Aluminum complexes with Schiff base bridged bis(indolyl) ligands: synthesis, structure, and catalytic activity for polymerization of rac-lactide

Abstract

A series of aluminum complexes with Schiff base bridged indolyl ligands were synthesized as rac-lactide polymerization catalysts.

Alkoxy-Functionalized Schiff-Base Ligation at Aluminum and Zinc: Synthesis, Structures and ROP Capability

“…Looking at the zinc complexes (Table 3, entries 5-8), it is evident that 5 bearing Schiff-base ligands with 3,4,5-methoxy substituents is also the most effective catalyst in terms of rate, molecular weight and control. In general, polymers catalyzed by the zinc complexes 5 _ 8 possessed very narrow distributions (PDI: 1.03-1.18), indicating less transesterification during the polymerization process [26]. Complex 5 bearing the 3,4,5-methoxy substituents exhibited better activity than did 6 with 2,4,6-methoxy substituents, 7 with 2,4-methoxy substituents and 8 without any methoxy substituents, as was seen for the organoaluminum complexes.…”

“…Anal. Calcd for C 26 The synthesis of 4 was carried out following the previous report [25]. A mixture of L 4 H (3.68 g, 11.89 mmol) and AlMe 3 (6 mL, 12.00 mmol) in toluene (20 mL) was stirred for 12 h at 150 • C. Volatile materials were removed under vacuum to give yellow needle crystals, and then acetonitrile (20 mL) was transferred to the suspension.…”

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

“…This topic has been described in depth in recent reviews, not only from the catalyst design point of view, but also with respect to scope of monomer [96,97]. 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].…”

Mechanism of Initiation Stereocontrol in Polymerization of rac-Lactide by Aluminum Complexes Supported by Indolide–Imine Ligands

“…Recently, we reported predictions by theory of cyclic ester polymerization efficiency for a series of aluminum catalysts, including the complex L 7 AlOBn supported by a novel analog of salen incorporating indolide arms connected at their 7position (Figure 1). 5 Subsequent synthesis of L 7 AlOBn and studies of the kinetics of ROTEP of ε-caprolactone by the complex confirmed the prediction, validating the theoretical approach toward catalyst design. In that work, the X-ray crystal structure of the complex revealed a chiral structure with the ligand twisted such that the indolide rings are inequivalent.…”

“…NMR spectroscopy showed the rings to be equivalent, however, suggesting operation of a fluxional process in solution. In view of these structural attributes and analogies to efficacious (salen)AlOR systems (for example, (TBSsalen)-AlOR, with Y = CH 2 CMe 2 CH 2 , R 1 = H, R 2 = tBuMe 2 Si), 4n we hypothesized that L 7 AlOBn might exert stereocontrol in ROTEP of rac-LA.…”