Novel hybrid aluminium(iii)–catalen complexes as highly active catalysts for lactide polymerisation: towards industrial relevance

Abstract

A series of novel Al(iii) complexes are prepared that show remarkable activity under the industrially preferred conditions.

Make or break: Mg(ii)- and Zn(ii)-catalen complexes for PLA production and recycling of commodity polyesters

“…Interestingly, a highly unusual tetrameric Mg(II)-complex based on an amine-deprotonated derivative of 2H 2 was isolated and characterised by XRD (Fig. 2 35 Polymerisation of rac-LA All Zn(II)-and Mg(II)-complexes were trialled in the ROP of rac-LA under solvent-free conditions (130 and 180°C) in alignment with industrial practices (Table 1). Industrially, solvents are a significant source of waste and thus catalysts that operate under melt conditions are highly desirable.…”

“…3,[10][11][12][13][14] Recent research has primarily sought to address toxicity concerns associated with the industry standard, Sn(Oct) 2 , through the development of biocompatible and environmentally benign alternatives. [15][16][17] Consequently, a diverse range of metals have been explored, including Al(III) [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] and group(IV), [36][37][38][39][40][41][42][43][44][45][46][47][48][49] with a particular focus on retaining activity whilst maintaining stereocontrol. Metals most pertinent to this report include Zn(II) and Mg(II), which are cheap and non-toxic.…”

“…124 We recently reported a series of highly active Al(III)-complexes supported by a catalen framework for lactide polymerisation, observing unprecedented activity in the melt. 35 However, these complexes are inactive for PLA methanolysis.…”

Synthesis of Biodegradable Polymers: A Review on the Use of Schiff-Base Metal Complexes as Catalysts for the Ring Opening Polymerization (ROP) of Cyclic Esters

“…In this regard, systems based on alkaline-earth metals, as well as zinc and iron are highly attractive and, as demonstrated in this review, are drawing increasing attention. Nevertheless, only limited examples [71,78,108] are capable of affording polymers with sufficiently high M n to be industrially relevant. The use of such benign metals in combination with multidentate or macrocyclic ligands can access new families of homo-and hetero-multinuclear species showing enhanced performances due to cooperative effects [109,140].…”

“…Early reports mainly concerned chiral- [98][99][100] and achiral [101][102][103][104] Salen complexes, while Salalen [105,106] or related systems [107] have been subsequently introduced. Very recently, a set of Al catalysts bearing a novel Catalen scaffold has been reported by the group of Jones [108]. One of these systems exhibited the highest activity known to date for an Al complex in the melt ROP of r-LA.…”