title: Yttrium phosphasalen initiators for rac-lactide polymerization: excellent rates and high iso-selectivities.
abstract: Highly active yttrium phosphasalen initiators for the stereocontrolled ring-opening polymerization of rac-lactide are reported. The initiators are coordinated by a new class of ancillary ligand: an iminophosphorane derivative of the popular "salen" ligand, termed "phosphasalen". Changing the phosphasalen structure enables access to high iso-selectivities (P(i) = 0.84) or hetero-selectivities (P(s) = 0.87). The initiators also show very high rates, excellent polymerization control, and tolerance to low loadings; furthermore, no chiral auxiliaries/ligands are needed for the stereocontrol. The combination of such high rates with high iso-selectivities is very unusual.
authors.affiliation: Department of Chemistry, Imperial College London, London SW7 2AZ, UK.
authors.forename: Clare
authors.initials: C
authors.lastname: Bakewell
authors.forename: Thi-Phuong-Anh
authors.initials: TP
authors.lastname: Cao
authors.forename: Nicholas
authors.initials: N
authors.lastname: Long
authors.forename: Xavier F
authors.initials: XF
authors.lastname: Le Goff
authors.forename: Audrey
authors.initials: A
authors.lastname: Auffrant
authors.forename: Charlotte K
authors.initials: CK
authors.lastname: Williams
mesh_terms: D004146:Dioxanes / Q000737:chemistry*; D005029:Ethylenediamines / Q000737:chemistry*; D008024:Ligands; D008958:Models, Molecular; D011091:Polyesters / Q000138:chemical synthesis*; D058105:Polymerization; D013237:Stereoisomerism; D015019:Yttrium / Q000737:chemistry*
chemical_list: D004146:Dioxanes; D005029:Ethylenediamines; D008024:Ligands; D011091:Polyesters; C033616:poly(lactide); D015019:Yttrium; C011452:disalicylaldehyde ethylenediamine; C091880:dilactide