Structural and mechanistic studies of co-ordination compounds. Part 18. Preparation and hydrolysis of trans-bromo- and chloro-cyano-(5,5,7,12,12,14-hexamethyl-1,4,8,11-tetra-azacyclotetradeca-7,14-diene)cobalt(III) cations

Abstract

Complexes trans-[Co(CN)(L¹)X]ⁿ⁺[L¹= 5,5,7,12,12,14-hexamethyl-1,4,8,11 -tetra-azacyclotetradeca- 7,14-diene; X = Cl, Br, or OH₂] and trans-[CoL¹(OH₂)(SO₃)]⁺ have been prepared, and the acid and base hydrolyses of the halogeno-complexes have been studied over a range of temperature. For the acid hydrolysis, a linear free-energy relation has been established between the kinetic data of cyanotetra-aminecobalt(III) complexes and those of the corresponding azido- and isothiocyanato-complexes. The base hydrolysis of these complexes is discussed in terms of a ‘limiting’S_N1 (CB)mechanism in which the formation of a reactive amido-conjugate base is the rate-determining step.