Heteroatom insertion reactions of polyhedral borane anions

Andrew Edward Wille, University of Pennsylvania


Heteroatom containing boron clusters, because of their hybrid "electron-deficient" and "electron-precise" natures, frequently exhibit unusual structural, bonding and reactivity properties. However, there are few general routes for heteroatom insertion that allow the rational synthesis of these compounds. The research described in this dissertation has resulted in new synthetic pathways for heteroatom insertion into polyhedral borane anions, based on the use of a borane anion as a nucleophile to attack and insert electrophilic groups. The insertion reactions of borane anions with sulfur, nitriles and polarized acetylenes have been shown to yield new dithiaboranes, carbaboranes and azacarbaboranes, and the reactivity of these new heteroatom boranes was explored. Sulfur insertion was accomplished in the reaction of nido-6-SB$\rm\sb9H\sb{10\sp-}$ with elemental sulfur, which results in sulfur insertion to produce arachno-2,3-S$\rm\sb2B\sb9H\sb{10\sp-}$. Further reaction of arachno-2,3-S$\rm\sb2B\sb9H\sb{10\sp-}$ produces arachno-2-H-2,3-S$\rm\sb2B\sb9H\sb{10}$, arachno-2-CH$\sb3$-2,3-S$\rm\sb2B\sb9H\sb{10}$ and arachno-2-CH$\sb2$I-2,3-S$\rm\sb2B\sb9H\sb{10}$. A synthetic sequence for nitrile insertion, involving the initial nucleophilic attack of the isoelectronic nido-5,6-C$\rm\sb2B\sb8H\sb{11\sp-}$ or nido-B$\rm\sb{10}H\sb{13\sp-}$ anions at a nitrile carbon, has been found to yield the new azacarborane clusters arachno-7-CH$\sb3$-5,7,14,12-C$\rm\sb3NB\sb8H\sb{11\sp-}$ and arachno-7-R-7,12-CNB$\rm\sb{10}H\sb{13\sp-}$, respectively. Further reactions of arachno-7-R-7,1 2-CNB$\rm\sb{10}H\sb{13\sp-}$ generated a series of new azacarbaboranes, including hypho-12-R-12,13-CNB$\rm\sb9H\sb{15}$, hypho-12-R-12,13-CNB$\rm\sb9H\sb{14\sp-}$, hypho-12-R-12,11-CNB$\rm\sb9H\sb{14\sp-}$, hypho-8-R-8,13-CNB$\rm\sb8H\sb{14}$ and hypho-8-R-8,13-CNB$\rm\sb8H\sb{13\sp-}$. Carbon insertion was observed in the reactions of the isomeric carborane anions, arachno-6,7-C$\rm\sb2B\sb7H\sb{12\sp-}$ and arachno-6,7-C$\rm\sb2B\sb7H\sb{12\sp-}$, and the nido-B$\rm\sb{10}H\sb{14\sp-}$ anion, with polarized acetylenes, leading to carbon insertion and generation of new di- and tricarbaboranes, including nido-6-(MeOC(O)CH$\sb2$)-5,6,10-C$\rm\sb3B\sb7H\sb{10}$. Other results include a structural study of arachno-4-CB$\rm\sb8H\sb{13\sp-}$, using both single crystal X-ray crystallography and ab initio/IGLO/NMR calculations.

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Recommended Citation

Wille, Andrew Edward, "Heteroatom insertion reactions of polyhedral borane anions" (1996). Dissertations available from ProQuest. AAI9628025.