Dinuclear Iron Complex-Catalyzed Cross-Coupling of Primary Alkyl Fluorides with Aryl Grignard Reagents

Iron-catalyzed cross-coupling of nonactivated primary alkyl fluorides with aryl Grignard reagents has been achieved by using the low-coordinate dinuclear iron complex [(IPr₂Me₂)­Fe­(μ₂-NDipp)₂Fe­(IPr₂Me₂)] as the catalyst. This iron-catalyzed C­(sp³)–F bond arylation reaction is applicable to a variety of aryl Grignard reagents and primary alkyl fluorides. The product pattern suggests the involvement of a radical-type mechanism for its C–F bond scission step

Regio- and Stereoselective Hydrosilylation of Alkynes Catalyzed by Three-Coordinate Cobalt(I) Alkyl and Silyl Complexes

A three-coordinate cobalt­(I) complex exhibits high catalytic efficiency and selectivity as well as good functional group compatibility in alkyne hydro­silyl­ation. [Co­(IAd)­(PPh₃)­(CH₂­TMS)] (<b>1</b>) (IAd = 1,3-diadamantyl­imidazol-2-yl­idene) facilitates regio- and stereo­selective hydro­silyl­ation of terminal, symmetrical internal, and trimethyl­silyl-substituted unsymmetrical internal alkynes to produce single hydro­silyl­ation products in the forms of β-(<i>E</i>)-silyl­alkenes, (<i>E</i>)-silyl­alkenes, and (<i>Z</i>)-α,α-disilyl­alkenes, respectively, in high yields. The comparable catalytic efficiency and selectivity of the Co­(I) silyl complex [Co­(IAd)­(PPh₃)­(SiHPh₂)] that was prepared from the reaction of <b>1</b> with H₂SiPh₂, and the isolation of an alkyne Co­(I) complex [Co­(IAd)­(η²-PhCCPh)­(CH₂­TMS)] from the reaction of <b>1</b> with the acetyl­ene, point out a modified Chalk–Harrod catalytic cycle for these hydro­silyl­ation reactions. The high selectivity is thought to be governed by steric factors

Regio- and Stereoselective Hydrosilylation of Alkynes Catalyzed by Three-Coordinate Cobalt(I) Alkyl and Silyl Complexes

A three-coordinate cobalt­(I) complex exhibits high catalytic efficiency and selectivity as well as good functional group compatibility in alkyne hydro­silyl­ation. [Co­(IAd)­(PPh₃)­(CH₂­TMS)] (<b>1</b>) (IAd = 1,3-diadamantyl­imidazol-2-yl­idene) facilitates regio- and stereo­selective hydro­silyl­ation of terminal, symmetrical internal, and trimethyl­silyl-substituted unsymmetrical internal alkynes to produce single hydro­silyl­ation products in the forms of β-(<i>E</i>)-silyl­alkenes, (<i>E</i>)-silyl­alkenes, and (<i>Z</i>)-α,α-disilyl­alkenes, respectively, in high yields. The comparable catalytic efficiency and selectivity of the Co­(I) silyl complex [Co­(IAd)­(PPh₃)­(SiHPh₂)] that was prepared from the reaction of <b>1</b> with H₂SiPh₂, and the isolation of an alkyne Co­(I) complex [Co­(IAd)­(η²-PhCCPh)­(CH₂­TMS)] from the reaction of <b>1</b> with the acetyl­ene, point out a modified Chalk–Harrod catalytic cycle for these hydro­silyl­ation reactions. The high selectivity is thought to be governed by steric factors

Monomeric Bis(anilido)iron(II) Complexes with <i>N</i>‑Heterocyclic Carbene Ligation: Synthesis, Characterization, and Redox Reactivity toward Aryl Halides

Using monodentate <i>N</i>-heterocyclic carbenes as the ancillary ligands, seven monomeric bis­(anilido)­iron­(II) complexes [(IPr₂Me₂)₂Fe­(NHAr)₂] (IPr₂Me₂ = 2,5-diisopropyl-3,4-dimethylimidazol-1-ylidene; Ar = Ph, C₆H₄-2-Pr^<i>i</i>, Mes, C₆H₃-2,6-Cl₂, Dipp) and [(IPr)­Fe­(NHAr)₂] (IPr = 2,5-di­(2,6-diisopropylphenyl)­imidazol-1-ylidene; Ar = C₆H₃-2,6-Cl₂, Dipp) have been prepared by the one-pot reactions of [Fe­(Mes)₂]₂ with the corresponding <i>N</i>-heterocyclic carbenes, and anilines. These high-spin diamido complexes have been fully characterized by ¹H NMR, solution magnetic susceptibility, UV–vis, IR, X-ray diffraction, cyclic voltammetry, as well as elemental analysis. The strong affinity of the <i>N</i>-heterocyclic carbene ligands toward ferrous centers, and the steric protection exerted by the NHC ligands are the key factors to stabilize these bis­(anilido)­iron complexes in a monomeric manner. Reactivity studies revealed the four-coordinate complex [(IPr₂Me₂)₂Fe­(NHMes)₂] can react with 1 equiv of 1-iodo-3,5-dimethylbenzene or 1-bromo-3,5-dimethylbenzene in C₆D₆ and THF-d₈ to furnish 1-C₆D₅-3,5-Me₂C₆H₃, and 5-D-1,3-Me₂C₆H₃, respectively. Under similar conditions, the three-coordinate compound [(IPr)­Fe­(NHDipp)₂] is inert toward these halides

Intramolecular C(sp³)–H Bond Activation Reactions of Low-Valent Cobalt Complexes with Coordination Unsaturation

Intramolecular C­(sp³)–H bond activation reactions mediated by low-valent cobalt, both Co­(I) and Co(0), have been observed in the reactions of the three-coordinate cobalt complex [Co­(IMes)₂Cl] (IMes = 1,3-dimesitylimidazol-2-ylidene) with alkylation reagents and sodium amalgam. The reactions with alkylation reagents gave [Co­(IMes)­(IMes′)­(N₂)], featuring a metalated IMes′ anion, whereas the one-electron-reduction reaction afforded [Co­(IMes′)₂]. The Co­(II) complex can react with CO, isocyanide, and a diazo compound to furnish interesting cobalt complexes bearing functionalized N-heterocyclic carbene ligands. The establishment of these conversions demonstrates the capability of low-valent cobalt with coordination unsaturation to mediate C­(sp³)–H bond activation and functionalization

Monomeric Bis(anilido)iron(II) Complexes with <i>N</i>‑Heterocyclic Carbene Ligation: Synthesis, Characterization, and Redox Reactivity toward Aryl Halides

Using monodentate <i>N</i>-heterocyclic carbenes as the ancillary ligands, seven monomeric bis­(anilido)­iron­(II) complexes [(IPr₂Me₂)₂Fe­(NHAr)₂] (IPr₂Me₂ = 2,5-diisopropyl-3,4-dimethylimidazol-1-ylidene; Ar = Ph, C₆H₄-2-Pr^<i>i</i>, Mes, C₆H₃-2,6-Cl₂, Dipp) and [(IPr)­Fe­(NHAr)₂] (IPr = 2,5-di­(2,6-diisopropylphenyl)­imidazol-1-ylidene; Ar = C₆H₃-2,6-Cl₂, Dipp) have been prepared by the one-pot reactions of [Fe­(Mes)₂]₂ with the corresponding <i>N</i>-heterocyclic carbenes, and anilines. These high-spin diamido complexes have been fully characterized by ¹H NMR, solution magnetic susceptibility, UV–vis, IR, X-ray diffraction, cyclic voltammetry, as well as elemental analysis. The strong affinity of the <i>N</i>-heterocyclic carbene ligands toward ferrous centers, and the steric protection exerted by the NHC ligands are the key factors to stabilize these bis­(anilido)­iron complexes in a monomeric manner. Reactivity studies revealed the four-coordinate complex [(IPr₂Me₂)₂Fe­(NHMes)₂] can react with 1 equiv of 1-iodo-3,5-dimethylbenzene or 1-bromo-3,5-dimethylbenzene in C₆D₆ and THF-d₈ to furnish 1-C₆D₅-3,5-Me₂C₆H₃, and 5-D-1,3-Me₂C₆H₃, respectively. Under similar conditions, the three-coordinate compound [(IPr)­Fe­(NHDipp)₂] is inert toward these halides

Facile Reversibility by Design: Tuning Small Molecule Capture and Activation by Single Component Frustrated Lewis Pairs

A series of single component FLPs has been investigated for small molecule capture, with the finding that through tuning of both the thermodynamics of binding/activation and the degree of preorganization (i.e., Δ<i>S</i>^⧧) reversibility can be brought about at (or close to) room temperature. Thus, the dimethylxanthene system {(C₆H₄)₂(O)­CMe₂}­(PMes₂)­(B­(C₆F₅)₂): (i) heterolytically cleaves dihydrogen to give an equilibrium mixture of FLP and H₂ activation product in solution at room temperature and (ii) reversibly captures nitrous oxide (uptake at room temperature, 1 atm; release at 323 K)

Facile Reversibility by Design: Tuning Small Molecule Capture and Activation by Single Component Frustrated Lewis Pairs

A series of single component FLPs has been investigated for small molecule capture, with the finding that through tuning of both the thermodynamics of binding/activation and the degree of preorganization (i.e., Δ<i>S</i>^⧧) reversibility can be brought about at (or close to) room temperature. Thus, the dimethylxanthene system {(C₆H₄)₂(O)­CMe₂}­(PMes₂)­(B­(C₆F₅)₂): (i) heterolytically cleaves dihydrogen to give an equilibrium mixture of FLP and H₂ activation product in solution at room temperature and (ii) reversibly captures nitrous oxide (uptake at room temperature, 1 atm; release at 323 K)