Unprecedented icosahedral clusters built of polyantimony: from single [Ni0.5@{Sb6Ni6(CO)8}]4− and [Ni@{Sb7Ni5(CO)6}]3− to the Sb84−-linked dimer [(Sb8){Sb7Ni5(CO)4}2]6−

Abstract

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 [Ni_0.5@{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.