1-Methylcytosine and cytidine complexes of platinum(II) stabilized by trimethylphosphine. Synthesis and characterization

Abstract

The interaction of cis-[Pt(PMe₃)₂(H₂O)₂]²⁺ with 1-methylcytosine (4-amino-1-methyl-1H-pyrimidin-2-one)(myct) and cytidine (4-amino-1-β-D-ribofuranosyl-1H-pyrimidin-2-one)(Cyd) has been investigated by ¹H and ³¹P NMR spectroscopy. The compounds cis-[Pt(PMe₃)₂(myct)₂][NO₃]₂ and cis-[Pt(PMe₃)₂(Cyd)₂][NO₃]₂ have been isolated and the molecular structure of the nucleobase derivative determined by single-crystal X-ray diffraction techniques. The crystals of cis-[Pt(PMe₃)₂-(mcyt)₂][NO₃]₂ are triclinic, space group P, with a= 12.363(2), b= 11.479(2), c= 9.645(2)Å, α= 87.5(2). β= 73.9(2), γ= 84.5(2)° and Z= 2. The structure was solved by heavy-atom methods and refined by least-squares techniques to R(F)= 0.067 for 4112 observed reflections with F 7δ(F). The platinum atom is in a distorted square-planar environment with the phosphine ligands in cis position [P–Pt–P 94.5(3)°] and the two N(3)-bonded nucleobases in a head-to-til arrangement. The interbase dihedral angle is 94.2(3)° and the platinum co-ordination plane forms a dihedral angle of 74.1(3)° with the pyrimidine ring planes. The Pt–P and Pt–N(3) bond distances are 2.256(5), 2.254(5) and 2.092(9), 2.108(9)Å, respectively. Strong interbase [NH₂(4)⋯ O(2′) 2.95(1)Å] and base–nitrate anion hydrogen bonds are observed. The ¹³C and ¹⁹⁵Pt NMR data of these nucleobase and nucleoside adducts are also reported and discussed.