Low-coordinate rare-earth complexes of the asymmetric 2,4-di-tert-butylphenolate ligand prepared by redoxtransmetallation/protolysis reactions, and their reactivity towards ring-opening polymerisation

Clark, Lawrence, Deacon, Glen B., Forsyth, Craig M., Junk, Peter C., Mountford, Philip, and Townley, Josh P. (2010) Low-coordinate rare-earth complexes of the asymmetric 2,4-di-tert-butylphenolate ligand prepared by redoxtransmetallation/protolysis reactions, and their reactivity towards ring-opening polymerisation. Dalton Transactions, 39 (29). pp. 6693-6704.

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View at Publisher Website: http://dx.doi.org/10.1039/c0dt00023j
 
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Abstract

New trivalent lanthanoid aryloxide complexes have been prepared by redoxtransmetallation/protolysis (rtp) reactions using 2,4-di-tert-butylphenol (dbpH). Mononuclear octahedral complexes from tetrahydrofuran (thf) were of the type [Ln(dbp)3(thf)3] (Ln = La (1), Pr (2), Nd (3), Gd (4), Er (5)). The lanthanoid contraction results in the rather subtle change in stereochemistry from meridional (La, Pr, Nd, Gd) to facial (Er). An analogous reaction with neodymium in dimethoxyethane (dme), resulted in the isolation of the seven coordinate [Nd(dbp)3(dme)2] (6), and this is comparable with the thf complexes in terms of steric crowding. Dinuclear complexes of the type [Ln2(dbp)6(thf)2], (Ln = Nd (7), Er (8)) were obtained when 1 and 5 were recrystallised from toluene. These dimeric complexes contain two bridging and four terminal phenolates, as well as a single coordinated molecule of thf at each metal. A similar structural motif was observed for the products when the reaction was performed in diethyl ether, and in the absence of a solvent, yielding [Nd2(dbp)6(Et2O)2] (9) and [Nd2(dbp)6(dbpH)2] (10) respectively. Complexes 3 and 4 alone were efficient but poorly-controlled initiators for the ROP of rac-lactide, but with an excess of BnOH as a co-initiator they showed features consistent with immortal polymerisation. Use of BnNH2 led to well-controlled, amine-initiated immortal ROP of rac-lactide, only the second report of this type of process for a group 3 or lanthanoid system.

Item ID: 29668
Item Type: Article (Research - C1)
ISSN: 1477-9234
Keywords: x-ray structures; aryloxo-lanthanoids; crystal-structures; structural-characterization; organoamido-lanthanoids; lactide polymerization; = tetrahydrofuran; alkoxides; initiators; transmetalation
Funders: Australian Research Council (ARC), Monash Research Graduate School
Date Deposited: 02 Oct 2013 10:34
FoR Codes: 03 CHEMICAL SCIENCES > 0302 Inorganic Chemistry > 030202 f-Block Chemistry @ 100%
SEO Codes: 97 EXPANDING KNOWLEDGE > 970103 Expanding Knowledge in the Chemical Sciences @ 100%
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