1-Methylisocytosine as a ligand for (dien)MII (M = Pt, Pd) and Pt-promoted deamination to 1-methyluracil

Abstract 1-Methylisocytosine (1-MeIC) can be protonated at the endocyclic N(3) position (p K a of 1-MeICH + , 4.02 ± 0.04) or complexed at this position with (dien)M II (M = Pt, Pd). X-ray crystal structures of the protonated species 1 as well as the Pd ( 2 ) and Pt ( 3 ) complexes are reported, and gas phase structures of the cation 2 and 3 have been calculated by ab initio methods. These results are compared with results from X-ray crystallography. At high pH, the Pt complex 3 undergoes deamination of the exocyclic N(2)H 2 group to the 1-methyluracilate complex. As compared to the situation with 1-methylcytosine (1-MeC), the accelerating effect of (dien)Pt II is much less pronounced, however.