Abstract: Pt-containing compound with the formula {Pt.sup.II (w)(x)(y)(z)} or {Pt.sup.IV (u)(v)(w)(x)(y)(z)}, wherein u, v, w, x, y and z represent whether or not the same whether or not interconnected ligands, of which at least one is a leaving ligand and at least one of the remaining ligands represents a detectable marker group. According to the invention (CH.sub.3).sub.2 SO, Cl or H.sub.2 O appears to be suitable as a leaving ligand while as detectable marker group a fluorescent group merits preference and is the ligand fluorescein or tetramethyl rhodamine. A suitable Pt-containing compounds is {Pt(ethylenediamine)(Me.sub.2 SO)(fluorescein-NH(CS)-NHCH.sub.3)} (PtF). Further, the invention comprises a process for the preparation of the Pt-containing compounds, where the Pt-containing compounds are prepared in a manner known per se for analogous compounds.