Nucleophilic Reactivity at a=CH Arm of a Lutidine-Based CNC/Rh System: Unusual Alkyne and CO2Activation; 35476902

Hermosilla, P. (Universidad de Zaragoza) ; García-Orduña, P. ; Sanz Miguel, P. J. (Universidad de Zaragoza) ; Polo, V. (Universidad de Zaragoza) ; Casado, M. A. (Universidad de Zaragoza)

Resumen: Reaction of an amido pincer complex (CNC)*Rh(CO)] (1) (CNC* is the deprotonated form of CNC) with carbon dioxide gave a neutral complex (CNC-CO2)Mes*Rh(CO)] (2), which is the result of a C-C bond-forming reaction between the deprotonated arm of the CNC* ligand and CO2. The molecular structure of 2 showed a zwitterionic complex, where the CO2 moiety is covalently connected to the former =CH arm of the CNC* pincer ligand. The unusual structure of 1 allowed us to explore the reactivity of the CO2 moiety with selected primary amines RNH2 (benzylamine and ammonia), which afforded cationic complexes (CNC)MesRh(CO)]HRNC(O)O] (R = Bz (3), H (4)). Compounds 3 and 4 are the result of a C-N coupling between the incoming amine and the CO2 fragment covalently connected to the pincer ligand in 2, a process that involves protonation of the "CH-CO2"fragment in 2 from the respective amines. Once revealed the nucleophilic character of the =CH fragment in 1, we explored its reactivity with alkynes, a study that enlightened a novel reactivity trend in alkyne activation. Reaction of 1 with terminal alkynes RCCH (R = Ph, 2-py, 4-C6H4-CF3) yielded neutral complexes (CNC-CH=CHR)Mes*Rh(CO)] (R = Ph (5), 2-py (6), 4-C6H4-CF3 (7)) in good yields. Deuterium labeling experiments with PhCCD confirmed that complex 5 is the product of a formal insertion of the alkyne into the C(sp2)-H bond of the deprotonated arm in 1. This structural proposal was further confirmed by the X-ray molecular structure of phenyl complex 5, which showed the alkyne covalently linked to the pincer ligand. Besides, this novel transformation was analyzed by DFT methods and showed a metal-ligand cooperative mechanism, based on the initial electrophilic attack of the alkyne to the =CH arm of the CNCMes* ligand (making a new C-C bond) followed by the action of a protic base (HN(SiMe3)2), which is able to perform a proton rearrangement that leads to the final product 5. © 2022 American Chemical Society.

Idioma: Inglés

DOI: 10.1021/acs.inorgchem.2c00617

Año: 2022

Publicado en: Inorganic Chemistry 66, 18 (2022), 7120–7129
ISSN: 0020-1669

Factor impacto JCR: 4.6 (2022)

Categ. JCR: CHEMISTRY, INORGANIC & NUCLEAR rank: 5 / 42 = 0.119 (2022) - Q1 - T1

Factor impacto CITESCORE: 8.0 - Chemistry (Q1)

Factor impacto SCIMAGO: 0.997 - Chemistry (miscellaneous) (Q1) - Physical and Theoretical Chemistry (Q1) - Inorganic Chemistry (Q1)

Financiación: info:eu-repo/grantAgreement/ES/DGA-FSE/E42-20R
Financiación: info:eu-repo/grantAgreement/ES/MINECO-FEDER/PGC2018-099383-B-I00

Tipo y forma: Article (PostPrint)

Área (Departamento): Área Química Inorgánica (Dpto. Química Inorgánica)
Área (Departamento): Área Química Física (Dpto. Química Física)