Synthesis, characterization, and reactivity of trans-[PtCl(R ' R '' SO)(A)(2)]NO3 (R ' R '' SO = Me2SO, MeBzSO, MePhSO; A = NH3, py, pic). Crystal structure of trans-[PtCl(Me2SO)(py)(2)]

Trans complexes such as trans-[PtCl2(NH3)(2)] have historically been consid ered therapeutically inactive. The use of planar ligands such as pyridine g reatly enhances the cytotoxicity of the trans geometry. The complexes trans -[PtCl(R 'R " SO)(A)(2)]NO3 (R 'R " SO = substituted sulfoxides such as dim ethyl (Me2SO), methyl benzyl (MeBzSO), and methyl phenyl sulfoxide (MePhSO) and A = NH3, pyridine (py) and 4-methytpyridine or picoline (pic)) were pr epared for comparison of the chemical reactivity between ammine and pyridin e ligands. The X-ray crystal structure determination for trans-[PtCl(Me2SO) (py)(2)]NO3 confirmed the geometry with S-bound Me2SO. The crystals are ort horhombic, space group P2(1)2(1)2(1). With Cell dimensions a = 7.888(2) Ang strom, b = 14.740(3) Angstrom, 15.626(5) Angstrom, and Z = 4. The geometry around the platinum atom is square planar with l(Pt-Cl) = 2.304(4) Angstrom , l(Pt-S) = 2.218(5) Angstrom, and l(Pt-N) = 2.03(1) and 2.02(1) Angstrom. Bond angles are normal with Cl-Pt-S = 177.9(2)degrees, Cl-Pt-N-1 = 88.0(4)d egrees, Cl-Pt-N-2 = 89.3(5)degrees, S-Pt-N-1 = 93,8(4)degrees, S-Pt-N-2 = 8 8.9(4)degrees, and N-1-Pt-N-2 = 177.2(6)degrees. The intensity data were co llected with Mo Ka radiation with lambda = 0.710 69 Angstrom. Refinement wa s by full-matrix least-squares methods to a final R value of 3.80%. Unlike trans-[PtCl2(NH3)(2)], trans-[PtCl2(A)(2)] (A = py or pie) complexes do not react with Me2SO. The solvolytic products of cis-[PtCl2(A)(2)] (A = py or pie) were characterized. Studies of displacement of the sulfoxide by chlori de were performed using HPLC. The sulfoxide was displaced faster for the py ridine complex relative to the ammine complex. Chemical studies comparing t he reactivity of trans-[PtCl(R 'R " SO)(amine)(2)]NO3 with a model nucleoti de, guanosine 5'-monophosphate (GMP), showed that the reaction gave two pri ncipal products: the species [Pt(R 'R " SO)(amine)(2)(N7-GMP)], which react s with a second equivalent of GMP, forming [Pt(amine)(2)(N7-GMP)(2)]. The r eaction pathways were different, however, for the pyridine complexes in com parison to the NH3 species, with sulfoxide displacement again being signifi cantly faster for the pyridine case.