Remarkable effect of alkali metal on polymerization of cyclic esters catalyzed by samarium–alkali metal multinuclear alkoxide clusters

Abstract

The remarkable effect of alkali metal on catalytic reactivity of samarium-alkali metal multinuclear alkoxide clusters is systematically studied. Three samarium-alkali metal multinuclear alkoxide clusters are synthesized in high yield by the reaction of anhydrous SmCl(3) with different molar ratios of alkali metal alkoxide and MOH (M = Na or K) in tetrahydrofuran (THF). These clusters were fully characterized by elemental analysis, IR, (1)H NMR and single-crystal structural analysis. These clusters exhibited good catalytic activity for the ring-opening polymerization of ε-caprolactone (ε-CL), L-lactide (L-LA) and trimethylene carbonate (TMC). It is interesting to note that the catalytic activity is much influenced by the alkali metals of the clusters. For the polymerization of these cyclic esters, the catalytic activities all increase with the increase of the molar ratio of alkali metal to samarium metal.

Alkali-Metal-Mediated Synergistic Effects in Polar Main Group Organometallic Chemistry

“…42 The heterobimetallic product [(THF) 11) can all act as single component initiators for ringopening polymerization of the cyclic ester monomers εcaprolactone (ε-CL), L-lactide (L-LA), and trimethylene carbonate. 43 An interesting sodium−potassium synergistic effect is observed when comparing activities as for example the hetero potassium−sodium cluster 14 could polymerize 15 000 equiv of ε-CL in 1 min at 25 °C, and the polymer yield could still reach 66% when the monomer/initiator ratio increased to 20 000, whereas the homometallic potassium and sodium clusters 12 and 13 gave much lower activities with the desired results at 25 °C only achieved when the molar ratio of monomer/initiator is decreased to 10 000 or 6000 respectively. However, this increased activity also correlates with an increase in the alkali metal/samarium molar ratio.…”

“…The homoalkali-metal samarium cluster complexes [Sm 4 K 2 O­(OCH 2 CH 2 NMe 2 ) 26 ­(OH) 6 ] ( 12 ), and [Sm 2 Na 8 ­(OCH 2 CH 2 NMe 2 ) 12 ­(OH) 2 ] ( 13 ), and the heteroalkali-metallic analogue [Sm 2 K 12 Na 4 ­(OCH 2 CH 2 NMe 2 ) 18 ­(OH) 4 ] ( 14 , Figure ) can all act as single component initiators for ring-opening polymerization of the cyclic ester monomers ε-caprolactone (ε-CL), l -lactide (L-LA), and trimethylene carbonate …”

Magnesium complexes containing biphenyl-based tridentate imino-phenolate ligands for ring-opening polymerization of rac-lactide and α-methyltrimethylene carbonate

“…Various types of metal-based catalysts [49][50][51][52][53][54][55] are also known to be efficient initiators for the ROP of trimethylene carbonate (TMC). Unfortunately, polymerizations of similar chiral cyclic carbonates, for instance, α-methyltrimethylene carbonate (α-MeTMC), have scarcely been explored.…”

Large Heterometallic Dy12Na6 Cage-like Cluster Supported by in Situ Generated Ligand

“…Inspired by the quest of a new system for a heterometallic cluster, researchers attempted to introduce AM ions into a lanthanide cluster for generating innovative AM-Ln clusters with fascinating properties. Representative cases for the reported AM-Ln clusters are K 20 Sm 4 , 15 ) clusters, the development of AM-Ln cluster is still in its infancy.…”

“…Inspired by the quest of a new system for a heterometallic cluster, researchers attempted to introduce AM ions into a lanthanide cluster for generating innovative AM-Ln clusters with fascinating properties. Representative cases for the reported AM-Ln clusters are K 20 Sm 4 , Na 6 Eu 9 , NaLn 12 , NaCe 10 . However, compared with the large nuclearity and fascinating structures in TM-Ln (e.g., La 76 Ni 60 , Cu 36 Ln 24 4 ) and TM-TM′ (e.g., Mn 36 Ni 4 , 5 Cu 17 Mn 28 6 ) clusters, the development of AM-Ln cluster is still in its infancy.…”