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Issue 2, 2015
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Amido rare-earth complexes supported by an ansa bis(amidinate) ligand with a rigid 1,8-naphthalene linker: synthesis, structures and catalytic activity in rac-lactide polymerization and hydrophosphonylation of carbonyl compounds

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Abstract

A synthetic approach to rare-earth amido complexes coordinated by an ansa bis(amidinate) ligand with a 1,8-naphthalene linker was developed and allowed for the synthesis of a series of complexes [1,8-C10H6{NC(tBu)N-2,6-Me2C6H3}2]LnN(SiMe3)2(THF)n (Ln = Y, n = 0 (2); Ln = Sm, n = 1 (3); Ln = Nd, n = 1 (4)) in reasonable yields. Complexes 2–4 initiate ring-opening polymerization (ROP) of rac-lactide and enable complete conversion of 100–250 equiv. of monomer within 60–90 min at 25 °C. The obtained polylactides feature atactic structures and moderate molecular-weight distributions (Mw/Mn = 1.30–2.12). The experimental Mn values of the obtained polymers are found to be significantly higher than the calculated ones due to a slow initiation stage. Effective immortal ROP of lactide with 3–5 equiv. of isopropanol per metal center was performed using complexes 2–4 as the catalysts. The systems 2–4/iPrOH exhibit higher activities in ROP and allow for complete conversion of 100–300 equiv. of rac-lactide to polymer within 30–60 min at 25 °C and provide a living polymerization mode and very narrow polydispersities (Mw/Mn = 1.13–1.27). Complexes 2–4 as well as related borohydrides [1,8-C10H6{NC(tBu)N-2,6-Me2C6H3}2]Ln(BH4)(μ-BH4)Li(THF)2 (Ln = Sm, Nd) catalyze hydrophosphonylation of aldehydes at room temperature with good reaction rates and hydrophosphonylation of benzylideneacetone at 65 °C.

Graphical abstract: Amido rare-earth complexes supported by an ansa bis(amidinate) ligand with a rigid 1,8-naphthalene linker: synthesis, structures and catalytic activity in rac-lactide polymerization and hydrophosphonylation of carbonyl compounds

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Publication details

The article was received on 30 Sep 2014, accepted on 11 Nov 2014 and first published on 12 Nov 2014


Article type: Paper
DOI: 10.1039/C4NJ01698J
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New J. Chem., 2015,39, 1083-1093

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    Amido rare-earth complexes supported by an ansa bis(amidinate) ligand with a rigid 1,8-naphthalene linker: synthesis, structures and catalytic activity in rac-lactide polymerization and hydrophosphonylation of carbonyl compounds

    M. V. Yakovenko, N. Yu. Udilova, T. A. Glukhova, A. V. Cherkasov, G. K. Fukin and A. A. Trifonov, New J. Chem., 2015, 39, 1083
    DOI: 10.1039/C4NJ01698J

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