25th Anniversary of Molecules—Recent Advances in Green Chemistry

Abstract

Green Chemistry has been defined by the EPA as the design of chemical products and processes that reduce or eliminate the use or generation of hazardous substances [...]

Revisiting Stereoselective Propene Polymerization Mechanisms: Insights through the Activation Strain Model

“…We have reported earlier on stereoselectivity of this system [48] and several of its variations. [29] Propagation happens at a single site of the catalyst, and unlike the other systems studied here there is only a single TS for irregular insertion (Figure S2).…”

“…Of this broad range, only 3 produces syndiotactic PP (sPP), while the other five produce iPP. A computational analysis of stereoelectronic factors responsible for the stereoselectivity of system 5 by our combined DFT/ASM−NEDA approach has already been reported [28,29] . Parts of those results will be repeated here for completeness and comparison.…”

“…A computational analysis of stereoelectronic factors responsible for the stereoselectivity of system 5 by our combined DFT/ASMÀ NEDA approach has already been reported. [28,29] Parts of those results will be repeated here for completeness and comparison. For system 5, the active species model used contains the original pyridylamide ligand modified by monomer insertion into the HfÀ C aryl bond (see the red part of 5 in Scheme 2).…”

%VBur index and steric maps: from predictive catalysis to machine learning

“…And still in polymerization, Talarico and coworkers in 2023 combined the steric maps and %V Bur concepts with the energy decomposition analysis using the associated activation strain model (ASM) and this led to unveil the origins of the stereoselectivity for propene polymerization promoted by pyridylamido-type nonmetallocene systems. 281 The correlation between the precise modification of the ligand and the resulting stereoregularity in propene derived polymers was systematically elucidated. This encompassed factors such as the size of the metallacycle, the nature of the bridge within the molecule, and the substituents located at the ortho-position of the aniline fragments.…”

Predicting the propene stereoselectivity on transition metal catalysts: A daunting task for density functional theory

“…13 System III is a stereorigid tetradentate system (ONNO) 14 whose octahedral coordination environment is similar to that of traditional heterogeneous ZN systems used industrially and polymerizes iPP with a percentage of mm triads of 87%. 15,16 System IV, a pyridylamido-Hf complex, 17 displays several unusual features because it undergoes in situ ligand modification by the monomer, [18][19][20][21][22][23] which leads to the formation of an active species characterized by a C 1 -symmetry and high level of isoselectivity ([mmmm] 4 = 91%). 17 The mechanistic aspects of propene polymerization promoted by the aforementioned catalysts have been thoroughly investigated by means of quantum chemical (QC) computations rooted in the density functional theory (DFT).…”