Platinum(IV) organometallics I. Syntheses of trans-di(carboxylato)ethane-1,2-diamine- cis-bis(pentafluoro-phenyl)platinum(IV) complexes and the X-ray crystal structure of the n-butanoato derivative

Abstract

The complex Pt(C 6F 5) 2(OH) 2(en) (en = ethane-1,2-diamine) has been prepared by oxidation of Pt(C 6F 5) 2(en) hydrogen peroxide in acetone. Treatment of the platinum(IV) complex with acid anhydrides, (RCO) 2O ( R = Me, Et, nPr, or iPr ), in ether yields cis, trans-Pt(C 6F 5) 2(O 2CR) 2(en) complexes. The stereochemistry was established by an X-ray diffraction study of Pt(C 6F 5) 2(O 2C nPr) 2(en), which has an octahedral arrangement involving trans unidentate butanoate ligands and cis-C 6F 5 groups, and by spectroscopic similarities between the complexes. There is hydrogen bonding between uncoordinated carboxyl oxygens and NH groups, and between one ortho-fluorine of each C 6F 5 group and an NH group. The 19F NMR spectra show five fluorine resonances at −50 °C, indicative of unsymmetrical C 6F 5 groups with restricted rotation, and this is consistent with features of the solid state structure of cis, trans-Pr(C 6F 5) 2(O 2C nPr) 2(en). Preliminary examination of the biological activity of the complexes against L1210 and L1210/DDP mouse leukemia cells in culture has been made.