Facile cyanamide-ammonia coupling mediated by cis- and trans-[Pt L] centers and giving metal-bound guanidines

Diffusion of ammonia into CHCl solutions of the dialkylcyanamide complexes cis- or trans-[PtCl(RCN)] (R = NMe, NEt, NCH) at 20-25°C leads to metal-mediated cyanamide-ammonia coupling to furnish, depending on reaction time, one or another type of novel bisguanidine compound, i.e. the molecular cis- or trans-[PtCl{NH=C(NH)R}] (cis-1-3 and trans-1-3) and the cationic cis- or trans-[Pt(NH) {NH=C(NH)R}](Cl) (cis-4-6 and trans-4-6) complexes. Compounds cis-1-3 or trans-1-3 were converted to cis-4-6 or trans-4-6, accordingly, upon prolonged treatment with NH in CHCl. The ammination of the relevant nitrile complexes cis- or trans-[PtCl(RCN)] (R = Et, CHPh, Ph) in CHCl solutions affords only the cationic compounds cis- or trans-[Pt(NH){NH=C(NH)R} ](Cl) (cis-7-9 and trans-7-9). The formulation of 1-9 was supported by satisfactory C, H and N elemental analyses, agreeable ESI -MS (or FAB-MS), IR, H and C NMR spectroscopies. The structures of trans-1, trans-3, cis-4, trans-4, cis-7, and cis-9 were determined by single-crystal X-ray diffraction disclosing structural features and showing that the ammination gives ligated guanidines and amidines in the E- and Z-forms, respectively, where both correspond to the trans-addition of NH to the nitrile species. © The Royal Society of Chemistry 2008.