Organometallic calcium and strontium borohydrides as initiators for the polymerization of ε-caprolactone and L-lactide: combined experimental and computational investigations
| Autor: | Sophie M. Guillaume, Laurent Maron, Sebastian Marks, Liana Annunziata, Matthias Schmid, Peter W. Roesky, Cédric G. Jaffredo, Magdalena Kuzdrowska |
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| Rok vydání: | 2013 |
| Předmět: |
Stereochemistry
chemistry.chemical_element Borohydrides Calcium 010402 general chemistry 01 natural sciences Medicinal chemistry Polymerization Inorganic Chemistry Dioxanes chemistry.chemical_compound symbols.namesake Lactones Organometallic Compounds Caproates Strontium Lactide 010405 organic chemistry 0104 chemical sciences Gibbs free energy Monomer chemistry symbols Quantum Theory Single crystal Caprolactone |
| Zdroj: | Dalton transactions (Cambridge, England : 2003). 42(25) |
| ISSN: | 1477-9234 |
| Popis: | [Ca(BH4)2(THF)2] (1a), a known compound, was easily prepared following a convenient new procedure from [Ca(OMe)2] and BH3·THF in THF. Reaction of 1a with KCp* (Cp* = (η(5)-C5Me5)) and K{(Me3SiNPPh2)2CH} in a 1 : 1 ratio in THF resulted in the corresponding dimeric heteroleptic mono-borohydride derivatives [Cp*Ca(BH4)(THF)n]2 (2a) and [{(Me3SiNPPh2)2CH}Ca(BH4)(THF)2] (3a), respectively. Both compounds were fully characterized and the solid-state structure of 3a was established by single crystal X-ray diffraction. Compounds 1a, 2a, and 3a, together with the earlier reported compounds [Sr(BH4)2(THF)2] (1b), [Cp*Sr(BH4)(THF)2]2 (2b), and [{(Me3SiNPPh2)2CH}Sr(BH4)(THF)2] (3b), were used as initiators for the ROP of polar monomers. The general performances of the complexes in the ROP of ε-caprolactone and l-lactide demonstrate a relatively good control of the polymerization under the operating conditions established. α,ω-Dihydroxytelechelic poly(ε-caprolactone)s (PCLs) and poly(lactide)s (PLAs) were thus synthesized. DFT calculations on the initiation step of the ROP of ε-CL were carried out. Gibbs free energy profiles were determined for the three calcium complexes highlighting slightly more active calcium complexes as compared to strontium analogues, in agreement with experimental findings. |
| Databáze: | OpenAIRE |
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