MIXED-LIGAND COMPLEXES OF PALLADIUM(II) AND PLATINUM(II) WITH METHIONINE AND 2,4-DISUBSTITUTED PYRIMIDINES

Mixed ligand complexes of cis-[M(MetH)Cl2] (M=Pd2+ and Pt2+; MetH=methionine) with 2,4-disubstituted pyrimidines were prepared and characterised. The cis-[Pd(MetH)Cl2] complex reacted with cytosine (2-hydroxy-4-aminopyrimidine), isocytosine (2-amino-4-hydroxypyrimidine) and thiocytosine (2-thio-4-amino-pyrimidine) to form ternary complexes. cis-[Pt(MetH)Cl2] however reacted with cytosine, uracil (2,4-pyrimidine dione or 2,4-dihydroxypyrimidine) to yield the corresponding mixed ligand complexes. The primary ligand, methionine, binds to the metal ion through sulphur and amino nitrogen via a six membered chelate ring. The secondary ligands (substituted pyrimidines) bind to the Pd2+ or Pt2+ metal ion through the ring nitrogen (N3), as monodentate ligand. Thiocytosine however acts as a bidentate ligand, coordinating to the metal ion through-SH and ring nitrogen (N3). All complexes are 1:1 electrolytes, except the thiocytosine complex, which is a 1:2 electrolyte. © 1990 Chapman and Hall Ltd.