Reactivity of a Free Aluminylene towards Boron Lewis Acids: Accessing Aluminum‐Boron‐Bonded Species

The reactivity of a free aluminylene towards boron Lewis acids is reported, which gives rise to rare Al−B-bonded species with either an Al−B electron-sharing bond or an Al→B dative bond. This work showcases the potent synthon of free aluminylenes for unusual Al species.

Abstract

The reactivity of the free aluminylene [N]-Al (1) ([N]=1,8-bis(3,5-di-tert-butylphenyl)-3,6-di-tert-butylcarbazolyl) towards boron Lewis acids is investigated. A facile oxidative addition reaction of 1 with Ph₂BOBPh₂ furnishes an exceedingly scarce example of the free alumaborane [N]-Al(BPh₂)(OBPh₂) (2) with an Al−B electron-sharing bond. By contrast, complexation of 1 with B(C₆F₅)₃ and HB(C₆F₅)₂ gives rise to the corresponding Lewis adducts [N]-Al→B(C₆F₅)₃ (3) and [N]-Al→BH(C₆F₅)₂ (4), respectively, with an Al→B dative bond. Crystallization of 4 in Et₂O produces the adduct [N]-Al(Et₂O)→BH(C₆F₅)₂ (5). Quantum chemical calculations are carried out to understand the formation of 2 as well as the bonding situation of 3 and 5.

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