NOVEL CARBOPLATIN ANALOGS CONTAINING FLEXIBLE AND POTENTIALLY INTERCALATING LIGANDS - PREPARATION AND X-RAY CRYSTAL-STRUCTURES OF DI-2-PYRIDYL KETONE CYCLOBUTANEDICARBOXYLATE PLATINUM(II) AND OF 2,3-BIS(2-PYRIDYL)PYRAZINE CYCLOBUTANE DICARBOXYLATE PLATINUM(II)

The crystal structures of the cyclobutanedicarboxylate (cbdc) platinum (II) complexes of di-2-pyridyl ketone (dpk) 1, [Pt(dpk) (cbdc)] and of 2,3-bis(2-pyridyl)pyrazine (bpp) 2, [Pt(bpp) (cbdc)] . 2CH(2)Cl, have been determined by X-ray crystallography. Crystal data are: 1, orthor hombic space group Pbcn, a = 16.164(3), b = 10.749(2), c = 18.601(3) A ngstrom, V = 3232(1) Angstrom(3) and Z = 8; 2, triclinic space group < P(1)over bar>, a = 9.437(2), b = 15.424(3), c = 9.342(2) Angstrom, alp ha = 107.45(2), beta = 91.92(1), gamma = 82.68(1), V = 1287(1) Angstro m(3) and Z = 2. In the former structure, the dpk ligand did not underg o the metal promoted hydration reaction to yield a facial tridentate l igand. It binds the platinum in a bidentate fashion retaining the sp(2 ) hybridization around the carbonyl carbon. The conformational strain is relieved by distortion of the planar ligand through rotation of the pyridyl rings around the bonds connecting them to the carbonyl group to yield a non-planar ligand. In the second structure (bpp complex), t he chelating pyrazine and pyridyl rings are coplanar and the non-ligat ing pyridyl ring is nearly perpendicular to them. (C) 1997 Elsevier Sc ience S.A.