748781-65-9Relevant academic research and scientific papers
New pentadentate carboxylate-derivatized sulfur ligands affording water soluble iron complexes with [Fe(NS4)] cores that bind small molecules (CO, NO, PMe3) as co-ligands
Sellmann, Dieter,Peters, Kai P.,Heinemann, Frank W.
, p. 581 - 590 (2004)
In the search for polydentate sulfur ligands that are able to form water-soluble iron complexes which can bind nitrogenase relevant molecules, the new pentadentate ligands pyCO2MeS4-H2 [2,6-bis[2-mercapto-3-(methoxycarbonyl)phenylthio]dimethylpyridine] (1) and pyCO2HS4-H2 [2,6-bis(2-mercapto-3- carboxyphenylthio)dimethylpyridine] (2) having NS4 donor atom sets and terminal thiolate donors have been synthesized. The starting material was CO2MeS2-H2 (2,3-dimercapto benzoic acid methyl ester) which was alkylated with 2,6-bis[(tosyloxy)methyl]pyridine. The problem of specifically achieving regioselective monoalkylation of this 1,2-benzene-dithiol derivative was solved by carrying out the alkylation of CO2MeS2-H2 at -78 °C in the presence of stoichiometric amounts of a base. Saponification of 1 afforded the carboxylic acid derivative. Coordination of pyCO2MeS42- to FeII in the presence of co-ligands (L = CO, PMe3) yielded the complexes [Fe(L)(pyCO2MeS4)] where L = CO (5) or PMe3 (4). Upon treatment with NOBF4, complex 5 afforded [Fe(NO)(pyCO2MeS4)]BF4 (7) which could be subsequently converted to the isolable 19 valence electron species [Fe(NO)(pyCO2MeS4)] (8) upon reduction with N 2H4. In the absence of potential co-ligands, coordination of pyCO2MeS42- to FeII afforded the dinuclear complex [Fe(pyCO2MeS4)]2 (6) whilst coordination to NiII gave [Ni(pyCO2MeS4)] x (3). Solubility of these complexes in water could be achieved by replacing the CO2Me groups with CO2H substituents. The ligand pyCO2HS42- afforded the iron complexes [Fe(L)(pyCO2HS4)] [L = CO (10) and PMe3 (12)] and [Fe(NO)(pyCO2HS4)]BF4 (11). Both 10 and 12 could be reversibly deprotonated to give the corresponding water-soluble salts (NMe4)2[Fe(L)(pyCO2S4)] with L = CO {(NMe4)2 [9]} and PMe3 {(NMe4) 2 [13]}. The complexes were characterized by elemental analysis, spectroscopic methods and X-ray structural determinations. The molecular structure of [Fe(PMe3)(pyCO2HS4)] (12) was found to exhibit inter- and intramolecular O-H...O and O-H...S hydrogen bonds which serve as models for proton transfer steps from external sources to the active sites of metal sulfur enzymes. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.
