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The complex reactivity of β-diketiminato magnesium(I) dimers towards pinacolborane: implications for catalysis

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Abstract

Reactions between the borane, HBpin (pin = pinacolato), and three magnesium(I) dimers, [{(ArNacnac)Mg–}2] (ArNacnac = [(ArNCMe)2CH]; Ar = xylyl (Xyl), mesityl (Mes) or 2,6-diethylphenyl (Dep)), have been carried out in 2 : 1, 5 : 1 and 20 : 1 ratios. In all cases, NMR spectroscopic studies have revealed complex mixtures of many known and novel products from these reactions. From extracts of the crude reaction mixtures, low yields of ten compounds, representing six different types of complexes between β-diketiminato magnesium fragments and boron containing ligands, have been isolated and crystallographically characterised. These include unprecedented examples of compounds in which the γ-carbon of the β-diketiminate ligand has been activated by boron hydride fragments. In addition, boryloxide (OBpin), borate ([B(pin)2] or [(pin)BH2]), B–O bond ruptured [pinBH2], a diborane(5) dianion, or BH3 have been shown to be incorporated into the isolated complexes. The complexity of the products of the reported reactions are discussed in light of recently published patents and papers which report that magnesium(I) dimers act as efficient catalysts, or as pre-catalysts to well defined catalysts, for the hydroboration of a variety of unsaturated substrates by HBpin. Our results strongly suggest that magnesium(I) dimers are not catalysts in these reactions, and that there are many more potential (pre-)catalysts that are generated in these reactions, than have previously been reported.

Graphical abstract: The complex reactivity of β-diketiminato magnesium(i) dimers towards pinacolborane: implications for catalysis

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Publication details

The article was received on 13 Mar 2019, accepted on 05 Apr 2019 and first published on 08 Apr 2019


Article type: Paper
DOI: 10.1039/C9DT01085H
Citation: Dalton Trans., 2019, Advance Article

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    The complex reactivity of β-diketiminato magnesium(I) dimers towards pinacolborane: implications for catalysis

    D. D. L. Jones, A. J. R. Matthews and C. Jones, Dalton Trans., 2019, Advance Article , DOI: 10.1039/C9DT01085H

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