Preparation, crystal structure and kinetics of acid hydrolysis of an isomer of [Cr(picdien)Cl][ZnCl4][picdien = 1,9-bis(2′-pyridyl)-2,5,8-triazanonane]

Abstract

The complex [Cr(picdien)Cl][ZnCl₄][picdien = 1,9-bis(2′-pyridyl)-2,5,8-triazanonane] has been prepared and its structure determined by a single-crystal X-ray diffraction study of the triclinic crystals: a= 9.118(3), b= 9.581(5), c= 14.042(5)Å, α= 78.04(3), β= 86.37(3)°, and γ= 76.56(3)°. The complex cation has the anti-αβ configuration. The kinetics of aquation of the perchlorate salt has been studied in dilute aqueous nitric acid solution, [complex]= 5 × 10^–3 mol dm^–3. The rate constants are independent of [H⁺] over the range 0.10 < [H ⁺] < 0.001 mol dm^–3; k_25°C= 6.0 × l0^–6s^–1, ΔH^‡= 93.1 ± 2.2 kJ mol^–1, ΔS^‡=–32.9 ± 6.9 J K^–1 mol^–1.