Pt(II) and Pt(IV) chloride complexes with 1,2,4-triazolo-[1,5α]-pyrimidines: trans-[Pt(tp) 2 Cl 2 ], trans-[Pt(dmtp) 2 Cl 2 ], trans-[Pt(tp) 2 Cl 4 ] and trans-[Pt(dmtp) 2 Cl 4 ] where tp=1,2,4-triazolo-[1,5α]-pyrimidine and dmtp=5,7-dimethyl-1,2,4-triazolo-[1,5α]-pyrimidine were synthesised and studied by 1 H, 1 3 C, 1 5 N, 1 9 5 Pt NMR and IR spectroscopies. Significant 1 5 N NMR upfield coordination shifts (92-96 ppm) were observed for the N(3) atom indicating that this nitrogen is the metallation site. The X-ray structure of an ionic pair (dmtpH) 2 [PtCl 6 ] {bis(5,7-dimethyl-1,2,4-triazolo-[1,5α]-pyrimidinium) hexachloroplatinate(IV)} was determined, exhibiting the presence of unique (dmtpH) 2 2 + dimeric cations, protonated at N(3), N(3') atoms and linked by hydrogen bonding.