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Issue 24, 2011
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Equilibrium studies of the reactions of palladium(II) bis(imidazolin-2-imine) complexes with biologically relevant nucleophiles. The crystal structures of [(TLtBu)PdCl]ClO4 and [(BLiPr)PdCl2]

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Abstract

The kinetics and the mechanism of the substitution reactions of the complex [(TLtBu)PdCl]+, where TLtBu is 2,6-bis[(1,3-di-tert-butylimidazolin-2-imino)methyl]pyridine, with nucleophiles (guanosine-5′-monophosphate (5′-GMP), L-Methionine (L-Met) and L-Histidine (L-His)) were studied using variable-temperature stopped-flow techniques in aqueous 0.1 M NaClO4 with 10 mM NaCl at 298 K. The order of reactivity is: L-Met > 5′-GMP > L-His. The formation equilibria of [(BLiPr)Pd(H2O)2]2+, where BLiPr is 1,2-bis(1,3diisopropyl-4,5-dimethylimidazolin-2-imino)ethane, and [(TLtBu)Pd(H2O)]2+ with some biologically relevant ligands (L-Met, 5′-GMP and L-His) were also studied. The stoichiometry and stability constants of the newly formed complexes are reported, and the concentration distribution of the various complex species has been evaluated as a function of pH. Comparing the values of logβ1,1,0 for 5′-GMP, L-His and L-Met complexes, the most stable complex is with 5′-GMP followed by L-His and L-Met for both complexes, [(BLiPr)Pd(H2O)2]2+ and [(TLtBu)Pd(H2O)]2+. The crystal structures of [(TLtBu)PdCl]ClO4 and [(BLiPr)PdCl2] were determined by X-ray diffraction. The coordination geometries around the palladium atoms are distorted square-planar, with the Pd–N1 distance to the central nitrogen atom of the TLtBu ligand, 1.944(2) Å, being shorter than those to the other two nitrogen atoms of TLtBu, viz. 2.034(3) and 2.038(2) Å. The BLiPr complex displays similar Pd–N distances of 2.031(2) and 2.047(2) Å.

Graphical abstract: Equilibrium studies of the reactions of palladium(ii) bis(imidazolin-2-imine) complexes with biologically relevant nucleophiles. The crystal structures of [(TLtBu)PdCl]ClO4 and [(BLiPr)PdCl2]

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Publication details

The article was received on 21 Feb 2011, accepted on 04 Apr 2011 and first published on 19 May 2011


Article type: Paper
DOI: 10.1039/C1DT10289C
Citation: Dalton Trans., 2011,40, 6515-6523
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    Equilibrium studies of the reactions of palladium(II) bis(imidazolin-2-imine) complexes with biologically relevant nucleophiles. The crystal structures of [(TLtBu)PdCl]ClO4 and [(BLiPr)PdCl2]

    J. Bogojeski, R. Jelić, D. Petrović, E. Herdtweck, P. G. Jones, M. Tamm and Ž. D. Bugarčić, Dalton Trans., 2011, 40, 6515
    DOI: 10.1039/C1DT10289C

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