Synthesis, characterization of bulky aluminium alkoxide and application in the ring-opening polymerization of ε-Caprolactone

The reaction of 2,2′-dihydroxy-3,3′,5,5′-tetra-tert-butyl-1,1′-diphenyl (TBBP-H2) with AlMe3 in tetrahydrofuran gives [(TBBP)Al(CH3)(THF)] (1) in high yield. 1 further reacts with 2-propanol to afford dimeric aluminium complex [(TBBP)Al(μ-OiPr)]2 (2). Catalytic studies of complex 2 indicate that 2 can efficiently initiate the ring-opening polymerization of ε-Caprolactone under a controlled manner, yielding polymers with narrow molecular weight distribution.

Graphical abstractThe reaction of 2,2′-dihydroxy-3,3′,5,5′-tetra-tert-butyl-1,1′-diphenyl (TBBP-H2) with Al(Me)3 and iPrOH in a ratio of 1:1:1:1 in n-hexane gives complex of [(TBBP)Al(μ-OiPr)]2 (2). Experimental results show that complex 2 is an efficient catalyst for the ring-opening polymerization of ε-Caprolactone with “living” and “immortal” characters.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Aluminium complexes supported by TBBP2− ligand have been prepared and fully characterized. ► Fine crystals 1 and 2 were obtained by crystallization from THF and toluene. ► Complex 2 catalyzes the polymerization of ε-Caprolactone with “living” and “immortal” characters.