Synthetic Siderophores of the Tetrazolylenol Type: Iron(III) Complexes and Three‐Dimensional Iron(II) Coordination Polymers

One electron decides whether the coordination of tetrazolenol ligands (HL) with Fe ions leads to the mononuclear complex [FeL₃] (Fe^III) or the three‐dimensional coordination polymer [(FeL₂)_n] 1 (Fe^II). A representationof 1 is shown (right) along with its “monomer”. The linkage occurs by coordination of the CN groups. The crucial test supporting a polymeric structure for 1 was provided by Mössbauer spectroscopy. At 1.6 K a weak antiferromagnetic ordering arises, which can be attributed to cooperative spin‐spin exchange processes. R = Me₃CCH₂. (Figure Presented.)