Catalysts for Regio- and Stereoselective C(sp³)–H Deuteration of Tricyclohexylphosphine with Benzene-d₆ Generated via Dehydrochlorination of Chlorido(dihydrido)iridium Complexes Containing a Xanthene-Based Bis(silyl) Chelate Ligand

Abstract

The catalytic C(sp 3 )−H deuteration of tricyclohexylphosphine (PCy 3 ) with excess benzene-d 6 at 60 °C was achieved using the iridium catalyst precursor Ir(κ 2 Si,Si-xantsil)(H) 2 (PCy 3 )Cl (1), in the presence of (Me 3 Al) 2 •DABCO (xantsil = (9,9-dimethylxanthene-4,5diyl)bis(dimethylsilyl), DABCO = 1,4-diazabicyclo[2.2.2]octane). In this reaction, the 3,5-equatorial and 4-axial C−Hs of PCy 3 were selectively deuterated, chiefly affording P(Cy-d 3 ) 3 . To gain insight into the reaction mechanism, iridium complexes bearing an asymmetric and bulkier bis(silyl)−xanthene chelate ligand with SiMe 2 and Si(p-Tol) 2 coordinating moieties, namely, Ir(κ 2 Si,Si-xantSi Me Si p-Tol )(H) 2 (L)Cl (L = pyridine (2-py) or PCy 3 (2-PCy)), were synthesized, and similar reactions using them were examined under stoichiometric and catalytic conditions. The stoichiometric reaction of 2-py with (Me 3 Al) 2 •DABCO at 60 °C resulted in dehydrochlorination to give the dinuclear complex [Ir(μ-κ 1 Si:η 6 ,κ 1 Si-xantSi Me Si p-Tol )(H)] 2 (3). On the other hand, the analogous reaction of 2-PCy in benzene at 60 °C afforded the thermally unstable Ir(xantSi Me Si p-Tol )(H)(PCy 3 ) (4). When this reaction was performed in benzene-d 6 , the partially deuterated analogue Ir(xantSi Me Si p-Tol )(D)(PCy 3 -d n ) (4-D) was formed due to the deuteration of Ir−H and some C(sp 3 )−Hs of PCy 3 of 4 via H/D exchange with benzene-d 6 . Moreover, 2-PCy showed catalytic activity similar to that of 1. On the basis of these results, it is suggested that 4 and 4-D functioned as active species for the catalytic deuteration of PCy 3 using 2-PCy.

Metal complexes containing silicon‐based pincer ligands: Reactivity and application in small molecule activation

“…Still, unique reactivity of the [SiXSi] metal complexes can be expected via σ‐interaction (vide infra) or metal–ligand cooperation. [SiOSi] and [SiNSi] ligands, (9,9‐dimethylxanthene‐4,5‐diyl)bis(dimethylsilane) and 2,6‐bis[(dimethylsilyl)methyl]pyridine were developed by the Tobita group 73–81 . It is worth noting that the oxygen donor of the [SiOSi] disilylxanthene ligand is hemilabile, allowing for the facile coordination of substrates to the metal center and catalytic SiH and CH bond activation 78–80 .…”

“…[73][74][75][76][77][78][79][80][81] It is worth noting that the oxygen donor of the [SiOSi] disilylxanthene ligand is hemilabile, allowing for the facile coordination of substrates to the metal center and catalytic Si H and C H bond activation. [78][79][80] Other [SiNSi] and [SiCSi] ligand backbones were also reported by Driess and co-workers, in which the silyl donors were replaced with silylenes to enhance the σ-donor ability of silicon. [82][83][84][85] Shimada and co-workers reported a nickel complex supported by a [SiSiSi]-type bis (2-silylphenyl)silane ligand.…”

“…[SiOSi] and [SiNSi] ligands, (9,9-dimethylxanthene-4,5-diyl)bis(dimethylsilane) and 2,6-bis[(dimethylsilyl)methyl]pyridine were developed by the Tobita group. [73][74][75][76][77][78][79][80][81] It is worth noting that the oxygen donor of the [SiOSi] disilylxanthene ligand is hemilabile, allowing for the facile coordination of substrates to the metal center and catalytic Si H and C H bond activation. [78][79][80] Other [SiNSi] and [SiCSi] ligand backbones were also reported by Driess and co-workers, in which the silyl donors were replaced with silylenes to enhance the σ-donor ability of silicon.…”

Iridium Complexes with a Naphthyridine-Based Si,N-Ligand: Synthesis and Catalytic Activity toward Olefin Hydrogenation

“…During the course of our studies on metal complexes featuring silyl multidentate ligands, , we have recently synthesized dirhodium complex C bearing a silyl-1,8-naphthyridine-based Si , N -ligand (abbreviated as napySi) (Figure c) . Due to the strong trans influence of the silyl ligand, C has a vacant coordination site (a Lewis acidic center) trans to the silyl moiety on each metal center, which is adjacent to a lone pair on the uncoordinated nitrogen atom of the naphthyridine moiety .…”

Iridium and rhodium complexes bearing a silyl-bipyridine pincer ligand: synthesis, structures and catalytic activity for C–H borylation of arenes

“…Our group has previously developed several silyl-containing multidentate ligands such as SiOSi-, 9 SiOP- 10 and SiNN-type 11 ligands and used them to synthesise metal catalysts. Among them, the silyl-pyridine-amine-based SiNN-pincer iridium complex showed high activity for the catalytic Si–H deuteration of trialkylsilanes with benzene- d 6 via the activation of the C(sp 2 )–D bonds under very mild conditions (room temperature).…”