Investigation into the reactivity of 16-electron complexes Cp#Co(S2C2B10H10) (Cp# = Cp, Cp*) towards methyl diazoacetate and toluenesulphonyl azide

Abstract

A three-component reaction of the 16-electron half-sandwich complex Cp*Co(S₂C₂B₁₀H₁₀) (2) with methyl diazoacetate (MDA) and toluenesulphonyl azide (TsN₃) gave di-inserted products Cp*Co(S₂C₂B₁₀H₁₀)(C–CO₂Me)(CHCO₂Me)(NHTs) (3) and Cp*Co(S₂C₂B₁₀H₁₀)(CHCO₂Me)(CHCO₂Me)(N₃Ts) (4), where MDA and TsN₃ in a molar ratio of 2 : 1 were inserted into the Co–S bond to form a five-membered metallacyclic ring with different coordination modes. Its two-component reaction with MDA affording complexes Cp*Co(S₂C₂B₉H₉)(CH₂CO₂Me)(CHCO₂Me) (5), Cp*Co(S₂C₂B₁₀H₁₀)(CH₂CO₂) (6) and Cp*Co(S₂C₂B₉H₉) (CH₂CO₂) (7) proved that the abovementioned three-component reaction is not a simple stepwise reaction. For another 16-electron half-sandwich complex CpCo(S₂C₂B₁₀H₁₀) (1), two stepwise reaction routes were designed to achieve its incorporation with MDA and TsN₃. The reaction occurred via the alkylidene-bridged adduct CpCo(S₂C₂B₁₀H₁₀)(CHCO₂Me) (8) or the imido-bridged adduct CpCo(S₂C₂B₁₀H₁₀)(NTs) (9), and complex CpCo(S₂C₂B₁₀H₁₀)(CHCO₂Me)(NTs) (10) was isolated as the sole product in moderate yield. In each reaction route, one molecule of MDA and one molecule of TsN₃ insert into the two Co–S bonds of complex 1, respectively, with the loss of N₂. All the new complexes were characterized using NMR spectroscopy, mass spectrometry, IR spectroscopy, elemental analysis and X-ray structural analysis.