Nickel has a lot of compounds and complex which present the oxidation states -1, 0, +1, +2, +3, +4. The compounds of Ni (0) are quite usual, with special relevance to the carbonyl Ni(CO)4, and they are a very volatile colorless liquid their used used in material plating. The oxidation state +2 is the most common one, being known a great number of compounds, namely the hydroxide Ni(OH)2, the oxide NiO, salts of all the inorganic acids and of a great number of organic acids. Among these we refer the sulfate, usually used in electroplating solutions, the acetate, used as catalyst and mordant in the textile industry, the formate, used in the production of catalysts, the isodecylorthophosphate and the naphthenate, used as motor oil and lubricants additives, and many other, with several applications in the laboratory and in chemical industry.
Among the numerous nickel complexes (II), we refer to the di-n-butyldithiocarbamate, oxidation inhibitor in the industry of synthetic rubber, the dimethylglyoxime, used in analysis and as pigment in beauty products, the nickel phthalocyanine nickel (II), blue pigment used in the industry of the colorings, the nickelocene, organometallic compound used as catalyst, etc.
Most of the world production of nickel is used for producing alloys: inox steels for the metallurgical and mechanic industry, special steels for the aeronautical industry, cupro-nickel for the manufacture of coins, chromium-nickel for cutlery, iron-nickel for magnets, copper-nickel-zinc (German silver) for ornamental and domestic objects, etc. Another important fraction of this production is used in the plating of metallic pieces (electroplating) with ornamental purposes as a protection against corrosion. Among the remaining applications we refer the production of catalysts, especially the so-called Raney nickel, and compounds for multiple purposes.