Coordination Chemistry of trans-(NH3)2Pt(II) with Uracil Nucleobases. A Comparison with cis-(NH3)2Pt(II)

Abstract

Protonated and heteronuclear adducts as well as a series of Pt(IV) oxidation products derived from trans-a2PtL2 (a = NH3, NH2CH3, L = 1-methyluracil anion, C5H5N2O2, or uridine anion, C10HnN2O6) have been prepared and studied by spectroscopic methods and in two cases by X-ray crystallography. trans-(NH3)2Pt(C5H5N2O2)2Ag2(NO3)2H2O · H2O (7) crystallizes in the orthorhombic space group Pna21 with cell dimensions a = 13.206(6), b = 7.238(9), c = 22.051(10) Å, U = 2107.7 Å3, Z = 4. 7 forms a polymeric structure with PtAg2 entities linked via O(4) sites of the 1-methyluracilato ligands. Pt is coordinated through N(3), the Ag centers have a mixed O(2),O(4) coordination, trans,trans,trans-[(NH3)2Pt(OH)2(C5H6N2O2)2](NO3)2 (9) contains two N(3)-bound neutral 1-methyluracil ligands, hence rare tautomers of this model nucleobase. 9 crystallizes in the monoclinic system, space group P21/n with cell dimensions a = 7.098(1), b = 10.395(1), c = 13.295(2) Å, U = 980.4 Å3, Z = 2. While the chemistry leading to Pt(IV) oxidation products from trans-a.2PtL2 is similar to that of the cis-isomer, protonation as well as heteronuclear complex formation of trans-a2PtL2 is more difficult to accomplish than with the cis-isomer. This difference appears to be primarily of steric origin.