Reinterpretation of the vibrational spectroscopy of the medicinal bioinorganic synthon c,c,t-[Pt(NH[subscript 3])[subscript 2]Cl[subscript 2](OH)[subscript 2]]

Abstract

The Pt(IV) complex c,c,t-[Pt(NH[subscript 3])[subscript 2]Cl[subscript 2](OH)[subscript 2]] is an important intermediate in the synthesis of Pt(IV) anticancer prodrugs and has been investigated as an anticancer agent in its own right. An analysis of the vibrational spectroscopy of this molecule was previously reported (Faggiani et al., Can. J. Chem. 60:529, 1982), in which crystallographic determination of the structure of the complex permitted a site group approach. The space group, however, was incorrectly assigned. In the present study we have redetermined at high resolution crystal structures of c,c,t-[Pt(NH[subscript 3])[subscript 2]Cl[subscript 2](OH)[subscript 2]] and c,c,t-[Pt(NH[subscript 3])[subscript 2]Cl[subscript 2](OH)[subscript 2]]·H[subscript 2]O[subscript 2], which makes possible discussion of the effect of hydrogen bonding on the N–H and O–H vibrational bands. The correct crystallographic site symmetry of the platinum complex in the c,c,t-[Pt(NH[subscript 3])[subscript 2]Cl[subscript 2](OH)[subscript 2]] structure is used to conduct a new vibrational analysis using both group-theoretical and modern density functional theory methods. This analysis reveals the nature and symmetry of the “missing band” described in the original publication and suggests a possible explanation for its disappearance.