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Studies of 1,2-naphthoquinone mono-oximato complexes

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Musa, Yusuf (1991) Studies of 1,2-naphthoquinone mono-oximato complexes. Doctoral thesis, Polytechnic of North London.

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Abstract

The synthesis of 1,2-naphthoquinone I-oxime and 1,2- naphthoquinone 2-oxina complexes of rhodium and Iridium has been Investigated. In the case of rhodium, complexes of the type Rh(l-nqo)3 have been prepared by reacting 1 ,2-naphthoquinone 1-oxime with hydrated rhodium(III) chloride. Both products ware obtained as mixtures of isomers. The Interaction of 1,2- naphthoquinone 2-oxime with rhodium(lll) chloride yielded Rh(2-nqo)3 also as a mixture of Isomers. The trichelates were also obtained from the nitrosation of the appropriate naphthol in the presence of rhodium(Ill) chloride. In contrast, the corresponding reaction systems involving iridium gave very complex mixtures Involving both iridium containing species and organic products. One of the iridium products, [pyH][lr(1-nqo)C13 pyl, has been isolated in the pure state and characterised by X-ray crystallography. The complexes Ir(1-nqo)3 and lr(2-nqo)3 were also isolated but in low yields.

All trichelates ware shown to be diagmagnetic. None reacted with either pyridine or triphenylphosphine. These observations have been rationalised in terms of crystal field stabilisation energy. The behaviour of the rhodium and iridium complexes towards the Lewis bases contrasts that of analogous iron and cobalt complexes. The X-ray study of [pyH][lr(l-nqo)C13 py] has shown that the ligand is chelated to the metal as been observed in first transition series metal complexes derived from such ligands.

The use of 1,2-naphthoqulnone 1-oxime as a potential ligand for separating rhodium from iridium has been investigated. Optimum conditions for recovery of rhodium was established, as a technique for refining rhodium current process at Inco (Europe) Ltd.

The synthesis of cobalt, rhodium, copper, iron and nickel complexes of 1 ,2-naphthoquinone l-oxime-3,6- disulphonic acid (nRsH3) has been investigated and the complexes were isolated in solid form by developing a separation technique. Cobalt(III) and rhodium(III) salts reacted with the ligand to give metal complexes of type M(nRs Na)3 . The behaviour of the 1,2-naphthoquinone 1- oxime-3,6-disulphonic acid towards iron(ll) and iron(lll) or copper salts was shown to be more complex and interesting than previously reported. Both iron(II) and iron(III) chloride gave an Iron(II) product of the type Fe(nRs Na) whilst Iron(II) ammonium sulphate gave an Fe(II) product of the type Fe(nRs Na)2. The nickel salts gave a complex containing two ligands per metal, Ni(nRsHNa)2.

The complexes of Iron(II) and copper(Il) of 1 ,2-naphthoquinone l-oxime-3,6-disulphonic acid catalysed aerobic oxidation of catechols. The oxidation involved oxidative cleavage of the aromatic ring of catechol by molecular oxygen to give muconic acid anhydride and 2H-pyran-2-one in addition to benzoquinone. This behaviour is very similar to enzyme catalysed oxygenation.

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