Rare-earth metal-promoted (double) C–H-bond activation of a lutidinyl-functionalized alkoxy ligand: formation of [ONC] pincer-type ligands and implications for isoprene polymerization

Abstract

Steric pressure enforces the formation of dianionic and trianionic pincer-type ligands involving a rare alkylidene moiety in the latter case.

Catalytic Behavior of Cobalt Complexes Bearing Pyridine–Oxime Ligands in Isoprene Polymerization

“…The solvent was removed in the rotary evaporator and the product was dried under vacuum to give ligand. All the 1 H NMR and 13 C NMR of ligands were collected on a Bruker Avance III 400 MHz instrument (Bruker, Karlsruhe, Germany) at 298K, using tetramethyl silane (TMS; CIL, Andover, MA, USA) as internal standard.…”

“…L2: yellow solid, 2.1 g, 90% yield; 13 C NMR (100 MHz, CDCl 3 , 298 K) δ 151.5, 149.5, 149.0, 136.2, 123.9, 121.0, 62.4.…”

“…The polymer structure was analyzed by NMR spectra conducting on a Bruker Advance 400 spectrometer at 298 K. 1 H NMR (400 Hz, CDCl 3 ) and 13 C NMR spectra (100 Hz, CDCl 3 ) of polyisoprene were recorded by using trimethylsilane as internal reference. The polyisoprene microstructure of the 1,4 and 3,4 ratio was determined from 1 H NMR of the 1,4 =CH signals at 5.15 ppm and the 3,4 =CH 2 signal at 4.7 ppm.…”

“…To improve the activity of the transition metal catalyst, a variety of ligands containing pyridine, imine, phosphine and phenolate moieties have been applied to modify the electronic and steric environment at the metal's center. And, it has been proven that the ancillary ligand plays an important role in the catalytic process and polymer properties [12][13][14][15][16][17][18]. Therefore, much research has been focused on cobalt catalyst, which is known as the most versatile catalyst among the various transition metals, and has characteristics of low cost, high stability and easy preparation.…”

Stepwise Coordination Assembly Approach toward Aluminum-Lanthanide-based Compounds

“…Aluminum-lanthanide-based (Al-Ln) compounds can be used as precursors to prepare highly phase-pure uniform-size oxide-based materials such as LnAlO 3 perovskite and thin films. − Besides this, the synthesis and determination of crystalline Al-Ln-based complexes have received much interest for the luminescent and catalytic properties of the complexes. ,− Heteropentanuclear compounds [Al 3 (Mq) 4 (HMq)­(μ 3 –OH) 2 (μ–OH) 3 {Ln­(hfac) 3 } 2 ] (Mq = 2-methyl-8-hydroxylquinolinate; hfac = hexafluoroacetylacetonate) possess fluoride-enhanced Ln luminescence and white-light emission . By reacting LAlOH­(Me) (L = HC­(CMeNAr) 2 , Ar = 2,6- i Pr 2 C 6 H 3 ) with Cp 3 Ln compounds, Roesky and co-workers synthesized a new class of compounds containing an Ln–O–Al moiety with good catalytic activity for the polymerization of ε-caprolactone .…”