CoII, NiII and UO2II complexes with β-diketones and their arylhydrazone derivatives: Synthesis, structure and catalytic activity in Henry reaction.

The new uranyl, nickel and cobalt complexes, [UO 2 (L 1 ) 2 (R)] ( 1 ), [Ni(L 1 ) 2 ((CH 3 ) 2 S O) 2 ] ( 2 ), [Co(H 2 O) 4 (HL 2 ) 2 ]·2H 2 O ( 3 ) and [UO 2 (H 2 O) 2 (HL 2 ) 2 ]·2H 2 O ( 4 ), were prepared by reaction of UO 2 (CH 3 COO) 2 ·2H 2 O, Ni(CH 3 COO) 2 ·4H 2 O or Co(CH 3 COO) 2 ·4H 2 O with 1,3-diphenyl-propane-1,3-dione (H 2 L 1 ) or 4-(2-(2,4-dioxopentan-3-ylidene)hydrazinyl)benzoic acid (H 2 L 2 ) in the presence of N,N-diethylnicotinamide (R) (for 1 ). Complexes 1 – 4 were characterized by elemental analysis, IR spectroscopy, ESI-MS and single crystal X-ray diffraction technique. In both 1 and 2 the (L 1 ) − coordinates in a bidentate chelating mode where the UO 2 2+ in 1 exhibits a distorted pentagonal bipyramidal and Ni 2+ in 2 a distorted octahedral geometries. In 3 and 4 a hydrazone moiety containing an intramolecular resonance assisted hydrogen bond, with N–H⋯O distances of 2.5469(18) and 2.549(7) Å, respectively, was found in the coordinated ligand (HL 2 ) − . The supramolecular networks (packing diagrams) of 1 – 4 are constructed via hydrogen bonding, CH–π or π–π interactions. All the four complexes ( 1 – 4 ) act as a good catalyst towards the diastereoselective nitroaldol (Henry) reaction of aliphatic and aromatic aldehydes with nitroethane in different solvents such as acetonitrile, methanol or water. Complex 3 was found to be efficient catalyst for the Henry reaction in aqueous medium, providing β-nitroalcohols with good yields (68–91%) and diastereoselectivities ( syn / anti 77:23–73:27). [ABSTRACT FROM AUTHOR]