Isolation of Ruthenium–Indolizine Complexes: Insight into the Metal-Induced Cycloisomerization of Propargylic Pyridines

Abstract

A class of ruthenium−indolizine complexes was isolated and structurally characterized, and they represent the first examples of metalated indolizine species. Both experimental and theoretical investigations on the formation of these complexes support a 5-endo-dig cyclization mechanism and discount a vinylidene−5-exo-dig cyclization pathway.

Luminescent Ruthenium(II) Complex Bearing Bipyridine and N-Heterocyclic Carbene-based C∧N∧C Pincer Ligand for Live-Cell Imaging of Endocytosis

“…Complex 1 is emissive with λ em at 659 nm in CH 3 CN, and 648 nm in CH 3 CN-H 2 O 1:1 v/v mixture, upon photoexcitation at its lowest-energy absorption band. Importantly, its emission quantum yield (8.23 × 10 −3 in degassed CH 3 CN, 2.14 × 10 −3 in non-degassed CH 3 CN-H 2 O mixture) and lifetime (1.71 μs in degassed CH 3 CN, 0.34 μs in non-degassed CH 3 CN-H 2 O mixture) are more superior to its Cl − , CH 3 CN − , and t -BuNC-ligated analogues (≤2.98 × 10 −3 and ≤0.32 μs respectively in degassed CH 3 CN)31.…”

Acylruthenium Complexes from Reactions of RuCl2(PPh3)3 with Terminal Alkynes

“…There are only several examples of anti‐Markovnikov hydration of terminal alkynes involving ruthenium complexes without a half‐sandwich structure . These six‐coordinated complexes [Ru([9]aneS3)(bpy)(H 2 O)] 2+ ([9]aneS3=1,4,7‐trithiacyclononane, bpy=2,2’‐bipyridine), mer,trans ‐(PNP)RuCl 2 (PPh 3 ) (PNP=CH 3 CH 2 CH 2 N(CH 2 CH 2 PPh 2 ) 2 ), [Ru(bpy) 2 (H 2 O) 2 ] 2+ and [Ru(bpy*) 2 (H 2 O) 2 ] 2+ (bpy*=4,4’‐di‐ tert ‐butyl‐2,2’‐bipyridine), and cis ‐[Ru(bpy) 2 (H 2 O)Cl] +[12d] contain either a tridentate or a bidentate ligand. Anti‐Markovnikov hydration assisted by complexes with only monodentate ligands has not been demonstrated.…”

Ruthenium‐Induced Cyclization of Heteroatom‐Functionalized Alkynes: Progress, Challenges and Perspectives

“…Around the same time, Wong and co‐workers initiated a project to synthesize metalated heterocyclic complexes through metal‐induced cycloisomerization of heteroatom‐functionalized alkynes, and isolated some Ru–heterocyclic complexes arising from the “non‐vinylidene‐involving” pathways. In 2013 and 2014, they isolated Ru–indolizine complexes 7 from the reactions between pyridine‐substituted propargylic alcohols HC≡CC(OH)(2‐py)R ( S7 ) and Ru II precursors [Ru([9]aneS3)(bpy)(OH 2 )] 2+ and [Ru([14]aneS4)Cl 2 ] (Scheme ; [9]aneS3=1,4,7‐trithiacyclononane, [14]aneS4=1,4,8,11‐tetrathiacyclotetradecane) . For comparative studies, non‐pyridine‐substituted propargylic alcohol S8 was employed to react with the same Ru precursors, and the vinylidene‐derived products Ru–acyl complex 8 a and Ru–carbene complexes 8 b were obtained.…”

“… Potential energy surfaces calculated at the DFT level for the formation of 7 a via 5‐endo‐dig cyclization (blue) and Ru–vinylidene species 7 v via 1 , 2‐H shift (red) from Ru–alkyne π‐intermediate 7π . [Ru]=[Ru([9]aneS3)(bpy)] 2+ ; solvent=H 2 O …”