N-substituted ethylcarbamate complexes of thorium(IV) and lanthanum(III) nitrates

N-substituted ethylcarbamates form with thorium nitrate the complexes Th(NO₃)₄·3RHNC(O)OC₂H₅ (where R = CH₃, C₂H₅, C₆H₅(CH₃)CH) and with lanthanum nitrate the complexes La(NO₃)₃· 2RR′NC(O)OC₂H₅·3H₂O (where R = CH₃, C₂H₅, C₆H₅(CH₃)CH; R′ = H and R = CH₃, C₆H₅; R′ = C₂H₅ or R = R′ = CH₃). In addition the anhydrous La(NO₃)₃·3(C₂H₅)₂NC(O)OC₂H₅ has been isolated. From the IR spectra it is deduced that the carbamates coordinate the metal through the carbonyl oxygen atom and that the nitrato groups act as chelated ligands. ¹H nmr spectral data of the complexes are reported and discussed.     

The base-catalyzed isomerization of trans-RCo(H2O)L (L=5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene)

The sec, rac-CH₃Co(H₂O)L²⁺ (L=5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene) was prepared successfully via meso-CH₃Co(H₂O)L²⁺ in aqueous solution. The isomerizations from meso-RCo(H₂O)L²⁺ (R=CH₃, C₂H₅ and C₃H₇) and sec, rac-CH₃Co(H₂O)L²⁺ to pri, rac-RCo(H₂O)L²⁺ were both base catalyzed in aqueous solution. The kinetic results showed the reaction to be first order in both organocobalt complex and hydroxide ion with the reactivity order for the alkyl group being C₃H₇ ∼ C₂H₅ ? CH₃. However, the conversion from the most steric hindered isomer form of sec, rac- was slow. The ratio of the isomerization rate constants between meso-CH₃Co(H₂O)L²⁺ and sec, rac-CH₃Co(H₂O)L²⁺ to pri, rac-CH₃Co(H₂O)L²⁺ is almost a factor of 100. The thermodynamic activation parameters for these isomerization reactions were investigated.     

Amidino-complexes of iron(II) and (III)

Lithioamidines {R′N(Li)C(R)NR′, I; R = CH₃, R′ = C₆H₅, p-CH₃,C₆H₄} react with iron(III) chloride

in monoglyme to produce navy-blue, high spin Fe{R′NC(R)NR′}₃ complexes which are extremely air and moisture sensitive. The corresponding reaction when R = R′ = C₆H₅ produces a soluble red complex and an air-stable green complex, whereas when R = H, R′ = C₆H₅ and R = R′ = C₆H₅ and the reaction is started at ca. ?20°, red and green complexes respectively are formed. Though all the complexes are formulated Fe{R′NC(R)NR′}₃, their properties reflect association through bridging amidino-groups. Iron(II) chloride reacts with I(R = CH₃, R′ = p-CH₃C₆H₄) to form two complexes, one crimson and soluble in organic solvents, and one brown and insoluble, which are fomulated [Fe{R′NC(R)NR′}₂]_n. The iron(III) complexes failed to react with, or were decomposed by, a variety of reducing, electrophilic and nucleophilic reagents, though blue Fe{p-CH₃C₆H₄NC(CH₃)N-p-CH₃C₆H₄}₃ reacts readily with nitric oxide to form a purple addition complex from which the N-nitroso-compound p-CH₃C₆H₄NC(CH₃)N(NO)-p-CH₃C₆H₄ was obtained in high yield. Treatment of the corresponding brown iron(II) complex with nitric oxide gave no reaction.     

Isonicotinamide as entering ligand on trans-[Ru(NH3)4P(OR)3(H2O)]22+, (R = Me,Pr, iPr and Bu)

trans-[Ru(NH₃)₄P(OR)₃(H₂O)]²⁺ (R = Me, Pr, ⁱPr, and Bu) reacts with isonicotinamide at second-order- specific rates k₁ of 1.2, 2.3, 7.4 and 8.1 M⁻¹ s⁻(25 °C, μ = 0.10 NaCF₃COO/CH₃COOH), respectively, for R = Me, Pr, ⁱPr and Bu. The products trans- [Ru(NH₃)₄P(OR)₃isn](PF₆)₂ have been isolated and characterized by micro analysis, cyclic voltammetry, and electronic spectral data. The aquation rates k₋₁ for the isonicotinamide (isn) derivatives are 5.2 × 10⁻², 5.9 × 10⁻², 2.0 × 10⁻¹ and 3.4 × 10⁻¹ s⁻¹ for R= Me, Pf, Bu and ⁱPr, respectively. The activation parameters for the forward and backward reactions indicate the same mechanism for all of them. The substitution proceeds by a dissociative mechanism with a significant outer-sphere association of trans-[Ru(NH₃)₄P(OR)₃(H₂O)]²⁺ complexes with isn. Assuming k₁ as indicative of the lability of the coordinated water molecule on the monophosphite complexes, the following sequence of increasing trans-effect mav be proposed: P(OMe)₃ <P(OEt)₃ <P(OPr)₃ <P(OⁱPr)₃ <P(OBu)₃. The affinity of the monophosphite complexes for isn increases according to P(OMe)₃ ⋍ P(OⁱPr)₃ < P(OEt)₃ < P(OPr)₃ ⋍ P(OBu)₃.     

Cyclic and acyclic compartmental Schiff bases, their reduced analogues and related mononuclear and heterodinuclear complexes

[1+1] macrocyclic and [1+2] macroacyclic compartmental ligands (H₂L), containing one N₂O₂, N₃O₂, N₂O₃, N₄O₂ or O₂N₂O₂ Schiff base site and one O₂O_n (n=3, 4) crown-ether like site, have been prepared by self-condensation of the appropriate formyl- and amine precursors. The template procedure in the presence of sodium ion afforded Na₂(L) or Na(HL) · nH₂O. When reacted with the appropriate transition metal acetate hydrate, H₂L form M(L) · nH₂O, M(HL)(CH₃COO) · nH₂O, M(H₂L)(X)₂ · nH₂O (M=Cu²⁺, Co²⁺, Ni²⁺; X=CH₃COO⁻, Cl⁻) or Mn(L)(CH₃COO) · nH₂O according to the experimental conditions used. The same complexes have been prepared by condensation of the appropriate precursors in the presence of the desired metal ion. The Schiff bases H₂L have been reduced by NaBH₄ to the related polyamine derivatives H₂R, which form, when reacted with the appropriate metal ions, M(H₂R)(X)₂ (M= Co²⁺, Ni²⁺; X=CH₃COO⁻, Cl⁻), Cu(R) · nH₂O and Mn(R)(CH₃COO) · nH₂O. The prepared ligands and related complexes have been characterized by IR, NMR and mass spectrometry. The [1+1] cyclic nature of the macrocyclic polyamine systems and the site occupancy of sodium ion have been ascertained, at least for the sodium (I) complex with the macrocyclic ligand containing one N₃O₂ Schiff base and one O₂O₃ crown-ether like coordination chamber, by an X-ray structural determination. In this complex the asymmetric unit consists of one cyclic molecule of the ligand coordinated to a sodium ion by the five oxygen atoms of the ligand. The coordination geometry of the sodium ion can be described as a pentagonal pyramid with the metal ion occupying the vertex. In the mononuclear complexes with H₂L or H₂R the transition metal ion invariantly occupies the Schiff base site; the sodium ion, on the contrary, prefers the crown-ether like site. Accordingly, the heterodinuclear complexes [MNa(L)(CH₃COO)_x] (M=Cu²⁺, Co²⁺, Ni², x=1; M=Mn³⁺, x=2) have been synthesised by reacting the appropriate formyl and amine precursors in the presence of M(CH₃COO)_n · nH₂O and NaOH in a 1:1:1:2 molar ratio. The reaction of the mononuclear transition metal complexes with Na(CH₃COO) · nH₂O gives rise to the same heterodinuclear complexes. Similarly [MNa(R)(CH₃COO)_x] have been prepared by reaction of the appropriate polyamine ligand H₂R with the desired metal acetate hydrate and NaOH in 1:1:2 molar ratio.     

Photolytic CO-substitution reaction of organoiron thiocarboxylate derivatives CpFe(CO)2SCOR (R=alkyl, aryl) with diphosphines (Ph2P(CH2)nPPh2) (n=1-6): X-ray crystal structure of [CpFe(dppm)SCO(3,5-(NO2)2C6H3)]

The photolytic CO-substitution reaction of the organoiron thiocarboxylate complexes CpFe(CO)₂SCOR (R=CH₃, 2-CH₃C₆H₄, 2-NO₂C₆H₄, 4-NO₂C₆H₄, 3,5-(NO₂)₂C₆H₃) with diphosphines (Ph₂P(CH₂)_nPPh₂) [n=1 (dppm), n=2 (dppe), n=3 (dpppr), n=4 (dppb), n=5 (dppp), n=6 (dpph)] at room temperature using 1:2 (metal-ligand) molar ratio afforded exclusively the disubstituted complexes CpFe(Ph₂P(CH₂)_nPPh₂)SCOR when n=1, 2 and 3 and the monosubstituted analogs CpFe(CO)(Ph₂P(CH₂)_nPPh₂)SCOR when n=4, 5 and 6. This reaction was found to be strongly influenced by the backbone length of the diphosphine ligand, the nature of the R group of the thiocarboxylate moiety and the metal-ligand molar ratios. The crystal structure of CpFe(dppm)SCO(3,5-(NO₂)₂C₆H₃) was determined.     

Metal complexes with the ligand derived from 6-acetyl-1,3,7-trimethyllumazine and benzohydrazide. Molecular structures of two new Co(II) and Rh(III) complexes and analysis of in vitro antitumor activity

The structures and spectroscopic properties of new Mn(II), Co(II), Cd(II), Hg(II), Ag(I), Rh(III), and Ir(I) complexes with the ligand BZLMH derived from 6-acetyl-1,3,7-trimethyllumazine (lumazine = pteridine-2,4(1H,3H)-dione) and benzohydrazide are reported. Complexes have been characterized by elemental analyses, spectroscopic studies (IR, UV-vis, ¹H, ¹³C and ¹⁵N NMR) and magnetic measurements. In all the complexes, the lumazine-derived ligand appears to be coordinated in either tridentate (N5, N61 and O63) or tetradentate forms (O4, N5, N61 and O63). The molecular structures of the [Co(BZLMH)(H₂O)(CH₃CN)₂](ClO₄)₂ · CH₃CN and [RhCl₂(BZLM)(CH₃CN)] · CH₃CN complexes, determined by single crystal X-ray diffraction, have allowed to corroborate both coordination behaviours.The cytotoxic activity of the free ligand and complexes against human neuroblastoma NB69 cell line is also described. The differential analysis of the initial cytotoxic screening data has shown good activity only for the [RhCl₂(BZLM)(CH₃CN)] · CH₃CN compound at concentrations at around 2 μM; for the other complexes, a modulation of the cell growth was not found upon complexation, this non-specific effect strongly suggesting an apoptotic behaviour.     

Dioxouranium(VI) thiocyanate complexes of schiff bases of p-nitro,chloro, bromo,hydroxy and methoxy aniline and salicylaldehyde

A series of dioxouranium(VI) complexes was synthesised with some Schiff base ligands containing substituent groups at para positions to CHN groups. These molecules were obtained by the condensation of para-nitro, chloro, bromo, hydroxy, methyl and methoxy aniline with salicylaldehyde. The bidentate ligands formed complexes of the type UO₂(NCS)₂ (X-N-Sal)_n·mH₂O, where n = 2, m = 3, x = NO₂, Cl, Br and OH; n = 3, m = 2, x = CH₃ and OCH₃.Conductivity measurements indicate that all the complexes are non-electrolytes in nitromethane solution, whereas in DMF they correspond to 1:1 electrolytes.IR spectral data suggest that the molecules and not the anions of the Schiff base are coordinated to the central uranium atom. IR and Raman spectra suggest that the complexes UO₂(NCS)₂(X-N-Sal)₂· 3H₂O (X = NO₂, Cl, Br) have C_2h molecular symmetry, whereas UO₂(NCS)₂(X-N-Sal)₃·2H₂O (X = OCH₃, CH₃) have C_2v symmetry.The frequencies of UO_2(asym) (IR) and UO_2(sym) (R) in the complexes seem to vary with the various substituents of the Schiff base ligand, in the order:NO₂ > Cl > Br > OH > CH₃ > OCH₃     

Trimethylsilyloxo complexes of oxomolybdenum(V)

The complexes LMo^VIO₂X [L?=?hydrotris(3,5-dimethylpyrazol-1-yl)borate; X?=?Cl, Br, NCS, OPh, SPh, SCH₂Ph] are converted to air-stable complexes LMo^VO(OSiMe₃)X by one-electron coupled electron-electrophile transfer (CEET) reactions involving cobaltocene and the electrophilic reagent Me₃SiCl. These complexes may also be obtained from LMo^VO(OH)X by reaction with Me₃SiCl in the presence of base. LMo^VO(OSiMe₃)(SCH₂Ph) crystallises in space group P2₁/n, with a?=?8.526 (1) Å, b?=?23.141 (3) Å, c?=?16.499 (2) Å, β?=?103.75 (12)° and Z?=?4. The complex exhibits a distorted octahedral structure with a facially tridentate L ligand and mutually cis oxo [Mo=O?=?1.675 (4) Å], silyloxo [Mo–O?=?1.932 (4) Å] and thiolato [Mo–S?=?2.398 (2) Å] ligands. The detailed redox properties of LMo^VO(OR)X (R?=?SiMe₃, alkyl, aryl) differ from those of LMo^VO(OH)X. Centres [Mo^VO(OR)] are candidates for the stable "inhibited" forms of certain molybdenum enzymes formed under conditions which apparently disfavour the catalytically active [Mo^VO(OH)] centres. In the coordinating solvent pyridine (py), both LMo^VIO₂(SPh) and LMo^VO(OSiMe₃)(SPh) are reduced in one-electron steps to stable LMo^IVO(py)(SPh). LMo^IVO(py)(SR) complexes are also obtained from LMo^VIO₂(SR) (R?=?Ph, CH₂Ph, CHMe₂) via a two-electron oxygen atom transfer reaction with tertiary phosphines in pyridine. Consequently, the Mo(IV) product is accessible via a concerted two-electron step or via two one-electron steps.     

Kinetic studies of the reactions of pentacyanonitrosylferrate(2−) with ligands containing acidic methylene groups

The kinetic studies of the addition reactions of pentacyanonitrosylferrate(2−) (NP) with acidic methylene ligands of the form CH₂LL′ (L, L′ = -CN, -CONH₂; -CN, -CN; CH₃CO-, CH₃CO-) have been carried out in basic solutions. The increase in the second order rate constants for the formation of Fe(CN)₅N(O)CLL′⁴⁻ complexes with the increase of OH⁻ concentration indicated that ^?CHLL′ is the reactive species of the reactions. In addition to the pK_a, the lability of the methylene protons of the ligands in aqueous solution also governs the reactivity of the reactions. The nitrosation products were rather unstable with respect to the dissociation into and oxime compounds. The kinetic measurements showed that the rates of dissociation were first order and were rather insensitive to the hydroxide concentration for the ligands under study.     

Synthesis and theoretical analysis of the structures and bonding in five new neutral square planar bis[2,4-di(aryl)-1,3,5-triazapentadienato]nickel(II) complexes

Solvothermal reactions in methanol of nickel acetate tetrahydrate, Ni(OAc)₂ · 4H₂O, with benzonitrile derivatives NC(C₆H₄)X, where X is one of the electron withdrawing substituents -CN, -NO₂, or -CF₃, located at the m- or p-positions relative to -CN, yield complexes of the general formula Ni{HNC(R)-NC(R)-NH}₂. More specifically, 3-nitrobenzonitrile, 4-nitrobenzonitrile, 1,3-dicyanobenzene, 1,4-dicyanobenzene, and ααα-trifluoro-p-toluonitrile are found to react with Ni(OAc)₂ · 4H₂O to yield Ni{HNC(R)-NC(R)-NH}₂, where R = 3-(NO₂)C₆H₄, 4-(NO₂)C₆H₄, 3-(CN)C₆H₄, 4-(CN)C₆H₄, or 4-(CF₃)C₆H₄, respectively. Analogous reactions of nitriles lacking electron withdrawing groups do not occur under similar conditions. Solid-state structures have been determined for the complexes with p-NO₂, p-CN, and p-CF₃ substituents on the phenyl rings. In addition, we describe density functional theory (DFT) and natural bonding orbital theory (NBO) studies on a simplified analog of these compounds, aimed at understanding their molecular bonding. It is shown that the new compounds for which solid-state structures have been determined are model examples of coordination compounds containing robust ω-bonds.     

Synthesis and X-ray structures of rhenium(I) carbonyl aminoalkoxide and aminocarboxylate complexes

The complexes [Re{MeN(CH₂CH₂O)(CH₂CH₂OH)-κ³N,O,O}(CO)₃] (1), [Re{N(CH₂CH₂O)(CH₂CH₂OH)₂-κ³N,O,O}(CO)₃] (2), [Me₃NH]₂[(OC)₃Re{N(CH₂CO₂)₂-κ³N,O,O}CH₂CH₂{N(CH₂CO₂)₂-κ³N,O,O}Re(CO)₃] (3), [Me₃NH]₂[Re₂{μ₂-2,6-(O₂C)₂(C₅H₃N)-κ³N,O,O}₂(CO)₆] (4) and [Re₂{μ₂-2,6-(OCH₂)(C₅H₃N)(CH₂OH)-κ²N,O}₂(CO)₆] (5) were synthesized in high yields via the reactions of [Re₂(CO)₁₀] and Me₃NO with MeN(CH₂CH₂OH)₂, N(CH₂CH₂OH)₃, EDTA, pyridine-2,6-dicarboxylic acid and pyridine-2,6-dimethanol, respectively. Complexes 1-5 were characterized by IR and ¹H NMR spectroscopy, elemental analysis and X-ray crystallography.     

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.     

Synthesis and coordination chemistry of tripodal dialkyl[1,2-bis(diethylcarbamoyl)ethyl]phosphonates with lanthanide nitrates

Trifunctional dialkyl [1,2-bis(diethylcarbamoyl)- ethyl] phosphonates, (RO)₂P(O)CH[C(O)N(C₂H₅)₂]- [CH₂C(O)N(C₂H₅)₂] R  CH₃, C₂H₅, i-C₃H₇, n-C₆H₁₃ were prepared from the respective sodium salts, Na[(RO)₂P(O)CHC(O)N(C₂H₅)₂] and N,N- diethylchloroacetamide, and they were characterized by elemental analysis, mass, infrared and NMR spectroscopy. The molecular structure of (i-C₃H₇O)₂- P(O)CH[C(O)N(C₂H₅)₂][CH₂C(O)N(C₂H₅)₂] was determined by single crystal X-ray diffraction analysis and found to crystallize in the monoclinic space group P2₁/c with a=15.589(6), b=9.783(4), c= 16.283(7) Å, β = 110.90(3)°, Z = 4 and V= 2320(2) ų. The structure was solved by direct methods and blocked least-squares refinement converged with Rf = 5.7% and R_wF= 4.4% on 2266 unique data with F>4σ(F). Important bond distances include PO 1.459(3) Å, CHCO 1.228(3) Å and CHCH₂CO 1.223(3) Å. The coordination chemistry of the ligand with several lanthanides was examined, and the structure of the complex Gd(NO₃)₃{[(i-C₃H₇O)₂P(O)CH[C(O)N(C₂H₅)₂][CH₂C(O)N(C₂H₅)₂]}₂·H₂O was determined. The complex crystallized in the monoclinic space group P2₁/n with a = 13.524(5), b = 22.033(4), c = 19.604(4) Å β = 106.22(2)°, Z = 4 and V= 5609(3) ų. The structure was solved by heavy atom techniques and blocked least-squares refinement converged with R_F = 5.9% and R_wF = 4.1% on 5275 reflections with F > 4σ(F). Both trifunctional ligands were found to bond to Gd(III) through only the phosphoryl oxygen atoms. The remainder of the Gd coordination sphere was composed of three bidentate nitrate oxygen atoms and an oxygen bonded water molecule. Several important bond distances include GdO(phosphoryl)_av = 2.343(5) Å, GdO(nitrate)_av = 2.475(7) Å, GdO(water) = 2.354(5) Å, PO(phosphoryl)_av = 1.467(6) Å, CHCO_av = 1.242(10) Å and CHCH₂CO_av = 1.209(11) Å.     

Inductive influence of 4′-terpyridyl substituents on redox and spin state properties of iron(II) and cobalt(II) bis-terpyridyl complexes

A series of iron and cobalt bis-terpyridine (terpy) complexes were prepared with the general formula [M(R-terpy)₂](PF₆)₂, where M represents Co(II) and Fe(II), and R is the following terpyridine substituents in order of increasing electron-withdrawing behavior [(C₄H₈)N, (C₄H₉)NH, HO, CH₃O, CH₃-phenyl, H, Cl, CH₃SO, CH₃SO₂]. The complexes were prepared to investigate the extent of redox and spin state control that is attainable by simply varying the electron donating/withdrawing influence using a single substituent site on the terpyridine ligand. Cyclic voltammetry was used to assess the substituents influence on the M(III/II) redox couple. A plot of the M(III/II) redox potential (E_1/2) versus the electron donating/withdrawing nature of the substituents (Hammett constants), shows a strong linear trend for both metals; however, the substituents were observed to have a stronger influence on the Fe(III/II) couple. Solution magnetic susceptibility measurements at room temperature were carried out using standard NMR methodology (modified Evans method) where all of the Fe(II) complexes exhibited a diamagnetic, low spin (S = 0) behavior. In the cobalt series where R = H for [Co(R-terpy)₂]²⁺, the complex is known to be near the spin cross-over where the room temperature effective magnetic moment (μ_eff) in solution is ≈3.1 Bohr magnetons; however, in this study the μ_eff is observed to vary between 2.7 and 4.1 Bohr magnetons depending on the R-substituent.     

A comparative study of ferrocenyl carboxylate cadmium(II) complexes prepared by two different synthetic methods

Reaction of ferrocenyl carboxylate H₂bfcs with Cd(Ac)₂ · 2H₂O (H₂bfcs = 1,1′-bis(3-carboxy-1-oxopropyl)ferrocene) gives the mononuclear tetrahydrate precursor Cd(Hbfcs)₂(H₂O)₄ (1). Investigation on the substitution reactions of 1 with imidazole or 2,2′-bpy afforded two one-dimensional (1D) complexes {[Cd₂(bfcs)₂(C₃H₄N₂)₆] · 4H₂O}_n (2) and {[Cd(bfcs)(2,2′-bpy)(H₂O)] · 2H₂O}_n (4) (2,2′-bpy = 2,2′-bipyridine), respectively. However, the one-step reactions of H₂bfcs, Cd(Ac)₂ · 2H₂O with imidazole or 2,2′-bpy result in the formation of two different 1D complexes {[Cd(bfcs)(C₃H₄N₂)₂] · CH₃OH · 2H₂O}_n (3) and [Cd(bfcs)(CH₃OH)]_n (5). It can be seen from the results that applying different synthetic routes produce dissimilar complexes from however the same materials and under the same reaction conditions. In addition, investigations of differential pulse voltammetry of these four 1D complexes indicate that their half-wave potentials are slightly higher than that of H₂bfcs.     

Investigation on the coordination modes: Syntheses, characterization and crystal structures of diorganotin (IV) dichloride with 4(5)-imidazoledithiocarboxylic acid

A series of diorganotin (IV) complexes of the types of R₂SnCl(SSCC₃H₃N₂) (R = CH₃1, ⁿBu 2, C₆H₅3 and C₆H₅CH₂4), R₂Sn(SSCC₃H₃N₂)₂ (R = CH₃5, ⁿBu 6, C₆H₅7 and C₆H₅CH₂8) and R₂Sn(SSCC₃H₂N₂) (R = CH₃9, ⁿBu 10, C₆H₅11 and C₆H₅CH₂12) have been obtained by reactions of 4(5)-imidazoledithiocarboxylic acid with diorganotin (IV) dichlorides in the presence of sodium ethoxide. All complexes are characterized by elemental, IR, ¹H, ¹³C and ¹¹⁹Sn NMR spectra analyses. Also, the complexes 1, 7 and 9 are characterized by X-ray crystallography diffraction analyses, which reveal that the complex 1 is monomeric structure with five-coordinate tin (IV) atom, the complex 7 is monomeric structure with six-coordinate tin (IV) atom and the complex 9 is one-dimensional chain with five-coordinate tin (IV) atom.     

Copper(I)-organophosphine complexes of bis(3,5-dimethylpyrazol-1-yl)dithioacetate ligand

Copper(I) complexes have been synthesized from the reaction of CuCl, monodentate tertiary phosphines PR₃ (PR₃ = P(C₆H₅)₃; P(C₆H₅)₂(4-C₆H₄COOH); P(C₆H₅)₂(2-C₆H₄COOH); PTA, 1,3,5-triaza-7-phosphaadamantane; P(CH₂OH)₃, tris(hydroxymethyl)phosphine) and lithium bis(3,5-dimethylpyrazolyl)dithioacetate, Li[LCS₂]. Mono-nuclear complexes of the type [LCS₂]Cu[PR₃] have been obtained and characterized by elemental analyses, FT-IR, ESI-MS and multinuclear (¹H, ¹³C and ³¹P) NMR spectral data; in these complexes the ligand behaves as a κ³-N,N,S scorpionate system. One exception to this stoichiometry was observed in the complex [LCS₂]Cu[P(CH₂OH)₃]₂, where two phosphine co-ligands are coordinated to the copper(I) centre. The solid-state X-ray crystal structure of [LCS₂]Cu[P(C₆H₅)₃] has been determined. The [LCS₂]Cu[P(C₆H₅)₃] complex has a pseudo tetrahedral copper site where the bis(3,5-dimethylpyrazolyl)dithioacetate ligand acts as a κ³-N,N,S donor.     

Self-assembled synthesis, characterization and antimicrobial activity of zinc(II) salicylaldimine complexes

One-pot metal promoted reactions between salicylaldehyde and 4-methyl-1,3-phenylenediamine in the presence of metal salts acting as template agents yield zinc(II) salicylaldimine complexes containing N,N′-bis(salicylidene)-4-methyl-1,3-phenylenediamine (H₂L) as a result of the [2 + 1] Schiff base condensation. The complexes of formula [Zn(HL)Cl(H₂O)₂] · C₂H₅OH and [Zn(H₂L)₂Cl(NO₃)(H₂O)] · CH₃OH were characterized as powder solids and in solution by spectroscopic methods (IR, ¹H and ¹³C NMR, FAB-MS, ESI-MS, UV-Vis), thermogravimetric and elemental analysis, potentiometry, and tested for antimicrobial activity against Staphylococcusaureus in a minimum inhibitory concentration (MIC) experiment. In these two powder solid species, the salicylaldimine, formed in a self-assembly process, acts in two different coordination modes: as monodeprotonated bidentate chelator with an N,O donor set or as a neutral monodentate using exclusively oxygen as the donor atom without involving the nitrogen atoms in the coordination. However, crystals of these two complexes are isomorphous, with 1:2 metal:ligand stoichiometry, and display the latter, relatively rare coordination pattern. In solution, the presence of a 1:1 complex of monodeprotonated state is only detected. The complexes exhibit antimicrobial activity against S.aureus.     

Dicopper(II) complexes showing DNA hydrolase activity and monomeric adduct formation with bis(4-nitrophenyl)phosphate

Ferromagnetic dicopper(II) complexes [Cu₂(μ-O₂CCH₃)(μ-OH)(L)₂(μ-L¹)](PF₆)₂, where L = 1,10-phenanthroline (phen), L¹ = H₂O in 1 and L = dipyrido[3,2-d:2′,3′-f]quinoxaline (dpq), L¹ = CH₃CN in 2, are prepared and structurally characterized. Crystals of 1 and 2 belong to the monoclinic space group of P2₁/n and P2₁/m, respectively. The copper(II) centers display distorted square-pyramidal geometry having a phenanthroline base and two oxygen atoms of the bridging hydroxo and acetate group in the basal plane. The fifth coordination site has weak axially bound bridging solvent molecule H₂O in 1 and CH₃CN in 2. The Cu···Cu distances are 3.034 and 3.046 Å in 1 and 2, respectively. The complexes show efficient hydrolytic cleavage of supercoiled pUC19 DNA as evidenced from the mechanistic studies that include T4 DNA ligase experiments. The binuclear complexes form monomeric copper(II) adducts [Cu(L)₂(BNPP)](PF₆) (L = phen, 3; dpq, 4) with bis(4-nitrophenyl)phosphate (BNPP) as a model phosphodiester. The crystal structures of 3 and 4 reveal distorted trigonal bipyramidal geometry in which BNPP binds through the oxygen atom of the phosphate. The kinetic data of the DNA cleavage reactions of the binuclear complexes under pseudo- and true-Michaelis-Menten conditions indicate remarkable enhancement in the DNA hydrolysis rate in comparison to the control data.