Alkaline earth metal complexes of a chiral polyether as initiator for the ring-opening polymerization of lactide

Abstract

A chiral, tetradentate polyether ligand with a trans-1,2-cyclohexanediyl backbone, bis(methoxyethoxy)-trans-1,2-cyclohexane (5), was synthesized as both a racemate and the (S,S) enantiomer. 5 was found to form stable adducts with alkaline earth metal amides [M{N(SiMe(3))(2)}(2)(thf)(x)] (M = Mg (x = 0), Ca (x = 2) and Sr (x = 2/3)), [Ca{N(SiHMe(2))(2)}(2)(thf)] as well as with hydrocarbyl compounds [Mg(CH(2)SiMe(3))(2)] and [Ca(η(3)-C(3)H(5))(2)]. X-ray diffraction study of the bis(amide) [((S,S)-)Ca{N(SiMe(3))(2)}(2)] and of the bis(allyl) [(rac-5)Ca(η(3)-C(3)H(5))(2)] was performed. The complexes obtained were tested as initiators for the ring-opening polymerization of meso-, racemic and L-lactide.

Ring-opening polymerization of lactides by (pyrazol-1-ylmethyl)pyridine Zn(II) and Cu(II) complexes: Kinetics, mechanism and tacticity studies

“…4). Reports of Buffet et al 30 sharply contrast our results as they recorded molecular weights of 18 000 g mol -1 and 10 750 g mol -1 for poly(D,L-LA) and poly(L-LA), respectively. Consistent with living polymerization behaviour, molecular weights increased with percentage con-RESEARCH ARTICLE S.O.…”

Ring-opening polymerization of rac-lactide mediated by tetrametallic lithium and sodium diamino-bis(phenolate) complexes

“…Variation of the steric properties of the ligand is also readily achieved by changing either the backbone and/or the phenolate substituent. 15 To initiate the polymerization of lactide and ε-caprolactone, main group metals are often employed with these ligands: magnesium, [16][17][18][19][20][21][22][23][24][25][26][27] calcium, 16,26,28 barium, 29 aluminum [30][31][32][33][34][35] and indium 36,37 have all been used. In addition, alkali metals such as lithium 26,[38][39][40][41][42][43][44][45][46][47][48][49][50] and sodium 26,[50][51][52][53][54] bearing bulky ligands have shown promise in ROP of cyclic esters with few side reactions.…”

Synthesis and characterization of group 4 metal alkoxide complexes containing imine based bis-bidentate ligands: effective catalysts for the ring opening polymerization of lactides, epoxides and polymerization of ethylene

“…Bis( phenolate) complexes (salen, salan, salalen) of group 4 metals have had and continue to play an important role in the synthesis of PLA in a controlled and stereoselective manner. 6 Several complexes of tin, 7 lanthanides, 8 aluminium, 9 lithium, 10 magnesium, 11 calcium, 12 iron, 13 zinc, 14 bismuth, 15 group 4 metals 6a,16-18 as well as small organic molecules like ammonium betaines 19 and N-heterocyclic carbenes (NHCs) 20 have been reported to be initiators for the ROP of lactides and cyclic esters. 21 The ROP of epoxides has also attracted considerable interest because of its large commercial value.…”