Synthesis and Coordination Behavior of a Bipyridine Platinum(II) Complex with Thioglucose

A mononuclear platinum(II) complex with two monodentate-S H4tg– ligands, [Pt(H4tg-κS)2(bpy)] (1), was newly synthesized by the reaction of [PtCl2(bpy)] (bpy = 2,2′-bipyridyl) with NaH4tg (NaH4tg =1-thio-β-d-glucose sodium salt) in water. Complex 1 reacted with additional [PtCl2(bpy)] in water to give an S-bridged dinuclear complex, [Pt2(μ2-H4tg-κ1 S:κ1 S)2(bpy)2]2+ ([2]2+), in which a square-planar [Pt(H4tg)2(bpy)] unit binds to a [Pt(bpy)]2+ moiety through two thiolato groups. Treatments of 1 with Cu2+ and Ni2+ in water in the presence of bpy produced S-bridged dinuclear complexes [PtCu(μ2-H4tg-κ1 S:κ2 O,S)2(bpy)2]2+ ([3]2+) and [PtNi(μ2-H4tg-κ1 S:κ2 O,S)2(bpy)2]2+ ([4]2+), respectively, in which a square-planar [Pt(H4tg)2(bpy)] unit binds to a [M(bpy)]2+ (M = CuII, NiII) moiety through two thiolato and two hydroxyl groups to form a chiral [M(N)2(O)2(S)2] octahedron with the Δ configuration. On the other hand, similar treatment with Cd2+ in the presence of bpy resulted in the formation of an S-bridged trinuclear complex, [Cd{Pt(μ2-H4tg-κ1 S:κ2 O,S)(μ2-H4tg-κ1 S:κ1 S)(bpy)}2]2+ ([5]2+), in which each of two square-planar [Pt(H4tg)2(bpy)] units binds to a CdII ion through two thiolato groups and one hydroxyl group to form a chiral [Cd(O)2(S)4] octahedron with the Λ configuration. Of two geometrical configurations, syn and anti, which arise from the relative arrangement of two β-D-pyranose moieties, [2]2+ adopts the syn configuration with symmetric bridging sulfur atoms, while [3]2+, [4]2+, and [5]2+ all have the anti configuration with R configurational bridging sulfur atoms. All of the complexes were fully characterized by electronic absorption, CD, and NMR spectroscopies, along with single-crystal X-ray crystallography.