Geometry changes induced by negative hyperconjugative interactions involving carbonyl and thiocarbonyl groups

The Reaction of CO2 with a Borylnitrene: Formation of an 3-Oxaziridinone

The reaction of a borylnitrene with carbon dioxide is studied under cryogenic matrix isolation conditions. Photogenerated CatBN (Cat=catecholato) reacts with CO2 under formation of the cycloaddition product CatBNCO2 , a 3-oxaziridinone derivative, after photoexcitation (>550 nm). The product shows Fermi resonances between the CO stretching and ring deformation modes that cause unusual 13 C and 18 O isotopic shifts. A computational analysis of the 3-oxaziridinone shows this cyclic carbamate to be less strained than an α-lactone or an α-lactame.

CO-Reduction Chemistry: Reaction of a CO-Derived Formylhydridoborate with Carbon Monoxide, with Carbon Dioxide, and with Dihydrogen

Treatment of the bulky metallocene hydride Cp*₂Zr(H)OMes (Cp* = pentamethylcyclopentadienyl, Mes = mesityl) with Piers' borane [HB(C₆F₅)₂] and carbon monoxide (CO) gave the formylhydridoborate complex [Zr]-O═CH-BH(C₆F₅)₂ ([Zr] = Cp*₂Zr-OMes). From the dynamic NMR behavior, its endergonic equilibration with the [Zr]-O-CH₂-B(C₆F₅)₂ isomer was deduced, which showed typical reactions of an oxygen/boron frustrated Lewis pair. It was trapped with CO to give an O-[Zr] bonded borata-β-lactone. Trapping with carbon dioxide (CO₂) gave the respective O-[Zr] bonded cyclic boratacarbonate product. These reaction pathways were analyzed by density functional theory calculation. The formylhydridoborate complex was further reduced by dihydrogen via two steps; it reacted rapidly with H₂ to give Cp*₂Zr(OH)OMes and H₃C-B(C₆F₅)₂, which then slowly reacted further with H₂ to eventually give [Zr]-O(H)-B(H)(C₆F₅)₂ and methane (CH₄). Most complexes were characterized by X-ray diffraction.

Synthesis of Isolable Thiirane-2-thione (α-Dithiolactone) from Thioketene S-Oxide

Reaction of di-tert-butyl thioketene S-oxide with Lawesson reagent gave 3,3-di-tert-butylthiirane-2-thione in 88% yield. Oxidation of thiirane-2-thione with m-chloroperbenzoic acid afforded 3,3-di-tert-butylthiirane-2-thione S-oxide. The reaction of thiirane-thione was described.