Synthesis of 13-vertex dimetallacarboranes by electrophilic insertion into 12-vertex ruthenacarboranes

The electrophilic insertion of organometallic species into metallacarboranes was studied in detail for the model compound - the 12-vertex closo-ruthenacarborane anion [Cp*Ru(C₂B₉H₁₁)]^- (1). Reactions of the anion 1 with the 12-electron cationic species [M(ring)]⁺ (M(ring) = RuCp, RuCp* and Co(C₄Me₄)) gave the 13-vertex closo-dimetallacarboranes Cp*Ru(C₂B₉H₁₁)M(ring). Similar reactions of the neutral ruthenacarborane Cp*Ru(Me₂S-C₂B₉H₁₀) produce the cationic dimetallacarboranes [Cp*Ru(Me₂S-C₂B₉H₁₀)M(ring)]⁺. The symmetrical 13-vertex diruthenacarboranes (C₅R₅)Ru(R₂C₂B₉H₉)Ru(C₅R₅) can be prepared by the direct reactions of Tl₂[7,8-R₂-7,8-C₂B₉H₉] (R = H and Me) with two equivalents of [CpRu(MeCN)₃]⁺ or [Cp*RuCl]₄. The insertions of the 14-electron cationic species [M(ring)]⁺ (M(ring) = NiCp, NiCp* and Co(C₆Me₆)) into 1 gave the 13-vertex dimetallacarboranes Cp*Ru(C₂B₉H₁₁)M(ring), which have a distorted framework with one open face. The structures of Cp*Ru(C₂B₉H₁₁)Co(C₄Me₄) and Cp*Ru(C₂B₉H₁₁)NiCp were established by X-ray diffraction. Some of the 13-vertex dimetallacarboranes have two electrons less than required by Wade's rules. This violation is explained by the absence of the appropriate pathway for the distortion of the framework.