Rare-Earth Metal Complexes Supported by 1,3-Functionalized Indolyl-Based Ligands for Efficient Hydrosilylation of Alkenes

Abstract

Two different 1,3-functionalized indolyl-based proligands 1-(2-C 4 H 7 O)CH 2 -3-(2-t BuC 6 H 5 N�CH)C 8 H 5 N (HL 1 ) and 1-Me 2 NCH 2 CH 2 -3-(2-i PrC 6 H 5 N�CH)C 8 H 5 N (HL 2 ) were designed, prepared in high yields, and successfully applied to rare-earth metal chemistry showing different reactivities and different bondings with the central metals. The reactions of HL 1 with RE(CH 2 SiMe 3 ) 3 (THF) 2 provided two types of rare-earth metal complexes: the pincer type mononuclear complexes κ 3and the dinuclear rare-earth metal alkyl (per alkyl/per metal) complexes having the ligand in novel coordination modes {(η 1 :(μ-η 2 :η 1 ): 4), Dy(5), and Gd( 6)]. Meanwhile, the reactions of HL 2 with RE(CH 2 SiMe 3 ) 3 (THF) 2 led to the isolation and characterization of only the mononuclear rare-earth metal dialkyl complexes κ 3 -(L 2 )RE(CH 2 SiMe 3 ) 2 [L 2 = 1-Me 2 NCH 2 CH 2 -3-(2-i PrC 6 H 5 N�CH)C 8 H 4 N, RE = Lu(7), Gd(8)] bearing the ligand in the pincer chelate form. The mononuclear complexes were formed through the sp 2 C−H activation of the 2-indolyl moiety, while the dinuclear complexes were produced unexpectedly through the tandem 2-indolyl sp 2 C−H activation and C�N insertion into the RE− CH 2 SiMe 3 bond. These complexes were fully characterized by spectroscopic methods, elemental analyses, and single-crystal X-ray crystallography. The applications of the synthesized complexes as catalysts for the hydrosilylation of terminal alkenes with phenylsilane are described. Anti-Markovnikov addition products were produced by the hydrosilylation of aliphatic olefins, and Markovnikov addition products were isolated with aromatic olefins with high selectivity in the absence of cocatalysts. It is found that the dinuclear rare-earth alkyl complexes exhibited the best catalytic activity with the advantages of mild reaction conditions, short reaction time, low catalyst loading, and wide substrate applicability in comparison with the synthesized mononuclear complexes and the reported catalysts.

Tandem Synthesis of Linear Hydridopolycarbosilanes and Postfunctionalization by a Calcium Catalyst

“…A reaction that can form element–element bonds with extremely high conversion and high specificity is a prerequisite for the synthesis of polymers with high molecular weights by the step-growth polyaddition approach. Catalytic hydrosilylation of hydrosilanes and olefins to form Si–C bonds is one such reaction and has been well studied with a variety of catalysts, − including lanthanide, ,− actinide, , and transition-metal − ,,, and main group-metal complexes. , Thus, the precise stoichiometry reactions between hydrosilanes and olefins catalyzed by complex 1 were examined first. As shown in Table , aliphatic olefin (1-hexene) is regioselectively hydrosilylated to give anti-Markovnikov products (Table , runs 1 and 2, see Figure S26 in Supporting Information (SI)).…”

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

“…NCH 2 CH 2 -3-(2-i PrC 6 H 5 N�CH)C 8 H 4 N)] (Scheme 3, Figure 1), where complex 1a (Lu) was reported previously. 33 In the 1 34 but obviously shifted to downfield compared to that of the resonance of the C 2-ind of the proligand (δ = 151.5 ppm). 33 While the resonance of the C 2-ind in 1a was observed at 211.4 ppm.…”

“…33 In the 1 34 but obviously shifted to downfield compared to that of the resonance of the C 2-ind of the proligand (δ = 151.5 ppm). 33 While the resonance of the C 2-ind in 1a was observed at 211.4 ppm.…”

Rare-Earth-Catalyzed Regiodivergent Hydrosilylation of Aryl Alkenes

“…Thus, the previous researchers, e.g. Marks, Molander, Hou, Okuda Cui, and Wang, have conducted independently important work in rare-earth metal-catalyzed Markovnikov hydrosilylation of aryl alkenes.…”