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Thermodynamic and Kinetic Studies on Complex‐Formation Reactions of a Cobalt(II) Tripodal Tetraamine Complex
Author(s) -
Lu ZhongLin,
Hamza Mohamed S. A.,
van Eldik Rudi
Publication year - 2001
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/1099-0682(200102)2001:2<503::aid-ejic503>3.0.co;2-q
Subject(s) - chemistry , nucleophile , associative substitution , steric effects , sn2 reaction , ligand (biochemistry) , cobalt , trigonal bipyramidal molecular geometry , medicinal chemistry , kinetics , pyridine , photochemistry , stereochemistry , inorganic chemistry , crystallography , organic chemistry , catalysis , crystal structure , biochemistry , receptor , physics , quantum mechanics
Complex‐formation constants were determined for the reaction of [Co(Me 6 tren)(H 2 O)] 2+ with different pyridine‐ and imidazole‐based nucleophiles, and the kinetics of these reactions was studied as a function of entering ligand concentration, temperature, and pressure. The steric hindrance associated with the methyl substituents on the trigonal‐bipyramidal complex induces a sensitive control over the substitution mechanism from dissociative for the weaker and more bulky entering nucleophiles, to associative for the stronger and less bulky nucleophiles. A changeover in mechanism can be observed as a function of nucleophile concentration, in the case of 2‐MeImH as the entering ligand. The mechanistic assignments are based on the observed rate laws, and the activation parameters determined under limiting concentration conditions.