Synthesis, characterization, properties and structures of rhenium(II), -(III), and -(V) complexes containing amino acids conjugated with a 2-aminothiazole ligand

The one-step reaction of KReO4 with benzoylhydrazine in the presence of concentrated HCl and PPh3 afforded [ReV(NNC(Ph)O)(PPh3)2Cl2]1 which was converted with carbon monoxide into the dinitrogen Re(I) complex [ReN2(CO)2(PPh3)2Cl]2 in good yield. A new class of ligands, of general formula HLn (n = 1-5), was obtained by conjugation of N-protected amino acids and benzoic acid with 2-aminothiazole. Complex 2 reacted with HLn to give neutral Re(II) chelate complexes [Re(Ln)(CO)(PPh3)2Cl]5-9 (n = 1-5), by substitution of N2 and CO groups. The molecular structure of complex 9 was determined by X-ray diffraction. When reactions between [Re(NNC-(Ph)O)(PPh3)2Cl2]1 and HLn (n = 2, 5) were carried out in different stoichiometric ratios, neutral mono- and di-substituted Re(III) organodiazenido complexes [Re(NNCOPh)(L2,5)(PPh3)2Cl]10, 11 and [Re(NNCOPh)(L5)2-(PPh3)]12 were obtained. In these complexes the organodiazenido Re-N-N moiety adopts a linear conformation, as has been authenticated by X-ray ...