European Journal of Inorganic Chemistry

Nonsymmetrical (metallo)salen compounds are highly useful synthons for innovative homogeneous catalysis and the construction of macromolecular/supramolecular structures. This review focuses on the recent advances in synthetic salen chemistry devoted to unsymmetrical derivatives, and fascinating examples of their application potential are presented.

A cylindrical nanostructure containing six (p-cymene)Ru fragments and two bridging ligands was obtained by base-assisted reaction of a tris(dihydroxypyridine) ligand with [(p-cymene)RuCl₂]₂.

A controllable-assembly of metal chalcogenide nanoparticles onto ordered porous diatom meso/nanostructures by a sonochemical method has been developed. The inorganic replicas copy the morphology of the ordered porous structure and inherit its optical property. Photonic properties inthe replicas can be tuned by assembly of various metal chalcogenide semiconductors of different refractive indexes.

Silver salts are used as promoters for the cyclization to novel ferrocene-containing indolizine systems in only one step andwith the simultaneous activation of the 7-position of the heterocyclic ring.

The CO valence vibrations and short Ge^II–Mo bonds in fac-[(NHGe)₃Mo(CO)₃] and [Ni(NHGe)₄], both of which contain N-heterocyclic germylene ligands, indicate the weak donor and good π-acceptor properties of these ligands, in line with quantum chemical studies and their PES orbital ionization potentials. The ligand bending in the complexes may be due to packing effects.

Five new ternary cobalt antimonidesβ-RECoSb₃ (RE = La–Nd, Sm) have been synthesized and characterized. The structural relationship among parent, α- and β-type of RETSb₃ has been elucidated. The TB-LMTO calculations revealed thatLaCoSb₃ is an anisotropic metal and no spin-polarization occurred around the Fermi level.

Salts with the nitrogen-rich 5,5′-hydrazine-1,2-diylbis(tetrazolate) anion and alkaline earth metals were synthesized and fully characterized. The great thermal stability in combination with a high nitrogen content make the compounds interesting as ingredients for environmentally friendly pyrotechnic compositions.

To mimic effective shielding of reactive metal sites in metalloproteins, new polytopic ligands were prepared, and they form a cage-like structure upon coordination of Fe²⁺ and Ru²⁺. However, binding of Zn²⁺ and Cu²⁺ biometals to a vacant tris(pyrid-2-yl) site in the interior of the container appears to be disfavoured, indicating a negative allosteric effect.

Coprecipitation of Pd/MO_x via sol-gel routes leads to a strong Pd-support interaction. These catalysts are efficient in Heck reactions where the catalytically active species is generated by dissolution of Pd from the support. In consequence of the strong Pd-support interaction, this occurs only at high temperatures (≥ 160 °C) which are necessary for the activation of aryl bromides and chlorides.

A racemic cyclopalladated complex was efficiently resolved through the formation of its (S)-prolinato derivatives. The new chiral palladacycle showed high stereoselectivity in the chiral template-promoted asymmetric Diels–Alder reaction of coordinated 3,4-dimethyl-1-phenylphosphole and N,N-dimethylacrylamide.

Heterobridged μ-phenoxido, μ_1,1-azido, and μ-phenoxido μsyn–syn-benzoato-bridged binuclear copper(II) complexes with N₄O₃ coordinating heptadentate ligands were synthesized and characterized. The variable-temperature magnetic moments of thecomplexes were confirmed by using BS-DFT calculations. The benzoato-bridged Cu^II complex exhibits both catecholase and hydrolytic DNA cleavage activity.

Palladium(II) complexes with phosphane and symmetrically and unsymmetrically substituted benzimidazolin-2-ylidene ligands of types 2–6 were prepared and selected derivatives were characterized by X-ray diffraction. The NHC–phosphane complexes with unsymmetrically substituted NHC ligands of type 6 exhibit good catalytic activity in Mizoroki–Heck C–C coupling reactions.

Hydride is abstracted from alcoholic C–H groups by cyclopentadienone-ligated ruthenium(0) and iron(0) complexes. The reactions take place under mild conditions – even with an oxidant as weak as acetone – and show no kinetic order in re-oxidation of the metal hydride mediator. These mechanistic findings pave the way for more general and environmentally more benign C–H activation methods.

A tetrathiofulvalene ligand containing an amidopyridine moiety was prepared and it reaction with Fe(BF₄)₂·6H₂O and [M(CN)₄]^2– counterions led to the 2D polymers {Fe(ttf-adpy)₂[M(CN)₄]}·nH₂O (M^II = Ni, Pd and Pt). The hydrated compounds present a complete thermally induced two-step spin transition, whereas the nonhydrated materials are paramagnetic in the studied temperature range.

Group 4 metal catalysts containing a [OS]-type bidentate phenolato ligand were synthesized. On benzyl abstraction, the dibenzyl zirconium catalyst gives oligo(1-hexene) with a 2,1 regioselectivity. The tribenzyl zirconium catalyst produces isotactic poly(1-hexene) with high molecular weight.