From nitrobenzenes to substituted tetrahydroquinolines in a single step by a domino reduction/imine formation/aza-diels-alder reaction.

The three-component reaction between a nitrobenzene, an aldehyde, and a dienophile in the presence of iron powder as a reductant and montmorillonite K10 as a catalyst in aqueous citric acid delivers the products of an aza-Diels-Alder (Povarov) reaction with high endo-selectivity and yields up to 99%.

Formation of novel T-shaped NNN ligands via rare-earth metal-mediated Si-H activation.

Reactions of silylamides [Ln{N(SiHMe2)2}3(thf)2] with sterically crowded terphenylamine DmpNH2 (Dmp = 2,6-Mes2C6H3 with Mes = 2,4,6-Me3C6H2) afforded via a template reaction the formation of a new tridentate ligand, and derived complexes of composition [LnN{SiMe2N(Dmp)}2] (Ln = Ce, Pr) were obtained. Usage of the even more bulky amine Ar*NH2 (Ar* = 2,6-Trip2C6H3 with Trip = 2,4,6-iPr3C6H2) yielded the free protonated ligand NH{SiMe2NH(Ar*)}2.

Tuning spin-spin coupling in quinonoid-bridged dicopper(II) complexes through rational bridge variation.

Bridged metal complexes [{Cu(tmpa)}2(μ-L(1)-2H)](ClO4)2 (1), [{Cu(tmpa)}2(μ-L(2)-2H)](ClO4)2 (2), [{Cu(tmpa)}2(μ-L(3)-2H)](BPh4)2 (3), and [{Cu(tmpa)}2(μ-L(4)-2H)](ClO4)2 (4) (tmpa = tris(2-pyridylmethyl)amine, L(1) = chloranilic acid, L(2) = 2,5-dihydroxy-1,4-benzoquinone, L(3) = (2,5-di-[2-(methoxy)-anilino]-1,4-benzoquinone, L(4) = azophenine) were synthesized from copper(II) salts, tmpa, and the bridging quinonoid ligands in the presence of a base. X-ray structural characterization of the complexes showed a distorted octahedral environment around the copper(II) centers for the complexes 1-3, the donors being the nitrogen atoms of tmpa, and the nitrogen or oxygen donors of the bridging quinones. In contrast, the copper(II) centers in 4 display a distorted square-pyramidal coordination, where one of the pyridine arms of each tmpa remains uncoordinated.

Cobalt complexes with "Click"-derived functional tripodal ligands: spin crossover and coordination ambivalence.

We demonstrate the use of a Cu(I) catalyzed "Click" reaction in the synthesis of novel ligands for spin crossover complexes. The reaction between azides and alkynes was used to synthesize the reported tripodal ligand tris[(1-benzyl-1H-1,2,3-triazol-4-yl)methyl]amine, TBTA, and the new ligands tris[(1-cyclohexyl-1H-1,2,3-triazol-4-yl)methyl]amine, TCTA, and tris[(1-n-butyl-1H-1,2,3-triazol-4-yl)methyl]amine, TBuTA. Reactions of TBTA with Co(ClO(4))(2) lead to complexes of the form [Co(TBTA)(CH(3)CN)(3)](ClO(4))(2), 1, and [Co(TBTA)(2)](ClO(4))(2), 2, where complex formation can be controlled by the metal/ligand ratio and the complexes 1 and 2 can be chemically and reversibly switched from one form to another in solution resulting in coordination ambivalence.

One-pot synthesis of symmetric and asymmetric p-quinone ligands and unprecedented substituent induced reactivity in their dinuclear ruthenium complexes.

The compounds 2-[2-(trifluoromethyl)-anilino]-5-hydroxy-1,4-benzoquinone (L(1)), 2,5-di-[2-(trifluoromethyl)-anilino]-1,4-benzoquinone (L(2)), 2-[2-(methylthio)-anilino]-5-hydroxy-1,4-benzoquinone (L(3)), and 2,5-di-[2-(methylthio)-anilino]-1,4-benzoquinone (L(4)) were prepared in high yields by reacting 2,5-dihydroxy-1,4-benzoquinone with the corresponding amines in a one-pot synthesis in refluxing acetic acid. This straightforward and "green" synthesis delivers biologically relevant asymmetric p-quinones such as L(1) and L(3) in a rare, simple, one-step process. The proposed synthetic route is general and can be applied to generate a variety of such molecules with different substituents on the nitrogen atoms.

Benzo-1,3,2-diazaphospholide and benzo-1,3,2-diazaphospholium: an isoelectronic aromatic anion-cation pair.

Isoelectronic benzo-1,3,2-diazaphospholium cations and benzo-1,3,2-diazaphospholide anions were prepared from the same phosphazane precursor; both species display according to computational studies similar aromaticity as the neutral benzo-1,3,2-diazaphosphole but are chemically more stable due to their ionic nature.

Synthesis of bis(phosphinoferrocenyl) copper complexes from zwitterionic quinonoid ligands and their structural and redox properties.

Reactions of N,N'-di-n-butyl-2-amino-5-alcoholate-1,4-benzoquinonemonoiminium L(1), or N,N'-diisopropyl-2-amino-5-alcoholate-1,4-benzoquinonemonoiminium L(2) with [{(dppf)Cu}(2)(mu-Cl)(2)] (dppf = 1,1'-bis(diphenylphosphino)ferrocene) or [{(dispf)Cu}(2)(mu-Cl)(2)] (dispf = 1,1'-bis(diisopropylphosphino)ferrocene) led to the formation of the heterodinuclear complexes [(dppf)(CuL(1)(-H))] (2), [(dppf)(CuL(2)(-H))] (3), [(dispf)(CuL(1)(-H))] (4), and [(dispf)(CuL(2)(-H))] (5). The crystal structure of L(2) was determined by X-ray diffraction and shows that the molecule exists in a 6pi + 6pi zwitterionic form, with two chemically connected but electronically nonconjugated pi-subunits. The crystal structures of complexes 2-4 show a distorted tetrahedral coordination environment for the Cu(I) center and a more localized pi-system for the ligands.

Stabilizing the elusive ortho-quinone/copper(I) oxidation state combination through pi/pi interaction in an isolated complex.

The heterodinuclear compound [(PhenQ)Cu(dppf)](BF4), PhenQ = 9,10-phenanthrenequinone and dppf = 1,1'-bis(diphenylphosphino)ferrocene, was identified structurally and spectroscopically (NMR, IR, UV-vis) as a copper(I) complex of a completely unreduced ortho-quinone. Crystallographic and DFT calculation results suggest that this stabilization of a hitherto elusive arrangement is partially owed to intramolecular pi/pi interactions phenyl/PhenQ. Intermolecular PhenQ/PhenQ pi stacking is also observed in the crystal.