Rhenium(III), (IV) and (V) complexes with 6-hydroxypicolinic acid

The reaction of trans-[ReOBr3(PPh3)2] with 6-hydroxypicolinic acid (H2hpa) in ethanol led to the isolation of the doubly chelate-bridged complex (μ-O)(μ-hpa)2[ReIV2Br(OEt)(PPh3)2] (1). By using [ReOCl3(PPh3)2] as precursor, two products were isolated, i.e. (μ-Cl)(μ-O)(μ-hpa)-[ReIV2Cl2(OEt)(PPh3)2] (2) and [ReIIICl2(Hhpa)(PPh3)2] (3). The bromide equivalent of 3, i.e. [ReIIIBr2(Hhpa)(PPh3)2] (6), was obtained from the reaction of [ReOBr3(PPh3)2] with H2hpa in 2-propanol. The complexes cis-[ReOX2(Hhpa)(PPh3)] (X = Br (4); Cl (5)) were the only products formed by the reaction of [ReOX3(PPh3)2] with H2hpa in acetonitrile.73