Organocalcium compounds with catalytic activity for the ring-opening polymerization of lactones

Matthias Westerhausen, Stefan Schneiderbauer, Alexander N. Kneifel, Yvonne Söltl, Peter Mayer, Heinrich Nöth, Zhiyuan Zhong, Pieter J. Dijkstra, Jan Feijen

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Abstract

The equimolar reaction of calcium bis[bis(trimethylsilyl)amide] with 2,2,6,6-tetramethylheptane-3,5-dione (Htmhd) in THF yields liquid mononuclear [Ca(tmhd){N(SiMe3)2}(THF)3] (1). A similar reaction in toluene with a stoichiometric ratio of 2:3 gives the dinuclear complex [{(THF)Ca}2(tmhd)2(µ-tmhd){µ-N(SiMe3)2}] (2). The calcium atoms of these complexes are in a distorted octahedral environment. In 2 the complex consists of two octahedra connected by a common face of one nitrogen base and two oxygen atoms; the bridging Ca-N bond lengths are extremely large. The metalation of the tetradentate Jacobsen reagent with calcium bis[bis(trimethylsilyl)amide] in 1,2-dimethoxyethane (DME) gives the corresponding calcium complex 3, nearly quantitatively, as its DME adduct. The calcium atom is in an unusual trigonal prismatic coordination sphere. The metathesis reaction of 3 with tin(II) chloride yields the corresponding yellow tin(II) complex with the metal atom in a distorted square-pyramidal environment. Complexes 2 and 3 show catalytic reactivity in the ring-opening polymerization of cyclic esters such as lactones and lactides.
Original languageUndefined
Pages (from-to)3432-3439
JournalEuropean journal of inorganic chemistry
Volume18
Issue number18
DOIs
Publication statusPublished - 2003

Keywords

  • TiN
  • Calcium
  • Ring-opening polymerization
  • N ligands
  • O ligands
  • IR-71927
  • METIS-216620

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