Complexes of the {ReVOX2}+ (X = Cl, Br) core with single amino acid chelate derivatives

The reactions of 1 equiv. of the ligand 3-(ethoxycarbonylmethyl-pyridin-2-ylmethyl-amino)-propionic acid methyl ester (2) with the Re(V) starting materials [ReOX3(PPh3)2] (X = Cl, Br) in refluxing chloroform yielded the Re(V)-oxo dihalide complexes [ReOX2{(C5H4NCH2)N(CH2CO2)(C2H4CO2CH3)}] (X = Cl, 3; X = Br, 4). The complexes were characterized by elemental analysis, NMR and IR spectroscopy, cyclic voltammetry and X-ray crystallography. Complex 3 displays distorted octahedral coordination geometry with the tridentate ligand coordinating facially to the Re(V) center. The carboxylate oxygen atom occupies an axial site trans to the Redouble bond; length as m-dashO bond. The two chlorine atoms consequently adopt a cis configuration.