Three-Coordinate Iron(II) N-Heterocyclic Carbene Alkyl Complexes

Abstract

Mononuclear alkyl N-heterocyclic carbene complexes of the type Fe(NHC)R2, NHC = SIPri, IPri, R = CH2SiMe3, CH2C6H5, were prepared by the alkylation of “FeCl2(THF)1.5” with one equivalent per Fe of MgR2, in the presence of the NHC. Alkylation with 0.5 equiv of MgR2 under carefully controlled conditions gave Fe(NHC)(CH2SiMe3)Cl, NHC = SIPri, IPri. Magnetic and computational studies and structural determination by X-ray diffraction reveal three-coordinate high-spin (S = 2) alkyl complexes.

Iron-catalysed substrate-directed Suzuki biaryl cross-coupling

“…We have undertaken a variety of mechanistic studies, the first of which was to establish the lowest thermodynamically viable oxidation state that can be accessed by iron under the reaction conditions, since Fe(0), [33][34][35] , Fe(I) 36,37 and Fe(II) [38][39][40] complexes can all be supported by NHC ligands. 41 The boronate nucleophile acts as a reducing reagent for the iron;…”

Ligand Control of the Metal Coordination Sphere: Structures, Reactivity and Catalysis

“…Remarkably, the chlorido-alkyls are mononuclear species (Scheme 12). The underligated complexes 20, 23, 26, 31 and 32 have been previously reported by us [66][67][68]; all other complexes shown in Scheme 12 are new. The complex [Fe(NHC) Mes 2 ], where NHC = N,N'-diisopropyl-imidazol-2-ylidene, was reported simultaneously with our work [69].…”

“…For Fe, simple salt metathesis reactions using FeCl 2 and MgR 2 (THF) 2 (R = CH 2 SiMe 3 , CH 2 CMe 2 Ph, CH 2 Ph, mesityl), in the presence of IPr or SIPr in THF/dioxane was the method of choice. The alkylation was sequential (except for R = Mes); thus, adjustment of the stoichiometry led to either chlorido-alkyls or di-alkyls [68]. Remarkably, the chlorido-alkyls are mononuclear species (Scheme 12).…”

Iron complexes of a bidentate picolyl-NHC ligand: synthesis, structure and reactivity

“…Each Fe(II) centre adopts a distorted tetrahedral geometry displaying typical bond lengths. 42,51,52 The bite angle of the HL ligand in 5 (88.3(2)°) is similar to those of 2 and 3, while the bite angle of HL in 6 (86.05(7)°) is slightly smaller. Both 5 and 6 are thermally unstable and decompose in solution into intractable products at room temperature over a few days.…”