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.
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http://dx.doi.org/10.1039/c9dt01085h | DOI Listing |
Nat Commun
January 2025
Department of Chemistry, University of Bath, Bath, BA2 7AY, UK.
Copper is ubiquitous as a structural material, and as a reagent in (bio)chemical transformations. A vast number of chemical reactions rely on the near-inevitable preference of copper for positive oxidation states to make useful compounds. Here we show this electronic paradigm can be subverted in a stable compound with a copper-magnesium bond, which conforms to the formal oxidation state of Cu(-I).
View Article and Find Full Text PDFDalton Trans
October 2023
Research School of Chemistry, Australian National University, ACT, 2601, Australia.
The redox reaction between a bulky BODIPY and a magnesium(I) reducing agent leads to the formal one-electron reduction of the BODIPY, initially generating a dipyrromethene-centred radical compound that dimerises C-C bond formation. In contrast, reduction with magnesium anthracene leads to the formal two-electron reduction of the BODIPY, resulting in the formation of the corresponding anion.
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June 2023
Chemistry Research Laboratory, Department of Chemistry, Oxford, OX1 3TA, UK.
The complex diberyllocene, CpBeBeCp (Cp, cyclopentadienyl anion), has been the subject of numerous chemical investigations over the past five decades yet has eluded experimental characterization. We report the preparation and isolation of the compound by the reduction of beryllocene (BeCp) with a dimeric magnesium(I) complex and determination of its structure in the solid state by means of x-ray crystallography. Diberyllocene acts as a reductant in reactions that form beryllium-aluminum and beryllium-zinc bonds.
View Article and Find Full Text PDFChemistry
April 2023
School of Chemistry, Monash University, PO Box 23, Melbourne, VIC, 3800, Australia.
The aryl ketones, 9-fluorenone (fluor), 9-xanthenone (xanth) and 9,10-anthraquinone (anth), were reacted with β-diketiminato dimagnesium(I) compounds, [{( Nacnac)Mg} ] ( Nacnac=[HC(MeCNAr) ] , Ar=mesityl (Mes) or 2,6-diisopropylphenyl (Dip)). This gave stable magnesium ketyl complexes which are monomeric, [( Nacnac)(DMAP)Mg(fluor⋅)] (Ar=Mes or Dip, DMAP=4-dimethylaminopyridine) and [( Nacnac)Mg(xanth⋅)(xanth)]; dimeric, [{( Nacnac)Mg(μ-fluor⋅)} ], or tetrameric, [{( Nacnac)Mg(μ-anth⋅)} ]. In contrast, di-2-pyridylketone (OCPy ) is doubly reduced with [{( Nacnac)Mg} ] (Xyl=xylyl) to give a diamagnetic alkoxy/amido complex, [{( Nacnac)Mg} (μ-OCPy )].
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January 2022
Department of Chemistry, University of Oxford, 12 Mansfield Rd, Oxford OX1 3TA, UK.
We report on the reactivity of magnesium(I) dimers, [Mg(nacnac)] (nacnac = HC[C(Me)N(2,6-PrCH)] ([LMg]) and HC[C(Me)N(2,4,6-MeCH)] ([LMg])), towards the phosphaalkyne BuCP. The steric profile of the magnesium(I) dimer results in selectivity for different products. The larger diisopropylphenyl derivative yields exclusively the monomeric dimagnesiated phosphaalkene [LMg]PC(Bu)([LMg]) (1), while the mesityl derivative facilitates reductive coupling of two phosphaalkyne equivalents to give access to the 1,3-diphosphacyclobutadienediide [LMg][(Bu)CP](2).
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