Tracking the Structure-Reactivity Relationship of Zinc Guanidine-Pyridine Hybrid Complexes Initiating Lactide Polymerisation

Autor: Artjom Döring, Sonja Herres-Pawlis, Janna Börner, Ulrich Flörke, Dirk Kuckling
Rok vydání: 2010
Předmět:
Zdroj: Macromolecular Symposia. 296:354-365
ISSN: 1022-1360
Popis: Three zinc guanidine-pyridine hybrid complexes [Zn(TMGqu) 2 (CH 3 -SO 3 )][CH 3 SO 3 ] (1), [Zn(DMEGqu)(CH 3 SO 3 ) 2 ] (2) and [Zn(DMEGqU) 2 (CH 3 SO 3 )][CH 3 SO 3 ] (3) were synthesised, completely characterised and investigated on their activity in the solvent-free ring-opening polymerisation of D,L-lactide. It was proven that the bis-chelate trigonal-bipyramidally coordinated compounds 1 and 3 are able to act as initiators for lactide polymerisation, and polylactides with molecular weights (M w ) of around 28000 g/mol could be obtained with relatively narrow polydispersities. The tetrahedral complex 2 does not initiate lactide polymerisation. In an integrated approach of structural studies and DFT calculations, the active complexes 1 and 3 were analysed towards their structural and electronical pre-requisites in comparison to their more active triflate analogues 1 OTf and 3 OTf . The influence of coordination strength of the anionic component on the charge distribution within the complex and on the substrate accessibility to the zinc centre is highlighted as crucial factor for the polymerisation initiation. As result, it is shown that the mesylate complexes 1 and 3 have less positive charge on the zinc centre and the mesylate is stronger bound than the corresponding triflate in the triflate complexes 1 OTf and 3 OTf . Consequently, the reactivity of the complexes is directly correlated to the coordinational behaviour of the anionic component.
Databáze: OpenAIRE
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