[Bi₁₂Ni₇(CO)₄]^4–: Aggregation of Intermetalloid Clusters by Their Thermal Deligation and Oxidation

Reported are the synthesis and structure of the anionic intermetalloid cluster [Bi₁₂Ni₇(CO)₄]^4–. It was synthesized from the known smaller clusters Bi₃Ni₄(CO)₆^3–, Bi₃Ni₆(CO)₉^3–, and Ni@Bi₆Ni₆(CO)₈^4– by their aggregation as a result of thermal deligation and oxidation. The new cluster is structurally characterized by single-crystal X-ray diffraction in the compound (K­[crypt])₄[Bi₁₂Ni₇(CO)₄] (1), and its presence in solution is confirmed by electrospray mass spectrometry. It can be viewed as composed of a Ni-centered icosahedral core of Bi₆Ni₆(CO)₄ where two diametrically opposed Ni atoms are capped by Bi₃ triangles. However, its electron count is rationalized based on a structure made of fused tetrahedra.