The synthesis of silica-supported phosphine and phosphine oxide complexes of manganese(II) iodide and their reaction with sulphur dioxide

Abstract

MnL₂(Ph₂PCH₂CH₂·sil)(sil = silica surface) can be prepared from Ph₂PCH₂CH₂Si(OMe)₃ either by reaction with dehydrated silica and then with anhydrous manganese (II) iodide or vice versa. This complex reacts rapidly with sulphur dioxide in the solid state to yield an adduct with an essentially 1:1 Mn:SO₂ ratio. Applying a vacuum removes a considerable amount of the sulphur dioxide and the process of addition/desorption appears to be almost indefinitely repeatable. Peracetic acid oxidation of Ph₂PCH₂CH₂Si(OMe)₃ gives [Ph₂P(O)CH₂CH₂Si(O-)₃]_n from which [{Mnl₂[Ph₂P(O)CH₂CH₂Si(O-)₃]_1·5}_n] can be formed. This yellow complex rapidly deep red on exposure to sulphur dioxide to form a complex with a Mn:SO₂ ratio of 1:0.8; however, the reaction does not appear to be reversible.