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Dimeric aluminum chloride complexes of N-alkoxyalkyl-β-ketoimines: Activation with propylene oxide to form efficient lactide polymerization catalysts

Lookup NU author(s): Dr Simon Doherty, Dr John Errington, Neil Housley, Emeritus Professor Bill Clegg

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Abstract

The ter- and tetradentate N-alkoxyalkyl-β-ketoimines CH 3C(O)CH2C(NCH2CHROH)CH3 {L 1-3} react with diethylaluminum chloride to afford the dimeric chloride bridged complexes [{L1-3}AlCl]2 (1a-c), which are activated by addition of propylene oxide or cyclohexene oxide to afford efficient initiators for the ring-opening polymerization of (D,L)-lactide. The active species is believed to be a chloroalkoxide formed by nucleophilic ring opening of a coordinated PO by migration of the chloride coordinated to the adjacent aluminum center. The resulting polymers have a high molecular weight, close to that calculated for the monomer:initiator ratio of 100, and a narrow molecular weight distribution. While the corresponding aluminum methyl dimer [{L1}AlMe]2 (2a), formed by reaction of L1 (R = H) with AlMe3, is a poor inititaor for the polymeriation of (D,L)-lactide, addition of 2-chloroethanol affords a catalyst with an activity comparable to that of 1a/PO. The molecular weight and molecular weight distribution of the resulting polylactide is similar to that obtained with 1a/PO and consistent with formation of a similar chloroalkoxide initiator.


Publication metadata

Author(s): Doherty S, Errington RJ, Housley N, Clegg W

Publication type: Article

Publication status: Published

Journal: Organometallics

Year: 2004

Volume: 23

Issue: 10

Pages: 2382-2388

ISSN (print): 0276-7333

ISSN (electronic): 1520-6041

Publisher: American Chemical Society

URL: http://dx.doi.org/10.1021/om0343770

DOI: 10.1021/om0343770


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