Stabilization of Sb₄ Tetrahedra in Paramagnetic Transition Metal Carbonyl Complexes

We present a straightforward synthetic route to the novel chromium carbonyl-stabilized paramagnetic Sb₄-based cluster [Et₄N]₄[Sb₄Cr₆(CO)₂₈] ([Et₄N]₄[<b>1</b>]), which represented a rare example of the intact Sb₄ tetrahedron structurally characterized in the solid state. Complex <b>1</b> exhibited versatile reactivities toward groups 7-9 metal carbonyls, dioxygen, or [Cu(MeCN)₄][BF₄] to form selective orbital-controlled Sb₄-based products, including transmetalated paramagnetic complexes [Et₄N]₄[Sb₄Cr₅Mn(CO)₂₈]Br ([Et₄N]₄[<b>1-Mn</b>]Br), [Et₄N]₄[Sb₄Cr₂Fe₆(CO)₃₀] ([Et₄N]₄[<b>1-Fe</b>]), and [Et₄N]₂[Sb₄Cr₄Co₄(CO)₃₁] ([Et₄N]₂[<b>1-Co</b>]), the dioxygen-activated paramagnetic cluster [Et₄N]₄[O₂Sb₄Cr₆(CO)₂₈] ([Et₄N]₄[<b>1-O</b>_<b>2</b>]), or the spin-quenched complex [Et₄N]₂[Sb₄Cr₆(CO)₂₈] ([Et₄N]₂[<b>2</b>]), respectively. The structural nature, bonding properties, paramagnetism, and semiconductivity of these unprecedented transition metal carbonyl-protected Sb₄-based clusters were further realized with DFT calculations.