Carbon Monoxide Activation by a Molecular Aluminium Imide: C−O Bond Cleavage and C−C Bond Formation

Abstract

Anionic molecular imide complexes of aluminium are accessible via a rational synthetic approach involving the reactions of organo azides with a potassium aluminyl reagent. In the case of K2[(NON)Al(NDipp)]2 (NON=4,5‐bis(2,6‐diisopropylanilido)‐2,7‐di‐tert‐butyl‐9,9‐dimethyl‐xanthene; Dipp=2,6‐diisopropylphenyl) structural characterization by X‐ray crystallography reveals a short Al−N distance, which is thought primarily to be due to the low coordinate nature of the nitrogen centre. The Al−N unit is highly polar, and capable of the activation of relatively inert chemical bonds, such as those found in dihydrogen and carbon monoxide. In the case of CO, uptake of two molecules of the substrate leads to C−C coupling and C≡O bond cleavage. Thermodynamically, this is driven, at least in part, by Al−O bond formation. Mechanistically, a combination of quantum chemical and experimental observations suggests that the reaction proceeds via exchange of the NR and O substituents through intermediates featuring an aluminium‐bound isocyanate fragment.

Carbon–Carbon Bond Forming Reactions Promoted by Aluminyl and Alumoxane Anions: Introducing the Ethenetetraolate Ligand

“…We therefore reacted the isolated alumoxane anion “K[Al(NON Dipp )(O)]′ ({ b }: E=O) with carbon monoxide, which we postulated would proceed via a [2+2]‐cycloaddition to afford carbene { d } (Scheme ). Similar reactions of neutral, and anionic aluminium imides with CO have been reported.…”

Carbon–Carbon Bond Forming Reactions Promoted by Aluminyl and Alumoxane Anions: Introducing the Ethenetetraolate Ligand

“…[5b] We therefore reacted the isolated alumoxane anion "K[Al-(NON Dipp )(O)]' ({b}: E = O) with carbon monoxide, which we postulated would proceed via a [2+2]-cycloaddition to afford carbene {d} (Scheme 2). Similar reactions of neutral, [19] and anionic [20] aluminium imides with CO have been reported.…”

Sterically controlled reductive oligomerisations of CO by activated magnesium(i) compounds: deltate vs. ethenediolate formation

“…For example, this work has led to the discovery that low-valent metal and non-metal compounds, from across the periodic table, can reductively oligomerise CO to ethynediolate, [OC^CO] 2À , aromatic oxocarbon dianions, [C n O n ] 2À (n ¼ 2-6), and related species, under mild conditions. [4][5][6] From a historical perspective, it should be noted that alkali metals have been known to reductively oligomerise CO to salts of oxocarbon dianions since the early 19th century, though those salts have been poorly characterised. 7 In order to access well-dened s-block metal complexes of oxocarbon anions derived from CO, we have recently reported on reactions of this gas with reducing b-diketiminate coordinated magnesium(I) compounds.…”