Copper

Copper metal is one of the oldest metals known to man; copper beads found in Iraq date back to 9000 BC. Methods for refining copper from ores were discovered around 5000 BC. The use of copper in organic chemistry had to wait well into the twentieth century before it made any significant impact. The majority of the early studies on generating organocopper reagents relied primarily on transmetallation chemistry. The use of the traditional organolithium or Grignard precursors can be circumvented by using Rieke's highly reactive zerovalent copper, which undergoes direct oxidative addition to a wide variety of organic halides. The choice of ligand used in preparing the active copper is a critical factor affecting the reactivity of the active copper species. The use of phosphine ligands significantly enhanced the reactivity of active copper. In general, the more electron donating the phosphine, the more reactive the copper was toward oxidative addition.