Two AntiferromagneticTetradecanuclear Iron Oxo ClustersDerived from a Pentadecanuclear Cluster via Substitutions of ShellIron Polyhedra with Non-Metallic Oxoanions

Substituting certain atoms in a metal-oxo cluster (MOC) can enrich its structure, properties, and applications, often involving the replacement of one metal polyhedron with another that exhibits a comparable coordination environment. Herein, we synthesized three clusters <b>Fe</b>_<b>14</b><b>-SO</b>_<b>4</b>, <b>Fe</b>_<b>14</b><b>-SeO</b>_<b>4</b>, and <b>Fe</b>_<b>15</b>, with the crystal compositions of [Fe₁₄(SO₄)O₆(tea)₇Cl₆](FeCl₃OFeCl₃)_0.5·4(C₂H₃N)·18(H₂O) (tea = deprotonated triethanolamine), [Fe₁₄(SeO₄)O₆(tea)₇Cl₆](FeCl₃OFeCl₃)_0.5·(C₂H₃N)·20(H₂O), and [Fe₁₅O₆(tea)₈Cl₆](FeCl₄)₂·Cl·22(H₂O), using similar solvothermal methods. All three clusters exhibit similar cage-like structures, with <b>Fe</b>_<b>14</b><b>-XO</b>_<b>4</b> (X = S or Se) differing by substituting a shell iron polyhedron with a nonmetallic XO₄^2– tetrahedron. This substitution, facilitated by the weaker binding of the iron polyhedron in the cluster and its geometrical similarity to XO₄^2–, leads to more diverse coordination modes and weaker antiferromagnetic interactions of iron ions in <b>Fe</b>_<b>14</b><b>-XO</b>_<b>4</b> compared to <b>Fe</b>_<b>15</b>. Our study highlights the uncommon replacement of a metal polyhedron with a nonmetallic oxoanion and its effects on the structure and properties of MOCs.