Linking [MIII3] triangles with “double-headed” phenolic oximes

Abstract

Strapping two salicylaldoxime units together with aliphatic α,Ω-aminomethyl links in the 3-position gives ligands which allow the assembly of the polynuclear complexes [Fe₇O₂(OH)₆(H₂L1)₃(py)₆](BF₄)₅·6H₂O·14MeOH (1·6H₂O·14MeOH), [Fe₆O(OH)₇(H₂L2)₃](BF₄)₃·4H₂O·9MeOH (2·4H₂O·9MeOH) and [Mn₆O₂(OH)₂(H₂L1)₃(py)₄(MeCN)₂](BF₄)₅(NO₃)·3MeCN·H₂O·5py (3·3MeCN·H₂O·5py). In each case the metallic skeleton of the cluster is based on a trigonal prism in which two [M^III₃O] triangles are tethered together via three helically twisted double-headed oximes. The latter are present as H₂L²⁻ in which the oximic and phenolic O-atoms are deprotonated and the amino N-atoms protonated, with the oxime moieties bridging across the edges of the metal triangles. Both the identity of the metal ion and the length of the straps connecting the salicylaldoxime units have a major impact on the nuclearity and topology of the resultant cluster, with, perhaps counter-intuitively, the longer straps producing the “smallest” molecules.