Heterobimetallic aluminate derivatives with bulky phenoxide ligands: a catalyst for selective vinyl polymerization

Abstract

New aluminates as active catalysts for vinyl polymerization are described, as well as a strategy to crosslinked polymers from GMA in a controlled fashion.

Alkali‐Metal Mediation: Diversity of Applications in Main‐Group Organometallic Chemistry

“…Considering that alkali metals are non-toxic and found in the human body (especially Na and K), catalysts based on these innocuous metals are very attractive, since traces of the catalyst used can remain in the polymer; depending on which metal is present, this can potentially lead to harmful effects. Within the past two decades several suitable complexes for the ringopening polymerization of lactide have been reported and some general trends have been observed, such as the reactivity of the catalysts increases on descending the first main group from Li to Na to K. [42][43][44][45][46][47][48][49][50][51][52][53] This is attributed mainly to the larger size of the metal facilitating coordination of the substrate. However, the opposite trend is observed with regard to selectivity, as it decreases from Li to Na to K. [50,51,54] The lower Lewis acidity and the resulting weaker bond to the substrate can prevent the growth of long and defined polymeric chains.…”

“…One side is confined by a bulky ligand, which forms an ionic bond to the metal. Typically applied ligand classes incorporate oxygen [42–48, 53, 55–60] or nitrogen donors, [49, 61] or a combination of both types [50, 51, 54, 62–64] . Catalysts with electron richer ligands showed higher catalytic activity; [62, 63] whereas more steric bulk around the metal had a detrimental influence on the performance [46] .…”

“…Another important research area where alkali-metal catalysts are frequently applied is in the polymerization of lactide.P olylactide is non-toxic, biodegradable,a nd biocompatible. It is used widely in fields such as agriculture,p ackaging,f ood, and medicine.C onsidering that alkali metals are non-toxic and found in the human body (especially Na and K), catalysts based on these innocuous metals are very attractive, since traces of the catalyst used can remain in the polymer;d epending on which metal is present, this can potentially lead to harmful effects.W ithin the past two decades several suitable complexes for the ringopening polymerization of lactide have been reported and some general trends have been observed, such as the reactivity of the catalysts increases on descending the first main group from Li to Na to K. [42][43][44][45][46][47][48][49][50][51][52][53] This is attributed mainly to the larger size of the metal facilitating coordination of the substrate.H owever,t he opposite trend is observed with regard to selectivity,asitdecreases from Li to Na to K. [50,51,54] Thelower Lewis acidity and the resulting weaker bond to the substrate can prevent the growth of long and defined polymeric chains.T oo vercome this drawback, ag eneral catalyst design has been developed, which is depicted in Figure 4a.T he idea is to sandwich the catalytically active centre between the two planes,thereby embedding the cation in ad efined space to boost the interaction of the monomer and the active end of the polymer chain. One side is confined by ab ulky ligand, which forms an ionic bond to the metal.…”

Main group bimetallic partnerships for cooperative catalysis

“…Showcasing different reactivity profiles to single-metal aluminium initiators, alkali-metal aluminates [M I AlMe 2 (OR) 4 ] (M I = Li, 36a ; Na, 36b ; and K, 36c ; OR = 2,6-bis(diphenylmethyl)-4- tert -butylphenoxide) polymerize difunctional glycidyl methacrylate (GMA) via vinyl polymerization 52 whereas [AlMe 2 (OR) 2 ] promotes the selective polymerization of the oxirane group in GMA via ROP ( Fig. 9 ).…”

Alkalimetall‐Mediatoren: Vielfältige Anwendungen in der metallorganischen Chemie der Hauptgruppenelemente

“…B. ,d ass mit zunehmender Grçbedes Metalls innerhalb der ersten Hauptgruppe (von Li über Na, hinzu K) auch die entsprechende Reaktivität der eingesetzten Katalysatoren zunimmt. [42][43][44][45][46][47][48][49][50][51][52][53] Dies wird hauptsächlich auf die Grçße des Metalls zurückgeführt, da die Koordination des Substrats bei einer grçßeren Oberfläche einfacher ist. Hinsichtlich der Selektivitäti st jedoch ein gegenläufiger Tr end zu beobachten, welche von Li über Na zu K abnimmt.…”