Complexes of Nickel(II) and Copper(II) With 5,5,7-Trimethyl-1,4-Diazepane. Preparation and Kinetics of Acid-Hydrolysis

Abstract

The cyclic diamine 5,5,7-trimethyl-1,4-diazepane, tmdz, is formed by borohydride reduction of 5,7,7-trimethyl-2,3,6,7-tetrahydro-1H-1,4- diazepine , which is formed by a rapid reaction between ethanediamine and 4-methylpent-3-en-2-one. Salts of the cations [Ni( tmdz )₂]²⁺ and [Cu( tmdz )₂]²⁺ were prepared, and their properties are reported. The kinetics of hydrolysis of [Ni( tmdz )₂]²⁺ and [Cu( tmdz )₂]²⁺ and bis (1,4- diazepane )nickel(II), [Ni( dach )₂]²⁺, in aqueous HCl/NaCl media have been studied. Reaction rates are independent of acid concentration over the ranges used . Ni²⁺,0.1-1 mol l^-1 H+ in 1 mol l^-1 Cl ^-, k_obs(25°C) = 9.1(1)×10^-7 s^-1, k_obs(50°C) = 2.0(1)×10^-5 s^-1,ΔH^‡96(2)kJ mol^-1,0.08-4 mol l^-1, H⁺ in 4 mol l^-1 Cl ^-, k_obs (25°pC) = 2.0(3)°10^-7 s^-1. Cu²⁺, 0.04-1 mol l^-1 H⁺, 1 mol l^-1 Cl ^-, k^obs (25°C) = 0.028(2) s^-1, for the displacement of the second ligand . [Ni( dach )₂]²⁺, 0.1-1 mol l^-1 H⁺, 1 mol l^-1 Cl ^-, k_obs (25°C) = 0.051(2) s^-1. [Ni( tmdz )₂]²⁺ reacts more rapidly with NaOH/edta : 1 mol l^-1 NaOH , 0.1 mol l^-1, Na₂(edtaH₂), k_obs (25°C) = 7.3(3)×10^-3 s^-1, 0.5 mol l^-1 NaOH , 0.1 mol l^-1 Na₂(edtaH₂), k_obs (25°C) = 4.5(3)×10^-3 s^-1.