Bridging and Terminal Arrangement of Alkylperoxo Groups in Organoindium Peroxides

Four-Electron Reduction of O2 Using Distibines in the Presence of ortho-Quinones

This study, which aims to identify atypical platforms for the reduction of dioxygen, describes the reaction of O2 with two distibines, namely, 4,5-bis(diphenylstibino)-2,7-di-tert-butyl-9,9-dimethylxanthene and 4,5-bis(diphenylstibino)-2,7-di-tert-butyl-9,9-dimethyldihydroacridine, in the presence of an ortho-quinone such as phenanthraquinone. The reaction proceeds by oxidation of the two antimony atoms to the + V state in concert with reductive cleavage of the O2 molecule. As confirmed by 18O labeling experiments, the two resulting oxo units combine with the ortho-quinone to form an α,α,β,β-tetraolate ligand that bridges the two antimony(V) centers. This process, which has been studied both experimentally and computationally, involves the formation of asymmetric, mixed-valent derivatives featuring a stibine as well as a catecholatostiborane formed by oxidative addition of the quinone to only one of the antimony centers. Under aerobic conditions, the catecholatostiborane moiety reacts with O2 to form a semiquinone/peroxoantimony intermediate, as supported by NMR spectroscopy in the case of the dimethyldihydroacridine derivative. These intermediates swiftly evolve into the symmetrical bis(antimony(V)) α,α,β,β-tetraolate complexes via low barrier processes. Finally, the controlled protonolysis and reduction of the bis(antimony(V)) α,α,β,β-tetraolate complex based on the 9,9-dimethylxanthene platform have been investigated and shown to regenerate the starting distibine and the ortho-quinone. More importantly, these last reactions also produce two equivalents of water as the product of O2 reduction.

Unveiling Complexity of the Oxygenation of Aluminum Alkyls by the Isolation of Unique Alkylperoxide and Oxoalkoxide Compounds

While aluminum alkyls are often considered to be exemplary compounds of main-group organometallics and an in-depth understanding of their multifaceted chemistry is continually vital, the controlled oxygenation of organoaluminum complexes still remains a largely undeveloped area. In the course of our systematic studies on the relationship between the Lewis acidity of metal centers and noncovalent interactions in the secondary coordination sphere, we report the oxygenation of dialkylaluminum complexes incorporating a pyrrole–ester ligand, as purposefully selected dormant Lewis acidic octet-compliant model compounds, and the isolation and characterization of a new, dimeric aluminum tert-butylperoxide and an unique example of an aluminum oxoethoxide cluster. Our studies provide a more in-depth look at the diversity and complexity of the oxygenation chemistry of aluminum alkyls.

We report the reactions of dialkylaluminum complexes incorporating a pyrrole−ester ligand with dioxygen as well as the isolation of a novel aluminum tert-butylperoxide and an unique example of aluminum oxoethoxide. Our studies provide a more in-depth look at the diversity and complexity of the oxygenation chemistry of aluminum alkyls.

Boron-based stepwise dioxygen activation with 1,4,2,5-diazadiborinine

Activation of dioxygen (O2) by 1,4,2,5-diazadiborinine 1 is reported. Two boron centers in 1 undergo a formal [4 + 2] cycloaddition with O2 at room temperature affording a bicyclo[2.2.2] molecule 2 featuring a B-O-O-B unit. Treatment of 2 with an additional equivalent of 1 leads to the cleavage of the O-O bond in 2 concomitant with the formation of two B-O bonds to yield 4 involving the extremely rare B4C2N2O2 ten-membered rings. A series of these reactions demonstrate the stepwise scission of the O[double bond, length as m-dash]O π-bond and the O-O σ-bond of O2.