Salt‐Free Reduction of Nonprecious Transition‐Metal Compounds: Generation of Amorphous Ni Nanoparticles for Catalytic C–C Bond Formation

Abstract

A salt-free procedure for the generation of a wide variety of metal(0) particles, including Fe, Co, Ni, and Cu, was achieved using 2,3,5,6-tetramethyl-1,4-bis(trimethylsilyl)-1,4-diaza-2,5-cyclohexadiene (1), which reduced the corresponding metal precursors under mild conditions. Notably, Ni particles formed in situ from the treatment of Ni(acac)2 (acac = acetylacetonate) with 1 in toluene exhibited significant catalytic activity for reductive C-C bond-forming reactions of aryl halides in the presence of excess amounts of 1. By examination of high-magnification transmission electron microscopy images and electron diffraction patterns, we concluded that amorphous Ni nanoparticles (Ni aNPs) were essential for the high catalytic activity.

Chemo‐ and Regioselective Reduction of 5,15‐Diazaporphyrins Providing Antiaromatic Azaporphyrinoids

“…We then found that the use of N , N ′‐bis(trimethylsilyl)‐1,4‐dihydropyrazine 5 as a reductant for 1 M cleanly and selectively furnished N , N ′‐dihydrodiazaporphyrins 3 M (Scheme ). N , N ′‐Disilyl‐1,4‐dihydropyrazine 5 serves as a versatile and strong reducing reagent for group 4–6 metal and late transition metal chlorides ,. When we carried out the reaction of 1 Ni with 1.6 equivalents of 5 in THF at room temperature, complete conversion of 1 Ni was confirmed by 1 H NMR spectroscopy.…”

London Dispersion Interactions in Pnictogen Cations [ECl2]+ and [E=E]2+ (E=P, As, Sb) Supported by Anionic N‐Heterocyclic Carbenes

“…7 displays poor solubility in common organics olvents andi sonly sparingly soluble in THF,w hich prevented the separation of this compound from MgCl 2 .T herefore, 1,4-bis(trimethylsilyl)-1,4-dihydropyrazine (8)w as employed as as alt-free reductant that has been previously used for the generation of low-valent transition metal and main-group element compounds. [87][88][89] Thus, treatment of 4 with one equivalent of 8 in toluene gave 7 in 64 %y ield as ap ink solid, by simple filtration of the reaction mixturea nd washing with toluene and hexane. Diphosphene 5 and diarsene 6 were also prepared by this route in high purity, albeit in lower yields (5:4 2%, 6:5 0%), whichc an be ascribed to their higher solubility in hydrocarbon solvents.…”

Reductive Silylation Using a Bis‐silylated Diaza‐2,5‐cyclohexadiene

“…While it was originally envisioned that elimination of (Me 3 Si) 2 O from MO n by 1 might be a useful approach to MO n −1 , a recent application to support‐bound WO 3 gave instead tetravalent tungsten silyl esters, which is still a valuable 2 electron reduction, but without full elimination of W/O bonds and creation of lower metal coordination number . The method has also been applied to nanoparticle formation, silylation of B−F bonds and of α‐halo carbonyls, and deoxygenation of nitro compounds . In summary, the strengths and limitations of this attractive reagent are only just emerging …”