a long ethylene bridge and bulky Mes substituents, and hence the most shielded metal center.
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Simons,Bassler
, p. 880 (1941)
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Cross-Coupling Reactions of Alkyl Halides with Aryl Grignard Reagents Using a Tetrachloroferrate with an Innocent Countercation
Hashimoto, Toru,Maruyama, Tsubasa,Yamaguchi, Takamichi,Matsubara, Yutaka,Yamaguchi, Yoshitaka
supporting information, p. 4232 - 4236 (2019/08/16)
Bis(triphenylphosphoranylidene)ammonium tetrachloroferrate, (PPN)[FeCl4] (1), was evaluated as a catalyst for cross-coupling reactions. 1 exhibits high stability toward air and moisture and is an effective catalyst for the reaction of secondary alkyl halides with aryl Grignard reagents. The PPN cation is considered as an innocent counterpart to the iron center. We have developed an easy-to-handle iron catalyst for “ligand-free” cross-coupling reactions. (Figure presented.).
Pd-Catalyzed reductive heck reaction of olefins with aryl bromides for Csp2-Csp3 bond formation
Jin, Liqun,Qian, Jiaxia,Sun, Nan,Hu, Baoxiang,Shen, Zhenlu,Hu, Xinquan
supporting information, p. 5752 - 5755 (2018/06/07)
We developed a Pd-catalyzed intermolecular reductive Heck reaction to construct Csp2-Csp3 bonds between aryl bromides and olefins. Various styrene derivatives, acyclic and cyclic alkenes, were well tolerated to couple with varied aryl bromides in linear selectivity. Kinetic and deuterium labeling experiments suggested that i-PrOH provides a hydride through β-H elimination.