Synthesis and structure of metallacarboranes bearing carborane-fused cyclopentenyl and dicarbollyl-fused cyclopentene ligands.

New types of ligands, carborane-fused cyclopentenyl and dicarbollyl-fused cyclopentene, were conveniently prepared in high yields. Treatment of the lithium salt of carborane-fused cyclopentenyl anion, [1,2-[C(Me)CHC(Ph)]-1,2-C2B10H10]Li, with [Cp*RuCl]4 generated an 18-electron complex [η3:η2-(PhCCHCMe)C2B10H10]Ru(η5-Cp*). On the other hand, reaction of the dicarbollide salt, [7,8-(CH2CHCMe)-7,8-C2B9H9]Na2 with [(η6-p-cymene)RuCl2]2 or CoCl2/CpNa, afforded the salt metathesis product [η5-(CH2CHCMe)C2B9H9]Ru(η6-p-cymene) or [η5-(CH2CHCMe)C2B9H9]Co(η5-C5H5) in good yields. In contrast, [7,8-(CH2CHCMe)-7,8-C2B9H9]Na2 reacted with Ni(dppp)Cl2 (dppp = 1,3-bis(diphenylphosphino)propane) to give another 18-electron metallacarborane [η5-(CH2CHCMe)C2B9H9]Ni(dppp), in which one of the cage carbon atoms has been isomerized to the lower belt of the cage due to steric reasons. All these new metallacarborane compounds were fully characterized by NMR spectroscopy, high-resolution mass spectroscopy and single-crystal X-ray analyses.