Probing the role of secondary versus tertiary amine donor ligands for indium catalysts in lactide polymerization

Inorg Chem. 2014 Sep 15;53(18):9897-906. doi: 10.1021/ic501529f. Epub 2014 Aug 27.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amines / chemistry*
  • Catalysis
  • Dioxanes / chemistry*
  • Indium / chemistry*
  • Lactic Acid / chemistry*
  • Ligands
  • Polyesters
  • Polymerization*
  • Polymers / chemistry*

Substances

  • Amines
  • Dioxanes
  • Ligands
  • Polyesters
  • Polymers
  • Indium
  • Lactic Acid
  • poly(lactide)
  • dilactide