Costantino Solinas

Tetranuclear copper(II) complexes with polydentate hydrazone ligands: synthesis and X-ray structure

Abstract The synthesis and X-ray crystal structure of two copper(II) complexes, [Cu2(dappc)(OH2)3]2- [Cu2(dappc)(OH2)2(ClO4)]2)6·2H2O (I) (H2dappc=2,6-diacetylpyridine bis(2-pyridinecarbonylhydrazone)) and [Cu2(dapip′)Br]·2H2O, (II) (H3dapip′=2,6-diacetylpyridine 2-pyridinecarbonylhydrazone 2-(2′-pyridine carbonylhydrazono)phenylacetohydrazone) are reported. The interest of both structures pertains mainly to their tetranuclear nature with dimeric units related by an imposed center of symmetry. The structure of compound I is built up from two different complex cations, ClO4− anions and uncoordinated H2O molecules, while that of compound II consists of neutral complex molecules and solvating H2O molecules. During the formation of the latter complex the original H4dapip ligand (H4dapip=2,6-diacetylpyridine bis[2-(2′-pyridinecarbonylhydrazono)phenylacetohydrazone] has undergone a modification through a hydrolysis process, resulting in partial cleavage of one arm to give H3dapip′.

Easy access to a new class of anionic cyano-bridged di- and tri-nuclear organotin adducts. Crystal structure of [N(PPh3)2][ClPh3Sn(µ-NC)Ag(CN)]

Cyanometallates [N(PPh3)2][Ag(CN)2]1 and [N(PPh3)2]2[Pd(CN)4]2 reacted with SnPh3Cl, producing anionic complexes characterized by IR and 119Sn NMR spectroscopy, an X-ray structural analysis of the silver complex evidencing a Sn–NC–Ag bridging interaction; the crystal structure of 1 has also been determined for comparison.

Metal complexes of C2-symmetric chiral bipyridine ligands. X-ray structure of [bis(nitrato)(4S,5S)-2,2-dimethyl-4,5-bis(2-pyridyl)-1,3-dioxolane cobalt(II)]

Chelating properties of C2-symmetric chiral bipyridine ligands are discussed. In particular we report the syntheses of the cobalt(II), nickel(II), zinc(II) and copper(II) complexes of (4S,5S)-2,2-dimethyl-4,5-bis(2-pyridyl)-1,3-dioxolane. All compounds have been characterized by IR spectroscopy, and an X-ray diffraction analysis has been carried out on one of them: Co(L)(NO3)2. The ligand coordinates the cobalt atom by the two nitrogen donors N(1) and N(2). A seven-membered chelation ring is formed, presenting a remarkable non-crystallographic twofold pseudosymmetry around the axis connecting Co and the midpoint of the C(6)–C(7) bond. The metal also binds two monodentate nitrates, thus completing a distorted coordination tetrahedron.

A new polydentate hydrazonic ligand and its dinuclear copper(II) complex with different co-ordination environments

A new hydrazone derivative, di-2-pyridyl ketone [phenyl(semicarbazono)acetyl]hydrazone (H2L), has been prepared and examined as a chelating agent towards metal ions. The molecular structure of the copper complex [Cu2LCl2]·H2O consists of a pair of structurally distinct metal centres with different environments bound to the heptadentate hydrazonic ligand and held together by a –N–N– bridge.

Versatile behaviour of the cyclohexane-1,2-dione bis(semicarbazone) ligand in mono- and di-nuclear metal complexes

The chelating properties of cyclohexane-1,2-dione bis(semicarbazone)(H2chds) were considered by means of IR spectroscopy and the crystal structures of [Co2(H2chds)2(OH2)3(NO3)][NO3]31, [Ni(H2chds)2][NO3]2·2H2O 2 and H2chds·H2O. The structure of 1 is triclinic, space group P, with a= 13.616(2), b= 12.694(2), c= 11.537(2)A, α= 68.13(1), β= 63.37(1), γ= 70.01(1)°, Z= 2 and R= 0.0778. The crystals of 2 are also triclinic, space group P, a= 13.504(4), b= 13.221(5), c= 8.333(5)A; α= 98.00(3), β= 77.71(4), γ= 106.43(3)°, Z= 2 and R= 0.0688. The H2chds·H2O molecule crystallizes in the space group P21/c with a= 7.350(1), b= 15.469(3), c= 10.270(3)A; β= 93.98(2)°, Z= 4 and R= 0.0372. The behaviour of the ligand is different in each structure: in 1 nearly planar tetradentate and accommodated in the equatorial positions of pentagonal bipyramids; in 2 distorted-octahedral co-ordination is provided by two tridentate ligand molecules having one urea group free. The free molecule is nearly planar with a different conformation: its arms are folded in such a way that an intramolecular N–H ⋯ O hydrogen bond is allowed. The structure of 1 is quite original: dimers are formed by means of two carbonylic bridges; the apices of the two polyhedra are occupied by two water molecules and a nitrate ion and one water molecule respectively.