SYNTHESIS, CHARACTERIZATION, AND STRUCTURAL INVESTIGATION OF THE FIRST BIOINORGANIC TITANOCENE(IV) ALPHA-AMINO-ACID COMPLEXES PREPARED FROM THE ANTITUMOR AGENT TITANOCENE DICHLORIDE

Antitumor active titanocene dichloride [Cp(2)TiCl(2)] (Cp = eta(5)-C5H5) reacts with alpha-amino acids (aa = amino acid) in aqueous methanol to give the first bioinorganic titanium(IV) amino acid complexes [Cp(2)Ti(aa)(2)](2+)[Cl](-)(2) (aa: glycine, 1; L-alanine, 2; 2-methylalanine, 3). These compounds are of great interest as the first models involving titanocene complexes with cx-amino acids. The structure of 3 was determined by X-ray structure analysis. Complex 3 is monoclinic, space group C2/c, a = 9.0630(11) Angstrom, b = 28.173(9) Angstrom, C = 8.8967(9) Angstrom, beta 96.379(9)degrees, V = 2257.5(4) Angstrom(3), and Z = 4. It was established by X-ray analysis and vibrational spectroscopy that these compounds represent examples of very rare species in which the amino acids coordinate solely through the carboxylato group. All complexes have been characterized by chemical analyses (C/H/N/Cl), NMR (H-1, N-14/15), mass (EI; 3 in addition by DCI), infrared, and Raman spectroscopy.