Unprecedented Icosahedral Clusters Built of Polyantimony: From Single [Ni0.5@{Sb6Ni6(CO)8}]4− and [Ni@{Sb7Ni5(CO)6}]3− to Sb84−-linked Dimer [(Sb8){Sb7Ni5(CO)4}2]6−

The reactions of K2ZnSb (0.234 mol) and Ni(CO)2(PPh3)2 (x mol) in ethylenediamine (en) solutions of 18-crown-6 at 60 °C yielded half-centered [Ni0.5@{Sb6Ni6(CO)8}]4− (x = 0.023, 1) and fully embedded [Ni@{Sb7Ni5(CO)6}]3− (x = 0.047, 2), wherein the chair-like Sb6 subunit is bicapped by two Ni3 triangles to form the single Sb6Ni6 icosahedron of 1 and by the triangular Ni2Sb and Ni3 to form the single Sb7Ni5 icosahedron of 2. Surprisingly, a smaller amount of Ni(CO)2(PPh3)2 (x = 0.016) led to the formation of the unprecedented dimer [(Sb8){Sb7Ni5(CO)4}2]6− (4), wherein the Sb7Ni5 icosahedral unit built of boat-like Sb6, Ni2Sb and Ni3 is linked together by the realgar-like Sb8 to form the icosahedral dimer 4, providing a new way of thinking for the preparation of icosahedral oligomers/polymers. A similar hexa-anionic dimer (3) can be solely obtained using PBu4+ as the countercation under the same reaction conditions. The structure and bonding of this novel series of icosahedral clusters containing polyantimony were discussed for the first time.