Synthetic Route to Dinuclear Platinum(II) Complexes [{trans-PtCl(NH3)(2)}(2)(mu-L)](2+) (L = Aliphatic or Heterocyclic Diamine) as Potential Antitumor Agents, Exploiting the Mutual Activation of Hydroxido Ligands and Ammonium Groups

A simple and efficient method for the synthesis of potentially antitumor-active dinuclear platinum complexes of the general formula [{trans-PtCl(NH3)2}2(μ-L)](n+2)+ (L = aliphatic or heterocyclic diamine; n = charge of L) is presented. The procedure is based on the mutual in situ activation of trans-[PtCl(OH)(NH 3)2] and the linker L in the form of a diammonium salt. This synthetic pathway yielded the Farrell compound [{trans-PtCl(NH 3)2}2{μ-NH2(CH2) 6NH2}]Cl2 (BBR3005) in quantitative yield. Using the same procedure, we prepared the new pyrazolate-bridged compound [{trans-PtCl(NH3)2}2(μ-pz)]Cl, determined its X-ray structure, and tested its cytotoxicity against three wild-type and one cisplatin-resistant cell lines.