Synthesis and characterisation of mercaptoimidazole, mercaptopyrimidine and mercaptopyridine complexes of platinum(II) and platinum(III). The crystal and molecular structures of tetra(2-mercaptobenzimidazole)- and tetra(2-mercaptoimidazole)platinum(II) chloride

Reaction of K2[PtCl4] with 2-mercaptobenzimidazole (HL2) and 2-mercaptoimidazole (HL3) in aqueous ethanol afforded the new, crystalline, square-planar platinum(II) complexes [Pt(HL2)4]Cl2·EtOH (4) and [Pt(HL3)4]Cl2·2H2O (5), the crystal and molecular structures of which are reported. In both complexes the ligands are present in the thione form with coordination taking place through the sulphur atom only. The Pt-S bond lengths are 2.304(4) and 2.312(3) Å in complex (4) and 2.314(12) and 2.317(12) Å in complex (5). The S-Pt-S bond angles are 90.33(13) and 89.67(13)° in complex (4) and 94.46(4) and 85.54(4)° in complex (5). Reaction of the ligands 4-hydroxy-2-mercaptopyrimidine (HL4) and 2-mercaptopyridine (HL5) with K2[PtCl4] gave the new, dimeric platinum(III) complex [Pt2(L4)4Cl2] (6) and [Pt2(L5)4Cl2]·EtOH (7) which is similar to a previously reported complex prepared by a different method. In these complexes the organic ligands are bridging N, S donors, the chlorides are terminally coordinated to each platinum and there is a platinum-platinum bond. The reaction of 4-amino-2-mercaptopyrimidine (HL6) with K2[PtCl4] gave the monomeric platinum(II) complex cis-[Pt(HL6)2Cl2]·2H2O (8) in which each HL6 ligand is coordinated to the metal ion via the exocyclic amino group. Reaction of 4,6-dihydroxy-2-methylmercaptopyrimidine (HL7) with K2[PtCl4] gave the dimeric platinum(II) complex of formula [Pt2(L7)2(HL7)2] Cl2 (9), which is suggested to contain bridging L7 and HL7 ligands. © 2001 Elsevier Science B.V.