Metal carbonyl compounds are organometallic in various aspects of their bonding, structure and reactions, and they are a good model system for understanding of the essence of transition metal organometallic chemistry.īinary metal carbonyl compounds that consist only of a metal and CO ligands are usually prepared by the direct reaction of the powder of a highly reactive metal and carbon monoxide, or by the reduction of a metal salt to zero valance followed by reaction with high-pressure carbon monoxide. with no organometallic character are usually excluded from organometallic compounds. Wilkinson (1973) was in recognition of this importance.Īccording to the definition of an organometallic compound, at least one direct bond between a metal and a carbon atom should exist, but CN complexes etc. While the various coordination modes of hydrocarbon ligands were determined one after another, the industrial importance of organometallic compounds of transition metals increased with the discoveries of olefin polymerization catalysts (Ziegler catalyst), homogeneous hydrogenation catalysts (Wilkinson catalyst), and development of catalysts for asymmetric synthesis, etc. It was also clearly demonstrated that the compound had a sandwich structure in which the five carbon atoms of the cyclopentadienyl groups bonded simultaneously to the central metal iron. It was a major discovery that ferrocene exhibited very high thermal stability in spite of the general view that the transition metal-carbon bonds were very unstable. The very unique bonding mode of this complex became clear by means of single crystal X-ray structural analysis, NMR spectra, infrared spectra, etc., and served as a starting point for subsequent developments in the field. The discovery of ferrocene, Fe(C 5H 5) 2, in 1951 was epoch-making for the chemistry of this field.
Hieber and others on metal carbonyl compounds was important in the 1930s, but the results of these studies were limited because of the underdeveloped techniques of structural analyses available at the time. Although an ethylene complex of platinum called Zeise's salt, K, tetracarbonylnickel, Ni(CO) 4, and pentacarbonyliron, Fe(CO) 5, which today are classified as organometallic compounds, were prepared in the 19th century, their bonding and structures were unknown. The organometallic chemistry of transition metals is comparatively new.
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