Nickel complexes oxygen

A cyclization reaction involving a half-formed bridge in which alkyl halide functions interact with (initially) coordinated oxygen atoms is illustrated by [2.9] (Kluiber Sasso, 1970). The X-ray structure of the red paramagnetic nickel complex (65) indicates that the macrocycle coordi-... 

The S-oxygenation of the hexaamine-dithiophenolate macrocycles should provide a potential entry into the novel class of binucleating polyamine-disulfonate and -disulfinate macrocycles. Indeed, such ligands can be prepared by the oxidation of dinuclear nickel complexes of the parent hexaaza-dithiopheno-late macrocycles followed by the decomposition of the oxidation products in acidic solution. The dinuclear nickel complexes [Nin2(L36)(L )]+ (L = Cr (70) and OAc (71)) of the hexaaza-diphenylsulfonate ligand (L36)2- (Fig. 38) are obtained by... 

Oxidation of organic substrates with molecular oxygen on nickel complexes is limited to a few known examples. 

Oxidation of carbon ligands with concomitant insertion has been observed in the reaction of methallyl nickel complexes with norbornene or strained olefins in general and oxygen (example 3, Table IX). 

Nickel Complexes of Oxygen- or Nitrogen-Containing Ligands... 

In this reaction the metal behaves as a Lewis acid and accepts a pair of electrons from the Lewis base (ligand). In this case the ligand is water, with the oxygen atom donating one of its lone pairs to the nickel. The oxygen atom is called the donor atom. In this complex, there are six donor atoms. 

The use of six equivalents of dihydrogen peroxide leads to a clean conversion of the dithiolate complex to the disulfonate compound. Earlier studies on oxidation of nickel thiolates showed that oxidations with dioxygen stop at monosulfinates. Our observation and the characterization of the first chelating bis-sulfonato nickel complex formed from the direct oxidation of a mononuclear nickel dithiolate, may also provide new insight into the chemistry of sulfur-rich nickel-containing enzymes in the presence of oxygen. 

As seen from Scheme 7.2, the epoxy-ring cleavage and nickel oxidation proceed simultaneously. The nickel-oxygen bond is formed. This results in the formation of the carbon-nickel biradical in which Ph-CH fragment can rotate freely. The cleavage of the (NiO)-C bond leads to the formation of a mixture of styrenes. At early reaction stages (30 min), cis and trans olefins are formed in 50 50 ratio. After a prolonged contact (30 h), when all possible transformations should be completed, the trans isomer becomes the main product and cis trans ratio becomes 5 95. Such enrichment of the mixture with the trans isomer follows from the formation of the di-P-(trimethylsilyl)styrene anion-radical and its isomerization. The styrene formed interacts with an excess of the nickel complex. 

Even if the C104 ion is commonly believed to experience a scarce tendency to act as a ligand, nonetheless coordination of perchlorate as a monodentate ligand through an oxygen atom has been proposed in a number of nickel complexes containing alkylamines,1676 pyridine and substituted pyridines,1677-1680 arylamines such as aniline and substituted anilines,1681 phosphine and arsine oxides1682,1683 (Table 84). 

In Table 108 significant examples of nickel(II) complexes with mixed-donor macrocycles of various denticity are reported. Apart from the nitrogen atoms, the heteroatoms in the macrocyclic rings are usually either O or S, or in a few cases P. Few examples of nickel complexes with macrocycles containing all-sulfur or all-phosphorus donor atoms have been reported to date they are also included in Table 108. In nickel(II) complexes formed by mixed-donor penta- and hexa-dentate ligands the oxygen atoms of the macrocycle are often only weakly coordinated or are not coordinated at all. 

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