Electrophilic behaviour of co-ordinated nitrogen mono-oxide: preparation and reactions of halogenonitrosylbis[o-phenylenebis(dimethylarsine)]osmium complexes

Abstract

The complexes trans-[Os(pdma)₂X(NO)]X₂·H₂O [X = Cl, Br, or I; pdma =o-phenylenebis(dimethylarsine)] were prepared from [OsX₅(NO)]^2– and pdma. They react reversibly with [OH]^– to give [Os(pdma)₂X(NO₂)]. The complex [Os(pdma)₂Cl(NO)]Cl₂·H₂O and hydrazine hydrate give [Os(pdma)₂Cl(N₃)], which reacts with O₂ to give [Os(pdma)₂Cl(NO₂)] and with HCl to give trans-[Os(pdma)₂Cl(N₂)]Cl. Treatment of a mixture of [Os(pdma)₂Cl(N₃)] and [Os(pdma)₂Cl(NO₂)] with HCl gives trans-[Os(pdma)₂Cl(N₂)]Cl and cis-[Os(pdma)₂Cl(NO)]Cl₂. The complex cis-[Os(pdma)₂Cl(NO)]Cl₂ and [OH]^– gives trans-[Os(pdma)₂(NO)(OH)]Cl₂. Treatment of trans-[Os(pdma)₂Cl(NO)]Cl₂·H₂O with phenylhydrazine gives trans-[Os(pdma)₂Cl(N₂)]Cl and [Os(pdma)₂Cl(ONNNHPh)]. The latter complex undergoes free-radical reactions with O₂ in various solvents to give [Os(pdma)₂Cl(N₂)]Cl, [Os(pdma)₂Cl(NO₂)], or [Os(pdma)₂Cl(NO)]Cl₂·H₂O, or mixtures of these, depending on the conditions. The complex [Os(pdma)₂Cl(NO)]Cl₂·H₂O and hydroxylamine gave trans-[Os(pdma)₂(NO)(OH)]Cl₂ together with other unidentified products. The physical and chemical properties of all the complexes are reported.