A new ionic pentanuclear FeIII cluster, namely, triethylazanium tetrakis(μ2‐5‐amino‐1,2,3,4‐tetrazolido)tetrakis(μ3‐4‐chloro‐2‐{[(1H‐tetrazol‐1‐id‐5‐yl)imino]methyl}phenolato)di‐μ3‐oxido‐pentairon(III) acetonitrile monosolvate monohydrate, (C6H16N)[Fe5(C8H4ClN5O)4(CH2N5)4O2]·CH3CN·H2O, was synthesized using microvial synthesis methods and characterized by elemental analysis, FT–IR spectroscopy, single‐crystal X‐ray diffraction and thermogravimetric analysis. Magnetic studies reveal that the complex displays dominant antiferromagnetic intracluster interactions between the FeIII ions through the μ3‐oxide bridges. [ABSTRACT FROM AUTHOR]