Aqueous Phase Synthesis of Size-Tunable Copper Nanocubes for Efficient Aryl Alkyne Hydroboration

Copper nanocubes with average sizes of 82, 95, and 108 nm have been synthesized in an aqueous mixture of cetyltrimethylammonium chloride (CTAC) surfactant, copper acetate, and sodium ascorbate reductant heated at 100 oC for 40 min. Copper nanowires with an average length of 25 m can also be prepared this way by simply increasing the volume of sodium ascorbate introduced. Small shifts in the plasmonic absorption band positions with tunable particle sizes have been observed. The copper nanocubes were employed to catalyze hydroboration of phenylacetylene and various substituted aryl alkynes with 100% (E)-product selectivity and 82‒95% product yields. The copper nanocubes are cheap to make and should catalyze a broad scope of organic coupling reactions.