Indium complexes incorporating bidentate substituted pyrrole ligand: Synthesis, characterization, and ring-opening polymerization of ε-caprolactone

The reactions of InCl3 with two and three equivalents of lithium (2-dimethylaminomethyl)pyrrolate (1) in diethyl ether solutions afford In[C4H3N(CH2NMe2)]2Cl (2) and In[C4H3N(CH2NMe2)]3 (3) in 92% and 50% yield, respectively. Subsequent reactions of 2 with MeLi and Li(CCPh) yield In[C4H3N(CH2NMe2)]2Me (4) and In[C4H3N(CH2NMe2)]2(CCPh) (5), respectively. All compounds were confirmed by 1H and 13C NMR spectroscopy and compounds 3, 4, and 5 were further characterized by single-crystal X-ray crystallography. Compounds 2, 3, and 4 showed moderate catalytic activity toward the ring-opening polymerization of ε-caprolactone.

Graphical abstractCompounds In[C4H3N(CH2NMe2)]2Cl (2) and In[C4H3N(CH2NMe2)]3 (3) were synthesized from the reactions of lithium (2-dimethylaminomethyl)pyrrolate (1) with InCl3 in 1:2 or 1:3 ratio. Further reacting 2 with MeLi and Li(CCPh) afforded In[C4H3N(CH2NMe2)]2Me (4) and In[C4H3N(CH2NMe2)]2(CCPh) (5), respectively. Compounds 2, 3, and 4 showed moderate catalytic activity toward the ring-opening polymerization of ε-caprolactone.Figure optionsDownload full-size imageDownload as PowerPoint slide