Redox-Induced Reversible Rearrangement of a Dimetallaallyl Ligand on the Trinuclear Cluster of Ruthenium. Mechanistic Aspects of Formation of the Face-Capping μ3-C3 Ring on the Triruthenium Plane

The dicationic complexes [(Cp*Ru)3(μ3-CH)(μ3-η3-C3H2Me)(μ-H)]2+ (7a,b; Cp* = η5-C5Me5), containing a μ3-η3-C3 ring on the Ru3 triangle, were obtained by the reaction of a μ3-methylidyne μ3-η1:η3:η1-2-methyldiruthenaallyl complex, (Cp*Ru)3(μ-H)(μ3-η1:η3:η1-CHCMeCH)(μ3-CH) (5a), with 2 equiv of ferrocenium salt. The μ3-η3-C3 ring was structurally characterized for the monocationic complex [(Cp*Ru)3(μ3-CH)(μ3-η3-C3H2Me)]+ (8), which was obtained by deprotonation of a mixture of the regioisomers 7a,b. The carbenic character of the carbons in the μ3-η3-C3 ring was shown in the unusually long C−C bond distances and JC-H values. CV analysis of 5a strongly indicates that transformation of the dimetallaallyl moiety to the μ3-C3 ring occurred on the dicationic Ru3 centers, as well as isolation of a paramagnetic intermediate, [(Cp*Ru)3(μ3-CH)(μ3-η1:η3:η1-CHCMeCH)(μ-H)]+ (6), containing a μ3-diruthenaallyl ligand.