Synthesis and Structural Characterization of Some New Magnesium Formamidinates

In Situ Grignard Metalation Method for the Synthesis of Hauser Bases

The in situ Grignard Metalation Method (iGMM) is a straightforward one-pot procedure to quickly produce multigram amounts of Hauser bases R2 N-MgBr which are valuable and vastly used metalation reagents and novel electrolytes for magnesium batteries. During addition of bromoethane to a suspension of Mg metal and secondary amine at room temperature in an ethereal solvent, a smooth reaction yields R2 N-MgBr under evolution of ethane within a few hours. A Schlenk equilibrium is operative, interconverting the Hauser bases into their solvated homoleptic congeners Mg(NR2 )2 and MgBr2 depending on the solvent. Scope and preconditions are studied, and side reactions limiting the yield have been investigated. DOSY NMR experiments and X-ray crystal structures of characteristic examples clarify aggregation in solution and the solid state.

Synthesis and Coordination Chemistry of 3,4-Ethylene-Bridged 1,1,2,5-Tetrasubstituted Biguanides

The synthesis of 3,4-ethylene-bridged 1,1,2,5-tetrasubstituted biguanides is reported, which are accessible by three alternative routes. Exemplary molecular structures of the ligand and an observed side product have been elucidated by X-ray diffraction analysis. Mono- and dinuclear complexes of the biguanide in both its neutral and monoanionic forms were obtained, including examples of aluminum, copper, magnesium, potassium, tin, and zinc, indicating a versatile coordination behavior, as evidenced by means of single-crystal X-ray diffraction analysis.

Bora-amidinate as a cooperative ligand in group 2 metal catalysis

Syntheses and crystal structures of the monomeric bora-amidinate (bam) complexes ^DIPPNBN-Mg·(THF)₃ and ^DIPPNBN-Ca·(THF)₄ are presented; ^DIPPNBN = HB[N(2,6-iPr₂-C₆H₃)]₂. The simplicity of their ¹H NMR spectra in THF-d₈ suggest that their monomeric solid state structures are retained in solution. ^DIPPNBN-Mg·(THF)₃ in C₆D₆, however, is in equilibrium with a dimeric species. Calculations (B3PW91/6-311++G**) reveal a very high localized negative charge (NPA: -1.103) on the N atoms in ^DIPPNBN-Mg. The strongly basic properties of the bam ligand are in agreement with catalytic activity of these complexes in the intramolecular alkene hydroamination. A mechanism is proposed in which the bam ligand is non-innocent and cooperative, playing an active role in substrate deprotonation and product protonation.

Metal-free access of bulky N,N′-diarylcarbodiimides and their reduction: bulky N,N′-diarylformamidines

A facile synthetic protocol for the preparation of N,N′-diarylcarbodiimides and their reduction with sodium borohydride in ethanol to obtain N,N′-diarylformamidines has been demonstrated.