The dinuclear Pt(III) compounds [Pt(pymS) 2Cl] 2 ( A) (pymS=the anion of pyrimidine-2-thione) and [Pt(2-TU) 2I] 2 ( B) (2-TU=the anion of 2-thiouracil) have been prepared and their structures determined by X-ray diffraction methods. Compound A is mono- clinic, space group P2 1/ n, with a=10.404(4), b= 13.345(3), c=17.522(3) Å, β=103.61(2)°, V= 2364 Å 3, and Z=4; B is triclinic, space group P 1 , a=10.925(13), b=11.896(4), c=13.639(6) Å, α= 92.05(3), β=99.74(7), γ=110.28(7)°, V=1630 Å 3, and Z=2. The halogen atoms occupy the axial positions of the dinuclear unit in which two Pt atoms are bridged by four thione ligands. Compound A differs from B and from previously reported [Pt(pymS) 2I] 2 ( C) in that in A one of the Pt atoms is coordinated to one N atom and three S atoms of the thione bridges, while the other Pt is bonded to three N atoms and one S atom. The PtPt bond length in A (2.518(1) Å) is shorter than that (2.554(1) Å) in C. [Pt(pymS) 2Br] 2 ( D) has also been isolated and is believed to have a similar structure to C. Pt(2-mer- capto-4-methylpyrimidinato) 2X (X= Cl, I) and Pt 2(pymS) 5Cl were also obtained, but not in suitable crystalline form for X-ray characterisation. Attempts to prepare Pt 2(pymS) 5Br gare crystals which X-ray study showed to be dinuclear [Pt 2(pymS) 4BrX] ( E), with X corresponding to partial occupancy of one axial position by a pymS − anion, coordinated by S, and by halide. Crystal data for E are: monoclinic, space group P2 1/ n, a=12.632(7), b=14.302(6), c=15.109(7) Å, β=91.95(4)°, V=2728 Å 3, and Z =4. Several Pt(II) complexes with related thiones and some pyrimidine-2-one ligands are briefly reported.