Reactions of organometallic complexes with carbon monoxide. Part I. Carbonylation and reduction of arylmercury(II) complexes and some related reactions of ethylene

Abstract

The reactions of phenylmercury(II) complexes with carbon monoxide have been investigated to establish whether ‘carbonylation’ reactions take place. The basic nitrate, (HgPh)₂(OH,NO₃), is the only complex that yields useful amounts of benzoic acid derivatives. The pattern of reactivity of the complexes, HgPhX is reminiscent of that of mercury(II) salts and follows the ‘hardness’ of X. In aqueous solution, oxyanion complexes are reduced either to diphenylmercury and mercury or to mercury alone; this is consistent with attack of HgPh⁺ or H⁺ on a mercurated formic acid derivative. Similar reactions occur in benzene but the reduction of nitric acid by carbon monoxide as it is formed has a buffer effect which prevents reductive cleavage of (HgPh)₂(OH,NO₃). Benzoato(phenyl)-mercury is formed together with decomposition products from the reaction intermediate, benzoyl nitrate. This decomposition is very pressure sensitive, yielding benzoic anhydride at high pressure and biphenyl derivatives at low pressure. Carbonylation of (HgPh)₂(OH,ClO₄) also gives a small yield of benzoic acid. In methanol solution HgPh(CO·OMe) is formed by addition reactions of carbon monoxide when X = OH^– or AcO^–. The basic nitrate yields, also, some diphenylmercury but mainly methyl benzoate and methyl benzoylformate. Phenylmercury(II) complexes also add ethylene forming HgPh(CH₂CH₂OMe).