Rh Complexes with Pincer Carbene CNC Lutidine-Based Ligands: Reactivity Studies toward H2 Addition

Hermosilla P. (Universidad de Zaragoza) ; García-Orduña P. ; Lahoz F.J. ; Polo V. (Universidad de Zaragoza) ; Casado M.A. (Universidad de Zaragoza)

Resumen: Lutidine-based NHCs pincer precursors CNCMe and CNCMes were combined with [Rh(acac)(nbd)] (acac = acetylacetonate; nbd = 2, 5-norbornadiene) in the presence of Cs2CO3 to yield complexes [(CNC)MeRh(nbd)]PF6 (3) and [(CNC)MesRh(NCMe)]PF6 (4), respectively. While in 3, the nbd diolefin remains coordinated, in 4, the voluminous mesityl ligands induce nbd decoordination, so acetonitrile stabilizes Rh(I) adduct 4, which in turn undergoes substitution reactions with a number of neutral ligands to produce cationic complexes [(CNC)MesRh(L)]PF6 (L = CO (5), PMe2Ph (6), PEt3 (7), C2H4 (8)). These complexes have been studied through VT NMR measurements and the molecular structures by X-ray crystallography in the case of adducts 4-7. Deprotonation reactions on cationic complexes 3-6 with hard bases yielded the corresponding neutral complexes [(CNC)*MeRh(nbd)] (9) and mesityl derivatives [(CNC)*MesRh(L)] (L = NCCH3 (10), CO (11), PMe2Ph (12)), all of which are dearomatized complexes due to the deprotonation of one of the methylene arms, a situation confirmed by the X-ray molecular structure of carbonyl adduct 5. We studied the reactivity toward dihydrogen with neutral adducts 11 and 12. The electron rich phosphane 12 adds H2 through oxidative addition, affording the bis(hydrido) Rh(III) complex [(CNC)*MesRh(PMe2Ph)H2] (14). However, the carbonyl adduct 11 reacts with H2 in a different way, so that the central pyridinic ring becomes hydrogenated, breaking the aromaticity and leading to complex [(CNC-H2)*MesRh(CO)] (13), isolated as a mixture of two isomers. DFT studies were carried out in order to establish the mechanisms followed on these hydrogenations, finding that, while the phosphane adduct reacts following an oxidative addition mechanism, the carbonyl complex follows a more complex base-induced profile due to the instability of hydride carbonyl species. © 2021 American Chemical Society.

Idioma: Inglés

DOI: 10.1021/acs.organomet.1c00453

Año: 2021

Publicado en: Organometallics 40, 22 (2021), 3720-3732
ISSN: 0276-7333

Factor impacto JCR: 3.837 (2021)

Categ. JCR: CHEMISTRY, ORGANIC rank: 15 / 56 = 0.268 (2021) - Q2 - T1
Categ. JCR: CHEMISTRY, INORGANIC & NUCLEAR rank: 12 / 46 = 0.261 (2021) - Q2 - T1

Factor impacto SCIMAGO: 0.994 - Organic 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)