Ludwig Mond (One of the founders of ICI) produced a colourless liquid with CO and Nickel in 1888. The isolated substance was heavy, colourless, boiled at 34oC and easily decomposed when heated leaving pure nickel. Experimentally it was found that there were 4 CO atoms per Nickel atom. Hence the first Carbonyl compound had been formed Ni(CO)4. Such a reaction was to proove a gold mine for Mond. The process could be used to make high purity Nickel.
Such an unusual compound caught the imagination of chemists al over the world. Soon Berthelod in France ws to make Fe(CO)5. Due to their large industrial use, metal carbonyls have become one of th most impotant organometallic compounds.