Issue 24, 2011

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]

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]

Supplementary files

Article information

Article type
Paper
Submitted
21 Feb 2011
Accepted
04 Apr 2011
First published
19 May 2011

Dalton Trans., 2011,40, 6515-6523

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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