Isomer abundance of bis(β-diketonato) complexes of titanium(IV). Crystal structures of the antitumor compound budotitane [Ti IV(bzac) 2(OEt) 2] and of its dichloro-derivative [Ti IV(bzac) 2Cl 2] (bzac=1-phenylbutane-1,3-dionate)

Abstract

The molecular tumor inhibiting titanium compound budotitane [Ti IV(bzac) 2(OEt) 2] ( 1) and its dichloro-derivative [Ti IV(bzac) 2Cl 2] ( 2) (bzac=1-phenylbutane-1,3-dionate) have been crystallized and characterized by X-ray crystallography and further physical methods. Budotitane ( 1) crystallizes in the tetragonal, non-centrosymmetric space group P4 1 with two molecules in the asymmetric unit. Both molecules adopt the cis– cis– trans configuration with the acetyl ends of the benzoylacetonate ligands in the trans position. The dichloro-derivative of budotitane, [Ti IV(bzac) 2Cl 2] ( 2) crystallizes in the monoclinic, centrosymmetric space group P2 1/ n with one molecule only in the asymmetric unit. In contrast to budotitane ( 1), ( 2) shows a cis– trans– cis arrangement with the benzoyl groups in the trans position. In both complexes there are equal numbers of Δ and Λ enantiomers within the unit cell. The phenyl groups in ( 1) as well as in ( 2) are in approximately coplanar conjugation to the metal enolate rings. The thermal degradation of budotitane ( 1) was investigated in the temperature range from 25 °C up to 800 °C and reveals the formation of Ti IVO(bzac 2−) as an intermediate and of the rutile phase of TiO 2 as a final product. It may be worthwhile to introduce budotitane in the form of isomerically pure crystals in the preparation of the drug used for future tests.