Metal Carbonyls

Metal Carbonyls

 

compounds of metals with carbon monoxide, with the general formula Mem (COn). Nickel car-bonyl, Ni(CO)4, was the first to be discovered (1890), and since then the carbonyls of several metals and nonmetals have been prepared. Metal carbonyls may be either “mononuclear” or “polynuclear,” depending on the number of metal atoms in the molecule; compound metal carbonyls, such as [Co(CO)4]2Zn, also exist.

The carbonyls of nickel, iron, osmium, and ruthenium are liquids; most other carbonyls are crystalline. Metal carbonyls are diamagnetic, highly volatile, and extremely toxic. Only halide carbonyls, Me(CO)X, which are stable only in a carbon monoxide atmosphere, exist for copper, silver, and gold. Metal carbonyls decompose when heated above a certain temperature, releasing carbon monoxide and metal in a finely dispersed state. The physical properties of the principal metal carbonyls are presented in Table 1 (the carbonyls shown are readily soluble in organic solvents).

Table 1. Physical properties of some metal carbonyls
 Boiling point (°C)Melting point (°C)Density at 20°C (g/cm3)Solubility in water
Fe(CO)5......103-201.455
Co(CO)4.....511.827insoluble
Ni(CO)4....43-191.310low
Ru(CO)5.....-22insoluble

A common method of preparing metal carbonyls involves the reaction of carbon monoxide with metals or their salts at high temperatures and pressures. The metal carbonyls that are of the greatest commercial significance are nickel carbonyl, Ni(CO)4; cobalt carbonyl, Co(CO)4; and iron carbonyl, Fe(CO)5. Carbonyls are used for the preparation of pure metals, which form upon their thermal dissociation. Thermal dissociation of cobalt, nickel, and chromium carbonyls is used in the application of metallic coatings, particularly on surfaces of complex shape. Cobalt and nickel carbonyls are catalysts in important chemical processes—for example, in the synthesis of carboxylic acids and their derivatives from olefins, and in the synthesis of acrylic acid from acetylene during hydroformylation:

Metal carbonyls are good antiknock compounds for motor fuels; however, the formation of oxides that are difficult to remove takes place during combustion. Certain carbonyls serve in the preparation of absolutely pure carbon monoxide.

REFERENCES

Belozerskii, N. A. Karbonily metallov. Moscow, 1958.
Khimiia koordinatsionnykh soedinenii. Edited by J. Bailar and D. Busch. Moscow, 1960. (Translated from English.)
Khimiia metalloorganicheskikh soedinenii. Edited by H. Zeiss. Moscow, 1964. Pages 538–604. (Translated from English.)

N. A. NESMEIANOV

References in periodicals archive ?
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Vieira, "Metal carbonyl prodrugs: CO delivery and beyond," in Bioorganometallic Chemistry: Applications in Drug Discovery, Biocatalysis, and Imaging, pp.
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Covering first metal complexes then transition metal chemistry, they discuss such topics as the correct empirical formula of complexes, isomerism and stereochemistry, metal carbonyls and nitrosyls, the vanadium group, and the actinides.
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These values are in close resemblance to the values of v (CO) vibration for other nitrogen containing disubstituted group-6 metal carbonyls [13, 16, 18, 19].
They have discovered that they can [make] organometallic compounds such as metal carbonyls, many of which are too unstable to prepare by conventional methods.
R&D at Leeds has seen the application of supercritical fluid carbon dioxide (SC-[CO.sub.2]) for the fractionation of polymers, dyeing of textiles and paper, production of fine particles by dissolving and precipitating metal carbonyls, and isolation of naturally occurring pesticides from plant matter.
The first seven chapters discuss medicinal chemistry, covering the topics of organometallic enzyme inhibitors, organometallic steroid analogs, chirality in chemotherapeutics, gold complexes, the antimalarial ferroquine, metal carbonyls as prodrugs, and the electronics of nitrosyl and thiol iron complexes.
The complexes, 1-9 were prepared by the photochemical reactions of metal carbonyls M[(CO).sub.6] (M = Cr, Mo, W) with [SB.sup.1], [SB.sup.2], [SB.sup.3] and were obtained in 65 -75% yields by the method given below.
Metal carbonyl complexes have found wide use in industrial applications as catalysts after the first binary complex, Ni[(CO).sub.4], was synthesized by Mond in 1890, although the first metal carbonyl complex, [[Pt(CO)[Cl.sub.2]].sub.2] was synthesized in 1868 [1].