Access to a peri‐Annulated Aluminium Compound via C−H Bond Activation by a Cyclic Bis‐Aluminylene

• Published in: Chemistry : a European journal 2024-04, Vol.30 (22), p.e202400293-n/a
• Main Authors: Merschel, Arne, Vishnevskiy, Yury V., Neumann, Beate, Stammler, Hans‐Georg, Ghadwal, Rajendra S.
• Format: Article
• Language: English
• Subjects: aluminium; Aluminum; Aluminum compounds; carbene; C−H activation; Halides; Hydrogen bonds; Magnetic resonance spectroscopy; main-group; Molecular structure; NMR spectroscopy; peri-annulation; Single crystals; X-ray diffraction
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.202400293

Carbocyclic aluminium halides [(ADC)AlX2]2 (2‐X) (X=F, Cl, and I) based on an anionic dicarbene (ADC=PhC{N(Dipp)C}2, Dipp = 2,6‐iPr2C6H3) framework are prepared as crystalline solids by dehydrohalogenations of the alane [(ADC)AlH2]2 (1). KC8 reduction of 2‐I affords the peri‐annulated Al(III) compound [(ADCH)AlH]2 (4) (ADCH=PhC{N(Dipp)C2(DippH)N}, DippH=2‐iPr,6‐(Me2C)C6H3)) as a colorless crystalline solid in 76 % yield. The formation of 4 suggests intramolecular insertion of the putative bis‐aluminylene species [(ADC)Al]2 (3) into the methine C−H bond of HCMe2 group. Calculations predict singlet ground state for 3, while the conversion of 3 into 4 is thermodynamically favored by 61 kcal/mol. Compounds 2‐F, 2‐Cl, 2‐I, and 4 have been characterized by NMR spectroscopy and their solid‐state molecular structures have been established by single crystal X‐ray diffraction. KC8 reduction of 2‐I with a catalytic amount the NHC (IMe4) has been shown to afford the peri‐annulated compound 4 as a colorless crystalline solid. The formation of 4 suggests intramolecular insertion of the putative bis‐aluminylene 3 into the C−H bonds of HCMe2 groups. Calculations predict singlet ground state for 3 while the conversion of 3 into 4 is thermodynamically favored by 61 kcal/mol.