Ligand substitution on (N,N-dimethylformamide)[2,2′,2″-tri(N,N-dimethylamino)triethylamine]cobalt(II)

Abstract

The selectivity exhibited by [Co(hmtren)(dmf)]²⁺[hmtren = N(CH₂CH₂NMe₂)₃, dmf = HCONMe₂] for substitution of dmf by NCS^–, N₃^–, and Br^–, and the observed Iigand-substitution rate laws are consistent with the operation of an I_a mechanism. This contrasts with an earlier observation that [Cu(hmtren)(dmf)]²⁺ undergoes ligand substitution through an I_d mechanism. These new data support the argument, adduced previously from dmf exchange studies, that the tendency for ligand substitution in the [M(hmtren)(dmf)]²⁺ species (M = first-row transition metal) to occur through an associative (a) activation mode increases as the electronic occupancy of the d orbitals decreases.