Metal salicylaldimine chelates

Effects of Different Metal Salicylaldimine Chelates. Varying the central metal profoundly affected catalytic and inhibitory properties. There were only small quantitative variations, however, between N-phenyl- and V-butylsalicylaldimines having the same central metal atom. The only other salicylaldimines where catalyst-inhibitor conversion could be demonstrated were those of copper (II). With copper (II) both the catalytic and the inhibitory effects are much less pronounced than for cobalt (II). Surprisingly nickel (II) complexes behaved like conventional catalysts for hydrocarbon autoxidation—i.e., the rate is proportional to... 

The four remaining papers all deal with the catalysis of liquid-phase oxidation processes by transition metal ions (6). A. T. Betts and N. Uri show in particular how metal complexes can either catalyze or inhibit oxidation according to their concentration. In this investigation, various hydrocarbons (especially 2,6,10,14-tetramethylpentadecane) were used as substrates, and metal ions were present either as salicylaldimine or di-isopropylsalicylate chelates. These compounds are considerably soluble in non-polar media, and this makes it possible to examine their effect over a much wider range of concentration than is usually accessible in this type of work. These studies show that catalyst-inhibitor conversion is always... 

The initial reactions of this type were used to produce copper(II) complexes of salicylaldimines, where additional coordination support is provided by the phenolic oxygen atoms (equation l).10 11 Similar use can be made of pyridine-2-carbaldehyde in the formation of imine chelates. For example, the combination of pyridine-2-carbaldehyde and 2-aminobenzenethiol in the presence of metal ions yields tridentate complexes (Scheme l).12 If the reaction is carried out in the absence of the metal ion, the benzothiazolidine (1) is isolated. Thus the metal ion is essential for the formation of the imine product in this case. Metal complexes of the related tridentate ligands (2),13 (3),14 (4)li and (5)16 can be prepared similarly. 

A number of chelates, structurally similar to bis[iV-(carboxymethyl methyl ester)salicylaldimine]copper(II), undergo repeated ester exchange. When this compound, which has a trans square-planar structure (LV), is refluxed in n-butyl alcohol for about 10 minutes, transesterification of the amino acid methyl ester occurs to give the butyl ester. When the compound is refluxed with n-butylamine, the corresponding butylamide is obtained (168, 202). Transesterification does not occur, however, with (1-carbo-methoxy)pentamethylenebis(salicylaldimine-l,5)copper(II), since the configuration of this compound is fixed in the cis form by the pentamethylene ring (LVI) (202). An important function of the metal ion is therefore to position the reactive centers in such a manner that the reaction is facilitated. The mechanism proposed for transesterification involves an attack by the... 

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