Synthesis, reactivity and structural study of diastereomeric titanium complexes with amino acid derived N- and O-π donor ligands

Two diastereomeric Ti(IV) complexes of the type [Ti(Cl)(NMe2)(OCH2CH(CH2Ph)N(R))]2 (where R=iPr or cyclo-C6H11) have been synthesized by protonolysis of TiCl(NMe2)3 with the corresponding N-substituted amino alcohols. The chiral ligands were synthesized in a two-step procedure from l-phenylalanine ethyl ester. The complexes bridge through the amino alcohol oxygen atoms, and contain terminal chlorides. The remaining dimethylamide group can be replaced by a protonolysis reaction with 2,6-diisopropylphenol. The bulky disubstituted phenoxide ligand does not inhibit dimerization, and the amino alcohol oxygen bridged complex [Ti(Cl)(O-2,6-iPr2C6H3)(OCH2CH(CH2Ph)NR)]2 is obtained. The dimeric nature of the complexes was established by X-ray crystallography.