Reductive Al−B σ‐Bond Formation in Alumaboranes: Facile Scission of Polar Multiple Bonds
Zeynep Güven, Lars Denker, Daniela Wullschläger, Juan Pablo Martínez, Bartosz Trzaskowski, René Frank
Abstract
Abstract We present facile access to an alumaborane species with electron precise Al−B σ‐bond. The reductive rearrangement of 1‐(AlI 2 ), 8‐(BMes 2 ) naphthalene (Mes=2,4,6‐Me 3 C 6 H 2 ) affords the alumaborane species cyclo ‐(1,8‐C 10 H 6 )‐[1‐Al(Mes)(OEt 2 )‐8‐B(Mes)] with a covalent Al−B σ‐bond. The Al−B σ‐bond performs the reductive scission of multiple bonds: S=C(N i PrCMe) 2 affords the naphthalene bridged motif B−S−Al(NHC), NHC= N ‐heterocyclic carbene, while O=CPh 2 is deoxygenated to afford an B−O−Al bridged species with incorporation of the remaining ≡CPh 2 fragment into the naphthalene scaffold. The reaction with isonitrile Xyl‐N≡C (Xyl=2,6‐Me 2 C 6 H 4 ) 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 H 6 )‐[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.