New icosahedral heterometallic nickel carbonyl clusters containing bismuth

Abstract

The new [Ni₁₁Bi₂(CO)₁₈]^n–(n= 2 or 3) cluster anions have been obtained as a mixture by reaction of [Ni₆(CO)₁₂]^2– with 0.5–0.7 equivalents of BiCl₃ in tetrahydrofuran. Subsequent controlled oxidation or reduction of this mixture selectively affords the two anions. They have been isolated in the solid state as tetrasubstituted ammonium salts. The corresponding [Ni₁₁Bi₂(CO)₁₈]^4– tetraanion has only been obtained in solution by chemical or electrochemical reduction of the parent di- or tri-anion. All these compounds have been chemically and spectroscopically characterized, and the structure of [NEt₄]₃[Ni₁₁Bi₂(CO)₁₈] has been ascertained by X-ray diffraction [orthorhombic, space group Pccn, a= 14.573(2), b= 19.638(4), c= 21.248(3)Å, Z= 4, R= 0.0501]. The geometry of the trianion is based on a nickel-centred Ni₁₀Bi₂(µ₁₂-Ni)(CO)₁₈ icosahedral core. Relevant average bond distances are Ni–Ni_{intrapentagonal} 2.810 Å, Ni–Ni_{interpentagonal} 2.506 Å, Ni–Ni_inner-outer 2.595 Å, Bi–Ni_inner 2.507 Å and Bi–Ni_outer 2.819 Å. The corresponding di- and tetra-anions probably possess a closely related structure as shown by the electrochemical reversibility of their electron-transfer processes and by the similarity of the IR patterns of the three compounds.