Structural features of group V A xanthates. The crystal and molecular structures of tris(O-isopropylxanthatoarsenic(III), antimony(III) and -bismuth(II)

The crystal structures of the title compounds, M(S₂COⁱC₃H₇)₃, M = As(III), (1); Sb(III), (2); and Bi(III), (3) have been determined by three dimensional X-ray diffraction techniques and refined by a least square method. Crystals of (1) and (2) are isomorphous and both crystallize in the rhombohedral space group R$\text{3}$, with unit cell parameters for (1) a_hex = 11.559(2), c_hex = 28.131(3) Å and for (2) a_hex = 11.696(2) and c_hex = 28.135(2) Å, Z = 6. The central metal atom in both (1) and (2) is coordinated by three asymmetrically chelating xanthate ligands [AsS 2.305(2) and 2.978(2) Å and SbS 2.508(1) and 3.006(1) Å] which form a distorted octahedral environment consistent with the presence of a stereochemically active lone pair of electrons. Crystals of (3) are orthorhombic, space group Pnma, Z = 4 with dimensions a = 11.003(3), b = 20.833(4) and c = 9.428(2) Å. The environment of the bismuth atom in (3) is seven coordinate and is comprised of six sulphur atoms, derived from three asymmetrically coordinating xanthate ligands, and a bridging sulphur atom from a neighbouring molecule which results in the formation a polymeric array. For (1) final R and R_W 0.050 and 0.047 respectively for 936 reflections [I ? 3σ(I); (2) R 0.040, R_w 0.040 for 1455 reflections I ? 2σ(I)]; and (3) R 0.052, R_w 0.039 for 1796 reflections [I ? 2σ(I).     

The crystal and molecular structure of O-ethylxanthato-bis(quinolin-8-olato)antimony(III) and a redetermination for tris(O-ethylxanthato)antimony(III)

The crystal structures of the title compounds Sb(C₉H₆NO)₂(S₂COC₂H₅) (1) and Sb(S₂COC₂H₅)₃ (2) have been determined by three dimensional X-ray diffraction techniques and refined by a least squares method; final R 0.049 for 2911 reflections [I ? 3σ(I)] for (1) and R 0.047, R_w 0.046 for 846 reflections [I ? 2σ(I)] for (2). Crystals of (1) are triclinic, space group P1, a = 10.825(2), b = 11.131(2), c = 8.911(1) Å, α = 109.45(1), β = 95.92(1) and γ = 93.02(1)° with Z = 2. Crystals of (2) are rhombohedral, space group R$\text{3}$, a_rhomb = 10.138(3) Å and α = 103.43(2)°. The environment of the Sb atom in (1) is based on a pentagonal bipyramidal geometry consisting of the six donor atoms of the three chelating ligands and a stereochemically active lone-pair of electrons which occupies the remaining axial position. The xanthate ligand chelates the Sb atom almost symmetrically with two long SbS bonds of 3.059(2) and 3.171(2) Å. In contrast the xanthate ligands in (2) chelate the Sb atom with asymmetric SbS bonds of 2.511(2) and 3.002(3) Å.     

Dialkyl- and alkylenedithiophosphates of gallium(III)

Gallium(III) tris-dialkyldithiophosphates, Ga[S₂P(OR)₂]₃ (R = C₂H₅, n-C₃H₇, i-C₃H₇, n-C₄H₉ and i-C₄H₉) and gallium(III) tris-alkylenedithiophosphates, Ga(S₂$\text{POGO}$)₃ [G = -CH₂C(C₂H₅)₂CH₂-, -C(CH₃)₂C(CH₃)₂ and -C(CH₃)₂CH₂CH(CH₃)] have been synthesized for the first time by the reactions of gallium(III) chloride with the alkali metal salt of the corresponding ligand in anhydrous benzene in 1:3 molar ratio respectively.These compounds are crystalline solids or viscous liquids and are soluble in common organic solvents, in which they show monomeric behaviour. Based on elemental analyses, molecular weight determinations, IR and NMR (¹H and ³¹P) spectral data, chelate octahedral structures have been proposed for these derivatives.     

S-allyl-3-(2-pyridyl-methylene)dithiocarbazate ligand and its manganese(II), cobalt(III) and nickel(II) complexes

A new NNS tridentate ligand, S-allyl-3-(2-pyridyl-methylene)dithiocarbazate (HL) has been prepared. Three coordination complexes, Mn(L)₂ (1), [Co(L)₂]NO₃ (2) and Ni(L)₂ (3) (L⁻ is the deprotonated monoanionic form of HL) have been synthesized and characterized by elemental analysis, molar conductivity, FT-IR, ¹H NMR and UV-Vis spectroscopy. 1 and 3 are neutral complexes, while 2 is cationic with nitrate as the counter ion. Single crystal X-ray diffraction analysis shows that bis-chelate complexes have a distorted octahedral geometry in which two ligands in thiolate tautomeric form coordinate to the metal center through N atoms of the pyridine and imino moieties and one S atom. Molecular geometry from X-ray analysis, molecular geometry optimization, atomic charges distribution and bond analysis of the ligand and complexes have been performed using the density functional theory (DFT) with the B3LYP functional.     

Secondary ligand-metal interactions in rhodium(III) and iridium(III) phosphoramidite complexes

The synthesis, characterization, and application in asymmetric catalytic cyclopropanation of Rh(III) and Ir(III) complexes containing (S_a,R_C,R_C)-O,O′-[1,1′-binaphthyl-2,2′-diyl]-N,N′-bis[1-phenyl-ethyl]phosphoramidite (1) are reported. The X-ray structures of the half-sandwich complexes [MCl₂(C₅Me₅)(1,κP)] (M = Rh, 2a; M = Ir, 2b) show that the metal-phosphoramidite bond is significantly shorter in the Ir(III) analog. Chloride abstraction from 2a (with CF₃SO₃SiMe₃ or with CF₃SO₃Me) and from 2b (with AgSbF₆) gives the cationic species [MCl(C₅Me₅)(1,2-η-1,κP)]⁺ (M = Rh, 3a; M = Ir, 3b), which display a secondary interaction between the metal and a dangling phenethyl group (NCH(CH₃)Ph) of the phosphoramidite ligand, as indicated by NMR spectroscopic studies. Complexes 3a and 3b slowly decompose in solution. In the case of 3b, the binuclear species [Ir₂Cl₃(C₅Me₅)₂]⁺ is slowly formed, as indicated by an X-ray study. Preliminary catalytic tests showed that 3a cyclopropanates styrene with moderate yield (35%) and diastereoselectivity (70:30 trans:cis ratio) and with 32% ee (for the trans isomer).     

Metal dependent coordination of biomolecular ligand: X-ray crystal structures of copper, cobalt and calcium complexes of (3-hydroxy-5-(hydroxymethyl)-2-methylisonicotinic acid) 5-phosphate, an oxidized pyridoxal 5-phosphate

X-ray crystal analyses of divalent copper, cobalt and calcium complexes of monoanionic (3-hydroxy-5-(hydroxymethyl)-2-methylisonicotinic acid) 5-phosphate (L₁C₈H₉NO₇P⁻) revealed the chemical compositions of Cu ---L·3H₂O(1), Co ---L·5H₂O(2) and Ca·L₂·7H₂O (3) and the coordination structures which depend on the coordination abilities and chemical properties of the respective metal ions. Although 1 and 2 crystals showed similar features, i.e., presence of the metal ion at the crystallographic center of symmetry and octahedral six-coordination, the patterns of coordination with the ligand molecules differed. While direct coordination to the L carboxyl oxygen was observed in 1 crystals, all ligation positions in 2 crystals were occupied by water molecules. On the other hand, 3 crystals formed a pentagonal bipyramidal structure (seven-coordination), where oxygens of L phosphates and water molecules coordinated to the calcium ion. Each of the complex structures showed characteristic molecular packing depending on the pattern of coordination to the respective metal ion. L is monoanionic in all complex crystals, where the phosphate and carboxyl groups are deprotonated and pyridine nitrogen is protonated, and is neutralized by each metal ion. Crystal data: 1, monoclinic, space group P2₁/c, A = 5.4129(6), B = 10.515(2), C = 22.770(2) Å, β = 91.853(9)°, Z = 4, R = 0.0404 for 1834 observed reflections; 2, triclinic, space group

Full-size image

, c = 6.789(3) Å, α = 96.84(3), β = 109.10(3), γ = 100.50(2)°, Z = 2, R = 0.0684 for 1605 observed reflections; 3, triclinic, , a = 10.069(2), B = 14.501(3), c = 10.051(1) Å, α = 100.75(1), β = 97.28(2), γ = 76.18(2)°, Z = 2, R = 0.0540 for 3637 observed reflections.     

trans-Bis[(thiocyanato-S)(1-methylimidazoline-2(3H)-thione)-μ2-(1-methylimidazoline-2(3H)-thione)copper(I)]: preparation, thermal analysis and crystal structure

1-Methylimidazoline-2(3H)-thione (mimtH) and copper(I) thiocyanate in refluxing ethanolacetonitrile produce a colourless, diamagnetic complex, [Cu₂(mimtH)₄(SCN)₂], which crystallises in an orthorhombic cell (a=8.0724(3), b=15.9545(6), c=21.3357(8) Å), space GROUP=Pbca, Z=4, final R=0.0319 from 2427 observed reflections F>4σ_c(F)). In the dimeric complex the copper(I) atoms are pseudo-tetrahedrally coordinated by pairs of, respectively, asymmetrically μ₂-S bridging mimtH, terminal monodentate-S mimtH, (Cu---S=2.290(1) Å), and terminal monodentate-S thiocyanate, (Cu---S=2.332(1) Å). Each pair of ligands is trans-related to its partner across crystallographic centres of symmetry, consequently, each copper(I) atom has an identical S₄ donor set with angles at the metal ranging from 95.9(1)° to 121.8(1)°. The centro-symmetric Cu₂S₂ core is rhomboid with Cu---S=2.377(1) and 2.457(1) Å, Cu---S_br---Cu=72.6(1)° and Cu---Cu, S_br---S_br separation distances of 2.861(1) and 3.897(2) Å, respectively. Thermal decomposition of the complex in flowing air, (133–1000 °C), involves de-sulfurisation of mimtH and thiocyanate with concomitant production of copper(II) sulfide followed by oxidation to copper(II) oxide.     

First example of thiostannates with lanthanide-containing counter cations: Solvothermal synthesis, crystal structures and properties of thiostannates with neodymium(III) and gadolinium(III) complexes of bidentate and tridentate amino ligands

Three new lanthanide thiostannates [Ln₂(en)₆(μ₂-OH)₂]Sn₂S₆ (Ln = Nd (1), Gd (2); en = ethylenediamine) and [Gd(dien)₃]₂[(Sn₂S₆)Cl₂] (3) (dien = diethylenetriamine) were first synthesized by treating LnCl₃ with SnCl₄ and S under mild solvothermal conditions. Compounds 1 and 2 are isostructural. They consist of a binuclear lanthanide(III) complex [Ln₂(en)₆(μ₂-OH)₂]⁴⁺ cation and a dimeric [Sn₂S₆]⁴⁻ anion. The anion is built up by two SnS₄ tetrahedra sharing a common edge. The Nd³⁺ and Gd³⁺ ions are in an eight-coordinated environment forming distorted bicapped trigonal prisms. Compound 3 is composed of two monouclear [Gd(dien)₃]³⁺ complex cations, a [Sn₂S₆]⁴⁻ anion, and two chlorine ions. The Gd³⁺ ion has a nine-coordinated environment forming a distorted tricapped trigonal prism. In compounds 1-3, extensive hydrogen bonds are formed leading to three-dimensional networks of anions and cations. The band gaps of 2.42 eV for 1 and 3.17 eV for 2 have been derived from optical absorption spectra. The new lanthanide compounds might be the precursors for ternary lanthanide thiostannates by the heat treatment under nitrogen atmosphere to get rid of organic components.     

Cyclometalated rhodium(III) and iridium(III) complexes containing amino acids as N,O-chelates

The synthesis of bis-cyclometalated aminocarboxylato complexes [M(α-aminocarboxylato)(ptpy)₂] (M = Rh, 3, 4, 5; M = Ir, 6, 7, 8), ptpy = 2-(p-tolyl)pyridinato; aminocarboxylato = glycinato, l-alaninato, l-prolinato) from [{M(μ-Cl)(ptpy)₂}₂] (M = Rh, 1; M = Ir, 2) is described. The molecular structure of [Ir(l-alaninato)(ptpy)₂] (7) was confirmed by a single-crystal X-ray diffraction study. Compound 7 crystallized from methanol-iso-hexane in the space group P2₁. For 7 the two diastereoisomers Δ_Ir, S_C and Λ_Ir, S_C were found crystallizing twice per unit. Absorption and emission spectra were recorded. The rhodium compounds are weak yellow-green and the iridium species strong green emitters.     

Rhenium(III) and technetium(III) complexes with 2-mercapto-1,3-azole ligands and X-ray crystal structures

Reactions of labile [MCl₃(PPh₃)₂(NCMe)] (M = Tc, Re) precursors with 1H-benzoimidazole-2-thiol (H₂L¹), 5-methyl-1H-benzoimidazole-2-thiol (H₂L²) and 1H-imidazole-2-thiol (H₂L³), in the presence of PPh₃ and [AsPh₄]Cl gave a new series of trigonal bipyramidal M(III) complexes [AsPh₄]{[M(PPh₃)Cl(H₂L^1-3)₃]Cl₃} (M = Re, 1-3; M = Tc, 4-6). The molecular structures of 1 and 3 were determined by X-ray diffraction. When the reactions were carried out with benzothiazole-2-thiol (HL⁴) and benzoxazole-2-thiol (HL⁵), neutral paramagnetic monosubstituted M(III) complexes [M(PPh₃)₂Cl₂(L^4,5)] (M = Re, 8, 9; M = Tc, 10, 11) were obtained. In these compounds, the central metal ions adopt an octahedral coordination geometry as authenticated by single crystal X-ray diffraction analysis of 8 and 11. Rhenium and technetium complexes 1, 4 and rhenium chelate compounds 8, 9 have been also synthesized by reduction of [MO₄]⁻ with PPh₃ and HCl in the presence of the appropriate ligand. All the complexes were characterized by elemental analyses, FTIR and NMR spectroscopy.     

The structures of bis(1H,5H-S-methylisothiocarbonohydrazidium) di-μ-chloro-octachlorodibismuthate(III) tetrahydrate and tris(1H-S-methylisothiocarbonohydrazidium) esachlorobismuthate(III)

The structures of bis(1H⁺,5H⁺-S-methylisothiocarbonohydrazidium) di-μ-chlorooctachlorodibismuthate(III) tetrahydrate: (C₂H₁₀N₄S)₂(Bi₂Cl₁₀)· 4H₂O (compound [I]) and of tris(1H⁺-S-methylisothiocarbonohydrazidium) esachlorobismuthate(III): (C₂H₉N₄S)₃(BiCl_5.67I_0.33) (compound [II]) were determined from single crystal X-ray diffractometer data. Both compounds crystallize as triclinic (P ); crystals [I] with Z = 1 formula unit in a cell of constants: A = 10.621(3), B = 9.989(5), C = 7.439(3) Å, α = 88.31(2), β = 84.51(2), γ = 68.88(2)°, final R = 0.0427 for 2229 unique reflections with I 2σ(I); crystals [II] with Z = 2 and cell dimensions: A = 14.109(4), B = 12.209(9), C = 8.206(7) Å, α = 103.54(3), β = 104.95(2), γ = 81.96(2)°, final R = 0.0411 for 3637 unique reflections (1 2σ(I)). The structure of [I] is built up of diprotonated organic cations, water molecules and dinuclear centrosymmetric [Bi₂Cl₁₀]⁴⁻ anions held together by N-HCl, N-HO, O-HCl hydrogen bonds and Van der Waals interactions. The [Bi₂Cl₁₀]⁴⁻ complex consists of two edge-sharing octahedra in which three pairs of bonds of similar length are observed (Bi-Cl_av = 2.602(5), 2.712(4), 2.855(5) Å). The structure of [II] consists of monoprotonated cations and [BiCl_5.67I_0.33]³⁻ anions held together by a tridimensional network of hydrogen bonds. Each bismuth atom is octahedrally surrounded by six chlorine atoms, one of which is statistically substituted by a iodine atom.     

Homogeneous CO hydrogenation and transfer hydrogenation catalyzed by ruthenium(II) complexes containing optically active Ph2PCH(Ph)CH(Me)NH2 and 1,2-C5H8(PPh2)2 ligands

Combination of (1S,2S)-cyclopentanediylbis(diphenylphosphine) with [Ru(η⁴-C₈H₁₂){η³-(CH₂)₂CMe}₂] afforded the chelate complex [Ru{η³-(CH₂)₂CMe}₂{(1S,2S)-C₅H₈(PPh₂)₂}] (1), which gave (OC-6-13)-[RuCl₂{(1S,2S)-C₅H₈(PPh₂)₂}{(1S,2S)-Ph₂PCH(Ph)CH(Me)NH₂}] (2) upon reaction with methanolic HCl in acetone, followed by the addition of the β-aminophosphine in DMF. The (P ∩ N)₂-chelated complexes (OC-6-13)-[RuCl₂{(1S,2S)-Ph₂PCH(Ph)CH(Me)NH₂}₂] (3) and (OC-6-13)-[RuCl₂{(1R,2S)-Ph₂PCH(Ph)CH(Me)NH₂}₂] (4) resulted from RuCl₃ · 3H₂O and the P,N ligands under reducing conditions. The crystal structures of 3 and 4 were determined by single-crystal X-ray diffraction. Following activation by KOBu-t in isopropanol, compounds 2–4 catalyzed the enantioselective transfer hydrogenation of acetophenone with i-PrOH as the hydrogen source as well as the direct hydrogenation of the ketone by H₂ in low to moderate e.e. (up to 67%).     

Iminophosphorane-organogold(III) complexes induce cell death through mitochondrial ROS production

Gold compounds are being investigated as potential antitumor drugs. Some gold(III) derivatives have been shown to induce cell death in solid tumors but their mechanism of action differs from that of cisplatin, since most of these compounds do not bind to DNA. We have explored cellular events triggered by three different iminophosphorane-organogold(III) compounds in leukemia cells (a neutral compound with two chloride ligands [Au{κ²-C,N-C₆H₄(PPh₂ = N(C₆H₅)-2}Cl₂] 1, and two cationic compounds with either a dithiocarbamate ligand [Au{κ²-C,N-C₆H₄(PPh₂ = N(C₆H₅)-2}(S₂CN-Me₂)]PF₆2, or a water-soluble phosphine and a chloride ligand [Au{κ²-C,N-C₆H₄(PPh₂ = N(C₆H₅)-2}(P{Cp(m-C₆H₄-SO₃Na)₂}₃) Cl]PF₆3). All three compounds showed higher toxicity against leukemia cells when compared to normal T-lymphocytes. Compounds 1 and 2 induced both necrosis and apoptosis, while 3 was mainly apoptotic. Necrotic cell death induced by 1 and 2 was Bax/Bak- and caspase-independent, while apoptosis induced by 3 was Bax/Bak-dependent. Reactive oxygen species (ROS) production at the mitochondrial level was a critical step in the antitumor effect of these compounds.     

Guaianolides and elemanolides from Vernonia anthelmintica

Two new guaianolides, (1R,4R,5S,6R,7R,8S)-8,15-dihydroxyguaia-10(14),11(13)-dien-12,6-olide (1) and (1R,4R,5S,6R,7R,8S,11S)-8,15-dihydroxyguaia-10(14)-en-6,12-olide (2), and two known elemanolides, (4S,5R,6R,7R,8S,10R,11S)-11,13-dihydrovernolepin (3) and (5R,6R,7R,8S,10R,11S)-melitensin (4) were isolated from the aerial parts of Vernonia anthelmintica Willd. The structures of these compounds were determined on the basis of IR, UV, MS, 1D-NMR and 2D-NMR, and their absolute configurations were deduced using the CD exciton chirality method and single-crystal X-ray diffraction. The possible biosynthetic relationships of compounds 1–4 are postulated. Compounds 1–4 were evaluated for their cytotoxicity against HL-60 and SMMC-7721 cell lines.     

Synthesis, structure, and catalytic activity of chiral Cu(II) and Ag(I) complexes with (S,S)-1,2-diaminocyclohexane-based N4-donor ligands

Condensation of (S,S)-1,2-cyclohexanediamine with 2 equiv. of 2-pyridine carboxaldehyde in toluene in the presence of molecular sieves at 70 °C gives N,N′-bis(pyridin-2-ylmethylene)-(S,S)-1,2-cyclohexanediamine (S,S-1) in 95% yield. Reduction of 1 with an excess of NaBH₄ in MeOH at 50 °C gives N,N′-bis(pyridin-2-ylmethyl)-(S,S)-1,2-cyclohexanediamine (S,S-2) in 90% yield. Reaction of 1 or 2 with 1 equiv. of CuCl₂ · 2H₂O in methanol gives complexes [N-(pyridin-2-ylmethylene)-(S,S)-1,2-cyclohexanediamine]CuCl₂ (3) and [Cu(S,S-2)(H₂O)]Cl₂ · H₂O (4), respectively, in good yields. Complex 4 can further react with 1 equiv. of CuCl₂ · 2H₂O in methanol to give [Cu(S,S-2)][CuCl₄] (5) in 75% yield. The rigidity of the ligand coupled with the steric effect of the free anion plays an important role in the formation of the helicates. Treatment of ligand S,S-1 with AgNO₃ induces a polymer helicate {[Ag(S,S-1)][NO₃]}_n (6), while reaction of ligand 2 with AgPF₆ or AgNO₃ in methanol affords a mononuclear single helicate [Ag(S,S-2)][PF₆] (7) or a dinuclear double helicate [Ag₂(S,S-2)₂][NO₃]₂ · 2CH₃OH (8) in good yields, respectively. All compounds have been characterized by various spectroscopic data and elemental analyses. Compounds 1, 3-5, 7 and 8 have been further subjected to single-crystal X-ray diffraction analyses. The Cu(II) complexes do not show catalytic activity for allylation reaction, in contrast to Ag(I) complexes, but they do show catalytic activity for Henry reaction (nitroaldol reaction) that Ag(I) complexes do not.     

Discovery of (1R,6S)-5-[4-(1-cyclobutyl-piperidin-4-yloxy)-phenyl]-3,4-diaza-bicyclo[4.1.0]hept-4-en-2-one (R,S-4a): Histamine H3 receptor inverse agonist demonstrating potent cognitive enhancing and wake promoting activity

A series of fused cyclopropyl-4,5-dihydropyridazin-3-one (3,4-diaza-bicyclo[4.1.0]hept-4-en-2-one) phenoxypiperidine analogs was designed and synthesized, leading to the identification of (1R,6S)-5-[4-(1-cyclobutyl-piperidin-4-yloxy)-phenyl]-3,4-diaza-bicyclo[4.1.0]hept-4-en-2-one (R,S-4a) as a second-generation pyridazin-3-one H₃R antagonist. Compound R,S-4a was a potent H₃R functional antagonist in vivo in the rat dipsogenia model, demonstrated potent wake activity in the rat EEG/EMG model, and enhanced short-term memory in the rat social recognition memory model at doses as low as 0.03–0.3 mg/kg po.     

Imidazolate-bridged dicopper(II) and copper(II)–zinc(II) complexes of macrocyclic ligand with methylimidazol pendants: Model study of copper(II)–zinc(II) superoxide dismutase

Two new homo- and hetero-dinuclear complexes, [Cu₂L(im)](ClO₄)₃4H₂O (1) and [CuZnL(im)](ClO₄)₃4H₂O (2) (where Im=1H-1midazole and L = 3, 6, 9, 16, 19, 22-hexaaza-6, 19-bis(1H-imidazol-4-ylmethyl)tricycle[22, 2, 2, 2^11,14]triaconta-1, 11, 13, 24, 27, 29-hexaene) were synthesized and characterized as model compounds for the active site of copper(II)–zinc(II) superoxide dismutase (Cu₂Zn₂–SOD). X-ray crystal structure analysis revealed that the metal centers in both complexes exhibit distorted trigonal-bipyramid coordination geometry and the CuCu and CuZn distances are both 6.02 Å. Magnetic and ESR spectral measurements of 1 showed antiferromagnetic exchange interactions between the imidazolate-bridged Cu(II) ions. The ESR spectrum of 2 displays typical signals of mononuclear Cu(II) complex, demonstrating the formation of heterodinuclear complex 2 rather than a mixture of homodinuclear Cu(II)/Zn(II) complexes. pH-dependent ESR and UV–visible spectral measurements manifest that the imidazolate exists as a bridging ligand from pH 6 to 11 for both complexes. The IC₅₀ values of 1.96 and 1.57 μM [per Cu(II) ion] for 1 and 2 suggest that they are good models for the Cu₂Zn₂–SOD.     

Stereoisomers of Mn(III) complexes of ethylenebis[(o-hydroxyphenyl)glycine]

We have prepared the Mn(III) complexes rac-Na[Mn(EHPG)]·3H₂O (1) and rac,meso-Na[Mn(EHPG)]·H₂O (2), where H₄EHPG is ethylenebis[(o-hydroxyphenyl)glycine], and determined their X-ray crystal structures. Complex 1 contains N(S,S)C(R,R) configurations at the N and C stereogenic centres, whilst in the unit cell of complex 2 there are two independent molecules, 2a (meso) and 2b (rac), with N(R,R)C(S,R) and N(R,R)C(S,S) configurations, respectively. Enantiomers of each complex are also present. The Mn(III) centres have Jahn-Teller-distorted octahedral geometry. The rac isomer has two long axial MnO(carboxylate) bonds (2.162-2.202 Å) and the equatorial plane contains two short MnN bonds (2.012-2.063 Å) trans to short MnO(phenolate) bonds (1.865-1.901 Å). The meso isomer has long axial MnN (2.194 Å) and MnO(carboxylate) (2.152 Å) bonds, and shorter equatorial MnN (2.005 Å) trans to MnO(phenolate) (1.901 Å) and MnO(carboxylate) (1.988 Å) trans to O(phenolate) (1.897 Å) bonds.     

Mono- and dinuclear Fe(III) complexes with the N2O2 donor 5-chlorosalicylideneimine ligands; synthesis, X-ray structural characterization and magnetic properties

Two novel monomeric [C₁₈H₁₇Cl₃N₂O₂Fe] (1) and dimeric [C₃₈H₃₆N₄O₄Cl₆Fe₂] (2) Fe(III) tetradentate Schiff base complexes have been synthesized and their crystal structures have been determined by single crystal X-ray diffraction analysis. In complex (1) the Schiff base ligand coordinates toward one iron atom in a tetradentate mode and each iron atom is five coordinated with the coordination geometry around iron atom which can be described as a distorted square pyramid. The presence of a short (2.89 Å) non-bonding interatomic Fe···O distances between adjacent monomeric Fe(III) complexes results in the formation of a dimer. Structural analysis of compound (2) shows that the structure is a centrosymmetric dimer in which the six coordinated Fe(III) atoms are linked by μ-phenoxo bridges from one of the phenolic oxygen atoms of each Schiff base ligand to the opposite metal center. The variable-temperature (2-300 K) magnetic susceptibility (χ) data of these two compounds have been investigated. The results show that for both complexes Fe(III) centers are in the high spin configuration (S = 5/2) and indicate antiferromagnetic spin-exchange interaction between Fe(III) ions. The obtained results are briefly discussed using magnetostructural correlations developed for other class of iron(III) complexes.     

Differential effects of Co(III), Ni(II), and Ru(III) amine complexes on Sindbis virus

Transition metal complexes [Co(cyclen)(NH₃)₂](ClO₄)₃⋅H₂O (cyclen = 1,4,7,10-tetraazacyclododecane) (2), [Co(NH₃)₅(OH₂)](CF₃SO₃)₃ (3) [Ni(NH₃)₆]Br₂ (4) and [Ru(NH₃)₆]Cl₃ (5) were tested against Sindbis infected baby hamster kidney (BHK) cells and show differential effects from the previously reported anti-viral complex [Co(NH₃)₆]Cl₃ (1). The macrocyclic complex 2 and labile aqua complex 3 show either no or little effect on the survival on Sindbis virus-infected cells as compared to that for 1, which show a monotonic increase in % BHK cell survival. Nickel and ruthenium ammine complexes 4 and 5 had a moderate influence of cell survival. While the results showed some anti-viral activity for some of the structural variations, it appears that 1, with its potential to be a broad-spectrum anti-viral compound, occupies a unique position in its ability to both significantly enhance cell survival and to decrease viral expression of infected cells. We also show that 1 also shows anti-viral activity against Adenovirus lending support to the broad-spectrum potential of this complex.