Ligand dynamics and reactivity of a non-innocent homoleptic iron complex (N,N)2Fe stabilized by phen-type ligands

• Published in: Journal of organometallic chemistry 2023-10, Vol.999, p.122796, Article 122796
• Main Authors: Féo, Mae, Djebbar, Faycel, Zhurkin, Fedor, Binet, Laurent, Touati, Nadia, Leech, Matthew C., Lam, Kevin, Brémond, Eric, Lefèvre, Guillaume
• Format: Article
• Language: English
• Subjects: Chemical Sciences; cycloaddition; Iron catalysis; NMR; paramagnetism; reductive coupling
• ISSN: 0022-328X; 1872-8561; 0022-328X
• DOI: 10.1016/j.jorganchem.2023.122796

•A low-valent non-innocent iron complex supported by phen-type ligands efficiently promotes reductive coupling of heteroaryl halides;•High efficiency of this complex in alkyne [2+2+2] cycloaddition is enhanced by assistance of main-group salts;•Analysis of the non-innocent electronic structure of this complex by means of DFT calculations allows a thorough analysis of its temperature-variable 1H NMR spectral properties. We report in this work the spectroscopic and reactivity properties of a non-innocent paramagnetic iron complex (bcp•–)2FeII featuring formally a Fe° center stabilized by two bathocuproine (bcp) ligands. The origin of the paramagnetic 1H NMR behavior is analyzed by means of DFT calculations, and shows that two electronic states of the complex contribute to its spectroscopic properties. The dynamics of the coordination sphere in (bcp•–)2FeII is governed by the duality between the two electronic descriptions (bcp•–)2FeII, and (bcp)2Fe0. The strong antiferromagnetic coupling between the reduced bcp scaffolds and the ferrous ion in (bcp•–)2FeII makes substitution of the bcp•– ligand difficult; however, the reduced (bcp)2Fe° character allows substitution of bcp by π-accepting ligands, such as alkynes, which can be activated in catalytic cycloadditions with the assistance of main-group salts. (bcp•–)2FeII also shows reductive activity towards a variety of organic electrophiles, and preliminary results using this complex as a catalyst for the reductive coupling of heteroaryl chlorides are discussed. [Display omitted]