Homoleptic and heteroleptic Au(i) complexes containing the new [Co5C(CO)12]− cluster as ligand

Abstract

The new [{Co₅C(CO)₁₂}Au{Co(CO)₄}]⁻, [1]⁻, cluster has been obtained from the reaction of [Co₆C(CO)₁₅]²⁻ with two equivalents of [AuCl₄]⁻. [1]⁻ reacts with an excess of HBF₄ resulting in the formation of [{Co₅C(CO)₁₂}₂Au]⁻, [2]⁻. The new derivatives [Co₅C(CO)₁₂(AuPPh₃)], 3, and [Co₅C(CO)₁₁(AuPPh₃)₃], 4, have been obtained by reacting [2]⁻ with two and four equivalents of [Au(PPh₃)Cl], respectively. All the new species have been structurally characterised by means of X-ray crystallography as their [NEt₄][1], [NEt₄][2], [NMe₃(CH₂Ph)][2], 3 and 4·thf·0.5C₆H₁₄ salts and solvates. [2]⁻ may be viewed as a homoleptic Au(I) complex containing two [Co₅C(CO)₁₂]⁻ clusters as ligands. Similarly, [1]⁻ and 3 are heteroleptic Au(I) complexes containing one [Co₅C(CO)₁₂]⁻ cluster ligand as well as [Co(CO)₄]⁻ or PPh₃. Conversely, 4 contains the [Co₅C(CO)₁₁]³⁻ cluster stabilized by three [AuPPh₃]⁺ fragments. [1]⁻ and [2]⁻ have been investigated in solution by means of electrochemical and spectroelectrochemical methods, revealing a very rich redox propensity to form the closely related [1]ⁿ⁻ (n = 1–3) and [2]ⁿ⁻ (n = 0–3) species.