Synthesis, Structure, and Reactivity of New Rhodium and Iridium Complexes, Bearing a Highly Electron-Donating PNP System. Iridium-Mediated Vinylic C−H Bond Activation

Abstract

Reaction of the new highly electron-donating PNP ligand [2,6-bis-(di-tert-butylphosphinomethyl)pyridine] (1) with [Rh(COE) 2 Cl] 2 (COE ) cyclooctene) at room temperature resulted in formation of the neutral Rh(I) complex [Rh(PNP)Cl] (2). Unsaturated cationic complexes [Rh(PNP)(CH 3 CN)]BF 4 (3) and [Rh(PNP)(C 2 H 4 )]SO 3 CF 3 (4) were obtained in reaction of 1 with [(COE) 2 Rh(CH 3 CN) 2 ]BF 4 and [(C 2 H 4 ) 2 Rh(THF) 2 ]SO 3 CF 3 , respectively. Upon reaction of the PNP ligand 1 with [Ir(COE) 2 Cl] 2 , facile vinylic C-H activation takes place, yielding the hydrido-vinyl complex [ClIr(PNP)(H)(C 8 H 13 )] ( 5). Also, coordination of ligand 1 to the cationic iridium complex [Ir(COD) 2 ]BF 4 (COD ) cyclooctadiene) in RCN (R ) CH 3 , CH(CH 3 ) 2 , C(CH 3 ) 3 ) led to iridium insertion into a vinylic C-H bond, resulting in complexes [(RCN)-Ir(PNP)(H)(C 8 H 11 )]BF 4 (6a-c). The hydrido-vinyl complexes 6a,c readily react with H 2 (2 atm) at room temperature, affording the iridium dihydride complexes [(RCN)Ir(PNP)-(H) 2 ]BF 4 (R ) CH 3 , C(CH 3 ) 3 ) (7a,b).

Cationic iridium complexes of the Xantphos ligand. Flexible coordination modes and the isolation of the hydride insertion product with an alkene

“…This carbon signal is also the lowest frequency one in the 13{1H} NMR spectrum and shows no correlation to other protons, suggesting an IreCHR 2 group. The 31 [17] ligands. The formation of a s, h 2 -C 8 H 13 ligand from insertion of a hydride into a coordinated COD ligand has been reported previously [26,27].…”

Neutral Tridentate PNP Ligands and Their Hybrid Analogues: Versatile Non‐Innocent Scaffolds for Homogeneous Catalysis

“…[32] Rieger and co-workers described the phenyl-, tolyl-, and mesityl-substituted PNP Ar ligands by following the same procedure. [33] Kawatsure and Hartwig reported the selective lithiation of 2,6-lutidine (2,6-dimethylpyridine) and subsequent reaction of the lithiated species with chlorophosphine reagents, which again showcases the tert-butyl analogue 12…”

Complexation and C–H bond activation of 1,5-cyclooctadiene on triosmium carbonyl clusters

“…Nevertheless, both allylic and vinylic C-H bond activations of 1,5-COD ligand were recently illustrated in an Ir(I) system [18,19].…”