Kinetics of the reaction of Ni(II) ions with pyridine in water: a polarographic study

Bulmer, Rachel; Caldin, E. F.; Walton, Anne

doi:10.1039/tf9716703343

Cited by 10 publications

(2 citation statements)

References 1 publication

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“…Although the k f value reported for Ni(II) reacting with NH 3 in acetonitrile is also anomalously large, this latter value is acknowledged to be in error by a factor of 2 or more. Moreover, the k f value obtained for Ni(II) reacting with pyridine in acetonitrile 24 is apparently in line with expectations when compared to the corresponding aqueous result . The second possibility, that the application of theoretical steric factors derived from aqueous reactions may be inaccurate in acetonitrile, appears unlikely because our data for the reaction of Ni(CH 3 CN) 6 2+ with Me 2 -2,3,2-S 4 tend to support the fact that they are of the correct order of magnitude.…”

Section: Discussionsupporting

confidence: 72%

Formation and Dissociation Kinetics and Crystal Structures of Nickel(II)−Macrocyclic Tetrathiaether Complexes in Acetonitrile. Comparison to Nickel(II)−Macrocyclic Tetramines

et al. 2000

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Complex formation and dissociation rate constants have been independently determined for solvated nickel(II) ion reacting with eight macrocyclic tetrathiaether ligands and one acyclic analogue in acetonitrile at 25 degrees C, mu = 0.15 M. The macrocyclic ligands include 1,4,8,11-tetrathiacyclotetradecane ([14]aneS4) and seven derivatives in which one or both ethylene bridges have been substituted by cis- or trans-1,2-cyclohexane, while the acyclic ligand is 2,5,9,12-tetrathiatridecane (Me2-2,3,2-S4). In contrast to similar complex formation kinetic studies on Ni(II) reacting with corresponding macrocyclic tetramines in acetonitrile and N,N-dimethylformamide (DMF), the kinetics of complex formation with the macrocyclic tetrathiaethers show no evidence of slow conformational changes following the initial coordination process. The differing behavior is ascribed to the fact that such conformational changes require donor atom inversion, which is readily accommodated by thiaether sulfurs but requires abstraction of a hydrogen from a nitrogen (to form a temporary amide). The latter process is not facilitated in solvents of low protophilicity. The rate-determining step in the formation reactions appears to be at the point of first-bond formation for the acyclic tetrathiaether but shifts to the point of chelate ring closure (i.e., second-bond formation) for the macrocyclic tetrathiaether complexes. The formation rate constants for Ni(II) with the macrocyclic tetrathiaethers parallel those previously obtained for Cu(II) reacting with the same ligands in 80% methanol-20% water (w/w). By contrast, the Ni(II) dissociation rate constants show significant variations from the trends in the Cu(II) behavior. Crystal structures are reported for the Ni(II) complexes formed with all five dicyclohexanediyl-substituted macrocyclic tetrathiaethers. All but one are low-spin species.

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Section: Discussionsupporting

confidence: 72%

Formation and Dissociation Kinetics and Crystal Structures of Nickel(II)−Macrocyclic Tetrathiaether Complexes in Acetonitrile. Comparison to Nickel(II)−Macrocyclic Tetramines

et al. 2000

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“…The reduction potential of this species is nearly 0.29 V more positive than that of the Ni(II) aquaion, and is close to that obtained for the other Ni(II) complexes with N-coordinated ligands inducing prewave [31,[43][44][45][46][47][48][49], but differ significantly from values reported by Banica (À0.78 V) [29] and Cakir (À0.94 V) [30]. It should be noted that Cakir et al [30] performed their experiments in ammonium tartrate solution (at pH ca.…”

Section: Ni(ii)-nicotinamide Systemsupporting

confidence: 78%