Bulletin of the Chemical Society of Japan
Online ISSN : 1348-0634
Print ISSN : 0009-2673
ISSN-L : 0009-2673
Kinetic Studies on the Stability Enhancement of Mixed Ligand Copper(II) Complexs with 2,2′-Bipyridyl and Acetylacetonate
Megumu MunakataKatsumi Yamada
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1978 Volume 51 Issue 12 Pages 3500-3504

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Abstract

The rate constants for the formation and dissociation of the binary Cu2+-acetylacetonate(acac) complex and the ternary 2,2′-bipyridyl(bpy)-Cu2+-acac complex have been determined by the temperature-jump method. For the reactions Cu2++acac\oversetk1b\undersetk-1b\ ightleftharpoonsCu(acac)+, Cu(acac)++acac\oversetk2b\undersetk-2b\ ightleftharpoonsCu(acac)2, and Cu(bpy)2++acac\oversetk1t\undersetk-1t\ ightleftharpoonsCu-(bpy)(acac)+, the rate constants are k1b=9.0×108 M−1 s−1, k-1b=3.2 s−1, k2b=7.0×107 M−1 s−1, k-2b=13 s−1, k1t=1.1×109 M−1 s−1 and k-1t=1.9 s−1. A comparison of the reactions shows that the forward rate for the Cu(bpy)-(acac)+ formation is larger than that for Cu(acac)+ and, subsequently, the rate of the complex formation between Cu(bpy)2+ and acac is enhanced by the coordinating bpy. On the other hand, the reverse rate for the ternary complexation reaction is smaller than for the binary. This illustrates that the dissociation of acac of Cu(bpy)-(acac)+ becomes more difficult owing to the coordination of the bpy. The above two effects of the bpy may be driving forces producing high stability, i.e., a positive value of ΔlogK\left(K=\frac[Cu(bpy)[L][Cu(bpy)][L]\ ight) for the ternary copper(II) complexes with bpy and other ligands containing O as donor atoms.

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