The co-ordination of small molecules by manganese(II) phosphine complexes. Part 3. The dependence on the nature of the halogen in [MnX2(PR3)](X = Cl, Br, or I; R3= PhMe2, PhEt2, PhPrn2, PhBun2, PhBui3, Prn3, Bun3, or Ph3) on adduct formation with sulphur dioxide in the solid state and in tetrahydrofuran solution

Abstract

The reaction of the complexes [MnX₂(PR₃)](X = Cl, Br, or I; R₃= PhMe₂, PhEt₂, PhPrⁿ₂, PhBuⁿ₂, PhBuⁱ₂, Prⁿ₃, Buⁿ₃, or Ph₃) with sulphur dioxide in the solid state, in toluene slurries and in tetrahydrofuran (thf) has been studied. In all three systems a strong dependence on the nature of the halide is observed. For X = Cl, no reaction takes place; for X = I, all complexes irreversibly absorb SO₂; for X = Br a borderline exists and the nature of the phosphine is important, viz. trialkylphosphines promote SO₂ binding, whereas complexes containing phenyl-substituted phosphines (except PPhMe₂) are inactive towards SO₂. The reaction stoicheiometry is unusual, [MnX₂(PR₃)(SO₂)_x](for measurements in the solid state x= 0.66, for thf solution x= 0.65–0.76). Although [MnI₂(PPh₃)] does not bind dioxygen it forms an adduct with sulphur dioxide in the solid state and in thf.