Reactions of metalloalkynes VII. Protonation of ruthenium ethyne-1,2-diyl complexes

The acid–base chemistry of some ruthenium ethyne-1,2-diyl complexes, [{Ru(CO)2(η-C5H4R)}2(μ2-CC)] (R=H, Me) has been investigated. Initial protonation of [{Ru(CO)2{η-C5H4R}}2(μ2-CC)] gave the unexpected complex cation, crystallised as the BF4 salt, [{Ru(CO)2(η-C5H4R}}3(μ3-CC)][BF4] (R=Me structurally characterised). This synthesis proved to be unreliable but subsequent, careful protonation experiments gave excellent yields of the protonated ethyne-1,2-diyl complexes, [{Ru(CO)2{η-C5H4R)}2(μ2-η1:η2-CCH)](BF4) (R=Me structurally characterised) which could be deprotonated in high yield to return the starting ethyne-1,2-diyl complexes.