Synthesis,spectral, and catalytic studies of ruthenium(II) unsymmetrical Schiff-base complexes

Unsymmetrically-substituted ruthenium(II) Schiff-base complexes, [Ru(CO)(B)(L ^x )] [B = PPh₃, AsPh₃ or Py; L ^x = dianion of tetradentate unsymmetrical Schiff-base ligand; x = 4–7, L⁴ = salen-o-hyac, L⁵ = valen-o-hyac, L⁶ = salphen-o-hyac, L⁷ = valen-2-hacn], were prepared and characterized by analytical, IR, electronic, and ¹H NMR spectral studies. The new complexes were tested for their catalytic activity towards the oxidation of benzylalcohol to benzaldehyde.     

Fe (III) complexes of a bis-benzimidazolyl diamide ligand: spectral and catalytic studies

A new tetradentate bis benzimidaozlyl diamide ligand N,N'-Bis (benzimidazol-2-yl-methyl)-hexane-1,6-dicarboxamide (GBSA) has been synthesized and utilized to prepare new Fe(III) complexes with exogenous anionic ligand X=Cl(-) and NO(3)(-). Isomer shift values are in the range found for Iron in the +3 oxidation state while Quadrupole Splitting indicates large distortion from a six coordinate geometry, a finding supported by low temperature EPR work. The E(1/2) values are found to be quite cathodic indicating stability of the Iron (III) complexes. The oxidation of alcohols was investigated using [Fe(GBSA)Cl(3)] as the catalyst with TBHP as an alternate source of oxygen. The respective carbonyl products have been isolated and characterized by (1)H NMR, electronic spectroscopy, mass and IR spectral studies.     

Synthesis and catalytic activity of binuclear cobalt(II) and nickel(II) complexes

Summary Binuclear Ni^II and Co^II complexes derived from 2,6-diformyl-4-methylphenol and various aromatic monoamines have been prepared and investigated. The Ni^II complexes have Ni₂LCl₃ composition while the Co^II complexes have Co₂L₂Cl₂ composition, where L represents the organic ligand. The complexes are active catalysts in the oxidation of 3,5-di-t-butylcatechol (3,5-DTBC) by dioxygen, but less so than their Cu analogues. This result is attributed to the absence of antiferromagnetic coupling between the metal centres.     

Synthesis,spectral characterization and catalytic applications of Ru(II) complexes with amide ligands

Ruthenium(II) complexes of the type, RuCl₂(NO)(PPh₃)(L₂) (where L = amide ligand) have been synthesized and characterized on the basis of their elemental analysis IR, ¹H-, ¹³C-, ³¹P-NMR spectra. Amide ligand behaved as a bidentate ligand. The probable structures of these complexes have been discussed. They were used as catalysts for the hydrolysis of drugs viz. rivastigmine tartrate and neostigmine bromide. The percent yields of hydrolyzed products of these drugs were determined spectrophotometrically.     

Synthesis, spectral characterization and catalytic studies of new ruthenium(II) chalcone thiosemicarbazone complexes

A series of new hexa-coordinated ruthenium(II) complexes of the type [Ru(CO)(EPh₃)(B)(L)] (E = P or As; B = PPh₃, AsPh₃ or Py; L = chalcone thiosemicarbazone) have been prepared by reacting [RuHCl(CO)(EPh₃)₂(B)] (E = P or As; B = PPh₃, AsPh₃ or Py) with chalcone thiosemicarbazones in benzene under reflux. The new complexes have been characterized by analytical and spectroscopic (IR, UV-vis, ¹H, ³¹P and ¹³C NMR) methods. On the basis of data obtained, an octahedral structure was assigned for all of the complexes. The chalcone thiosemicarbazones behave as dianionic tridentate O, N, S donors and coordinate to ruthenium via the phenolic oxygen of chalcone, the imine nitrogen of thiosemicarbazone and thienol sulfur. The new complexes exhibit catalytic activity for the oxidation of primary and secondary alcohols to their corresponding aldehydes and ketones and they were also found to be efficient catalysts for the transfer hydrogenation of carbonyl compounds.     

Synthesis, structure and catalytic activity of thioether-phosphane complexes of Pd(II) and Pt(II)

New thioether-phosphanes 2-RSC6H4CH2PPh2(RS-PPh2: R = Me, tBu, Ph) and the corresponding complexes [PdCl2(MeS-PPh2)], [PdCl2(tBuS-PPh2)], [PdCl2(PhS-PPh2)], [PdClMe(MeS-PPh2)] and [PtMe2(MeS-PPh2)] have been prepared, characterized and the X-ray crystal structures of all complexes determined. Whilst Pd(II) complexes of RS-PPh2 show low activity for CO/ethene copolymerisation, the complexes [PdCl2(RS-PPh2)] have been found to be very efficient for the Heck arylation of n-butylacrylate with bromobenzene under aerobic conditions.     

Synthesis, spectral studies of cobalt(II) tetrathiocyanoto dicuperate(I) complexes with some acylhydrazones and their antimicrobial activity

Cobalt(II) complexes of the type Co[Cu(NCS)₂]₂ · L, where L is acetophenonebenzoylhydrazone (Abh), acetophenoneisonicotinoylhydrazone (Ainh), acetophenonesalicyloylhydrazone (Ash), acetophenoneanthraniloylhydrazone (Aah), p-hydroxyacetophenonebenzoylhydrazone (Phabh), p-hydroxyacetophenoneisonicotinoylhydrazone (Phainh), p-hydroxyacetophenonesalicyloylhydrazone (Phash), and p-hydroxyacetophenoneanthraniloylhydrazone (Phaah) were synthesized and characterized by elemental analyses, molar conductance, magnetic moments, electronic and IR spectra, and X-ray diffraction studies. The complexes are insoluble in common organic solvents and are non-electrolytes. These complexes are coordinated through the >C=O and >C=N groups of the hydrazone ligands. The magnetic moments and electronic spectra suggest a spin-free octahedral geometry around Co(II). The X-ray diffraction parameters (a, b, c) for Co[Cu(SCN)₂]₂ · Ainh and Co[Cu(SCN)₂]₂ · Phabh correspond to orthorhombic and tetragonal crystal lattices, respectively. The complexes show a fair antifungal and antibacterial activity against a number of fungi and bacteria. The activity increases with increasing concentration of the compounds. The text was submitted by the authors in English.     

Synthesis,spectral studies of copper(II)tetrathiocyanato dithallate(I) complexes with some acylhydrazones and their antimicrobial activity

Heterobimetallic complexes of Cu[Tl(SCN)₂]₂ ·; L (where L?=?acetophenone benzoylhydrazone(abh), acetophenone isonicotinoyl hydrazone(ainh), acetophenone salicyloylhydrazone(ash), acetophenone anthraniloyl hydrazone(aah), p-hydroxy acetophenone benzoylhydrazone (phabh), p-hydroxy acetophenone isonicotinoyl hydrazone (phainh), p-hydroxy acetophenone salicyloylhydrazone(phash) and p-hydroxy acetophenone anthraniloyl hydrazone(phaah) were synthesized and characterized. Electronic spectra and μ_eff values suggest a distorted octahedral environment around copper(II). SCN groups bridge between two metal centers and the ligands are coordinated through >C=O and >C=N–groups. Thermal studies (TGA and DTA) on Cu[Tl(SCN)₂]₂?·?ainh indicate multi step decomposition of both endothermic and exothermic nature. ESR data show axial spectra for all the complexes and d _{x²???y ²} as the ground state. Powder X-ray diffraction parameters for some of the complexes correspond to orthorhombic crystal lattice. The complexes show significant antifungal activity against Rizoctonia sp. and Stemphylium sp. and moderate antibacterial activity against Clostridium sp. and Pseudomonas sp. The activity increases at higher concentration of the compound.     

Synthesis,characterization and catalytic activity of halo-methyl-bis(salicylaldehyde)ethylenediamine cobalt(II) complexes

The synthesis, characterization and catalytic activity of a series of tetra-halo-dimethyl salen and di-halo-tetramethyl-salen ligands are reported in this paper: α,α′-dimethyl-Salen (dMeSalen) (L¹); 3,3′,5,5′-tetrachloro-α,α′-dimethyl-Salen, (tCldMeSalen) (L²); 3,3′-dibromo-5,5′-dichloro-α,α′-dimethyl-Salen, (dCldBrdMeSalen) (L³); 3,3′,5,5′-tetrabromo-α,α′-dimethyl-Salen, (tBrdMeSalen) (L⁴); 3,3′,5,5′-tetraiodo-α,α′-dimethyl-salen, (tIdMeSalen) (L⁵); 3,3′-dichloro-5,5′,α,α′-tetramethyl-Salen (dCltMeSalen) (L⁶); 3,3′-dibromo-5,5′,α,α′-tetramethyl-Salen (dBrtMeSalen) (L⁷); and 3,3′-diiodo-5,5′,α,α′-tetramethyl-Salen (dItMeSalen) (L⁸) (Salen = bis(salicylaldehyde)ethylenediamine). Upon reaction with Co(II) ions, these ligands form complexes with square planar geometry that have been characterized by elemental analysis, cyclic voltammetry, UV–Vis, IR and EPR spectroscopies. In the presence of pyridine the obtained Co(II) complexes were found able to bind reversibly O₂, which was shown by EPR spectroscopy and cyclic voltammetry. They were also found able to catalyze the oxidation of 2,6-di-tert-butylphenol (DtBuP) (9) with formation of 2,6-di-tert-butyl-1,4-benzoquinone (DtBuQ) (10) and 2,6,2′,6′-tetra-tert-butyl-1,1′-diphenobenzoquinone (TtBuDQ) (11). These properties are first influenced by the coordination of pyridine in axial position of the Co(II) ion that causes an increase of the electronic density on the cobalt ion and as a consequence a decrease in the E_1/2 value and an increase of the reducing power of the Co(II) complex. It is noteworthy that, under those conditions the complexes also show a remarkable quasi-reversible behaviour. Second, complex properties are also influenced by the substituents (methyl and halogen) grafted on the aromatic ring and on the azomethynic groups. The donating methyl substituent on the azomethynic groups causes a decrease in the E_1/2 value, whereas the halogen substituents on the aromatic rings have two effects: a mesomeric donating effect that tends to lower the redox potential of the complex, and a steric effect that tends to decrease the conjugation of the ligand and then to increase the redox potential of the Co(II) complex. In pyridine, the steric effect predominates, which causes both an increase of the redox potential and a decrease of the selectivity of the oxidation of phenol 9. As a result of all these effects, it then appears that the best catalysts to realize the selective oxidation of 2,6-di-tert-butyl-phenol (9) by O₂ are the Co complexes of ligands bearing CH₃ donating substituents, Co(dMeSalen) 1 (2CH₃ substituents), and Co-di-halo-tetra-methyl-salen complexes 6, 7 and 8 (4CH₃ substituents), in the presence of pyridine.     

Synthesis, crystal structure, spectral studies, and catechol oxidase activity of trigonal bipyramidal Cu(II) complexes derived from a tetradentate diamide bisbenzimidazole ligand

A new benzimidazole-based diamide ligand-N,N'-bis(glycine-2- benzimidazolyl)hexanediamide (GBHA)-has been synthesized and utilized to prepare Cu(II) complexes of general composition [Cu(GBHA)X]X, where X is an exogenous anionic ligand (X = Cl(-), NO(3)(-), SCN(-)). The X-ray structure of one of the complexes, [Cu(GBHA)Cl]Cl.H(2)O.CH(3)OH, has been obtained. The compound crystallizes in the monoclinic space group C2/c with unit cell dimensions a = 26.464(3) A, b = 10.2210(8) A, c = 20.444(2) A, alpha = 90 degrees, beta = 106.554(7) degrees, gamma = 90 degrees, V= 5300.7(9) A(3), and Z = 8. To the best of our knowledge, the [Cu(GBHA)Cl]Cl.H(2)O.CH(3)OH complex is the first structurally characterized mononuclear trigonal bipyramidal copper(II) bisbenzimidazole diamide complex having coordinated amide carbonyl oxygen. The coordination geometry around the Cu(II) ion is distorted trigonal bipyramidal (tau = 0.59). Two carbonyl oxygen atoms and a chlorine atom form the equatorial plane, while the two benzimidazole imine nitrogen atoms occupy the axial positions. The geometry of the Cu(II) center in the solid state is not preserved in DMSO solution, changing to square pyramidal, as suggested by the low-temperature EPR data g( parallel) > g( perpendicular) > 2.0023. All the complexes display a quasi-reversible redox wave due to the Cu(II)/Cu(I) reduction process. E(1/2) values shift anodically from Cl(-) < NO(3)(-) < SCN(-), indicating that the bound Cl(-) ion stabilizes the Cu(II) ion while the N-bonded SCN(-) ion destabilizes the Cu(II) state in the complex. When calculated against NHE, the redox potentials turn out to be quite positive as compared to other copper(II) benzimidazole bound complexes (Nakao, Y.; Onoda, M.; Sakurai, T.; Nakahara, A.; Kinoshita, L.; Ooi, S. Inorg. Chim. Acta 1988, 151, 55. Addison, A. W.; Hendricks, H. M. J.; Reedijk, J.; Thompson, L. K. Inorg. Chem. 1981, 20 (1), 103. Sivagnanam, U.; Palaniandavar, M. J. Chem. Soc., Dalton Trans. 1994, 2277. Palaniandavar, M.; Pandiyan, T.; Laxminarayan, M.; Manohar, H. J. Chem. Soc., Dalton Trans. 1995, 457. Sakurai, T.; Oi, H.; Nakahara, A. Inorg. Chim. Acta 1984, 92, 131). It is therefore concluded that binding of amide carbonyl oxygen destabilizes the Cu(II) state. The complex [Cu(II)(GBHA)(NO(3))](NO(3)) could be successfully reduced by the addition of dihydroxybenzenes to the corresponding [Cu(I)(GBHA)](NO(3)). (1)H NMR of the reduced complex shows slightly broadened and shifted (1)H signals. The reduction of the Cu(II) complex presumably occurs with the corresponding 2e(-) oxidation of the quinol to quinone. Such a conversion is reminiscent of the functioning of a copper-containing catechol oxidase from sweet potatoes and the met form of the enzyme tyrosinase.     

Bis(imino)pyridine palladium(II) complexes: Synthesis, structure and catalytic activity

Bis(imino)pyridine palladium(II) complexes 3-6 were synthesized by two different methods. The structure of complexes 3 and 4 has been confirmed by X-ray structure analysis. The catalytic studies show that bis(imino)pyridine palladium(II) complexes are highly efficient catalysts in the Suzuki-Miyaura reaction and the complex 4 was used to catalyze the synthesis of fluorinated liquid crystalline compounds via Suzuki coupling reaction.     

Synthesis and characterisation of some complexes of manganese(II) and iron(II) picrates with heterocyclic amines

Summary Complexes of manganese(II) and iron(II) picrates with various bidentate (L) and monodentate (L) heterocyclic bases have been synthesised; their compositions have been established as [ML₃]A₂ (1), [ML₂ · 2 H₂O]A₂ (2), [ML₆]A₂ (3) and [ML4 · 2 H₂O]A₂ (4), where M = Fe^II and Mn^II, L = 2,2-bipyridyl (bipy) and 1,10-phenanthroline (phen) in (1), A = picrate anion; M = Mn^II, L = bipy and phen in (2); M = Fe^II, L = pyridine (py), 4-picoline (4-pic) and 3-picoline (3-pic) in (3); M = Mn^II, L = py, 4-pic, quinoline (quin) and 2,6-lutidine (2,6-lut) in (4) and also M = Fe^II, L = quin and 2,6-lut.     

Synthesis,spectral and magnetic studies of some mixed ligand complexes of spin-free cobalt(II)

The reactions of acetylacetone, methyl acetoacetate and ethyl acetoacetate derivatives of cobalt(II) with diamines and hydroxyquinoline have resulted in the isolation of hexacoordinated complexes of the stoichiometry Co(L)₂(L′); where L = acetylacetone (AA), methyl acetoacetate (MeAA) or ethyl acetoacetate (EtAA) and L′ = ethylenediamine (En), propylenediamine (Pn) or 8-hydroxyquinoline. Their magnetic, IR and electronic spectral properties have been used to establish the stereochemistry. The values of the Racah interelectronic repulsion parameter (B) and crystal field splitting energy (10Dq) have been calculated using numerical as well as graphical procedures.     

Synthesis, spectral, and biological studies of some metal(II) complexes with benzil salicylaldehyde acyldihydrazones

Complexes of the general formula [M(Bsodh)]Cl and [M(Bsmdh)]Cl, where M = Co(II), Ni(II), Cu(II), Zn(II,) and Cd(II) (HBsodh = benzil salicylaldehyde oxalic acid dihydrazone and HBsmdh = benzil salicylaldehyde malonic acid dihydrazone) were synthesized and characterized by elemental analyses, molar conductance, magnetic moments, electronic, ESR, infrared spectra, and X-ray diffraction studies. The complexes are stable solids insoluble in common organic solvents and 1: 1 electrolytes. The magnetic moments and electronic spectra reveal a square-planar geometry for [M(Bsodh)]Cl and a six-coordinate octahedral geometry for [M(Bsmdh)]Cl. The HBsodh ligand bonds to the metal ion via one >C=O, two >C=N−, and one deprotonated phenolate group, whereas HBsmdh bonds through three >C=O, two >C=N−, and one phenolate group. The lattice parameters for [Co(Bsodh)]Cl and [Ni(Bsmdh)]Cl correspond to tetragonal and orthorhombic crystal lattices, respectively. ESR spectral data indicate the presence of an unpaired electron in of the Cu²⁺ ion. The ligands, as well as their metal complexes, show significant antibacterial activity against Bacillus subtilis and Pseudomonas fluorescens. The text was submitted by the authors in English.     

Synthesis,characterization and superoxide dismutase activity of some octahedral nickel(II) complexes

Four new mixed ligand nickel(II) complexes viz., [Ni(tren)(phen)](ClO₄)₂ (1), [Ni(tren)(bipy)](ClO₄)₂ (2), [Ni(SAA)(PMDT)] · 2H₂O (3) and [Ni(SAA)(TPTZ)] (4) (tren = tris(2-aminoethylamine), phen = 1,10-phenanthroline, bipy = 2,2′-bipyridine, SAA = salicylidene anthranilic acid, PMDT = N,N,N′,N″,N″-pentamethyldiethylenetriamine, TPTZ = 2,4,6-tri(2-pyridyl)-1,3,5-triazine) have been synthesized and characterized by means of elemental analysis, spectroscopic, magnetic susceptibility and cyclic voltammetric measurements. Single crystal X-ray analysis of [Ni(tren)(phen)](ClO₄)₂ (1) and [Ni(SAA)(PMDT)] · 2H₂O (3) has revealed the presence of a distorted octahedral geometry. Superoxide dismutase activity of these complexes has also been measured.     

Synthesis, anticancer and antibacterial activity of some novel mononuclear Ru(II) complexes

In search of potential anticancer drug candidates in ruthenium complexes, a series of mononuclear ruthenium complexes of the type [Ru(phen)(2)(nmit)]Cl(2) (Ru1), [Ru(bpy)(2)(nmit)]Cl(2) (Ru2), [Ru(phen)(2)(icpl)]Cl(2) (Ru3), Ru(bpy)(2)(icpl)]Cl(2) (Ru4) (phen=1,10-phenanthroline; bpy=2,2'-bipyridine; nmit=N-methyl-isatin-3-thiosemicarbazone, icpl=isatin-3-(4-Cl-phenyl)thiosemicarbazone) and [Ru(phen)(2)(aze)]Cl(2) (Ru5), [Ru(bpy)(2)(aze)]Cl(2) (Ru6) (aze=acetazolamide) and [Ru(phen)(2)(R-tsc)](ClO(4))(2) (R=methyl (Ru7), ethyl (Ru8), cyclohexyl (Ru9), 4-Cl-phenyl (10), 4-Br-phenyl (Ru11), and 4-EtO-phenyl (Ru12), tsc=thiosemicarbazone) were prepared and characterized by elemental analysis, FTIR, (1)H-NMR and FAB-MS. Effect of these complexes on the growth of a transplantable murine tumor cell line (Ehrlich Ascites Carcinoma) and their antibacterial activity were studied. In cancer study the effect of hematological profile of the tumor hosts have also been studied. In the cancer study, the complexes Ru1-Ru4, Ru10 and Ru11 have remarkably decreased the tumor volume and viable ascitic cell count as indicated by trypan blue dye exclusion test (p<0.05). Treatment with the ruthenium complexes prolonged the lifespan of Ehrlich Ascites Carcinoma (EAC) bearing mice. Tumor inhibition by the ruthenium chelates was followed by improvements in hemoglobin, RBC and WBC values. All the complexes showed antibacterial activity, except Ru5 and Ru6. Thus, the results suggest that these ruthenium complexes have significant antitumor property and antibacterial activity. The results also reflect that the drug does not adversely affect the hematological profiles as compared to that of cisplatin on the host.     

Synthesis, characterization and catalytic activity of organolanthanide(II) complexes with heterocyclic-functionalized fluorenyl ligands

Two series of new organolanthanide(II) complexes with tetrahydro-2H-pyranyl- or N-piperidineethyl-functionalized fluorenyl ligands were synthesized via one-electron reductive elimination reaction. Treatments of [(Me₃Si)₂N]₃Ln^III(μ-Cl)Li(THF)₃ with 2 equiv. of C₅H₉OCH₂C₁₃H₉ (1) or C₅H₁₀NCH₂CH₂C₁₃H₉ (2), respectively, in toluene at about 80 °C produced, after workup, the corresponding organolanthanide(II) complexes with formula [η⁵:η¹-C₅H₉OCH₂C₁₃H₈]₂Ln^II (Ln = Yb (3), Ln = Eu (4)) and [η⁵:η¹-C₅H₁₀NCH₂CH₂C₁₃H₈]₂Ln^II (Ln = Yb (5), Ln = Eu (6)) in good yields. All the compounds were fully characterized by spectroscopic methods and elemental analyses. The structures of complexes 3, 4, and 6 were additionally determined by single-crystal X-ray analyses. It represents the first example of solvent-free organolanthanide(II) complexes with fluorenyl ligands. The catalytic properties of the organolanthanide(II) complexes on the polymerization of ε-caprolactone and methyl methacrylate have been studied. The temperatures, solvents and coordination effects on the catalytic activities of the complexes were examined.     

Synthesis,spectral characterization,crystal structures of lanthanide(III) pyrrolidine dithiocarbamate complexes and their catalytic activity

A series of lanthanide(III) pyrrolidine dithiocarbamate complexes [Ln(Pyrrol-Dtc)₃(Phen)] {Pyrrol-Dtc = pyrrolidine dithiocarbamate; Phen = 1,10-phenanthroline; Ln = La(III), Ce(III), Pr(III), Nd(III), Sm(III), Gd(III), Tb(III), Dy(III), Er(III)} have been synthesized and structurally characterized. The molecular structures of [La(Pyrrol-Dtc)₃(Phen)], [Pr(Pyrrol-Dtc)₃(Phen)], [Sm(Pyrrol-Dtc)₃(Phen)], and [Dy(Pyrrol-Dtc)₃(Phen)] have been confirmed using single crystal XRD studies. The results reveal that in these complexes, the central Ln(III) ion is coordinated to three Pyrrol-Dtc and one Phen and possesses a distorted dodecahedron geometry. Catalytic activity of these complexes in trimethylsilylcyanation reaction has been studied.