Mono-, Di- and Trinuclear Pt(II), Mononuclear Pt(IV), Mixed Pt(II),Pt( IV), Mixed Pt(II),Ag(I) Complexes of 9-Methyladenine (9-MeA), and the X-Ray Structure of ((dien)Pt(9-MeA-N1))(NO3)2×H2O.