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

Abstract

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.