Zinc(II) complexes containing N′-aromatic group substituted N,N′,N-bis((1H-pyrazol-1-yl)methyl)amines: Synthesis, characterization, and polymerizations of methyl methacrylate and rac-lactide

Abstract

A solution of 3,5-dimethylaniline (2.50 mL, 20.0 mmol) in CH 2 Cl 2 (50.0 mL) was slowly added to a solution of 1H-pyrazole-1-methanol (3.93 g, 40.0 mmol) in CH 2 Cl 2 (50.0 mL). The reaction solution was stirred at ambient temperature for 72 h and filtered. The

Synthesis, structures, and catalytic efficiency in ring opening polymerization of rac-lactide with tridentate vs. bidentate cobalt(ii), zinc(ii), and cadmium(ii) complexes containing N-substituted N,N-bis((3,5-dimethyl-1H-pyrazol-1-yl)methyl)amine ligands

“… 87 In comparison with the previously reported Zn( ii ) system bearing N , N ′, N -bis((1 H -pyrazol-1-yl)methyl)amines derivatives as ligands ( P r = 0.95 at −50 °C with 90% conversion), the current system exhibited higher activity and comparable heteroselectivity (97% conversion with P r = 0.94 at −25 °C). 49 Moreover, in comparison with the complexes of the tetradentate N , N , N , N -bis(pyrazolyl)methane ligand with Zn( ii ) and Fe( ii ) ( P r = 0.79) used as catalysts, 88 our system exhibited superior activity and stereoselectivity ( P r = 0.94). Co( ii )-based catalysts previously studied by our group, comprising N , N -bis((3,5-dimethyl-1 H -pyrazol-1-yl)methyl)-3,5-dimethylaniline and N , N -bis((3,5-dimethyl-1 H -pyrazol-1-yl)methyl)-4-methoxyaniline as ligands, afforded PLAs of lower molecular weight and heterotacticity ( P r = 0.81–0.85 at −50 °C) but narrower PDI value range (1.13–1.21).…”

“… 48 In a recently published study conducted by our group, we focused on developing late transition metal complexes based on N , N -bis((1 H -pyrazol-1-yl)methyl)amine derivatives with various amine substituents, and we studied their catalytic performances in the ROP of rac -LA. 49 The catalytic capabilities of these complexes and the stereoselectivity they afforded were promising, and the relevant reactions yielded PLAs of moderate-to-high molecular weight. 50,51 In the present contribution, we intended to study the catalytic properties of N -substituted N , N -bis((3,5-dimethyl-1 H -pyrazol-1-yl)methyl)amine-based Zn( ii ), Co( ii ), and Cd( ii ) complexes in the ROP of rac -LA.…”

Stereoselective polymerization of methyl methacrylate and rac-lactide mediated by iminomethylpyridine based Cu(ii) complexes

“…Efforts have been directed toward decoupling polymeric materials from fossil fuel feedstocks using biological sources 63,64 to decrease the amount of plastic waste ending up in the environment. Our research focuses on the stereoselective ROP of rac-LA, 65,66 the efficacy of iminomethylpyridine based Cu(II) complexes to mediate polymerization of rac-LA and to focus on the role played by the auxiliary ligand on inuencing catalytic efficiency, molecular weight, as well as stereoselectivity. The dimethyl derivatives…”

“…Determined by gel permeation chromatography (GPC) in THF, relative to polystyrene standard (corrected using the Mark-Houwink factor of 0.58). 65,66 e Probability of heterotactic enchainment (P r ) were calculated on the basis of homonuclear decoupled 1 H NMR spectra according to literature. 45,46 The alkyl group then acts as a nucleophile and opens the LA ring (Scheme S1 †).…”

“…For instance, [L E CuCl 2 ] displayed a higher activity with a more exible propylene backbone compared to [L A CuCl 2 ] with the ethylene backbone, despite of having identical dimethyl amine substituents (Table 4, entries 3 and 7). However, [L C CuCl 2 ] (1.80 Â 65,66 e Probability of heterotactic enchainment (P r ) were calculated on the basis of homonuclear decoupled 1 H NMR spectra according to literature. 45,46 This journal is © The which has distortion angles of 73.83 and 77.61 .…”