Synthesis and Characterization of Rare-Earth Metal Complexes Bearing a 2-N,N-Dimethylamino-Ethylene-Imino-Functionalized Indolyl Ligand and Their Catalytic Activities Toward Hydrosilylation of Imines

Abstract

The reactions of 2-N,N-dimethylamino-ethylene-imino-functionalized indolyl proligand 2-(Me 2 NCH 2 CH 2 N = CH)C 8 H 5 NH (HL) with [(Me 3 Si) 2 N] 3 RE(μ-Cl)Li(THF) 3 in toluene afforded a series of rare-earth metal amido complexes [κ 3 -(N,N,N)-2-(Me 2 NCH 2 CH 2 N = CH)C 8 H 5 N]RE[N(SiMe 3 ) 2 ] 2 (RE = Y (1a), Nd (1b), Sm (1c), Gd (1d), Dy (1e), Er (1f), and Yb (1g)). While the reaction of HL with [(Me 3 Si) 2 N] 3 Eu(μ-Cl)Li(THF) 3 produced the europium(II) complex in a dimeric form [{(η 5μ-η 1 :η 2), which is believed to have happened through the homolysis of the Eu−N bond. Further reaction of complex 1a with PhCH�NPh provided an unexpected rare-earth metal complex [κ 2 -(N,N)-PhN{PhCH(CH 2 SiMe 2 )}N(SiMe 3 )]YL (7) through the sp 3 C−H bond activation of the methyl on the silicon atom to form a Y−C bond followed by the insertion of the C�N bond of the imine PhCH�NPh to form an amido group connected to the central metal. All complexes were characterized by spectroscopic methods, elemental analyses, and single-crystal X-ray diffraction, and complexes 1a−1c and 7 were additionally characterized by NMR spectroscopy. The catalytic performance of complexes 1a−1g for the hydrosilylation of imines was investigated, and the catalytic mechanism was proposed based on the experimental results.

Synthesis and Reactivity of the Rare-Earth Metal Complexes Bearing the Indol-2-yl-Based NCN Pincer Ligand

“…Transition metal complexes with pincer ligands have been successfully utilized to catalyze a wide variety of transformations. − Chiral pincer metal complexes are used in asymmetric catalytic reactions . Rare-earth metal pincer complexes have been demonstrated to exhibit excellent performance in the activation of small molecules like H 2 , CO, and silanes, , the catalytic conversion of unsaturated organic substrates, − the and regioselective and stereoselective catalytic polymerization of conjugated dienes …”

“…Based on the multicoordination modes and nonsymmetric motif of the indolyl skeleton and the easy regulation of the pincer ligands, different NCN, NCO, and NCC pincer proligands (Scheme ) and corresponding complexes were designed and synthesized. These complexes showed excellent catalytic performance in olefin polymerization, c hydroboration of nitriles, a and hydrosilylation of imines. c Recently, it was found that 1,3-functionalized indole can form the indol-2-yl-based NCN pincer rare-earth complexes, which exhibited excellent activity toward the hydrosilylation of terminal olefins; however, the reactivity of the nonsymmetric pincer rare-earth metal complexes toward organic compounds has received less attention. Thus, a series of pincer rare-earth metal dialkyl complexes bearing 1,3-functionality indolyl skeletons were synthesized, and their reactivity toward various organic compounds and o -carborane has been explored with the disclosure of various reactivity patterns, such as sp 2 C–H bond activation, σ -bond metathesis, migration insertion, and homolytic redox reaction.…”

Zinc-Catalyzed Chemoselective Reduction of Nitriles to N-Silylimines through Hydrosilylation: Insights into the Reaction Mechanism

“…Various procedures have been developed for the hydrosilylation of different functional groups such as alkene, ,, alkyne, ,, imine, − carbonyls, and carboxylic derivatives. − Additionally, there are numerous reports on catalytic double hydrosilylation of nitriles to 1,1-disilylamines. ,, However, partial mono-hydrosilylation of nitriles to N-silyl aldimines remains a significant challenge. Due to N-silylimines being much more reactive than nitriles, these are further reduced to give the disilylamine products. ,, In addition, N-silylimines are very unstable . These N-silylated imines are suitable precursors in medicinal chemistry, nitrogen-containing organic compounds, and silicon-containing polymers. , N-silylimines are key intermediates for further functionalization .…”