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[1]), which represented a rare example of the intact Sb4 tetrahedron structurally characterized in the solid state. Complex 1 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[1-Mn]Br), [Et4N]4[Sb4Cr2Fe6(CO)30] ([Et4N]4[1-Fe]), and [Et4N]2[Sb4Cr4Co4(CO)31] ([Et4N]2[1-Co]), the dioxygen-activated paramagnetic cluster [Et4N]4[O2Sb4Cr6(CO)28] ([Et4N]4[1-O2]), or the spin-quenched complex [Et4N]2[Sb4Cr6(CO)28] ([Et4N]2[2]), 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.