Dioxobridged complexes of molybdenum (IV) and tungsten (IV) with N-alkylphenothiazines and their interactions with L-cysteine and L-histidine

Six new dioxobridged complexes of molybdenum (IV) and tungsten (IV) with N-alkylphenothiazines having the general formula M₂O₄(L)₂(H₂O)₂ [where M = molybdenum or tungsten and L = N-alkylphenothiazines] have been synthesised. The complexes have been characterised on the basis of analytical, molar conductance, magnetic susceptibility, spectral data, TGA and DTA. The low magnetic moments for the complexes are due to spin-spin interaction or metal-metal bonding. The interactions of these complexes with some biologically important amino acids have been studied.     

Basicity of transiton metal carbonyl complexes : XIII. Reactions of the π-cyclopentadienyl complexes of molybdenum and tungsten with aprotic acids

The aprotic acids HgCl₂ and SnX₄ (X  Cl, Br) react with the π-complexes C₅H₅M(CO)(NO)(L) (II, M  Mo W; L  PPh₃) by attack at the metal center. With HgCl₂ complexes II yield stable neutral 1:1 adducts CpM(CO)(NO)(L)HgCl₂(III). In the case of SnCl₄, complexes II initially produce the ionic 1:2 adducts [CpM(CO)(NO)(L)(SnCl₃)]⁺SnCl₅^-(IV) which, as a result of oxidative elimination of CO, turn into the neutral complexes CpM(NO)(L)(SnCl₃)(Cl)(V). In reactions of II with SnBr₄ the corresponding CpM(NO)(L)(SnB₃)(Br) complexes are formed directly. The formation of III–V is accompanied by a considerable increase of the frequencies ν(CO) and ν(NO). The structures of the complexes IV (M  Mo) and V (M  Mo) have been established by an X-ray structure analysis.     

Diorganotin(IV) Complexes with Monohydrate Disodium Salt of Iminodiacetic Acid: Synthesis,Characterization, Crystal Structure and Biological Activities

Diorganotin(IV) derivatives have been synthesized by the reaction of R₂SnL₂ (R=n‐Bu 1 , Ph 2 ) with monohydrate disodium salt of iminodiacetic acid ( Na₂L ) in 1 : 1 M/L ratio under reflux conditions. The compounds have been characterized by FT‐IR, NMR (¹H and ¹³C) spectoscopy, electron ionization mass spectrometry (EIMS), thermogravimetric analyses (TGA) and single crystal XRD. FTIR data indicates a mono‐dentate binding mode of the carboxylic acid group as well as participation of the amino nitrogen and aqua oxygen in coordination with organotin(IV) moieties. NMR data demonstrates a tetra‐coordinated environment around tin(IV) in solution. Mass spectrometric and thermogravimetric analyses verify the close similarities between the molecular structures of both complexes. The thermal stability of diphenyltin(IV) derivative ( 2 ) was found slightly higher than that of the free ligand ( Na₂L ). Single crystal X‐ray analysis of the complex 1 have shown a hexa‐coordinated geometry around Sn(IV) with trans configuration. There are evidences for the existence of intermolecular hydrogen bonding in the structure of the complexes. The products displayed significant antibacterial and antifungal activities in contrast to the biologically inactive ligand precursor. However, the hemolytic cytoxicity of the complexes was comparatively high than the free ligand.     

Complexes of titanium(IV), vanadium(IV) and tin(IV) with schiff bases derived from 2-(2-aminophenyl)benzimidazole

Summary New titanium(IV), vanadium(IV) and tin(IV) complexes with Schiff bases derived from 2-(2-aminophenyl)benzimidazole with benzaldehyde (L₁) and salicylaldehyde (L₂) have been prepared and have the general formulae MX₄ · 2L (M = Ti, V or Sn; L = L₁ or L₂; X = Cl or Br).All the complexes have been characterized by elemental analyses, magnetic measurements, e.p.r., electronic and i.r. spectral studies. The results show that the Schiff bases act as monodentate ligands. Tentative structures for the complexes are suggested.     

Unusual metalloporphyrins : thorium and uranium complexes of octaethylporphyrin.

The action of thorium or uranium tetrachloride with octaethylporphyrin [(oep)H₂] affords the dichlorometal (IV) complexes [M(IV)(oep)Cl₂, L_n] (M(IV) = Th or U, L = benzonitrile, tetrahydrofuran or pyridine). Spectral properties of these complexes are in good agreement with a cis octa-coordination.     

Molecular complexes of cobalt(II) and Zinc(II) chlorides and bromides with 1-piperidinyl dimethylcarbamodithioate (L): Crystal structures of L and [ZnLBr<Subscript>2</Subscript>]

Complexes of MX₂(M = Co, Zn; X = Cl, Br) with 1-piperidinyl dimethylcarbamodithioate (L) of composition [MLX₂] have been synthesized. The compounds have been studied by elemental analysis; X-ray diffraction; thermogravimetry; conductometry; magnetochemistry; and IR, ¹H NMR, and electronic absorption spectroscopy. The ligand molecule is coordinated to the metal atoms in a bidentate chelating mode through the thione sulfur atom and the sulfenamide nitrogen atom to form a five-membered chelate ring. The structures of L and [ZnLBr₂] have been determined by X-ray crystallography.     

Organosilicon(IV) and organotin(IV) complexes as biocides and nematicides: synthetic,spectroscopic and biological studies of N∩N donor sulfonamide imine and its chelates

A brief account is given of the synthesis and stereochemistry and the antibacterial, antifungal, nematicidal and insecticidal behaviour of organosilicon(IV) and organotin(IV) complexes of a biologically potent ligand, 2‐acetylfuransulfaguanidine. The unimolar and bimolar substitution products have been characterized by elemental analyses, conductance measurements, molecular weight determinations, and spectral studies, viz. IR, ¹H NMR, ¹³C NMR, UV, ²⁹Si NMR and ¹¹⁹Sn NMR spectra. The data support the binding of the nitrogen atom to the metal atom in R₃M(N^∩N), [R₂M(N^∩N)₂ and R₂M(N^∩N)Cl [(R = Me/Ph and M = Si(IV) and Sn(IV)] types of complex. Based on these studies, with coordination number five and six a trigonal bipyramidal and an octahedral geometry have been proposed for the resulting derivatives. The free ligand (N^∩NH) and its respective metal complexes were tested in vitro against a number of microorganisms to assess their antimicrobial properties. The results are indeed positive. In addition to these studies, the complexes also show good nematicidal and insecticidal properties. The results of these findings have been discussed in detail. Copyright © 2004 John Wiley & Sons, Ltd.     

Microwave‐assisted synthesis,spectroscopy and biological aspects of binuclear titanocene chelates of isatin‐2,3‐bis(thiosemicarbazones)

The reactions of bis(cyclopentadienyl)titanium(IV) chloride with a new class of bis(thiosemicarbazones) (H₂L), derived by condensing isatin with different N(4)‐substituted thiosemicarbazides, have been studied both by a conventional stirring method and also using microwave technology. Binuclear products of type [{(η⁵‐C₅H₅)₂TiCl} ₂(L)] have been isolated in both cases. Tentative structural conclusions are drawn for the reaction products based upon analysis, electrical conductance, magnetic moment and spectral (UV‐visible, IR, ¹H NMR and ¹³C NMR) data. FAB mass spectra of these compounds were also recorded to confirm the binuclear structures. Studies were conducted to assess the growth inhibiting potential of the ligands and complexes against various fungal, viral and bacterial strains. Copyright © 2008 John Wiley & Sons, Ltd.     

Synthesis,spectroscopic and thermal studies on ruthenium(III), rhodium(III) and iridium(III) complexes with hydrazones derived from 2,6-diacetylpyridine and different aromatic hydrazides

Summary The reactions of MCl₃·3H₂O (M=Ru, Rh or Ir) with hydrazones have been studied by three different methods and complexes of the types [M(LH₂)(H₂O)₂]Cl₃, [M(L)Cl(H₂O)] and [M(LH₂)Cl₂]Cl·H₂O have been isolated. Tentative structural conclusions are drawn for these products based upon elemental analysis, electrical conductance, magnetic moment, and i.r. and¹H n.m.r. data. The thermal stability and mode of decomposition for the complexes have been studied by t.g.a., d.t.g. and d.s.c. techniques.     

Theoretical study of the structures of [M(18C6)](HFA)2 complexes (M = Ba,Sr, Pb,Cd, Mn; 18C6 = 18-crown-6; HFA = hexafluoroacetylacetonate anion)

The structures of the [M(18C6)]²⁺ cations (M = Ba, Sr, Pb, Cd, Mn) and their salts [M(18C6)](HFA)₂ and [M(18C6)](NO₃)₂ have been calculated by the density functional theory method (in the B3LYP/6-311++G** + LanL2Dz approximation). Upon geometry optimization, the gas-phase structures of compounds of different composition have been calculated; for them, the strength of binding of the central cation to the crown ether (18C6) and the degree of structural similarity have been evaluated. The structure of the [NH₄(18C6)]⁺ cation identified in a practical synthesis has also been considered. For metal cations acting as a central atom, NH ₄ ⁺ and [M(18C6)]²⁺ complex cations, as well as for intermediate and ultimate products [M(18C6)](NO₃)₂ and [M(18C6)](HFA)₂ (M = Ba, Sr, Pb, Cd, Mn), the electronic chemical potential and Pearson hardness, which enables the consideration of the propensity of various reagents to interact with each other in terms of the empirical HSAB principle (hard with hard and soft with soft), have been evaluated. Comparison of the estimates with the properties of the synthesized compounds with M = Ba, Sr, and Pb makes it possible to preliminarily verify the applicability of this principle to the systems under consideration and predict some properties of isostructural analogues important in the search for methods of synthesis of [M(18C6)](HFA)₂, where M = Cd and Mn. The possibility of establishing a correlation between the electron density of the system, stability, and hydrolytic activity of complexes has been shown.     

Template synthesis and characterization of oxovanadium(IV) complexes with tetraaza macrocyclic ligands and their activity on potato virus X

The oxovanadium(IV) complexes (I) of the type [VO(L)]SO₄ have been prepared using an in-situ method of synthesis with ligands derived from di-2-thienylethanedione with 1,2-diaminobenzene or 2,3-diaminopyridine. These parent complexes have been further reacted with μ-diketones to yield macrocyclic complexes (II) of types [VO(mac)]SO₄ (where mac = macrocyclic ligands derived by condensation of amino group of parent complex with μ-diketones), wherein the VO²⁺ cation acts as a template. Tentative structures of these complexes have been proposed on the basis of elemental analysis, electrical conductance, magnetic moments and spectral (infrared, electronic and electron spin resonance) data. The oxovanadium(IV) complexes are five coordinated wherein the tetraaza macrocyclic ligands act as tetradentate chelating agents. All the complexes are found to inhibit the infectivity of potato virus X, when checked using the test plant Chenopodium amaranticolor.     

SYNTHESIS AND CHARACTERISATION OF TIN(IV) AND ORGANOTIN(IV) COMPLEXES OF [N′-2-HYDROXYPHENYL-6-METHYLPYRIDINE-2-CARBALDIMINE. X-RAY CRYSTAL STRUCTURES OF n-BUTYLDICHLORO[N′-2-HYDROXYPHENYL-6-METHYLPYRIDINE-2-CARBALDIMINATO(1-)N,N′,O]TIN(IV) AND DIPHENYLCHLORO [N′-2-HYDROXYPHENYL-6-METHYL-PYRIDINE-2-CARBALDIMINATO(1-) N,N′,O]TIN(IV)

Abstract

The reactions of N′-2-hydroxyphenyl-6-methylpyridine-2-carbaldimine (LH) with tin(IV) chloride and organotin(IV) chlorides result in the formation of the corresponding tin(IV) and organotin(IV) complexes in which LH behaves as a uninegative tridentate ligand coordinating to the central tin atom via an N,N,O donor set. Crystal structure determinations of two of the compounds, n-butyldichloro[N′-2-hydroxyphenyl-6-methylpyridine-2-carbaldiminato(l-)N,N′,O]-tin(IV) (BuSnCl₂.L) and diphenylchloro[N′-2-hydroxyphenyl-6-methylpyridine-2-carbaldiminato(l-)N,N′,O]tin(IV) (Ph₂SnCl.L), have been performed and both structures feature distorted octahedral geometries about the tin centres. Systematic differences in the Sn-ligand separations are rationalised in terms of the reduced Lewis acidity of tin in Ph₂SnCl.L.     

Utilization of LVO 2? species (L2? is a tridentate ONS donor) as an inorganic analogue of carboxylate group: A journey to a new domain of coordination chemistry

The anionic cis-dioxovanadium (V) complex species LVO ₂ ^- of tridentate biprotic dithiocarbazate-based ligands H₂L (S-methyl-3-((5-R-2-hydroxyphenyl)methyl)dithiocabazate, R = H, L = L¹; and R = Br, L = L²) can bind alkali metal ions. The products [LVO₂M(H₂O)_n] (M = Na⁺, L = L¹,1; L = L², 2 and M = K⁺, L = L¹,3) have extended chain structures in the solid state, stabilized by strong hydrogen bonding and Coulombic interactions as revealed from X-ray crystallography. The LVO ₂ ^- moieties here behave like analogues of carboxylate groups and display interesting variations in their binding patterns. It appears thatl is a single stranded helicate with LVO ₂ ^- units forming the strands which surround the labile sodium ions occupying positions on the axis. The compounds are stable in water and methanol as solvents, while in aprotic solvents of higher donor strengths, viz. CH₃CN, DMF and DMSO, they undergo photo-induced reduction when exposed to visible light, yielding green solutions from their initial yellow colour. The putative product is a mixed-oxidation (μ-oxo)divanadium (IV/V) species as revealed from EPR, electronic spectroscopy, dynamic¹H NMR, and redox studies.     

Micellar Effect on the Reaction of Chromium(VI) Oxidation of L‐Sorbose in the Presence and Absence of Picolinic Acid in Aqueous Acid Media: A Kinetic Study

The kinetics and mechanism of chromic acid oxidation of L‐sorbose in the presence and absence of picolinic acid (PA) have been studied under the conditions, [L‐sorbose]_T » [PA]_T » [Cr(VI)]_T, at different temperatures. In the absence of PA, the monomeric chromic acid undergoes esterification with the substrate followed by the acid catalysed redox decomposition of the Cr(VI)‐substrate ester through glycol splitting to formaldehyde and the lactone of C₅‐aldonic acid and Cr(IV) which subsequently participates in the faster reactions. In the presence of PA, the Cr(VI)‐PA complex produced in a pre‐equilibrium step experiences a nucleophilic attack by the substrate to produce a ternary complex which decomposes through glycol splitting giving rise to the organic products and Cr(IV)‐PA complex. Both the uncatalysed and PA‐catalysed paths show the first‐order dependence on [L‐sorbose]_T and [Cr(VI)]_T. The PA‐catalysed path is first‐order in [PA]_T and it shows a fractional order in [H⁺]. The uncatalysed path shows a second‐order dependence on [H⁺]. In the presence of the surfactants like N‐cetylpyridinium chloride (CPC, a cationic surfactant) and sodium dodecyl sulfate (SDS, an anionic sulfate), the reaction orders remain unchanged. CPC has been found to inhibit both the uncatalysed and PA‐catalysed paths while SDS shows the rate accelerating effect for both the uncatalysed and PA‐catalysed paths. The observed micellar effects have been rationalised by considering the distribution of the reactants between the micellar and aqueous phases in terms of the proposed reaction mechanism.     

Reactions of bis(cyclopentadienyl)titanium(IV) and zirconium(IV) chlorides with 1,1′-diacetylferrocenyl bis(hydrazones). Formation of trimetallic derivatives

Bis(cyclopentadienyl)titanium(IV) and zirconium(IV) chlorides react with bis(hydrazones) derived from 1,1-diacetylferrocene in anhydrous THF in the presence of base to give complexes of the type [(Cp₂MCl)₂L] [M = Ti or Zr; LH₂ = ferrocenyl bis(hydrazones)]. Tentative structures are proposed for these complexes based upon elemental analyses, electrical conductance, magnetic moment and spectroscopic data.     

Three hexafluoridoiridates(IV), Ca[IrF6]·2H2O,Sr[IrF6]·2H2O and Ba[IrF6]

The structures of the hexafluoridoiridates(IV) of calcium, Ca[IrF₆]·2H₂O [calcium hexafluoridoiridate(IV) dihydrate], strontium, Sr[IrF₆]·2H₂O [strontium hexafluoridoiridate(IV) dihydrate], and barium, Ba[IrF₆] [barium hexafluoridoiridate(IV)], have been determined by single‐crystal X‐ray analysis. The first two compounds are isomorphous. Their metal cations are eight‐coordinated in a distorted square‐antiprismatic coordination environment, and their anions are represented by an almost ideal octahedron. These two structures can be described as frameworks in which all atoms occupy general positions. Sr[RhF₆] and Ba[RhF₆] have a different space group (, from powder diffraction data) but similar cell dimensions. The structures are very close to that of Ba[IrF₆]. The cation is in a cuboctahedral coordination. The metal atoms are located on special positions of symmetry, while the F atoms are in general positions.     

Synthesis,structural, and spectral studies of diorganotin(IV) complexes with 2–hydroxy-5-methylbenzaldehyde-N(4)-cyclohexylthiosemicarbazone

Three new diorganotin(IV) complexes, [Me₂Sn(L)] (2), [Bu₂Sn(L)] (3), and [Ph₂Sn(L)] (4) [where H₂L (1) = 2-hydroxy-5-methylbenzaldehyde-N(4)-cyclohexylthiosemicarbazone] have been synthesized by reacting the corresponding diorganotin(IV) dichloride with H₂L (1) in absolute methanol in the presence of potassium hydroxide. All the compounds have been characterized by CHN analyses, UV–vis, FT-IR, ¹H, ¹³C, and ¹¹⁹Sn NMR spectroscopy. The molecular structures of H₂L (1) and 2 have been confirmed by single crystal X-ray diffraction analysis. H₂L (1) is found to be in the thiol tautomeric form. The X-ray structure of 2 showed that H₂L is a tridentate ligand and binds to the tin(IV) atom via the phenolic oxygen, azomethine nitrogen, and thiolate sulfur. Complex 2 has a triclinic structure and the coordination geometry of tin(IV) is distorted trigonal bipyramidal. The sulfur and oxygen are in axial positions while the azomethine nitrogen of 1 and two methyl groups occupy the equatorial positions. The C-Sn-C angles determined from ¹J(¹¹⁹Sn, ¹³C) for 2, 3, and 4 are 124.35°, 123.11°, and 123.82°, respectively. The values of δ(¹¹⁹Sn) for 2, 3, and 4 are ?153.4, ?180.59, and ?158.3 ppm, respectively, indicating five-coordinate tin(IV). From NMR data a distorted trigonal-bipyramidal configuration at each tin is proposed.     

Synthesis,characterization and biological studies of oxovanadium(IV) complexes with triazole‐derived Schiff bases

A series of triazole‐derived Schiff bases (L¹–L⁵) and their oxovanadium(IV) complexes have been synthesized. The chemical structures of Schiff bases were characterized by their analytical (CHN analysis) and spectral (IR, ¹H and ¹³C NMR and mass spectrometry) data, and oxovanadium(IV) complexes were elucidated by their physical (magnetic susceptibility and conductivity), analytical (CHN analysis), conductance measurements and electronic spectral data. The molar conductivity data indicate the oxovanadium(IV) complexes to be non‐electrolyte. The Schiff bases act as bidentate and coordinate with the oxovanadium(IV)‐forming stoichiometry of a complex as [M (L‐H)₂] where M = VO and L = L¹–L⁵ in a square‐pyramidal geometry. The agar well diffusion method was used for in vitro antibacterial screening against E. coli, S. flexenari, P. aeruginosa, S. typhi, S. aureus and B. subtilis and for antifungal activity against T. longifucus, C. albican, A. flavus, M. canis, F. solani and C. glaberata. The biological activity data show the oxovanadium(IV) complexes to be more antibacterial and antifungal than the parent Schiff bases against one or more bacterial and fungal strains. Copyright © 2009 John Wiley & Sons, Ltd.     

A study on sorbitol-ceric ion initiated polymerization of acrylonitrile

The polymerization of acrylonitrile (M) initiated by the sorbitol (R)-Ce(IV) redox system has been studied in sulphuric acid in the range 30–40° under nitrogen. At moderately high concentrations of Ce(IV) (0.00015-0.02 M), the rate of polymerization (R_p) is proportional to $\text{[}\text{M}\text{]}{}^{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ and $\text{[}\text{R}\text{]}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ and the rate of Ce(IV) disappearance is proportional to [R] and [Ce(IV)]. At lower concentration of Ce(IV) (0.00005–0.00015 M) R_p is proportional to [M], [R]^1/2 and [Ce(IV)]^1/2 and rate of Ce(IV) disappearance is proportional to [R] and [Ce(IV)]. The effects of certain salts, acid, solvent and temperature on both rates have been investigated. A kinetic scheme involving mutual termination has been proposed and various rate and energy parameters evaluated. At still higher concentration of Ce(IV) (0.02 M), a linear mode of termination seems to operate.     

Biologically active organotin(IV) schiff base complexes

Organotin(IV) complexes with the general formulae R₃ML [R: alkyl (Et, Ph and Bz), M: Sn and L: 1,3-bis(2- hydroxybenzylidene)thiourea were synthesized. The newly synthesized schiff base and its complexes were characterized by elemental analysis, melting point, molecular weight determination, IR and NMR [¹H, ¹³C and ¹¹⁹Sn] spectral methods. In the light of these techniques, a tetrahedral geometry around the tin atom is proposed for the synthesized complexes. The experimental data have been compared with those in the literature which were found to coincide very well with the assigned structures. The ligands and their tin(IV) complexes were screened in vitro for their antibacterial activities. It was found that they possessed significant antibacterial activity and the effect of Ph₃SnL was possibly superior to those of Et₃SnL, Bz₃SnL and ligand. These findings add new insights onto the synthesis of antibacterial drugs as the synthesized compounds showed promising antimicrobial activity.