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-κ1S:κ1S)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-κ1S:κ2O,S)2(bpy)2]2+ ([3]2+) and [PtNi­(μ2-H4tg-κ1S:κ2O,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-κ1S:κ2O,S)­(μ2-H4tg-κ1S:κ1S)­(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.