Complexes of N,N'-substituted formamidines. I. Compounds [M{RNC(H)NR'}]n (M = CuI, AgI; R = p-tolyl ; R' = alkyl; n = 2, 4) and study of the dimer-dimer and dimer-tetramer equilibria in solution

Abstract

A series of complexes [M(RNC(H)NR']}n{ (M = Cu}I{, Ag}I{; R = p-tolyl; R' = methyl, ethyl, i-propyl, t-butyl, cyclohexyl; n = 2, 4) has been prepared. }1{H and }1{}3{C NMR studies, as a function of temperature, concentration, metal atom and alkyl substituent, show the presence of dimeric and tetrameric isomers. Starting with the two possible dimers it requires only one metal@?nitrogen bond in each dimer to be broken and two new metal@?nitrogen bonds to be formed to give four tetrameric isomers. These studies show that; (i) the dimer/tetramer ratio increases at higher temperatures; (ii) the size of the alkyl substituents determines the relatives ratio of the tetramers; (iii) the dimer/tetramer ratio increases with increasing bulkiness of the alkyl substitutents, and (iv) the dimer/tetramer ratio increases when Ag}I{ is replaced by Cu}I{.