Versatile organoaluminium catalysts based on heteroscorpionate ligands for the preparation of polyesters

Abstract

A series of alkyl aluminium complexes based on heteroscorpionate ligands were designed as catalysts for the ring-opening polymerisation of cyclic esters and ring-opening copolymerisation of epoxides and anhydrides. Treatment of AlX3 (X = Me, Et) with ligands bpzbeH [bpzbe = 1,1-bis(3,5-dimethylpyrazol-1-yl)-3,3-dimethyl-2-butoxide], bpzteH [bpzte = 2,2-bis(3,5-dimethylpyrazol-1-yl)-1-para-tolylethoxide], and (R,R)-bpzmmH [(R,R)-bpzmm = (1R)-1-{(1R)-6,6-dimethyl-bicyclo[3.1.1]-2-hepten-2-yl}-2,2-bis(3,5-dimethylpyrazol-1-yl)ethoxide] for 2 hours at 0 °C afforded the mononuclear dialkyl aluminium complexes [AlMe2{κ2-bpzbe}] (1), [AlEt2{κ2-bpzbe}] (2), [AlMe2{κ2-(R,R)-bpzmm}] (3) and [AlEt2{κ2-(R,R)-bpzmm}] (4), and the dinuclear dialkyl complexes [AlMe2{κ2-bpzte}]2 (5) and [AlEt2{κ2-bpzte}]2 (6). The molecular structures of the new complexes were determined by spectroscopic methods and confirmed by X-ray crystallography. The alkyl-containing aluminium complexes can act as highly efficient single-component initiators for the ring-opening polymerisation of ε-caprolactone and l-lactide and for the ring-opening copolymerisation of cyclohexene oxide and phthalic anhydride to give a range of biodegradable polyesters.

An Overview of Antibody Conjugated Polymeric Nanoparticles for Breast Cancer Therapy

“…Currently, structurally well-controlled polyesters, like PCL and PLA, FDA-approved polymers for DDS generation, are catalytically generated via ring opening polymerization (ROP) of lactone or lactide rings using organometallic catalysis. Nowadays, new promising strategies based on high technology and tailor-made building-block materials using chemical catalysis are used to obtain biodegradable and biocompatible polymers with controlled physical properties [19]. Recently, some examples of polyesters or polycarbonate architectures for DDS generation are being synthetized via ROP or ring opening copolymerization (ROCOP) [19,20].…”

“…Nowadays, new promising strategies based on high technology and tailor-made building-block materials using chemical catalysis are used to obtain biodegradable and biocompatible polymers with controlled physical properties [19]. Recently, some examples of polyesters or polycarbonate architectures for DDS generation are being synthetized via ROP or ring opening copolymerization (ROCOP) [19,20]. These novel methodologies to generate tailor-made biocompatible polymers are more attractive than the traditional way, facilitating their implementation in the field of nanomedicine.…”

NNNO‐Heteroscorpionate nickel (II) and cobalt (II) complexes for ethylene oligomerization: the unprecedented formation of odd carbon number olefins

“…[1] The catalytic properties of corresponding chromium-based complexes, which selectively trimerize ethylene to 1-hexene, have been studied in sufficient detail. [2][3][4] The use of heteroscorpionate complexes of transition, [5,6] sblock [7,8] and p-block [9,10] metals as catalysts for lactide and ε-caprolactone ring-opening polymerization has also attracted scientific attention in the last decade. At the same time, the heteroscorpionate complexes of the iron triad metals, unlike other N-donor ligands, [11,12] have been studied very superficially in the olefin coupling catalysis.…”

Ring-Opening Copolymerization of Cyclohexene Oxide and Cyclic Anhydrides Catalyzed by Bimetallic Scorpionate Zinc Catalysts

“…Commercial polyester materials are currently produced by polycondensation reactions between diols and diacids at high reaction temperature and prolonged reaction times to afford high-molecular weight polyesters [1,2]. In recent years, a broad range of biodegradable polyesters have been obtained via ring-opening polymerization (ROP) of cyclic esters (Scheme 1a) as a more sustainable alternative to traditional polyester materials [3][4][5][6][7][8][9][10]. In fact, polycaprolactone and polylactide have already been used for several applications [11][12][13][14].…”

“…The ROCOP reaction of epoxides and cyclic anhydrides requires the use of a catalyst system, which is usually comprised by a combination of a metal complex and a nucleophile source [15]. A wide range of metal complexes, including chromium [16][17][18][19][20], magnesium [21][22][23], 2 of 13 cobalt [24][25][26][27][28], manganese [26,29,30], iron [31][32][33][34], aluminum [3,[35][36][37][38][39][40] and zinc [41][42][43][44][45][46][47] has been used as catalysts for this process. Most of these complexes required the use of a cocatalyst such as tetrabutylammonium salts (TBAX), bis-(triphenylphospine)iminium salts (PPNX) or 4-dimethylaminopyridine (DMAP) to increase the efficiency and selectivity of the metal complex [15].…”