Molekulare Magnesiumhydride

Lanthanide Mimicking by Magnesium for Oxazolidinone Synthesis

In the last decade, magnesium complexes have emerged as a viable alternative to transition-metal catalysts for the hydrofunctionalization of unsaturated bonds. However, their potential for advanced catalytic reactions has not been thoroughly investigated. To address this gap, we have developed a novel magnesium amide compound (3) using a PNP framework that is both bulky and flexible. Our research demonstrates that compound 3 can effectively catalyze the synthesis of biologically significant oxazolidinone derivatives. This synthesis involves a tandem reaction of hydroalkoxylation and cyclohydroamination of isocyanate using propargyl alcohol. Furthermore, we conducted comprehensive theoretical calculations to gain insights into the reaction mechanism. It is important to note that these types of transformations have not been reported for magnesium and would significantly enhance the catalytic portfolio of the 7th most abundant element.

The Continuum Between Hexagonal Planar and Trigonal Planar Geometries

New heterometallic hydride complexes that involve the addition of {Mg-H} and {Zn-H} bonds to group 10 transition metals (Pd, Pt) are reported. The side-on coordination of a single {Mg-H} to Pd forms a well-defined σ-complex. In contrast, addition of three {Mg-H} or {Zn-H} bonds to Pd or Pt results in the formation of planar complexes with subtly different geometries. We compare their structures through experiment (X-ray diffraction, neutron diffraction, multinuclear NMR), computational methods (DFT, QTAIM, NCIPlot), and theoretical analysis (MO diagram, Walsh diagram). These species can be described as snapshots along a continuum of bonding between ideal trigonal planar and hexagonal planar geometries.

A Hexagonal Planar Metal Complex

A six-coordinate [ML₃ Z₃ ]-type transition-metal complex with a hexagonal planar geometry has been isolated and characterized, extending the scope of six-coordinate metal coordination compounds to those with a geometry beyond octahedral and trigonal prismatic.

A Stable Calcium Alumanyl

A seven-membered N,N'-heterocyclic potassium alumanyl nucleophile is introduced and utilised in the metathetical synthesis of Mg-Al and Ca-Al bonded derivatives. Both species have been characterised by experimental and theoretical means, allowing a rationalisation of the greater reactivity of the heavier group 2 species implied by an initial assay of their reactivity.

A Stable Calcium Alumanyl

A seven‐membered N,N′‐heterocyclic potassium alumanyl nucleophile is introduced and utilised in the metathetical synthesis of Mg−Al and Ca−Al bonded derivatives. Both species have been characterised by experimental and theoretical means, allowing a rationalisation of the greater reactivity of the heavier group 2 species implied by an initial assay of their reactivity.

Nucleophilic Aromatic Substitution at Benzene with Powerful Strontium Hydride and Alkyl Complexes

Key to the isolation of the first alkyl strontium complex was the synthesis of a strontium hydride complex that is stable towards ligand exchange reactions. This goal was achieved by using the super bulky β-diketiminate ligand ^DIPeP BDI (CH[C(Me)N-DIPeP]₂ , DIPeP=2,6-diisopentylphenyl). Reaction of ^DIPeP BDI-H with Sr[N(SiMe₃ )₂ ]₂ gave (^DIPeP BDI)SrN(SiMe₃ )₂ , which was converted with PhSiH₃ into [(^DIPeP BDI)SrH]₂ . Dissolved in C₆ D₆ , the strontium hydride complex is stable up to 70 °C. At 60 °C, H-D isotope exchange gave full conversion into [(^DIPeP BDI)SrD]₂ and C₆ D₅ H. Since H-D exchange with D₂ is facile, the strontium hydride complex served as a catalyst for the deuteration of C₆ H₆ by D₂ . Reaction of [(^DIPeP BDI)SrH]₂ with ethylene gave [(^DIPeP BDI)SrEt]₂ . The high reactivity of this alkyl strontium complex is demonstrated by facile ethylene polymerization and nucleophilic aromatic substitution with C₆ D₆ , giving alkylated aromatic products and [(^DIPeP BDI)SrD]₂ .