C−C and C−N Bond Activation, Lewis‐Base Coordination and One‐ and Two‐Electron Oxidation at a Linear Aminoborylene. Issue 16 (16th February 2023)

• Record Type: Journal Article
• Authors: Witte, Robert; Arrowsmith, Merle; Lamprecht, Anna; Schorr, Fabian; Krummenacher, Ivo; Braunschweig, Holger
• Is Part Of: Chemistry. Volume 29:Issue 16(2023)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2023-02-16
• Subjects: bond activation -- boraselenone -- dicoordinate borylene -- one-electron oxidation -- push-pull stabilization; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.202203663
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: A cyclic alkyl(amino)carbene (CAAC)‐stabilized dicoordinate aminoborylene is synthesized by the twofold reduction of a [(CAAC)BCl2 (TMP)] (TMP=2, 6‐tetramethylpiperidyl) precursor. NMR‐spectroscopic, X‐ray crystallographic and computational analyses confirm the cumulenic nature of the central C=B=N moiety. Irradiation of [(CAAC)B(TMP)] (2 ) resulted in an intramolecular C−C bond activation, leading to a doubly‐fused C10 BN heterocycle, while the reaction with acetonitrile resulted in an aryl migration from the CAAC to the acetonitrile nitrogen atom, concomitant with tautomerization of the latter to a boron‐bound allylamino ligand. One‐electron oxidation of 2 with CuX (X=Cl, Br) afforded the corresponding amino(halo)boryl radicals, which were characterized by EPR spectroscopy and DFT calculations. Placing 2 under an atmosphere of CO afforded the tricoordinate (CAAC, CO)‐stabilized aminoborylene. Finally, the twofold oxidation of 2 with chalcogens led, in the case of N2 O and sulfur, to the splitting of the B−CCAAC bond and formation of the 2, 4‐diamino‐1, 3, 2, 4‐dichalcogenadiboretanes and CAAC‐chalcogen adducts, whereas with selenium a monomeric boraselenone was isolated, which showed some degree of B−Se multiple bonding. Abstract : An isolable linear aminoborylene : A dicoordinate cyclic alkyl(amino)carbene (CAAC)‐stabilized aminoborylene isoelectronic with an allene undergoes intramolecular C−C bond activation under photolytic conditions, intramolecular aryl migration in the presence of acetonitrile, one‐electron oxidation with copper(I) halides to the corresponding haloboryl radicals, transition‐metal‐like binding of CO and reduction of N2 O, sulfur and selenium, the latter yielding a terminal boraselenone.