Aqueous solutions containing this metal are often blue or green.
A salt of this element is required for Sonogashira coupling. Its zero-valent form is used to couple aryl halides. Adding silicon dioxide and five equivalents of oxygen results in the very pure "blister" form of this metal. Adding formaldehyde to ethyne is accomplished by using its acetylide as a catalyst. Zinc dust activated by a small amount of it catalyzes the Simmons-Smith reaction. The aryl diazonium salt formed in the Sandmeyer reaction reacts with a halide of this element. Its iodide is added to an organolithium compound to form a Gilman reagent. This is the lightest metal to have one s-orbital electron above a filled d-electron shell. Aqueous solutions containing this metal are often blue or green. For 10 points, name this element which alloys with tin to make bronze and has an atomic number of 29.
A salt of this element is required for Sonogashira coupling.
copper [or Cu; or cuprum]