title: Probing the role of secondary versus tertiary amine donor ligands for indium catalysts in lactide polymerization.
abstract: The role of the central amine donor in a previously reported dinuclear indium catalyst, [N(Me2)N(H)O)InCl]2(μ-Cl)(μ-OEt) (1), for the polymerization of lactide was investigated through experimental methods. The solid state structural data of a series of dimeric complexes related to 1, including the previously reported bromide derivative [(N(Me2)N(H)O)InBr](μ-Br)(μ-OEt) (2) and the newly synthesized methylated derivative [(N(Me2)N(Me)O)InCl]2(μ-Cl)(μ-OEt) (6), showed that weak hydrogen bonding may be present within some of these complexes in the solid state. The polymerization of rac-lactide with 2, 6, and a related achiral complex [(L(H))InCl]2(μ-Cl)(μ-OEt) (8) synthesized for this study indicates that hydrogen bonding may not influence the reactivity of these compounds. The nature of the central amine donor may play a role in tuning the reactivity of these types of catalysts. Catalysts with central secondary amine donors, such as complexes 1, 2, and 8, are 2 orders of magnitude more reactive than those with central tertiary amine donors, such as complex 6.
authors.affiliation: Department of Chemistry, University of British Columbia , 2036 Main Mall, Vancouver, British Columbia V6T 1Z1, Canada.
authors.forename: Kimberly M
authors.initials: KM
authors.lastname: Osten
authors.forename: Dinesh C
authors.initials: DC
authors.lastname: Aluthge
authors.forename: Brian O
authors.initials: BO
authors.lastname: Patrick
authors.forename: Parisa
authors.initials: P
authors.lastname: Mehrkhodavandi
mesh_terms: D000588:Amines / Q000737:chemistry*; D002384:Catalysis; D004146:Dioxanes / Q000737:chemistry*; D007204:Indium / Q000737:chemistry*; D019344:Lactic Acid / Q000737:chemistry*; D008024:Ligands; D011091:Polyesters; D058105:Polymerization; D011108:Polymers / Q000737:chemistry*
chemical_list: D000588:Amines; D004146:Dioxanes; D008024:Ligands; D011091:Polyesters; D011108:Polymers; D007204:Indium; D019344:Lactic Acid; C033616:poly(lactide); C091880:dilactide