Rhenium and molybdenum oxo-complexes containing ligands related to N-hydroxyiminodipropionic acid

The reaction of N-hydroxy-2,2'-iminodipropionic acid with [PPh4][ReOBr4], [ReOCl3(PPh3)(3)], [ReOCl2(OEt)(PPh3)(2)] or [PPh4][MoOCl4(H2O)] has produced four novel complexes: [ReOBr3(C6H8NO5)](-), [ReOBr3(C3H3NO2)](-), [ReOCl2(R,S-idpa)](-)(H(3)idpa = 2,2'-iminodipropionic acid) and [MoO2Cl2(C3H4NO3)](-). All have been successfully crystallised as their [PPh4](+) salts which have been characterised by single-crystal X-ray diffraction. The anions [ReOBr3(C6H8NO5)](-)and [ReOBr3(C3H3NO2)](-) involve tetragonally distorted octahedral (ReOBr3)-O-V (N,O) centres with the bromides cis to the oxo-group; [ReOCl2(R,S-idpa)](-) involves a tetragonally distorted octahedral (ReOCl2)-O-V (O,N,O) centre with the 2Cl cis and O trans to the ore-group; [MoO2Cl2(C3H4NO3)](-) involves a skew-trapezoidal (MoO2Cl2)-O-VI (N,O) centre with essentially mutual cis ore-groups and trans chloro-groups. The dimensions of each of these co-ordination spheres are generally typical of related complexes; however, [ReOBr3(C3H3NO2)](-) involves an unusually short Re-O-oxo bond of 1.45(4) Angstrom. The organic moieties are considered to arise from rearrangement and/or fragmentation of N-hydroxy-2,2'-iminodipropionic acid, presumably under the influence of the metal centre.