TY - JOUR
T1 - New insights into the lactide polymerisation with neutral N-donor stabilised zinc complexes: Comparison of imidazolin-2-imine vs. guanidine complexes
AU - Borner, J
AU - Florke, U
AU - Gloge, T
AU - Bannenberg, T
AU - Tamm, M
AU - Jones, M D
AU - Doring, A
AU - Kuckling, D
AU - Herres-Pawlis, S
PY - 2010/2/1
Y1 - 2010/2/1
N2 - Two imidazolin-2-imine zinc complexes [Zn(8MeBL)Cl-2] (1) and [Zn(8MeBL)(OAc)(2)] (2) were synthesised, completely characterised and investigated for their activity in the solvent-free ring-opening polymerisation of D,L-lactide. It could be shown that these compounds are able to act as efficient initiators for lactide polymerisation,and polylactides with molecular weights (M-w) of around 23,000-55,000 g/mol could be obtained with relatively narrow polydispersities. 1 and 2 exhibit an advantageous combination of robustness towards humidity and high activity in the polymer melt. A comparative DFT study on 1 and 2 and their guanidine counterparts revealed that the two complex series possess a strikingly similar electronic structure. Although the imidazolin-2-imine is more basic, its zinc complexes have only a slightly greater positive charge on the zinc atom in comparison to the corresponding guanidine complexes. Accordingly, their activity in the initiation of the ring-opening polymerisation is increased which is directly related to the Lewis acidity of the zinc atom. These findings allow more insights into the mechanism of the lactide polymerisation with neutral N-donor stabilised zinc complexes. (C) 2009 Elsevier B.V. All rights reserved.
AB - Two imidazolin-2-imine zinc complexes [Zn(8MeBL)Cl-2] (1) and [Zn(8MeBL)(OAc)(2)] (2) were synthesised, completely characterised and investigated for their activity in the solvent-free ring-opening polymerisation of D,L-lactide. It could be shown that these compounds are able to act as efficient initiators for lactide polymerisation,and polylactides with molecular weights (M-w) of around 23,000-55,000 g/mol could be obtained with relatively narrow polydispersities. 1 and 2 exhibit an advantageous combination of robustness towards humidity and high activity in the polymer melt. A comparative DFT study on 1 and 2 and their guanidine counterparts revealed that the two complex series possess a strikingly similar electronic structure. Although the imidazolin-2-imine is more basic, its zinc complexes have only a slightly greater positive charge on the zinc atom in comparison to the corresponding guanidine complexes. Accordingly, their activity in the initiation of the ring-opening polymerisation is increased which is directly related to the Lewis acidity of the zinc atom. These findings allow more insights into the mechanism of the lactide polymerisation with neutral N-donor stabilised zinc complexes. (C) 2009 Elsevier B.V. All rights reserved.
UR - http://www.scopus.com/inward/record.url?scp=71349084604&partnerID=8YFLogxK
U2 - 10.1016/j.molcata.2009.10.012
DO - 10.1016/j.molcata.2009.10.012
M3 - Article
SN - 1381-1169
VL - 316
SP - 139
EP - 145
JO - Journal of Molecular Catalysis A: Chemical
JF - Journal of Molecular Catalysis A: Chemical
IS - 1-2
ER -