Visible spectrophotometry was used to study the kinetics of metal substitution in the system Cu(amben)/Ni-(DMF) 6 (ClO 4 ) 2 /R 4 NX in DMF at 298 K and I ) 0.2 M (Bu 4 NPF 6 ) (H 2 amben ) N,N′-ethylenebis(2aminobenzaldimine); X ) Br -, SCN -, Cl -; DMF ) N,N-dimethylformamide). The rate of nickel for copper substitution is markedly affected by the nature of the anion X, the order of reactivity being ClO 4 -< Br -< SCN -, Cl -. For X ) Cland under excess conditions [(Cu(amben)] , [Ni(DMF) 6 (ClO 4 ) 2 ], [BzEt 3 NCl]), the overall process is triphasic and multiwavelength analysis in the range 350-900 nm yields the experimental rate constants k obsd (1), k obsd (2), and k obsd (3). Rate constant k obsd (1) is nickel and chloride dependent, whereas k obsd (2) and k obsd (3) are not. For the rate of disappearance of Cu(amben and [Ni] tot refer to the total concentration of chloride and nickel, respectively). These dependencies suggest a second-order rate law, V ) k 1 [Cu(amben)]["NiCl 2 "], for the first step, with k 1 ) 64 ( 8 M -1 s -1 at 298 K. In view of the ligand properties of Cu(amben) it is concluded that the species "NiCl 2 " is tetrahedral Ni(DMF) 2 Cl 2 which reacts with Cu(amben) as ligand to form a binuclear adduct in the first step. It is suggested that the observed rate effects of the anions X are linked with their ability to favor the formation of nickel species with reduced coordination number, such as four-coordinate Ni(DMF) 2 X 2 . The mechanism of the overall process of nickel for copper substitution in Cu(amben) is discussed. The results of the analysis of the visible spectra of Cu(amben) and Ni-(amben) and of MO calculations on the charge distribution in these complexes are reported.
Aus den Di= äthanolaminen (I) und den Arsinsäurediamiden (II) entstehen die cyclischen Ester (III), die mit o‐Benzochinon (IV) zu den Arsatranen (V) reagieren.
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