New α-Keto Acid-Derived Hydrazone Ligands and Their Reaction With The {Re (CO) 3}+

Abstract

[Abstract] Two hydrazone ligands derived of phenylglyoxylic acid (HL1) and 4-hydroxyphenylpyruvic acid (HL2) were synthesized and their zwitterionic structures were determined by X-ray diffraction. The rhenium(I) complexes of formula [ReCl(HLn)(CO)3] were obtained by reaction of the ligands with [ReCl(CH3CN)2(CO)3]. The formation of the hydazonate complexes were also achieved. In the case of HL1 the trimetic complex [Re3(L1)3(CO)9] was isolated by using a basic medium. On the other hand, from storage of a solution of the [ReCl(HL2)(CO)3] complex, crystals of the [Re2(L2)2(CO)6] dimer could be obtained for their structural analysis by X-ray diffraction. The study of the crystalline structures is included. The coordination geometry around rhenium(I) can be described as octahedral with three carbon atoms in fac configuration. In all complexes a five-membered chelate ring is formed including two nitrogen atoms from the hydrazone chain and the pyridine group. In the mononuclear complexes the carboxylic group does not participates in the coordination but acts as a bridge to form the polynuclear compounds. The coordination mode of the ligands in all the complexes could be corroborated by comparative studies of the experimental and calculated (DFT) IR spectra.