N-Heterocyclic Carbene (NHC) Complexes of Rhodium and Iridium

Lee, Joo-Yeon; Yoo, Changho; Kwak, Jaesung; Kim, Min

doi:10.1016/b978-0-12-820206-7.00085-8

Cited by 1 publication

(2 citation statements)

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“…We selected two well-known imidazole-based NHC precursors ( L 1 and L 2 ) decorated with two pendant picolyl donor arms (Scheme ). These NHCs have already been used for the synthesis of various transition metal complexes, many of which showed good catalytic activity in various organic transformations. ,, Hence, we synthesized 1,3-bis(pyridin-2-ylmethyl)-1 H -imidazolium hexafluorophosphates ( L 1 and L 2 ) as NHC precursors by using a slightly modified literature procedure (Scheme ). Imidazolium chloride salts were prepared by reacting imidazole or substituted imidazole with 2-(chloromethyl)-pyridine hydrochloride in the presence of a base under reflux.…”

Section: Resultsmentioning

confidence: 99%

“…NHCs are widely used electron-rich ligands in homogeneous catalysis with transition metals due to the accessibility of a wide range of topologies with adjustable electronic and steric properties . In the past 20 years, various noble metal catalysts (Ru, Rh, Ir, and Pt) equipped with various NHCs have been utilized for the hydrosilylation of alkynes. Among base metals, a copper–NHC complex and several cobalt–NHC complexes ,,, showed catalytic activity for alkyne hydrosilylation.…”

Section: Introductionmentioning

confidence: 99%

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Hydrosilylation of Terminal Alkynes Catalyzed by an Air-Stable Manganese–NHC Complex

et al. 2023

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In recent years, catalysis with base metal manganese has received a significant amount of interest. Catalysis with manganese complexes having N-heterocyclic carbenes (NHCs) is relatively underdeveloped in comparison to the extensively investigated manganese catalysts possessing pincer ligands (particularly phosphine-based ligands). Herein, we describe the synthesis of two imidazolium salts decorated with picolyl arms (L 1 and L 2 ) as NHC precursors. Facile coordination of L 1 and L 2 with MnBr(CO) 5 in the presence of a base resulted in the formation manganese(I)−NHC complexes (1 and 2) as an air-stable solid in good isolated yield. Single-crystal X-ray analysis revealed the structure of the cationic complexes [Mn(CO) 3 (NHC)][PF 6 ] with tridentate N,C,N binding of the NHC ligand in a facile fashion. Along with a few known manganese(I) complexes, these Mn(I)−NHC complexes 1 and 2 were tested for the hydrosilylation of terminal alkynes. Complex 1 was proved to be an effective catalyst for the hydrosilylation of terminal alkynes with good selectivity toward the less thermodynamically stable β-(Z)-vinylsilanes. This method provided good regioselectivity (anti-Markovnikov addition) and stereoselectivity (β-(Z)-product). Experimental evidence suggested that the present hydrosilylation pathway involved an organometallic mechanism with manganese(I)−silyl species as a possible reactive intermediate.

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Section: Resultsmentioning

confidence: 99%