CYTOSINE NUCLEOBASE AS A TRIDENTATE LIGAND - METAL-BINDING TO N(3), N(4) AND O(2) IN TRANS-[(NH(2)ME)(2)PT(DMCYT)(2)AG-2][NO3](2) (DMCYT=1,5-DIMETHYLCYTOSINATE)

1,5-Dimethylcytosine (Hdmcyt). which is a model of the naturally occur ring 5-methylcytidine nucleobase, has been demonstrated to be capable of binding three metal ions simultaneously, via N(3), monodeprotonated N(4) and O(2). The compound trans-[(NH(2)Me)(2)Pt(dmcyt)(2)Ag-2][NO3] (2) 1 was prepared from trans-[Pt(NH(2)Me)(2)(Hdmyct-N-3)(2)] [NO3](2) and AgNO3 at alkaline pH. and its crystal structure determined. The P t ... Ag distances within the trinuclear cation are 2.892(1) and 3.040 (1) Angstrom. The compound is compared with related mixed Pt-Ag nucleo base complexes as well as other trinuclear d(10)-d(8)-d(10) systems. D espite the problem of differentiation of the nucleobase arrangement (h ead-to-head or head-to-tail) due to the pseudo-two-fold symmetry of th e 1,5-dimethylcytosine ligand, the head-to-head orientation has unambi guously been established by use of H-1 NMR spectroscopy following prec ipitation of AgCl.