Organocalcium Compounds with Catalytic Activity for the Ring-Opening Polymerization of Lactones


Westerhausen, Matthias and Schneiderbauer, Stefan and Kneifel, Alexander N. and Söltl, Yvonne and Mayer, Peter and Nöth, Heinrich and Zhong, Zhiyuan and Dijkstra, Pieter J. and Feijen, Jan (2003) Organocalcium Compounds with Catalytic Activity for the Ring-Opening Polymerization of Lactones. European Journal of Inorganic Chemistry, 2003 (18). pp. 3432-3439. ISSN 1434-1948

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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.
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Copyright:© 2003 Wiley InterScience
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