PHIC is prepared from the diaquo derivative cis-[Pt(diaminocyclohexane)(H2O)2](NO3)2 (II), which is obtained by addition of a stoichiometric amount of silver nitrato to cis-[PtCl2(diaminocyclohexane)] (I). Then isocitrate trisodium salt is added to the diaquo species (II) (1:1), and the mixtures heated to 60 C in the dark for 20 h. The yellow solution is concentrated. then treated with cold ethanol acetona (1:1) to give white PHIC precipitate. After the usual workup, PHIC is obtained (85%). The binding sites of the isocitrate ion to the platinum: diamino cyclohexane moiety have not been characterized.