The Recently Synthesized Dimagnesiabutadiene and the Analogous Dimetalla-Beryllium, -Calcium, -Strontium, and -Barium Compounds

Comparative Study of the Thermal Stabilities of the Experimentally Known High-Valent Fe(IV) Compounds Fe(1-norbornyl)4 and Fe(cyclohexyl)4

The high stability of the experimentally known homoleptic 1-norbornyl derivative (nor)₄Fe of iron in the unusual +4 oxidation state is a consequence of the high reaction barriers of the singlet or triplet potential surfaces constrained by the global dispersion attraction and the great steric demands of the norbornyl groups. The much more limited stability of the corresponding cyclohexyl derivative (cx)₄Fe may result from the conical intersection between the singlet potential surface and the quintet spin potential surface arising from the weaker dispersion attraction and the reduced steric effect of the cyclohexyl groups relative to the 1-norbornyl groups. In contrast, the high stability of the likewise experimentally known (cx)₄M (M = Ru or Os) structures results from the larger ligand field splitting (Δ) of the d-orbital energies for the second and third-row transition metals ruthenium and osmium relative to that of the first-row transition metal iron. The cyclohexyl derivative (cx)₄Fe is predicted to be reactive toward carbon monoxide to insert CO into up to two Fe-C bonds. However, the dispersion effect as well as the much larger size of the 1-norbornyl substituents prevents similar reactivity of (nor)₄Fe with carbon monoxide.

Unusual effects of the bulky 1-norbornyl group in cobalt carbonyl chemistry: low-energy structures with agostic hydrogen atoms

Low-energy (nor)Co(CO)_n (n = 3, 2) and (nor)₂Co₂(CO)_n (nor = 1-norbornyl; n = 6, 5) structures are found to have agostic hydrogen atoms from a CH₂ group adjacent to the Co–C bond forming C–H–Co bridges. In addition, low-energy structures are found with (nor)CO acyl ligands resulting from carbonyl migration.

Alkaline-earth metallacyclic complexes bearing a diborane-bridged tetraamide ligand: synthesis, structure and fluorescence property

A series of alkaline-earth (Mg, Ca, and Sr) metallacyclic complexes bearing a diborane-bridged tetraamide ligand were achieved for the first time through a clean one-step approach. All of these metallacycles were characterized by single-crystal X-ray diffraction analyses. UV-Vis absorption/emission spectroscopy showed deep blue fluorescence of these complexes.

Well-defined styryl and biphenyl calcium complexes from dilithio compounds and calcium iodide: synthesis, structure and reactivity toward nitrous oxide

Efficient synthesis and structure elucidation of carbon–calcium σ-bonded compounds are of remarkable interest and importance in organometallic chemistry of the heavier s-block metals.