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.