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

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. Small but mighty: Several nonprecious transition‐metal compounds were reduced into the corresponding metallic particles under salt‐free conditions using the organosilicon reductant 1. Amorphous Ni nanoparticles (Ni aNPs) generated by this method from Ni(acac)2 and 1 catalyzed reductive CC bond formation reactions.