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Issue 16, 2010
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Cationic organozinc complexes of a bis(phosphinimine) pincer ligand: synthesis, structural and polymerization studies

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Abstract

Cationic organozinc complexes of a neutral bis(phosphinimine) pincer ligand (L) have been prepared and structurally characterized. This recently introduced ligand was constructed from a dibenzofuran (dbf) framework with symmetric attachment of phosphinimine groups at the 4 and 6 positions. Starting from protonated derivatives [LH][B(C6F5)4] (1a), [LH][BPh4] (1b), or [LH2][BPh4]2 (1c), the complexes [LZnCH3][B(C6F5)4] (2a), [LZnCH3][BPh4] (2b), and [LZnOAc][BPh4] (3), were prepared via protonolysis of an appropriate alkylzinc precursor. The complex [LZnPh][BPh4] (4) is generated as a side-product in the synthesis of 2b. Solid-state structural studies have revealed the compounds to be charge separated cationic zinc species with 3-coordinate trigonal planar geometry. Preliminary studies have shown these complexes to be inactive for the polymerization of lactide. Upon modification of the initiating group to a methyl-(S)-lactate, however, complex [LZnOCH(Me)CO2Me][B(C6F5)4] (5) demonstrated significant polymerization activity at 60 °C. Additionally, NMR and mass spectrometry data confirmed a coordination-insertion mechanism was operative for this catalyst.

Graphical abstract: Cationic organozinc complexes of a bis(phosphinimine) pincer ligand: synthesis, structural and polymerization studies

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Publication details

The article was received on 09 Nov 2009, accepted on 12 Feb 2010 and first published on 11 Mar 2010


Article type: Paper
DOI: 10.1039/B922543A
Citation: Dalton Trans., 2010,39, 3861-3869
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    Cationic organozinc complexes of a bis(phosphinimine) pincer ligand: synthesis, structural and polymerization studies

    C. A. Wheaton and P. G. Hayes, Dalton Trans., 2010, 39, 3861
    DOI: 10.1039/B922543A

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