Structural Features of Titanium Complexes of Salicylaldiminato Derivatives of Amino Acids

摘要

Condensation of salicylaldehyde with amino acid derivatives gave the salicylaldimine derivatives 3 that reacted with TiCl_4 with release of HC1 to yield the chelate complexes [(SalPhgOMe)TiCl_3] (4a),[(SalValOMe)TiCl_3] (4b),and the dipeptide derivative [(SalAlaValOMe)TiCl3] (4d).The complex [(Sal~*PhgOMe)TiCl_3] (4c) was prepared analogously starting from 3,5-di-tert-butyl-2-hydroxybenzaldehyde and phenylglycine methyl ester.Complex rac-4a was characterized by X-ray diffraction and shown to feature a typical structure where the monoanionic ligand is tridentate,coordinating to the central titanium atom through both the phenol-ate oxygen atom and the ester carbonyl oxygen atom as well as through the imine nitrogen atom.A hydrolyzed carboxyl-ate analogue of 4a exhibits an analogous central structural framework.In this case,however,the overall structure of rac-5a was found to be a metallacyclic tetramer where four titanium atoms bind four such tridentate ligands.