Synthesis,physico-chemical and antimicrobial studies on acetylferrocenyl hydrazone derivatives of dichlorobis(cyclopentadienyl)hafnium(IV)

The reactions of Cp₂>HfCl₂> with hydrazones (LH) derived from acetylferrocene and aromatic acid hydrazides (benzoic, 2-chlorobenzoic, 3-nitrobenzoic and 4-toluic) in various stoichiometric ratios have been studied and the complexes of the types [Cp₂>Hf(L)Cl] and [CpHf(L)₃>] were obtained. Tentative structural conclusions are drawn for the reaction products based upon elemental analyses, electrical conductance, magnetic moment and spectral data (u.v.–vis, i.r., ¹>H-n.m.r. and ¹³>C-n.m.r.). Studies were conducted to assess the growth-inhibiting potential of the complexes synthesized, and the ligands, against various fungal and bacterial strains.     

Dinitrogen functionalization with bis(cyclopentadienyl) complexes of zirconium and hafnium

The rich chemistry of substituted bis(cyclopentadienyl)zirconium and hafnium complexes bearing side-on coordinated dinitrogen ligands is highlighted in this Perspective. Our studies in this area were initially motivated by the desire to understand side-on vs. end-on dinitrogen coordination in bimetallic zirconocene and hafnocene N2 compounds. In the cases where eta2,eta2-dinitrogen compounds were isolated, both structural and computational data have established significant imido character in the metal-nitrogen bonds. This additional bonding interaction, which is diminished in end-on complexes bearing both terminal and bridging N2 ligands, facilitates dinitrogen functionalization by non-polar reagents including dihydrogen, carbon-hydrogen bonds and weak Br?nsted acids such as water and ethanol. In hafnocene chemistry, where unwanted side-on, end-on isomerization is suppressed, cycloaddition of phenylisocyanate to coordinated N2 has also been accomplished. For N-H bond forming reactions involving H2, kinetic measurements, in addition to isotopic labelling and computational studies, are consistent with dinitrogen functionalization by 1,2-addition involving a highly ordered, four-centred transition structure.     

Darstellung,struktur und eigenschaften on bis(cyclopentadienyl)oxalatotitan(IV) und bis(cyclopentadienyl)bis(hydrogenmaleinato)titan(IV)

The reaction of (π-C₅H₅)₂TiCl₂ with oxalic acid or maleic acid in aqueous solution yields dicyclopentadienyloxalatotitanium(IV) or dicyclopentadienylbis(hydrogenmaleato)titanium(IV), respectively. X-ray analyses show that both compounds are monomeric. The oxalate group acts as bidentate chelating ligand and each of the hydrogenmaleate groups is bonded via one oxygen atom to the titanium atom.     

Thermal Decomposition of bis(cyclopentadienyl)hafnium compounds and their deuterated analogues

Thermal decomposition ranges of Cp₂HfR_, (R = Me, Ph) have been found by the DTA method. The thermal stability of hafnium derivatives greatly exceeds the stability of analogous titanium and zirconium compounds. Decomposition of Cp₂HfR₂ occurs by abstraction of σ-bonded groups which convert into RH. Hydrogen donors for the RH formation are both π-cyclopentadienyl and σ-bonded groups. The initial π-Cp₂Hf structure rearranges to form the (η⁵-Cp)-(η⁵,η¹-C₅H₄)Hf fragment. These react with HCl to produce Cp₂HfCl₂. It has been established that hydrogen exchange between cyclopentadienyl rings and methyl groups occurs during the thermal decomposition of Cp₂HfMe₂. As a result of the exchange process on thermal decomposition of Cp₂HfMe₂-d6, deuterium insertion into the cyclopentadienyl ring has been shown. The participation of solvent during the decomposition process of the hafnium derivatives has been studied.     

Synthesis and characterization of bis(cyclopentadienyl)bis(hexafluoroantimonato) titanium(IV)

Reaction of titanocene dichloride with two equivalents of silver hexafluoroantimonate in sulphur dioxide quantitatively yields Cp₂Ti(SbF₆)₂ (Cp = η⁵-C₅H₅) and AgCl. The titanocene bishexafluoroantimonate was recrystallized from SO₂ and characterized by chemical analysis, ¹H NMR, IR and mass spectroscopy.     

Salicylaldehydo chelates of bis(cyclopentadienyl) zirconium(IV)

A new series of organometallic ionic chelates of the type [Cp ₂Zr(sal)]⁺ [ROCS₂/RRNCS₂]^–, where Hsal = salicylaldehyde;R =Me, Et, i-Pr ori-Bu andR =R =Me, Et, i-Pr;R =Me,R = benzyl orR =Et,R =m-tolyl, have been synthesized in aqueous medium by the reaction of [Cp ₂Zr(sal)]⁺Cl^– andROCS ₂ ^– K⁺/RRNCS ₂ ^– Na⁺. These compounds have been characterized by chemical analyses, electrical conductance, electronic, IR and¹H-NMR spectral studies. These studies indicate that the complexes are 1:1 electrolytes and the salicylaldehyde ligand is chelating in all these complexes. Therefore, a tetrahedral coordination about the zirconium atom is proposed.

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Salicylaldehydo-Chelate von Bis(cyclopentadienyl)-zirkonium(IV)

Zusammenfassung Eine neue Gruppe von organometallischen ionischen Chelaten vom Typ [Cp ₂Zr(sal)]⁺ [ROCS₂/RRNCS₂]^– (mit Hsal = Salicyladehyd;R =Me, Et, i-Pr oderi-Bu undR =R =Me, Et, i-Pr;R =Me,R = Benzyl oderR =Et,R =m-Tolyl) wurde in wäßrigem Medium mittels der Reaktion von [Cp ₂Zr(sal)]⁺Cl^– mitROCS ₂ ^– K⁺/RRNCS ₂ ^– Na⁺ hergestellt. Die erhaltenen Verbindungen wurden mittels chemischer Analyse, elektrischer Leitfähigkeit und der IR- sowie¹H-NMR-Spektren charakterisiert. Diese Untersuchungen zeigen, daß die Komplexe 1:1-Elektrolyte sind, wobei der Salicylaldehyd-Ligand in allen Fällen an der Chelatbildung beteiligt ist. Es wird daher für das Zirkoniumatom eine tetrahedrale Koordination vorgeschlagen.

     

Preparation and characterization of bis(cyclopentadienyl)zirconium (IV) oximate complexes

Summary Oximate complexes of bis(cyclopentadienyl)zirconium(IV) chloride (Cp₂ZrCl₂ ) having the general formulae Cp₂Zr(Ox), Cp₂Zr(OxH)Cl and Cp₂Zr(OxH)₂ [where OxH₂ = RC₆H₄C(OH)R: NOH, R = H, Me, R= H, Me, Et, n-Pr; PhC: N(OH)CH(OH)Ph and RC : N(OH)N(OH): CR, R = H, Me and Ph] have been synthesized by reacting bis(cyclopentadienyl)zirconium(IV) chloride with the appropriate oxime in tetrahydrofuran in the presence of triethylamine at room temperature. The complexes have been characterized by their elemental analysis, i.r. and electronic spectra, molecular weight determination, electrical conductance and magnetic measurements.Reprints of this paper are not available.     

Synthesis, spectroscopic, thermal and antifungal studies on lanthanum(III) and praseodymium(III) derivatives of 1,1-diacetylferrocenyl hydrazones

A series of new coordination complexes of La(III) and Pr(III) with hydrazones, derived from 1,1-diacetylferrocene and different aromatic acid hydrazides have been synthesized and characterized by elemental analyses, electrical conductance, magnetic moment, IR, (1)H NMR, UV-vis spectra and molar conductance. The thermal behaviour of the complexes under non-isothermal condition was investigated by TG and DTG techniques. The antifungal activity of hydrazones and their corresponding complexes were also investigated.     

桥环二茂钛、锆、铁金属衍生物的研究

本文用β,β'-双环戊二烯基乙醚二钠与TiCl4, ZrCl4, (C5H5)TiCl3和FeCl2在四氢呋喃中反应合成了新型氧桥环戊二烯基钛、锆和铁衍生物。在企图合成硫桥环戊二烯基化合物时, 得到的却是四亚甲基桥联双环戊二烯基金属衍生物。(苯二亚甲基)双环戊二烯基二钠与FeCl2反应合成了对、间(苯二亚甲基)二茂铁。讨论了新化合物的X射线光电子能谱和Mossbauer谱。     

Microwave assisted synthesis,spectroscopic and antibacterial studies of titanocene chelates of Schiff bases derived from 3-substituted-4-amino-5-hydrazino-1,2,4-triazoles

The reactions of bis(cyclopentadienyl)titanium(IV) chloride with a new series of Schiff bases (LH₂), derived by condensing 3-(phenyl/2-chlorophenyl/4-nitrophenyl)-4-amino-5-hydrazino-1,2,4-triazoles with salicylaldehyde or 2-hydroxyacetophenone, have been studied both by conventional stirring method and also by using microwave technology. The products of type [(η⁵-C₅H₅)₂Ti(L)] have been isolated in both cases. Tentative structural conclusions are drawn for the reaction products based upon physico-chemical and spectroscopic methods. The ligands behave as dibasic, tetradentate chelating agents and a six-coordinated structure have been assigned to these derivatives. Studies were conducted to assess the growth inhibiting potential of the free Schiff bases and their complexes against various bacterial strains.     

Synthesis and structural studies of mono- and bis-n 5-cyclopentadienyl)hafnium(IV) derivatives of heterocyclic thioketones

Summary The reactions of dichlorobis(n ⁵-cyclopentadienyl)hafnium(IV) with four different classes of heterocyclic thioketoneviz., 3-substituted-4-amino-S-triazole-5-thiol, 1-substituted-2-thiohydantoin, 5-substituted 1, 3, 4-oxadiazole-2-thione and 1-substituted tetrazoline-5-thione were studied in anhydrous tetrahydrofuran in the presence of base. The reaction products were characterized on the basis of elemental analyses, electrical conductance, magnetic susceptibility and spectral (electronic, infrared and¹H n.m.r.) data.     

Multivariate spectrofluorimetry of ultra trace zirconium(IV) and hafnium(IV) assisted by several chemometrics methods

In the presence of sodium lauryl sulfate (SLS), an anionic surfactant, highly sensitive molecular fluorescence reactions occur between Zr(IV), Hf(IV) ions and quercetin (3, 3', 4', 5, 7-pentahydroxyflavone) in acidic medium to form stable ternary micellar ion-association complexes. Their lambda(ex(max))/lambda(em(max)) values are 435.0/497.9 and 435.0/492.0 nm, respectively, indicating their heavily overlapping fluorescence excitation and emission spectra. The linear ranges of their regression calibration curves are 0 to 0.20 and 0 to 0.12 mg l(-1), respectively, with 0.5 ng ml(-1) for all of sensitivities. The multivariate spectrofluorimetry of ultra trace or trace Zr(IV) and Hf(IV) without separation was performed using a partial least squares (PLS) algorithm and other algorithms. The optimum PLS computation conditions are wavelength point number of 21 and corresponding wavelength range from 450 to 540 nm oriented from lambda(em) 495 nm to two sides at combined intervals of 2.5 and 5.0 nm at a fixed lambda(ex)of 435.0 nm with an optimum calibration sample number of 12, and respective optimum abstracted factor numbers of 4 and 5. It was concluded that accuracy and precision of the determination results obtained for simulation and real soil samples were poor for LP-M, LP-P, OLS-P, KF-P, and TFA-P algorithms, moderate for OLS-M, KF-M, and TFA-M algorithms, and good for PLS algorithm.     

Refutation of the synthesis of tetrakis(cyclopentadienyl)cerium(IV)

Reaction of sodium cyclopentadienide with dipyridinium hexachlorocerate(IV) in tetrahydrofuran yields tris(cyclopentadienyl)cerium(III) and not tetrakis(cyclopentadienyl)cerium(IV).     

Diorganotin(IV) complexes with furan-2-carbohydrazone derivatives: synthesis,characterization, crystal structure and antibacterial activity

Four new diorganotin(IV) complexes, R₂SnL (L?=?L^a: R?=?Me 1, Ph 2; L?=?L^b: R?=?Me 3, and Ph 4), have been synthesized by reaction of hydrazone ONO donors, 5-bromo-2-hydroxybenzaldehyde furan-2-carbohydrazone (H₂L^a) and 2-hydroxynaphthaldehyde furan-2-carbohydrazone (H₂L^b) with diorganotin(IV) dichloride in the presence of a base. The compounds have been investigated by elemental analysis and IR, ¹H NMR, and ¹¹⁹Sn NMR spectroscopies. Spectroscopic studies show that the hydrazone is a tridentate dianionic ligand, coordinating via the imine nitrogen and phenolic and enolic oxygens. The structures of H₂L^b and 3 have also been confirmed by X-ray crystallography. The results show that the structure of 3 is a distorted square pyramid with imine nitrogen in apical position. The in vitro antibacterial activities of ligands and complexes have been evaluated against gram-positive (Bacillus cereus and Staphylococcus aureus) and gram-negative (Escherichia coli and Pseudomonas aeruginosa) bacteria. H₂L^a and H₂L^b show no activity but the diphenyltin(IV) complexes exhibit good activities towards two bacterial strains in comparison with standard bacterial drugs.     

Template synthesis, spectroscopic studies and biological screening of macrocyclic complexes derived from thiocarbohydrazide and benzil

A novel series of complexes of the type [M(TML)X₂]; where TML is a tetradentate macrocyclic ligand; M = Co(II), Ni(II), Cu(II) or Zn(II); X = Cl⁻, CH₃COO⁻ or NO ₃ ⁻ have been synthesized by template condensation of benzil and thiocarbohydrazide in the presence of divalent metal salts in methanolic medium. The complexes have been characterized with the help of elemental analyses, conductance measurements, molecular weight determination, magnetic measurements, electronic, NMR, infrared and far infrared spectral studies. Electronic spectra along with magnetic moments suggest the six coordinate octahedral geometry for these complexes. The low value of molar conductance indicates them to be non-electrolytes. The biological activities of metal complexes have been tested in vitro against a number of pathogenic bacteria to assess their inhibiting potential.