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

摘要

We present facile access to an alumaborane species with electron precise Al-B σ-bond. The reductive rearrangement of 1-(AlI2), 8-(BMes2) naphthalene (Mes=2,4,6-Me3C6H2) affords the alumaborane species cyclo-(1,8-C_(10)H6)-[1-Al(Mes)(OEt2)-8-B(Mes)] with a covalent Al-B σ-bond. The Al-B σ-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-C_(10)H6)-[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.