Nickel Complexes of Carboxylate-Containing Polydentate Ligands as Models for the Active Site of Urease

Summary, in English

Two new carboxylate-containing polydentate ligands have been synthesized, the symmetric ligand 2,6-bis[N-(N-(carboxylmethyl)-N-((1-methylimidazol)methyl)amine)methyl]-4-methylphenolate (BCIMP) and the corresponding asymmetric ligand 2-(N-isopropyl-N-((1-aminomethyl)-4-methylphenol (ICIMP). The ligands have been used to prepare model complexes for the active site of the dinuclear nickel enzyme urease, viz. [Ni2(BCIMP)Ac2]- (6), [Ni2(BCIMP)(Ph2Ac)2]- (7), [Ni2(ICIMP)(Ph2Ac)2] (14), [Ni4(ICIMP)2(Ph2Ac)2][ClO4]2 (15), [Ni4(ICIMP)2(Ph2Ac)2(DMF)2][ClO4]2 (16), and [Ni4(ICIMP)2(Ph2Ac)2(urea)(H2O)][ClO4]2 (17), where the latter complex contains urea coordinated in a unidentate fashion through the carbonyl oxygen. The N2O-N2O2 donor set of ICIMP provides a good framework for the preparation of urease models, but in some cases tetranuclear nickel complexes are formed due to coordination of the carboxylate moiety of one dinickel-ICIMP unit to one or both of the nickels of a second Ni2 unit. Reactivity and kinetics studies of 7 and 15 show that these model complexes catalyze hydrolysis of 2-hydroxypropyl p-nitrophenyl phosphate (HPNP) at basic pH. In this assay, complexes based on the asymmetric ligand ICIMP exhibit a significantly faster rate of hydrolysis than the corresponding BCIMP complexes. Magnetic measurements indicate that there are weak antiferromagnetic interactions between the nickel ions in complex 16.

• Author: Håkan Carlsson; Matti Haukka; Azzedine Bousseksou; Jean-Marc Latour; Ebbe Nordlander
• Department/s: Department of Chemistry
• Publishing year: 2004
• Language: English
• Pages: 8252-8262
• Publication/Series: Inorganic Chemistry
• Volume: 43
• Issue: 26
• Links: http://dx.doi.org/10.1021/ic049048u
• Document type: Journal article
• Publisher: The American Chemical Society (ACS)
• Topic: Inorganic Chemistry
• Status: Published
• ISBN/ISSN/Other: ISSN: 1520-510X