NHCs as Neutral Donors towards Polyphosphorus Complexes. Issue 69 (29th October 2020)

• Record Type: Journal Article
• Authors: Riedlberger, Felix; Todisco, Stefano; Mastrorilli, Piero; Timoshkin, Alexey Y.; Seidl, Michael; Scheer, Manfred
• Is Part Of: Chemistry. Volume 26:Issue 69(2020)
• Page Start: 16251
• Page End: 16255
• Publication Date: 2020-10-29
• Subjects: iron -- N-heterocyclic carbenes -- NMR spectroscopy -- nucleophilic attack -- phosphorus -- tantalum; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.202003393
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: The first adducts of NHCs (=N‐heterocyclic carbenes) with aromatic polyphosphorus complexes are reported. The reactions of [Cp*Fe(η 5 ‐P5 )] (1 ) (Cp*=pentamethyl‐cyclopentadienyl) with IMe (=1, 3, 4, 5‐tetramethylimidazolin‐2‐ylidene), IMes (=1, 3‐bis(2, 4, 6‐trimethylphenyl)‐imidazolin‐2‐ylidene) and IDipp (=1, 3‐bis(2, 6‐diisopropylphenyl)‐imidazolin‐2‐ylidene) led to the corresponding neutral adducts which can be isolated in the solid state. However, in solution, they quickly undergo a dissociative equilibrium between the adduct and 1 including the corresponding NHC. The equilibrium is influenced by the bulkiness of the NHC. [Cp′′Ta(CO)2 (η 4 ‐P4 )] (Cp′′=1, 3‐di‐ tert ‐butylcyclopentadienyl) reacts with IMe under P atom abstraction to give an unprecedented cyclo‐P3 ‐containing anionic tantalum complex. DFT calculations shed light onto the energetics of the reaction pathways. Abstract : Access to polyphosphorus complexes : A dynamic behavior between [Cp*Fe(η 5 ‐P5 )] and NHCs in solution is reported. NMR investigations showed a bond formation and bond breaking process between [Cp*Fe(η 5 ‐P5 )] and the NHCs. Despite this dynamic behavior in solution, adducts of [Cp*Fe(η 5 ‐P5 )] and NHCs can be isolated as solids. The tantalum complex [Cp′′Ta(CO)2 (η 4 ‐P4 )] reacts with the NHC via a phosphorus atom abstraction and a ring contraction to a novel anionic cyclo‐P3 complex.