PUB - Publikationen an der Universität Bielefeld

We report the room temperature dimerization of carbon monoxide mediated by C4/C5-vicinal anionic dicarbenes Li(ADC) (ADC = ArC{(Dipp)NC}2; Dipp = 2,6-iPr2C6H3; Ar = Ph, DMP (4-Me2NC6H4), Bp (4-PhC6H4)) to yield (E)-ethene-1,2-bis(olate) (i.e. -O-C=C-O- = COen) bridged mesoionic carbene (iMIC) lithium compounds (COen-[(iMIC)Li]2) (COen-[iMIC]2 = [ArC{(Dipp)NC}2-(CO)]2) in quantitative yields. COen-[(iMIC)Li]2 are highly colored stable solids, exhibit a strikingly small HOMO-LUMO energy gap, and readily undergo 2e-oxidations with selenium, CuCl (or CuCl2), and AgCl to afford the dinuclear compounds COon-[(iMIC)E]2 (E = Se, CuCl, AgCl) featuring a 1,2-dione bridged neutral bis-iMIC (COon-[iMIC]2 = {ArC{(Dipp)NC}2(C=O)). COen-[(iMIC)Li]2 undergo redox-neutral salt metathesis reactions with LiAlH4 and (Et2O)2BeBr2 and afford COen-[(iMIC)AlH2]2 and COen-[(iMIC)BeBr]2, in which the dianionic COen-moiety remains intact. All compounds have been characterized by NMR spectroscopy, mass spectrometry, and X-ray diffraction. Stereoelectronic properties of COon-[iMIC]2 are quantified by experimental and theoretical methods. © 2024 Wiley-VCH GmbH.