Properties of homoleptic carbonyls
المؤلف:
Peter Atkins, Tina Overton, Jonathan Rourke, Mark Weller, and Fraser Armstrong
المصدر:
Shriver and Atkins Inorganic Chemistry ,5th E
الجزء والصفحة:
555
2025-10-02
355
Properties of homoleptic carbonyls
Key points: All the mononuclear carbonyls are volatile; all the mononuclear and many of the poly nuclear carbonyls are soluble in hydrocarbon solvents; polynuclear carbonyls are coloured. Iron and nickel carbonyls are liquids at room temperature and pressure but all other com mon carbonyls are solids. All the mononuclear carbonyls are volatile; their vapour pressures at room temperature range from approximately 50 kPa for tetracarbonyl nickel (0) to approximately 10 Pa for hexacarbonyl tungsten (0). The high volatility of Ni (CO)4, coupled with its extremely high toxicity, means that unusual care is required in its handling. Al though the other carbonyls appear to be less toxic, they too must not be inhaled or allowed to touch the skin. Because they are nonpolar, all the mononuclear and many of the polynuclear carbonyls are soluble in hydrocarbon solvents. The most striking exception among the common carbonyls is nonacarbonyldiiron (0), [Fe2 (CO)9], which has a very low vapour pressure and is insoluble in solvents with which it does not react. By contrast, [Mn2 (CO)10 ] and [Co2(CO)8] are soluble in hydrocarbon solvents and sublime readily. Most of the mononuclear carbonyls are colourless or lightly coloured. Polynuclear carbonyls are coloured, the intensity of the colour increasing with the number of metal atoms. For example, pentacarbonyl iron(0) is a light straw-coloured liquid, nonacarbonyldiiron (0) forms golden-yellow flakes, and dodecacarbonyltriiron(0) is a deep green compound that looks black in the solid state. The colours of polynuclear carbonyls arise from electronic transitions between orbitals that are largely localized on the metal framework. The principal reactions of the metal centre of simple metal carbonyls are substitution (Section 22.21), oxidation, reduction, and condensation into clusters (Section 22.20). In certain cases, the CO ligand itself is also subject to attack by nucleophiles or electrophiles.
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