Kinetics of Acid-Hydrolysis of Nickel(II) and Copper(II) Compounds With the Cyclic Diamines 1,5-Diazocane and 4,4-Dimethyl-7-(5,5,7-trimethyl-1,4-diazepan-1-Yl)-5-azaheptan-2-ol

Abstract

The kinetics of acid-promoted hydrolysis reactions of nickel(II) and copper(ll) complexes of the cyclic diamines 1,5-diazocane ( daco ) and 4,4-dimethyl-7-(5,5,7-trimethyl-1,4-diazepan-1-yl)-5-azaheptan-2-ol (pyaz) in NaCl/HCl media ([Cl^-] = 2 mol dm^-3) are reported. For [Ni( daco )₂]^2+, beyond small [H+], an acid-limited rate constant of 2.0×10^-5 S^-l, involving dissociation of the first daco ligand, and for [Cu( daco )₂]²⁺ a similarly acid-limited rate constant of 1.5×10^-2 s^-l, involving dissociation of the second daco ligand, were measured at 50°C. For [Ni( pyaz )]²⁺ and [Cu ( pyaz )²⁺ the rates of the hydrolysis reactions are again acid-limited, effectively independent of acid with rate constant of 1.0×10^-2 s^-1 for [Ni( pyaz )]²⁺ while for [Cu( pyaz )]²⁺ the rate follows the expression k_obs , = 6.0×10^-2[H+]/(l+4.6[H+]) S^-l, both measured at 25°C.