Anation and solvent exchange on (N,N-Dimethylformamide)[2,2',2''-tri(N,N-dimethylamino) triethylamine]nickel(II) and solvent exchange on Bis(N,N-dimethylformamide)-[2,2',2''-triaminotriethylamine]nickel(II)

Abstract

Anation of [Ni{N(CH₂CH₂NMe₂)₃}(OCHNMe₂)]²⁺ by Br^-, N₃ ^- and NCS^- is characterized by rate laws consistent with the operation of an interchange mechanism (1) and the small variation of k₁ characterizing these processes suggest that the activation mode is probably dissociative (d). Typically for anation by NCS- k_i(298.2K) = 170 ± 6 s^-1, ∆H^‡ = 44.0 ± 2.1 kJ mol^-1 and ∆S^‡ =-54.7 ± 7.2 JK^-1 mol^-1. The exchange of OCHNMe₂ on [Ni{N(CH₂CH₂Nme₂}₃)-(OCHNMe₂)]²⁺ is characterized by k_ex(298.2 K)=203 ± 20s^-1, ∆H^‡ = 42.6 ± 2.0 kJ mol^-1 and ∆S^‡ = -58 ± 8 JK^-1 mol^-1(if it is assumed that this is the only nickel(II) species undergoing exchange) but the derivation of these parameters is complicated by the presence of a minor species believed to be [Ni{N(CH₂CH₂NMe₂)₃}(0CHNMe₂)₂]²⁺. Nevertheless the similarity of k_ex and k_i observed for Br^-, N₃^- and NCS^- are consistent with both OCHNMe₂ exchange and anation on [Ni {N(CH₂CH₂Nme₂)₃}(OCHNMe₂)]²⁺ proceeding predominantly through an I_d mechanism. For comparative purposes 0CHNMe₂ exchange on [Ni{N(CH₂CH₂NH_z)₃}(OCHNMe₂)₂]²⁺, which is characterized by k_ex(298.2 K) = (1.4 ± 0.2) × 10⁵ and (1.9 ± 0.9) × 10⁷ s^-1 for the non-equivalent OCHNMe₂ sites, has also been studied.