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- ki(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 kex(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 kex and ki 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 Id mechanism. For comparative purposes 0CHNMe2 exchange on [Ni{N(CH2CH2NHz)3}(OCHNMe2)2]2+, which is characterized by kex(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.