Influence of the terminal ligands on the redox properties of the {Pt2(μ-S)2} core in [Pt2(Ph2X(CH2)2XPh2)2(μ-S)2] (X = P or As) complexes and on their reactivity towards metal centres, protic acids and organic electrophiles

Abstract

In order to explore possible ways for modulating the unusually rich chemistry shown by complexes of formula [L₂Pt(μ-S)₂PtL₂] we have studied the influence of the nature of the terminal ligand L on the chemical properties of the {Pt₂(μ-S)₂} core. The systematic study we now report allows comparison of the behaviour of [Pt₂(dpae)₂(μ-S)₂] (dpae = Ph₂As(CH₂)₂AsPh₂) (1) with the already reported analogue [Pt₂(dppe)₂(μ-S)₂] (dppe = Ph₂P(CH₂)₂PPh₂). Complex 1 as well as the corresponding multimetallic derivatives [Pt(dpae){Pt₂(dpae)₂(μ-S)₂}](BPh₄)₂2, [M{Pt₂(dpae)₂(μ-S)₂}₂]X₂ (M = Cu^II, X = BF₄3; M = Zn^II, X = BPh₄4; M = Cd^II, X = ClO₄5; M = Hg^II, X = Cl 6 or X₂ = Cl_1.5[HCl₂]_0.56′) have been characterized in the solid phase and in solution. Comparison of structural parameters of 1 and 3–6′ with those of the corresponding phosphine analogues, together with the results of the electrochemical study for 1, allow us to conclude that replacement of dppe by dpae causes a decrease in basicity of the {Pt₂(μ-S)₂} core. The study of the reactivity of 1 towards CH₂Cl₂ and protic acids has led to the structural characterization of [Pt(dpae)(S₂CH₂)] 9 and [PtCl₂(dpae)] 10. Moreover, comparison with the reactivity of [Pt₂(dppe)₂(μ-S)₂] indicates that the stability of the intermediate species as well as the nature of the final products in both multistep reactions are sensitive to the nature of the terminal ligand.