Electronic Effect Rate Enhancement in the Stereoselective Living Coordinative Polymerization of α‑Olefins by α,α,α-Trifluoroacetamidinate-Modified Group 4 Metal CPAMCF3 Initiators
The C 1-symmetric cyclopentadienyl, α,α,α-trifluoroacetamidinate (CPAMCF3) group 4 metal dimethyl complexes, Cp*[N(Et)C(CF3)N(tBu)]M(Me)2 (Cp* = η5-C5Me5) for M = Zr (3) and Hf (4), serve as initiators for the stereoselective (isotactic) living coordination polymerization (LCP) of α-olefins...
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Published in | Organometallics Vol. 38; no. 2; pp. 213 - 217 |
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Main Authors | , , |
Format | Journal Article |
Language | English |
Published |
American Chemical Society
28.01.2019
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Online Access | Get full text |
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Summary: | The C 1-symmetric cyclopentadienyl, α,α,α-trifluoroacetamidinate (CPAMCF3) group 4 metal dimethyl complexes, Cp*[N(Et)C(CF3)N(tBu)]M(Me)2 (Cp* = η5-C5Me5) for M = Zr (3) and Hf (4), serve as initiators for the stereoselective (isotactic) living coordination polymerization (LCP) of α-olefins upon in situ “activation” using one equiv of the borate co-initiator, [PhNMe2H][B(C6F5)4]. For the LCP of 1-hexene using 4, a six-fold enhancement in the rate of polymerization, R p, is observed relative to the LCP of this same α-olefin when the nonfluorinated CPAMCH3 structural analogue, Cp*[N(Et)C(CH3)N(tBu)Hf(Me)2] (2), is employed as the preinitiator. For the LCP of propene, an eight-fold increase in R p using the CPAMCF3 preinitiator 4 now permits production of practical quantities of highly stereo- and regioregular isotactic polypropene (iPP) under reaction conditions that are not amenable for use with the corresponding CPAMCH3 preinitiator 2. These results provide strong support for a unique synergistic coupling of steric and electronic effects of the CPAMCF3 ligand environment. |
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ISSN: | 0276-7333 1520-6041 |
DOI: | 10.1021/acs.organomet.8b00839 |