Hinweise auf reversibles öffnen und schliessen einer metallmetall-bindung in dem trimethylsilylnitren-sulfido-cluster Os3(CO)9(μ3-S)(μ-3NSiMe3)

The thermal reaction of Os₃(CO)₁₂ with S(NSiMe₃)₂ yields the cluster compound Os₃(CO)₉(μ₃-S(μ₃-NSiMe₃. The structure of the molecule was solved by a single crystal X-ray structure analysis. In the solid state the osmium atoms define an “open” isosceles triangle which is bridged by both a sulphur and a trimethylslylnitrene ligand. The distance between the osmium atoms at the long edge of the triangle (3.498(2) Å compared to 2.774(2) and 2.777(2) Å for the short edges) suggests that these two Os atoms are not in bonding contract. A variable-temperature ¹³C NMR study reveals the structure of the molecule to be dynamic in solution; the spectra are indicative of the existence of two different structures at elevated temperatures. We interprete our findings as reconcilable with the assumption that a reversible closing and opening process of the Os-Os bonds can occur in solution.