Synthesis and spectral studies ofo-hydroxyacetophenone (N-benzoyl)glycyl hydrazone and some of its lanthanide(III) complexes

Summary o-Hydroxyacetophenone (N-benzoyl)glycyl hydrazone (o-HABzGH) has been characterized by i.r.,¹H n.m.r.,¹³C n.m.r. and mass spectral studies, and its complexes of the types [Ln(o-HABzGH)Cl₂(H₂O)₂]Cl and [Ln(o-HABzGH–2H)OH(H₂O)₃], where Ln=La, Pr, Nd, Sm and Eu, have been synthesized. The structures of the complexes have been studied by conductance, magnetic, electronic, i.r.,¹H n.m.r. and¹³C n.m.r. spectral techniques. The hypersensitive bands of the electronic spectra suggest coordination numbers six and seven around Nd^III in its adduct and neutral complexes respectively. I.r. and n.m.r. spectral data suggest a neutral bidentate behaviour for the ligand in the adducts and a dinegative tridentate nature in the neutral complexes.     

Cationic complexes of chelated bis(η-cyclopentadienyl)titanium(IV) with halometallates of gallium(III), indium(III) and thallium(III)

Summary Eight complexes of the chelated bis(-cyclopenta-dienyl)titanium(IV) cation. [-Cp₂TiL][MX₄] (L = acetyl-acetone, M = Ga^III, In^III or Ti^III: X = Cl, Br or I) have been isolated from aqueous solution and characterised by elemental analyses and i.r. data. Their ionic nature has been confirmed by conductance measurements.     

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.     

Boron Cluster Anions [BnHn]2– (n = 10, 12) in Reactions of Iron(II) and Iron(III) Complexation with 2, 2′‐Bipyridyl and 1, 10‐Phenanthroline

Complexation of Fe^II and Fe^III with azaheterocyclic ligands L (L = phen or bipy) were studied in the presence and in the absence of boron cluster anions [B_nH_n]^2– (n = 10, 12). The reactions were carried out in air at room temperature in organic solvents and/or water. In all the solvents used, well known [FeL₃]An (An = 2Cl^– or SO₄^2–) ferrous complexes were formed from Fe^II salts. Composition of ferric complexes with L ligands depends on the nature of solvent: either dinuclear oxo‐iron(III) chlorides [L₂ClFe^III–O–Fe^IIIL₂Cl]Cl₂ or ferric ferrates(III) [Fe^IIIL₂Cl₂][Fe^IIICl₄], or [Fe^IIIL₂Cl₂][Fe^IIICl₄L] were isolated from Fe^III salts. Introduction of the closo‐borate anions to a Fe³⁺(or Fe²⁺)/L/solv. mixture stabilizes ferrous cationic complexes [FeL₃]²⁺ in all the solvents used: only ferrous [FeL₃][B_nH_n] (n = 10, 12) complexes were isolated from all the reaction mixtures in the presence of boron cluster anions.     

Rhodium(III) halide complexes with sulphur donors. The crystal structure ofmer-tris(o-ethylthiocarbamate)-trichlororhodium(III)acetone(1/1)

Summary The complexes [Rh(TC)₃Cl₃] · Me₂CO and [Rh(TC)₃X₃] · 0.5 Me₂CO (TC=O-ethylthiocarbamate; X=Br or I) have been prepared and characterized by i.r. and¹H n.m.r. spectroscopy.The crystal structure of [Rh(TC)₃Cl₃] · Me₂CO has been determined by x-ray diffractometer data and refined to R=0.040. Crystals are monoclinic, space group P2₁, with a=9.101(5), b=15.785(8), c=8.776(5) Å, and =103.00(3)°; Dx=1.57 gcn^–3 for Z=2. The complex is monomeric with octahedral Rh. Relevant distances are Rh-Cl (trans to one another) 2.354(2) and 2.353(2) Å, Rh-Cl (trans to S) 2.388(2) Å; Rh-S (trans to one another) 2.376(3) and 2.369(3) Å, Rh-S (trans to Cl) 2.332(3) Å. There is intramolecular, and possibly intermolecular, hydrogen bonding in the structure.     

Novel bidentate ruthenium(III) Schiff base complexes: synthetic,spectral, electrochemical,catalytic and antimicrobial studies

Ru^III complexes of the type [RuX(L)₂(E)] (X = Cl or Br; L = novel bidentate Schiff base ligand; E = PPh₃ or AsPh₃) have been prepared by reacting [RuX₃(E)₃] or [RuBr₃(PPh₃)₂(MeOH)] with two novel bidentate Schiff base ligands derived from 4-(1-methyl-1-mesitylcyclobutane-3-yl)-2-aminothiazole, in a 1:2 molar ratio in benzene, and characterised by analytical, spectral (i.r., electronic, ¹H-, ¹³C- n.m.r., and e.p.r.) and electrochemical data. An octahedral structure has been tentatively proposed for all the new complexes. The thermal properties of the ligands and their complexes have been studied by t.g.a. The new Ru^III complexes are effective catalysts for the oxidation of alcohols to carbonyl compounds but are unable to oxidise alkenes in the presence of N-methylmorpholine-N-oxide (NMO) as co-oxidant. The antimicrobial activity of the ligands and complexes have also been tested against six microorganisms.     

Synthesis, Characterization and Antibacterial Activity of Some Transition Metal cis-3,7-dimethyl-2,6-octadiensemicarbazone Complexes

The synthesis and characterization of some transition metal cis-3,7-dimethyl-2,6-octadiensemicarbazone (CDOSC) complexes are reported. The ligand CDOSC yields: [ML₂ Cl₂] and [ML₂ Cl₂] Cl type complexes, where M = Cr^III, Mn^II, Fe^III, Co^II, Ni^II, Cu^II, Zn^II, Cd^II and Hg^II, L = CDOSC. Structures of the complexes were determined using elemental analysis, molar conductivity, magnetic measurements, i.r. and electronic, as well as n.m.r spectra. CDOSC acts as a bidentate ligand in all the complexes. All the newly synthesized metal complexes, as well as the ligand, were screened for their antibacterial activity. All the complexes exhibit strong inhibitory action against Gram (+) bacteria Staphylococcus aureus and Gram (−) bacteria Escherichia coli. The antibacterial activities of the complexes are stronger than those of the ligand CDOSC itself.     

Effects of chloride ions on electrochemical reactions of manganese(III) complexes

Electrochemical reactions of manganese(III) complexes, Mn^III(L)X (L; salen, salpn, 5-NO₂–salen or 5-NO₂–salpn, X; Cl, Br or NO₂) and Mn^III(L’)₂X (L’; N-Bu-sal, N-Oct–sal, N-Oct–5-Br–sal or N-Oct–5-NO₂–sal, X; Cl or Br), were investigated by voltammetry at a glassy carbon electrode in the absence/presence of Cl⁻ in acetonitrile solution. By the addition of Cl⁻, oxidation processes of Mn^III(L)X and Mn^III(L’)₂X have been found to be improved from quasi-reversible to reversible, and their oxidation products, [Mn^IV(L)X]⁺ and [Mn^IV(L’)₂X]⁺, were stabilized by the combination with Cl⁻ resulting in [Mn^IV(L)Cl₂] and [Mn^IV(L’)₂Cl₂], respectively. On the other hand, the reduction processes of Mn^III(L)X and Mn^III(L’)₂Cl were not so significantly affected by Cl⁻ as those observed for their oxidation. Other types of manganese(III) complexes and iron(III) complex were also investigated. The present study may clarify the role of Cl⁻ being involved in OEC (oxygen-evolving center) in photosystem II.     

Coordination compounds of 2-mercapto-1-methylimidazole with platinum(II), palladium(II), rhodium(III) and ruthenium(III)

Summary Complexes of 2-mercapto-1-methylimidazole (TMZ) with Pt^II, Pd^II, Rh^III and Ru^III of the general formulae Pt(TMZ)₂Cl₂, Pd(TMZ)₄Cl₂. Rh(TMZ)Cl₃ and Ru(TMZ)Cl₃ have been obtained. The thermal stabilities of the compounds were estimated by derivatographic measurements and the electron-donating atom of the measurements and the electron-donating atom of the ligand was identified from the i.r. absorbtion spectra. Lattice constants for the Pt^II and Pd^II complexes were estimated from their x-ray powder diffraction patterns.     

Ruthenium(II)/(III) complexes of bidentate acetyl hydrazide Schiff bases

A series of octahedral Ru^II/Ru^III complexes of the type [Ru(Y)(CO)(BAX)(PPh₃)₂] and [RuCl₂(BAX)(PPh₃)₂] (Y = H or Cl; BAX = benzaldehydeacetylhydrazone anion; X = H, Me, OMe, OH, Cl or NO₂) have been prepared and characterised by spectral, magnetic and cyclic voltammetric studies. The Ru^II complexes are low spin diamagnetic (S = 0) whereas the Ru^III complexes are low spin and paramagnetic (S = 1/2). These Ru^II and Ru^III complexes absorb in the visible region respectively at ca. 16,000 and 28,000 cm^–1 which bands are assigned to the MLCT. The correlation of the _max values of the Ru^III complexes with the ⁺ Hammett parameter, is linear, indicating the profound effect of substituents on the electron density of the central metal. I.r. spectral data reveals that the hydrazone is chelated to ruthenium through the hydrazinic nitrogen and the deprotonated enolic oxygen. The rhombic nature of the e.s.r. spectra of the Ru^III complexes indicates an asymmetry in the electronic environment around the Ru atom. Ru^II complexes in CH₂Cl₂ show an irreversible Ru^II/III redox couple at ca. 0.9–0.5 V, while the Ru^III complexes show two reversible redox couples in the –0.1–0.1 and 0.8–0.6 V range, indicating that the higher oxidation state of ruthenium is stabilised by hydrazones.     

(18-Crown-6)potassium tetrachloroferrate(III), dibromodichloroferrate(III), and tetrabromoferrate(III): Synthesis and crystal structures

Three new crystalline complexes are synthesized: [K(18-crown-6)]⁺ · An, where An = [FeCl₄]^?(I), [FeBr₂Cl₂]^? (II), and [FeBr₄]^? (III). The crystals of compounds I–III are cubic and isomorphic, space group Fd $ \bar 3 Three new crystalline complexes are synthesized: [K(18-crown-6)]⁺ · An, where An = [FeCl₄]⁻(I), [FeBr₂Cl₂]⁻ (II), and [FeBr₄]⁻ (III). The crystals of compounds I–III are cubic and isomorphic, space group Fd (Z = 16): a = 20.770(2) ? for I, 20.844(3) ? for II, and 20.878(4) ? for III. Structures I–III are solved by a direct method and refined by the full-matrix least-squares method in the anisotropic approximation to R = 0.047 (I), 0.059 (II), and 0.098 (III) for all 680 (I), 684 (II), and 686 (III) independent reflections. In two tetrahedral anions [Fe(1)X₄]⁻ and [Fe(2)X₄]⁻ in structures I–III, all halogen atoms (X = Cl and Br) are randomly disordered over three close positions relative to the crystallographic axes 3. Structures I–III contain the [K(18-crown-6)]⁺ host-quest complex cation. The K⁺ cation (CN = 8) resides in the cavity of the 18-crown-6 ligand and coordinated by its six O atoms and two disordered halogen X atoms. The coordination polyhedron of the K⁺ cation in complexes I–III is a distorted hexagonal bipyramid. Original Russian Text ? A.N. Chekhlov, 2008, published in Zhurnal Neorganicheskoi Khimii, 2008, Vol. 53, No. 9, pp. 1566–1570.     

Ligational behaviour of two biologically active N−S donors towards cobalt(III), iron(III), iron(II) and rhodium(III)

Summary The chelating behaviour of two biologically active ligands, pyridine-2-carboxaldehyde(4-phenyl) thiosemicarbazone(L₁H) and pyridine-2-carboxaldehyde thiosemicarbazone(LH), towards Fe^III, Co^III, Fe^II and Rh^III has been investigated. The ligands act as tridentate N–N–S donors, resulting in the formation of bis-chelate complexes of the type M^III(A)₂X·nH₂O (A=L₁ or L; X=Cl, ClO₄; M=Co^III, Rh^III, Fe^III), Fe^II(L₁H)₂SO₄·2H₂O and Fe^II(L₁)₂·H₂O. Biological activity of the ligands and the metal complexes in the form ofin vitro antibacterial activities towardsE. coli has been evaluated and the possible reasons for enhancement of the activity of ligands on coordination to metal ion is discussed.     

Studies on binuclear hydroxo/carboxylato-bridged manganese(III) complexes and a mononuclear manganese(III) complex involving salen type ligands

Synthesis of six hydroxo-bridged binuclear manganese(III) complexes of formulae [MnL-X-MnL](ClO₄) [X = OH (1–6)] along with a mononuclear manganese(III) complex (7) [Mn(L)(L′)(MeOH)₂] [HL′ = 2-(2-hydroxy-phen-yl)benzimidazole] and two carboxylate-bridged binuclear manganese(III) complexes (8) and (9) are described. The complexes have been characterized by the combination of i.r., u.v.-vis spectroscopy, magnetic moments and by their redox properties. The electronic spectra of all the complexes exhibit almost identical features consisting of two d–d bands at ca. 550 and 600 nm, one MLCT band at ca.400 nm, together with two π–π^* intra-ligand transitions at ca. 250 nm and ca.300 nm. Room temperature magnetic data range from μ = 2.7–3.0 BM indicates some super-exchange between the binuclear metal centers via bridging hydroxo/carboxylato groups. The X-ray crystal structure of the binuclear complex (5) revealed that it has a symmetric Mn^IIIN₂O₂ core bridged by a hydroxyl group. The X-ray analysis of the mononuclear complex (7) showed that the manganese-center possesses a distorted octahedral geometry. Electrochemical properties of hydroxo-bridged manganese(III) complexes (1–6) show identical features consisting of an irreversible and a quasi-reversible reduction corresponding to the Mn₂^III → Mn^IIMn^III → Mn^IIMn^II couples in the voltammogram. It was found that electron withdrawing substituents on the ligand result in easier reduction. Complex (7) displays an irreversible reduction at 0.08 V and a reversible oxidation at 0.45V assignable to the Mn^III → Mn^II reduction and Mn^III → Mn^IV oxidation, respectively. The carboxylate-bridged compound (8) exhibits two irreversible oxidations at 0.4 and 0.6 V, probably due to Mn₂^III → Mn^IIIMn^IV → Mn^IVMn^IV oxidations and shows a quasi-reversible reductive wave at −0.85 V, tentatively assigned to Mn₂^III → Mn^IIMn^III reduction.     

meso-(2-Pyridyl)-boron(III)-subporphyrin: Perimeter Iridium(III) Coordination

Peripherally metalated porphyrinoids are promising functional π-systems displaying characteristic optical, electronic, and catalytic properties. In this work, 5-(2-pyridyl)- and 5,10,15-tri(2-pyridyl)-B^III-subporphyrins were prepared and used to produce cyclometalated subporphyrins by reactions with [Cp*IrCl₂]₂, which proceeded through an efficient C−H activation to give the corresponding mono- and tri-Ir^III complexes, respectively. While the mono-Ir^III complex was obtained as a diastereomeric mixture, a C₃-symmetric tri-Ir^III complex with the three Cp*-units all at the concave side was predominantly obtained in a high yield of 90 %, which displays weak NIR phosphorescence even at room temperature in degassed CH₂Cl₂, differently from the mono-Ir^III complexes.     

Cobalt(II,III) and copper(II) complexes of 3-(2-furylidene) hydrazino-5,6-diphenyl-1,2,4-triazine

A new series of cobalt(II, III) and copper(II) complexes of 3-(2-furylidene) hydrazino-5,6-diphenyl-1,2,4-triazine (L) having formulae LM^IIX₂, L₂M^IIX₂ and LCo^IIIX₃, (X = Cl, OAc or ClO₄; M^II = Co^II or Cu^II) were isolated and characterized by elemental analyses, molar conductances, magnetic moments and i.r., electronic and e.s.r. spectral measurements. The i.r. spectra indicated that the ligand, L, behaves as a neutral bidentate towards divalent metal ions via a triazine-N, and azomethine-N, and acts as a tridentate towards cobalt(III) via the same two nitrogen atoms and the furan-O. The magnetic moments and electronic spectral data suggest a pseudo-tetrahedral geometry for [L₂Co]Cl₂, a diamagnetic tetragonally distorted octahedral geometry for [LCoCl₃], [LCo(OAc)₃] · 4H₂O and [LCo(H₂O)₃](ClO₄)₃ and a dimeric square pyramidal geometry for both [LCuCl₂] and [LCu(OAc)₂] · 2H₂O through bridged chloro and acetato ligands, respectively. The ligand field parameters (B, 10Dq and ) were evaluated from the electronic spectral data and magnetic moments and related to the bonding of the complexes. The X-band e.s.r. spectra showed three g values with large magnetic anisotropy for [L₂Co]Cl₂ in accordance with pseudo-tetrahedral Co^II complexes; axial pattern for [LCuCl₂], [LCu(OAc)₂] · 2H₂O and [L₂Cu(H₂O)₂](ClO₄)₂ with two g values and a signal due to M _s = ±2 transition for both chloro and acetato copper(II) complexes.     

Coordinated lanthanide metal complexes ofN-benzoylglycine hydrazide

Summary N-benzoylglycine hydrazide (BzGH) reacts with trivalent lanthanide metal ions forming complexes of the type [Ln(BzGH)₂Cl(H₂O)₂]Cl₂·nH₂O, where Ln=La^III, Pr^III, Nd^III, Sm^III, Eu^III, Gd^III, Tb^III, Dy^III, or Y^III;n=1 or 2. The structures of the complexes have been studied by conductance, magnetic, electronic, i.r.,¹H n.m.r. and¹³C n.m.r. spectral techniques. The nephelauxetic ratio, the bonding parameter, Sinha's parameter and the covalency angular overlap parameter have been calculated from the electronic spectra of Pr^III, Nd^III and Sm^III complexes. Seven-coordination is proposed in the Nd^III complex. The i.r. and¹H n.m.r. spectral data suggest bidentate BzGH in all the complexes.     

Complexes of 1-isonicotinoyl-4-benzoyl-3-thiosemicarbazide with manganese(II), iron(III), chromium(III), cobalt(II), nickel(II), copper(II) and zinc(II)

1-Isonicotinoyl-4-benzoyl-3-thiosemicarbazide (IBtsc) and its Cr^III, Mn^II, Fe^III, Co^II, Ni^II, Cu^II and Zn^II complexes have been prepared and characterized by elemental analyses, magnetic susceptibility measurements, u.v.–vis., i.r., n.m.r. and FAB mass spectral data. The room temperature e.s.r. spectra of the Cr^III, Fe^III and Cu^II complexes yield values, characteristic of octahedral, tetrahedral and square-planar complexes, respectively. The Mössbauer spectra of [Fe(IBtsc-H)Cl₂] at room temperature and at 78 K suggest the presence of high-spin Fe^III. The Ni^II, Cr^III and Cu^II complexes show semiconducting behaviour in the solid state, but the Zn^II complex is an insulator at room temperature. IBtsc and its soluble complexes have been screened against several bacteria, fungi and tumour cell lines.     

Ruthenium(II/III)‐Based Compounds with Encouraging Antiproliferative Activity against Non‐small‐Cell Lung Cancer

Hereby we present the synthesis of several ruthenium(II) and ruthenium(III) dithiocarbamato complexes. Proceeding from the Na[trans‐Ru^III(dmso)₂Cl₄] ( 2 ) and cis‐[Ru^II(dmso)₄Cl₂] ( 3 ) precursors, the diamagnetic, mixed‐ligand [Ru^IIL₂(dmso)₂] complexes 4 and 5 , the paramagnetic, neutral [Ru^IIIL₃] monomers 6 and 7 , the antiferromagnetically coupled ionic α‐[Ru^III₂L₅]Cl complexes 8 and 9 as well as the β‐[Ru^III₂L₅]Cl dinuclear species 10 and 11 (L=dimethyl‐ (DMDT) and pyrrolidinedithiocarbamate (PDT)) were obtained. All the compounds were fully characterised by elemental analysis as well as ¹H NMR and FTIR spectroscopy. Moreover, for the first time the crystal structures of the dinuclear β‐[Ru^III₂(dmdt)₅]BF₄ ? CHCl₃ ? CH₃CN and of the novel [Ru^IIL₂(dmso)₂] complexes were also determined and discussed. For both the mono‐ and dinuclear Ru^II and Ru^III complexes the central metal atoms assume a distorted octahedral geometry. Furthermore, in vitro cytotoxicity of the complexes has been evaluated on non‐small‐cell lung cancer (NSCLC) NCI‐H1975 cells. All the mono‐ and dinuclear Ru^III dithiocarbamato compounds (i.e., complexes 6 – 10 ) show interesting cytotoxic activity, up to one order of magnitude higher with respect to cisplatin. Otherwise, no significant antiproliferative effect for either the precursors 2 and 3 or the Ru^II complexes 4 and 5 has been observed.     

Four novel classes of heterobimetallic isopropoxides of chromium(III)

Four novel classes of hydrocarbon-soluble isopropoxometallates of chromium(III): [Cr{²-Zr(OPr ⁱ )₅}₃], [Cr- {²-M₂(OPr ⁱ )₉}₃] [M = Zr^IV, Sn^IV], [Cr{²-M(OPr ⁱ ) _x Cl}₃] (M = Al, x = 3; M = Nb, x = 5), and [Cr{⁴-Zr₂-(OPr ⁱ )₈Cl}Cl₂]/[Cr{³-Zr₂(OPr ⁱ )₈Cl}{²-Zr₂(OPr ⁱ )₈Cl}Cl] [ ⁿ represents the number of connectivity sites (n = 2, 3, 4) involved in binding Cr^III] have been prepared for the first time and characterized by the elemental analyses, spectroscopic (i.r., electronic) and magnetic susceptibility studies as well as molecular weight measurements. The [Cr{²-Ga(OPr ⁱ )₄}₃] derivative has also been prepared and its magnetic and electronic properties compared with the above four novel types of Cr^III complexes.     

Substituted dipyridylpyridazine rhodium(III) complexes

3,6-Bis(2-pyridyl)pyridazine derivatives (n-dppn) react with hydrated rhodium(III) chloride and bromide (prepared in situ) to give cis-[Rh(n-dppn)₂Cl₂]PF₆·xH₂O (n = 5, 6, 7, 8) and cis-[Rh(n-dppn)₂Br₂]Br·xH₂O (n = 5, 7) complexes, which have been characterized by elemental analyses, conductivity measurements, i.r., electronic and ¹H- and ¹³C-n.m.r. spectra.