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Metal Complexes with Macrocyclic Ligands. XV . The Complexation Kinetics of Open Chain and Cyclic Tetraazaligands with Ni 2+ in DMSO and DMF
Author(s) -
Hertli Liselotte,
Kaden Thomas A.
Publication year - 1981
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19810640106
Subject(s) - chemistry , steric effects , kinetics , dissociation (chemistry) , reaction rate constant , metal , ligand (biochemistry) , solvent , protonation , reactivity (psychology) , medicinal chemistry , molecule , solvent effects , stereochemistry , crystallography , inorganic chemistry , ion , organic chemistry , biochemistry , physics , receptor , alternative medicine , pathology , quantum mechanics , medicine
The complexation kinetics of 2,6,9, 13‐tetraazatetradecane (1) , 1,4,8, 11‐tetraazacyclotetradecane (2) and N,N′,N″,N '‐tetramethyl‐1,4,8, 11‐tetraazacyclotetradecane (3) with Ni 2+ were studied by the stopped‐flow technique in DMSO and DMF. The biomecular rate constants k L Ni ( Table 2 ) follow in both solvents the order 1 ≳ 2 > 3. The similar complexation rates of 1 and 2 in their unprotonated form indicate that for both the open chain and the cyclic ligand the same mechanism holds. By comparison with the solvent exchange the rate determining step of the complexation is the dissociation of the first solvent molecule in the outer‐sphere complex. The lower reactivity of 3 is probably due to steric effects. In the case of 2 a second step in the complexation process was observed and explained by a rearrangement of the ligand already coordinated to the metal ion.