Synthesis, characterization, properties and structures of rhenium-(ii), -(iii), and -(v) complexes containing amino acids conjugated with a 2-aminothiazole ligand

Abstract

The one-step reaction of KReO 4 with benzoylhydrazine in the presence of concentrated HCl and PPh 3 afforded [Re V (NNC(Ph)O)(PPh 3 ) 2 Cl 2 ] 1 which was converted with carbon monoxide into the dinitrogen Re() complex [ReN 2 (CO) 2 (PPh 3 ) 2 Cl] 2 in good yield. A new class of ligands, of general formula HL n (n = 1-5), was obtained by conjugation of N-protected amino acids and benzoic acid with 2-aminothiazole. Complex 2 reacted with HL n to give neutral Re() chelate complexes [Re(L n )(CO)(PPh 3 ) 2 Cl] 5-9 (n = 1-5), by substitution of N 2 and CO groups. The molecular structure of complex 9 was determined by X-ray diffraction. When reactions between [Re(NNC-(Ph)O)(PPh 3 ) 2 Cl 2 ] 1 and HL n (n = 2, 5) were carried out in different stoichiometric ratios, neutral mono-and di-substituted Re() organodiazenido complexes [Re(NNCOPh)(L 2,5 )(PPh 3 ) 2 Cl] 10, 11 and [Re(NNCOPh)(L 5 ) 2 -(PPh 3 )] 12 were obtained. In these complexes the organodiazenido Re-N-N moiety adopts a linear conformation, as has been authenticated by X-ray diffraction analysis for 11 and 12. Treatment of Re() dinitrogen precursors [ReN 2 (P) 4 Cl] (P = PMe 2 Ph, 3 and PMePh 2 , 4) with ligands resulted in interesting dinuclear oxo-(µ-oxo)-Re() species [Re 2 (O) 3 (L n ) 2 (P) 2 ] (P = PMe 2 Ph, n = 1, 13; n = 2, 14; n = 4, 15. P = PMePh 2 , n = 2, 16). Suitable crystals for an X-ray analysis have been obtained for complex 14. The structure represents one of the few cases where, for steric reasons, the Re-O-Re bridging unit is not linear but rather bent. All the compounds have been characterized by elemental analyses, IR and NMR spectroscopy. The Re() complexes 5-7 and 9 were further characterized by electrochemical measurements.

Synthesis and Structural Characterization of Dinuclear Oxorhenium(V) Complexes with Bidentate Imidazole Derivatives

“…Most Re 2 O 4þ 3 complexes contain at least one basic N-donor atom in the equatorial plane cis to the oxo ligands [7][8][9]. Water is in most cases the source of the bridging oxo group, intimating that the production or presence of hydroxide is crucial.…”

Novel oxorhenium complex of 4,5-diaza-fluoren-9-one-synthesis, spectroscopic characterization, X-Ray structure and DFT calculations

“…These compounds are important from the standpoint of catalysis, biological mimicry, multi electron-transfer reactions and metal-metal interactions [10][11][12]. Since the pioneering works of Johnson et al [13,14], some dinuclear rhenium complexes containing linear or bent Re 2 O 3 unit with aromatic N-donor ligands, such as pyridine, pyrazine, pyrimidine, 3,5-lutidine, 1,5,6-trimethylbenzimidazole, have been investigated structurally, spectroscopically and electrochemically [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30].…”

Design, synthesis, and antimalarial evaluation of thiazole-derived amino acids

“…Recently-mono and bis-thiazolium salts have also been reported to have potent antimalarial activity (Hamze et al, 2005). There are also some known simple coupling reactions between amino acids and heteroaromatic amines to form products of biological importance (Musso et al, 2001;Quelever et al, 2004;Lazzaro et al, 2002). In view of these observations, some novel [1-(thiazole-2-ylcarbamoyl)-alkyl]-carbamic acid tert-butyl esters have been synthesized to examine their in vitro antimalarial activities against Plasmodium falciparum.…”