TY - JOUR
T1 - Mono(imidazolin-2-iminato) Hafnium Complexes
T2 - Synthesis and Application in the Ring-Opening Polymerization of ε-Caprolactone and rac-Lactide
AU - Khononov, Maxim
AU - Liu, Heng
AU - Fridman, Natalia
AU - Tamm, Matthias
AU - Eisen, Moris S.
N1 - Publisher Copyright:
© 2022 by the authors.
PY - 2022/10
Y1 - 2022/10
N2 - Mono-substituted imidazolinX-2-iminato hafnium(IV) complexes (X = iPr, tBu, Mesityl, Dipp) were synthesized and fully characterized, including solid-state X-ray diffraction analysis. When the X group is small (iPr), a dimeric structure is obtained. In all the monomeric complexes, the Hf-N bond can be regarded as a double bond with similar electronic properties. The main difference among the monomeric complexes is the cone angle of the ligand, which induces varying steric hindrances around the metal center. When the monomeric complex of mono(bis(diisopropylphenyl)imidazolin-2-iminato) hafnium tribenzyl was reacted with three equivalents (equiv) of iPrOH, the benzyl groups were easily replaced, forming the corresponding tri-isopropoxide complex. However, when BnOH was used, dimeric complexes were obtained. When five equivalents of the corresponding alcohols (BnOH, iPrOH) were reacted with the monomeric complex, different dimeric complexes were obtained. Regardless of the high oxophilicity of the hafnium complexes, all complexes were active catalysts for the ring-opening polymerization (ROP) of ε-caprolactone. Dimeric complexes 5 and 6 were found to be the most active catalysts, enabling polymerization to occur in a living, immortal fashion, as well as the copolymerization of ε-caprolactone with rac-lactide, producing block copolymer PCL-b-LAC. The introduction of imidazolin-2-iminato ligands enables the tailoring of the oxophilicity of the complexes, allowing them to be active in catalytic processes with oxygen-containing substrates.
AB - Mono-substituted imidazolinX-2-iminato hafnium(IV) complexes (X = iPr, tBu, Mesityl, Dipp) were synthesized and fully characterized, including solid-state X-ray diffraction analysis. When the X group is small (iPr), a dimeric structure is obtained. In all the monomeric complexes, the Hf-N bond can be regarded as a double bond with similar electronic properties. The main difference among the monomeric complexes is the cone angle of the ligand, which induces varying steric hindrances around the metal center. When the monomeric complex of mono(bis(diisopropylphenyl)imidazolin-2-iminato) hafnium tribenzyl was reacted with three equivalents (equiv) of iPrOH, the benzyl groups were easily replaced, forming the corresponding tri-isopropoxide complex. However, when BnOH was used, dimeric complexes were obtained. When five equivalents of the corresponding alcohols (BnOH, iPrOH) were reacted with the monomeric complex, different dimeric complexes were obtained. Regardless of the high oxophilicity of the hafnium complexes, all complexes were active catalysts for the ring-opening polymerization (ROP) of ε-caprolactone. Dimeric complexes 5 and 6 were found to be the most active catalysts, enabling polymerization to occur in a living, immortal fashion, as well as the copolymerization of ε-caprolactone with rac-lactide, producing block copolymer PCL-b-LAC. The introduction of imidazolin-2-iminato ligands enables the tailoring of the oxophilicity of the complexes, allowing them to be active in catalytic processes with oxygen-containing substrates.
KW - hafnium complexes
KW - imidazolin-2-iminato
KW - polycaprolactone
KW - polylactide
UR - http://www.scopus.com/inward/record.url?scp=85140887874&partnerID=8YFLogxK
U2 - 10.3390/catal12101201
DO - 10.3390/catal12101201
M3 - 文章
AN - SCOPUS:85140887874
SN - 2073-4344
VL - 12
JO - Catalysts
JF - Catalysts
IS - 10
M1 - 1201
ER -