Platinum(II) complexes of 3,3′-disubstituted-2,2′-bypyridines. Synthesis, structures, cytotoxic effect and unusual solvolysis in DMSO

Abstract

The reaction of 3,3′-disubstituted-2,2′-bipyridines, 2,2′-bipyridyl-3,3′-dicarboxylic acid (H 2BDC) and 3,3′-dimethylol-2,2′-bipyridine (DMB) with potassium tetrachloroplatinate(II) in water gives Pt(H 2BDC)Cl 2 ( 1) and Pt(DMB)Cl 2 ( 2), respectively. Both complexes were characterized by elemental analysis and various spectroscopic techniques. The molecular structures of 1 and 2 have been determined by single-crystal X-ray diffraction. 1·2DMF: triclinic system, space group P 1, α=8.089(9) A ̊ , b=9.707(8) A ̊ c=15.541(4) A ̊ , α=106.88(6)° , β=100.41(3)°, γ=94.39(8)°, V=1137.8(2) A ̊ 3, Z=2 . 2: monoclinic system, space group P2, lc, α=7.849(5) A ̊ , b=16.125(3) A ̊ , c=21.613(5) A ̊ , β=94.10(2)°, V=2728.5(9) A ̊ 3, Z=8 . X-ray structures indicate that two pyridine rings of the bipyridyl ligand in both compounds cannot attain the coplanar state owing to the steric bulkiness of the substituents in the 3,3′-positions. The solvolysis of 1 in DMSO. characterized by 1H, 13C and 195Pt NMR spectra, leads to the unprecedented example for the complete release of the free amine ligand H 2BDC, yielding the formation of cis-[Pt(Me 2SO) 2Cl 2]. No antitumor activity was observed for 1 and 2 against the leukemia L1210 cell line.