Natalie V. Pervukhina

Metal complexes of the nitrile-substituted nitroxides

Abstract The chelates of the nitrile-substituted 3-imidazoline nitroxides with copper(II), cobalt(II), and nickel(II) have been synthesized and studied with X-ray diffraction and magnetic susceptibility measurements. The influence of the nitrile substituent on structural and magnetic features of the complexes are discussed.

To crystal chemistry of compounds of MHgYX (M = Cu, Ag, Y = S, Se, X = Cl, Br, I)

Abstract In the crystal structures MHgYX (M = Cu, Ag, Y = S, Se, X = Cl, Br, I) and also in CuHg2S2I and Ag2HgSI2 the packing of anions X and Y varies from the hexagonal closest packing (CuHgSI, CuHg2S2I, and α-AgHgSI) to a cubic space-centered packing (Ag2HgSI2, CuHgSBr (295 K), β-AgHgSI, and CuHgSBr (358 K). The packing regularity for large (I–) and smaller (S2–) anions is ensured because Hg2+ has linear coordination S—Hg—S (S—S ≈ 4.5 Å), which is comparable with I—I contacts in a joint close packing. S2–(Se2–) are surrounded in a tetrahedral manner and form stable groups (Hg,M)4Y where the most strong chemical bonds Hg—Y, M—Y, Hg—Hg (∼3.5 Å), Hg—M are concentrated. The chains, layers, and frameworks of (Hg,M)4Y tetrahedra form a “skeleton” and, thus, determine the structure form and the sizes of elementary cells.

The crystal structure of kelyanite, (Hg2)6(SbO6)BrCl2

Abstract The crystal structure of kelyanite, a rare mercury mineral that was found in oxidized mercuryantimony ores in the Kelyana deposit (Buryatia, Russia), has been determined. The preliminary formula of kelyanite was Hg34Sb3Cl3Br1O28 (assuming the presence of both the Hg1+ and Hg2+). In contrast to this assumption, kelyanite appears to contain only monovalent Hg and its revised formula is (Hg2)6(SbO6) BrCl2. Kelyanite is trigonal, space group P3, a = 13.560(4), c = 10.004(6) Å, V = 1593(1) Å3, and Z = 3. In the structure, Hg atoms form six crystallographically independent pairs [dumbbells of composition (Hg2)2+] with Hg-Hg distances of 2.482(3)-2.519(2) Å. The Hg and O atoms form O-Hg-Hg-O systems with Hg-O bond lengths of 1.98(3)-2.33(3) Å and HgHgO angles of 140.3(7)-168.3(9)°. Mercury atoms in the (Hg2)2+ dumbbells have additional coordination to O, Cl, and Br atoms [Hg-O 2.62(2) Å, Hg-Cl 2.68(1)-2.97(1) Å, and Hg-Br 3.00(1)-3.55(1) Å]. Three crystallographically independent Sb atoms are octahedrally coordinated by O atoms with Sb-O distances of 1.96-2.14 Å. The (Hg2)2+ dumbbells link the (SbO6) octahedra in a 3D structure.

Re(V) thiosalicylate complexes. Crystal structure of (Ph4As)[ReO(SC6H4CO2)2py]H2O

Abstract The Re(V) thiosalicylate complex [ReO(SC6H4CO2)2py]− was prepared from [ReO2(py)4]Cl and thiosalicylic acid and isolated as Ph4As+ (1) and Ph4P+ (2) salts. The structure of 1 was determined by X-ray crystallography.

Two Cu(hfac)2 complexes with the imidazoline nitroxide 4-amido-2,2-dimethyl-5,5-dimethoxy-3-imidazoline-1-oxyl. Conversion of a discrete molecular structure to a chain structure as a result of stoichiometric changes

Abstract The reaction of copper hexafluoroacetylacetonate with the stable nitroxide 4-amido-2,2-dimethyl-5,5-dimethoxy-3-imidazoline-l-oxyl (L) in a ratio of 2:1 in hexane yielded the Cu(hfac) 2 -saturated coordination chain polymer of composition [Cu(hfac) 2 ] 2 L. In [Cu(hfac) 2 ] 2 L, half of the Cu(hfac) 2 molecules coordinate L in bidentate fashion by the amide-group oxygen and the imine nitrogen of the heterocycle. The other Cu(hfac) 2 molecules arrange the above {Cu(hfac) 2 L} fragments in polymer chains by alternate coordination of either the N-O group, or the amide-group oxygens of two {Cu(hfac) 2 L} fragments to axial positions. As a result [Cu(hfac) 2 ] 2 LL involves three copper ions with coordination number 6 and with different coordination environments. For metal complexes with nitroxides, this mode of chain formation was observed for the first time. The magnetic properties of the complex are described in terms of an exchange cluster model with ferromagnetic intracluster exchange interactions.

Metal chelates of the amide-substituted nitroxides: the influence of hydrogen bonding on the structure of metal-nitroxide complexes

Abstract The amide function was introduced into metal chelates derived from 3-imidazoline-1-oxyl enaminoketones (MCo, Ni) with the aim of investigation of the influence of hydrogen bonding upon the structure and properties of metal-nitroxide complexes. The complexes obtained manifest strong tendency to include different solvents due to clathration, hydrogen bonding, or hydrogen bonding combined with coordinative bonding. The hydrogen bond patterns vary from linear chains arising from amide–amide interactions to complex 3D motifs formed with participation of the solvent molecules (water, methanol). The hydrogen bonds can act as magnetically innocent intermolecular junctions as well as exchange pathways between the paramagnetic centers. The magnetic properties of the complexes are presented and discussed in connection with their structure.

The competition of basicity and steric factors in the nitroxide donor functions in metal complexes: The study of M(hfac)2(M = Co, Ni) adducts with 3-imidazoline nitroxides

Abstract The similar nitroxides 2,2,5,5-tetramethyl-4-phenyl-3-imidazoline-1-oxyl (L1) and 2,2-dimethyl-5,5-dimethoxy-4-phenyl-3-imidazoline-1-oxyl (L2) from complexes of different composition on reaction with cobalt and nickel hexafluoroacetylacetonates: M(hfac)2L21 and M(hfac)2 (H2O)2L22. In the M(hfac)2L21 complexe the nitroxides are bonded to the metal ion through the nitroxide oxygen but the imine nitrogen does not participate in coordination for steric reasons. In M(hfac)2(H2O)2L22 the nitroxide moieties are H-bonded to the coordinated water molecules through the imine nitrogen atoms and methoxy oxygen atoms. The nitroxide L2 is unstable in the presence of Co(hfac)2 and on removal of water decomposes to yield the adduct with nitrone Co(hfac)2L23, L3 = 2,2-dimethyl-5-methoxy-4-phenyl-2H-imidazol 1-oxide. The complexes M(hfac)2L21 demonstrate strong antiferromagnetic coupling between the metal ion and nitroxides.

Synthesis and structural characterization of the first metal complex with an indole nitroxide

Abstract Copper hexafluoroacetylacetonate reacts with an indole nitroxide (1,2-dihydro-3-oxo-2,2-diphenyl-3H-indole-1-oxyl) in hexane to yield a trinuclear complex with two bridging nitroxides, bis-[μ-(1,2-dihydro-3-oxo-2,2-diphenyl3-H-indole1-1-oxyl)-O; O′]hexakis(hexafluoroacetylacetonato)tricopper(II), which has been structurally characterized by X-ray crystallography. The nitroxide functions of the paramagnetic ligands are coordinated to the terminal copper atoms. Magnetic measurements revealed strong antiferro-magnetic coupling between the spins of the nitroxides and of the terminal copper atoms.