Reductive Al-B σ-Bond Formation in Alumaboranes: Facile Scission of Polar Multiple Bonds

We present facile access to an alumaborane species with electron precise Al-B sigma-bond. The reductive rearrangement of 1-(AlI2), 8-(BMes(2)) naphthalene (Mes=2,4,6-Me3C6H2) affords the alumaborane species cyclo-(1,8-C10H6)-[1-Al(Mes)(OEt2)-8-B(Mes)] with a covalent Al-B sigma-bond. The Al-B sigma-bond performs the reductive scission of multiple bonds: S=C(NiPrCMe)(2) affords the naphthalene bridged motif B-S-Al(NHC), NHC=N-heterocyclic carbene, while O=CPh2 is deoxygenated to afford an B-O-Al bridged species with incorporation of the remaining CPh2 fragment into the naphthalene scaffold. The reaction with isonitrile Xyl-N C (Xyl=2,6-Me2C6H4) proceeds via a proposed (amino boryl) carbene species; which adds a second equivalent of isonitrile to ultimately form the Al-N-B bridged species cyclo-(1,8-C10H6)-[1-Al(Mes)-N(Xyl)-8-B{C(Mes)=C-N-Xyl}] with complete scission of the C N triple bond. The latter reaction is supported with isolated intermediates and by DFT calculations.