Solvent-free synthesis and key intermediate isolation in Ni2Dy2 catalyst development in the domino ring-opening electrocyclization reaction of furfural and amines

A solvent-free methodology that yields trans-4,5-diaminocyclopent-2-enones, main domains of natural products and a variety of N-heterocycles, is described. The bimetallic catalyst [NiII2DyIII2L4(DMF)6] 2(OTf) 2(DMF) (1) promotes the domino reaction of furfural and amines, with loadings as low as 0.01%, under stirring or microwave-assisted conditions to afford the corresponding frameworks in very good to excellent yields. Crystallographic and theoretical studies shed light on the exclusive formation of the trans-diastereoisomers via a 4π-conrotatory electrocyclization process elucidating the key step in the catalytic process

Polynuclear ampyrone based 3d coordination clusters

The use of the monoanionic Schiff base ligand (E)-4-(2-hydroxybenzylideneamino)-2,3-dimethyl-1-phenyl-1,2-dihydropyrazol-5-one in transition (Co, Ni and Cu) coordination chemistry yields mono-, tetra- and pentanuclear Coordination Clusters with different structural motifs. An organic transformation occurs in the ligand in the Cu compound for which theoretical studies are presented. Solution studies, topological issues and magnetic studies are discussed. The present results demonstrate the richness of the coordination chemistry of this monoprotic organic ligand, which promotes the formation of high-nuclearity CC

Heptanuclear disk-like MII3LnIII4 (M=Ni, Co) coordination clusters: synthesis, structures and magnetic properties

The synthesis, characterization, crystal structures and magnetic properties of isoskeletal heptanuclear disk-like MII 3LnIII 4 coordination clusters with the general formula [CoII 3LnIII 4(µ3- OH)6L6(CF3SO3)](CF3SO3)5] where Ln= Gd (2), Y (3) and [NiII 3LnIII 4(µ3- OH)6L6(CF3SO3)](CF3SO3)5] where Ln= Dy (4), Gd (5), Y (6) are presented. All the compounds are stable in solution as confirmed by ESI-MS. Magnetic studies were performed for compounds 2, 4, 5 and 6 and indicate ferromagnetic coupling while the magnetocaloric properties of 5 are characterized by ΔSm = -15.4 Jkg-1K -1 at T = 5.0 K and Tad = 5.9 K at T = 2.3 K, for µ0ΔH = 7 T

Structural and electronic control of the bidentate 1‐(2‐pyridyl)benzotriazole ligand in copper chemistry with application to catalysis in the A3 coupling reaction

The hybrid bidentate 1‐(2‐pyridyl)benzotriazole (pyb) ligand was introduced into 3d transition metal catalysis. Specifically, [CuII(OTf)2(pyb)2]⋅2 CH3CN (1) enables the synthesis of a wide range of propargylamines by the A3 coupling reaction at room temperature in the absence of additives. Experimental and high‐level theoretical calculations suggest that the bridging N atom of the ligand imposes exclusive trans coordination at Cu and allows ligand rotation, while the N atom of the pyridine group modulates charge distribution and flux, and thus orchestrates structural and electronic precatalyst control permitting alkyne binding with simultaneous activation of the C−H bond via a transient CuI species

Shedding light on the use of Cu(II)-salen complexes in the A3 coupling reaction

One Cu(II) complex, {Cu(II)L} (1S), has been synthesised, in two high yielding steps under ambient conditions, and characterised by single-crystal X-Ray diffraction (SXRD), IR, UV Vis, Circular Dichroism (CD), Elemental analysis, Thermogravimetric analysis (TGA) and Electron Spray Ionization Mass Spectroscopy (ESI-MS). This air-stable compound enables the generation, at room temperature and open-air, of twenty propargylamines, nine new, from secondary amines, aliphatic aldehydes and alkynes with a broad scope with yields up to 99%. Catalyst loadings can be as low as 1 mol%, while the recovered material retains its structural integrity and can be used up to 5 times without loss of its activity. Control experiments, SXRD, 2 cyclic voltammetry and theoretical studies shed light on the mechanism revealing that the key to success is the use of phenoxido salen based ligands. These ligands orchestrate topological control permitting alkyne binding with concomitant activation of the C–H bond and simultaneously acting as template temporarily accommodating the abstracted acetylenic proton, and continuous generating, via in-situ formed radicals and Single Electron Transfer (SET) mechanism, of a transient Cu(I) active site to facilitate this transformation. The scope and limitations of this protocol are discussed and presented

Zinc-dysprosium functionalized amyloid fibrils

The heterometallic Zn2Dy2 entity bearing partially saturated metal centres covalently decorates a highly ordered amyloid fibril core and the functionalised assembly exhibits catalytic Lewis acid behaviour