Supporting conformational change at metal centres. Part 1: octahedral systems

The X-ray crystal structures bis-((mu(2)-acetato-O)-mu-fac-(NN'-bis(salicylidene)-1,4-butane-diamine)-(methanol) nickel) nickel and bis-((mu-acetato-O,O')-mu-mer-(N,N'-bis(salicylidene)-1,4-butanediamine)-(dimethylformamido) nickel) nickel are presented. These elusive motifs complete a structure based matrix of compounds for nickel with the popular Schiff's base ligands NN'-bis(salicylidene)-1,2-ethylenediamine, NN'-bis(salicylidene)-1,3-propanediamine and NN'-bis(salicylidene)-1,4-butanediamine. Coupled with data from previously reported structures and data derived from the additional structures of bis-((mu-acetato-O,O')-mu-mer-(N,N'-bis(salicylidene)-1,3-propanediamine)-(pyridine) nickel) nickel and dichloro-(mu(2)-(NN'-bis(salicylidene)-1,3-propanediamine)-bis(pyridine) nickel) lead it is possible to provide an in depth analysis of the behaviour of these three ligand systems within a six coordinate environment. Although, the geometries observed for NN'-bis(salicylidene)-1,2-ethylenediamine and N,N'-bis(salicylidene)-1,3-propanediamine seem to be constrained by the chelate ring generated by the imine groups, the larger ring size of the N,N'-bis(salicylidene)-1,4-butanediamine derived chelate would seem to confer substantial flexibility in the backbone and as such, considerable variation in the potential geometry, i.e. mer and fac conformers of the complexes formed. (C) 2002 Elsevier Science Ltd. All rights reserved.