Nickel Tetracarbonyl, Ni(CO)₄

Nickel Tetracarbonyl, Ni(CO)₄, is obtained when carbon monoxide is passed over metallic nickel in a finely divided condition, such as is obtained by the reduction of nickel oxide in hydrogen at 400° C., the best temperature for obtaining the carbonyl being about 30-50° C. The carbonyl is condensed in a cooled vessel. The reaction may be advantageously carried out under a pressure of 2-100 atmospheres of carbon monoxide, in which case the temperature may be raised even to 250° C. without fear of decomposition.

Nickel carbonyl is a colourless liquid, boiling at 43.2° C. and solidifying at -25° C. Its density is 1.3185 at 17° C. At 50° C. its vapour density corresponds to the formula Ni(CO)₄ when determined in Victor Meyer's apparatus. In an atmosphere of carbon monoxide its density is normal up to 100° C., whilst in nitrogen its dissociation is practically complete at 155° C.

Nickel carbonyl reacts slowly with concentrated sulphuric acid, yielding carbon monoxide, hydrogen, and nickel sulphate.

Ni(CO)₄ + H₂SO₄ = NiSO₄ + H₂ + 4CO.

Solutions of nickel carbonyl in carbon tetrachloride react with chlorine, bromine, or iodine in similar solution, yielding carbon monoxide and the anhydrous halide. Thus:

Ni(CO)₄ + Cl₂ = NiCl₂ + 4CO.

Moist air decomposes the carbonyl as does also carbon disulphide.

When inhaled even in small quantities the vapour of nickel carbonyl is very poisonous, being decomposed in the lungs to carbon monoxide and a nickel derivative - possibly the basic carbonate.