Heteroleptic Dirhodium(II) Complexes with Redox‐Active Ferrocenyl Ligands: Synthesis, Electrochemical Properties, and Redox‐Responsive Chemoselectivity in Carbene C−H Insertion

• Published in: European journal of inorganic chemistry Vol. 2022; no. 12
• Main Authors: Ruzhylo, Illia, Sournia‐Saquet, Alix, Moreau, Alain, Delord, Tom, Manoury, Eric, Poli, Rinaldo, Labande, Agnès
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 27.04.2022; Wiley-VCH Verlag
• Subjects: Chemical Sciences; Coordination chemistry; Decomposition; Diazo compounds; Electrochemical analysis; Electrochemistry; Ferrocene; Inorganic chemistry; Insertion; Ligands; Mass spectrometry; NMR; Nuclear magnetic resonance; Oxidation; Rhodium; Rhodium compounds; Electrochemistry; Diazo compounds; Oxidation; Dirhodium; Ferrocene
• ISSN: 1434-1948; 1099-0682
• DOI: 10.1002/ejic.202200033

A series of original heteroleptic dirhodium(II) complexes (4 a–j) of formula [Rh2(OAc)3(L)], where L is a redox‐active ferrocenecarboxylate ligand, has been prepared. These dirhodium(II) complexes have been characterised by NMR, mass spectrometry and cyclic voltammetry. All complexes show a quasi‐reversible redox behaviour for the ferrocenyl unit. The latter can be selectively oxidised by [N(4‐C6H4Br)3]+BF4−. Four selected heteroleptic complexes 4 a, 4 b, 4 f and 4 i, have been evaluated as catalysts for the intramolecular decomposition of a diazo compound 5. The ratio between the aromatic substitution product 6 and the aliphatic C−H insertion product 7 increases (up to 19 % increase) when using the in situ generated oxidised form of the dirhodium(II) complexes (4 a+BF4− to 4 i+BF4−). This shows that the oxidation of the ferrocenecarboxylate ligand has an effect on the chemoselectivity of the dirhodium‐catalysed diazo decomposition, and thus that the electronic properties of a complex can be tuned without exchanging ligands. A series of new heteroleptic ferrocenyl dirhodium(II) complexes has been prepared and used to catalyse the intramolecular decomposition of a diazo substrate. Redox tuning of chemoselectivity was possible, as the aromatic substitution/aliphatic C−H insertion ratio increases upon oxidation of the ferrocenyl moiety, in electronic communication with the Rh centre.