Characteristics of the Carbonyls

The carbonyls are relatively simple compounds since they consist of only two components  

The atomic structure of the transition metals is such that the J shell is only partly filled. The first transition series (3d) comprises Sc, Ti, V, Cr, Mn, Fe, Co, and Ni the second (4d), Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, and Ag the third (5d), Hf, Ta, W, Re, Os, Ir, Pt, and Au. Carbonyl derivatives of at least one type are found for all these metals. Although only a few are presently used in CVD, many are being investigated as they constitute an interesting and potentially valuable group of precursor materials. 

The simplest transition metal carbonyls are mononuclear of the type M(CO)x, in other words those with only one metal atom. They are hydrophobic but soluble to some extent in nonpolar liquids, such as n-butane or propane. The dinuclear carbonyls are more complex but have the same general characteristics as the mononuclear carbonyls. The carbonyls, which are or could be used in CVD, are listed in Table 3.4 with some of their properties. 

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Both 1,2- and 2,1-benzisoxazoles with carbonyl groups in the 3-position show reactions such as those above, characteristic of the carbonyl function (67AHC(8)277,p. 296,329). 

An exhaustive characterization by EXAFS of cluster species obtained from the impregnation of Ir4(CO)i2 on MgO made it possible to determine that the size of the clusters obtained not only depends on the characteristics of the carbonylic complex and those of the oxide but also on the degree of hydroxylation of the support, which is determined by the thermal treatment carried out before adsorption of the complex [206]. 

The photolysis of aldehydes and ketones has been the subject of many investigations, and is adequately dealt with in standard texts on photochemistry. In a few instances, excitation of the carbonyl function can result in cyclization and the formation of heterocyclic systems, although this is usually accompanied by other processes more characteristic of the carbonyl group. 

Alkyl aryl tellurium compounds with a carbonyl group in the molecule undergo a variety of reactions characteristic of the carbonyl function. 

These two reactions are characteristic of the carbonyl group and are used in determining its presence in compounds. They have been of especial importance in the study of the sugars. 

By the reaction with hydrogen cyanide, HCN, forming cyan-hydrines, which are acid nitriles, with hydroxyl amine, H2NOH, forming oximes, and with phenyl hydrazine, H2N—NH—CeHs, forming hydrazones, all of which reactions are characteristic of the carbonyl group, carbohydrates in water solution are aldehyde or ketone compounds. 

Phenols (ArOH) also show both these bands, but the C 0 stretching appears at somewhat higher frequencies. Ethers show C—O stretching, but the 0-—H band is absent. Carboxylic acids and esters show C—O stretching, but give absorption characteristic of the carbonyl group, C O, as well. (For a comparison of certain oxygen compounds, see Table 20.3, p. 689.)... 

Alkoxides like Al(OR)3 will behave as fairly strong acid catalysts, owing to the tendency of the aluminum atom in these compounds to accept a share in a pair of electrons. In view of this fact it is to be expected that aluminum alkoxides will cause the amphoteric aldehydes to behave as bases, so that a simple ester results. As this behavior involves only the basic characteristics of the carbonyl group itself it makes little difference whether we have one, two, or no a-hydrogen atoms in the aldehyde an ester is the result. The first step is a typical acid-base neutralization reaction with the formation of a coordinate covalent bond ... 

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