Showing papers in "Transition Metal Chemistry in 1984"

Complexes of divalent nickel and copper with the Schiff base derived from 2-(2-aminophenyl)benzimidazole and benzaldehyde

Abstract: The reactions of divalent nickel and copper salts with the Schiff base derived from 2-(2-aminophenyl)benzimidazole and benzaldehyde, L, yield complexes of general formulae [CuL2X2] (X=Cl, Br, or ClO4), [CuL(SO4)], [CuL(SO4)] · 4H2O, and NiLX2 (X=Cl, Br, or NCS). All the complexes have been characterized by elemental analyses, magnetic measurements, e.s.r. electronic and i.r. spectral studies. The results show that the Schiff base acts as bidentate ligand through the pyridine-like imine nitrogen of imidazole ring and the azomethine nitrogen. Tentative structures of the complexes are suggested.

Hydrolysis of the palladium(II) ion in a sodium chloride medium

Abstract: The hydrolysis of the palladium(II) ion in a sodium chloride medium was studied by the e.m.f. method at 25 °C. The data show that the extent of the palladium hydrolysis depends upon the concentration of both palladium and sodium chloride medium. Thus, at a definite pH, the extent of the hydrolysis increases with increasing concentration of palladium, but decreases with increasing concentration of sodium chloride. The stability constants of the complexes obtained, PdOH+ and Pd4(OH) 4 4+ , also differ slightly depending upon the concentraton of sodium chloride. The observed medium effect is in agreement with the linear free energy relationship proposed for the metal ion hydrolysis.

Ionic strength dependence of formation constants. Part 4. Potentiometric study of the system Cu2+-Ni2+-citrate

Abstract: The ternary Cu2+-Ni2+-citrate (cit3−) system was investigated potentiometrically in aqueous solution, at different temperatures, 10≤t≤45°C, and ionic strengths, 0.03≤I≤0.8 mol dm−3, using potassium nitrate or tetraethylammonium bromide as background salt. Since the citrate anion forms weak complexes with potassium, the stability constants here reported differ according to whether the potassium association is considered or not. In the presence of both Cu2+ and Ni2+, the mixed metal species, [CuNi(cit)2H−2]4− is formed with citrate in solution, in addition to the various binary complexes. We have obtained the dependence for all the formation constants on ionic strength and temperature. The previous suggestions concerning a general equation for describing the dependence, log β=f(I), are confirmed; from the study of log β=f(T) we have obtained the values of thermodynamic parameters. The dependence of ΔH on ionic strength is discussed.

Synthesis and characterisation of copper(II), nickel(II) and palladium(II) complexes of some schiff bases of dehydroacetic acid

Abstract: Tri-and quadri-dentate Schiff bases have been synthesized from the reaction of dehydroacetic acid with diamines, aminoacids, aminophenols and aminoalcohols. The copper(II) and some nickel(II) and palladium(II) chelates of these ligands as well as copper(II) complexes of bidentate Schiff bases of dehydroacetic acid with anilines have been prepared and characterised by electronic, i.r. and n.m.r. spectral measurements and magnetic moments.

Cobalt(II) and nickel(II) complexes of some nitrogen-oxygen and nitrogen-sulphur ligands

Abstract: Cobalt(II) and nickel(II) complexes of some nitrogen-oxygen and nitrogen-sulphur ligandsviz., phenylpyruvic acid semicarbazone, (4-methylphenyl)pyruvic acid semicarbazone, phenylpyruvic acid thiosemicarbazone and (4-methylphenyl)-pyruvic acid thiosemicarbazone have been prepared and characterised by elemental analyses, room temperature magnetic moments, infrared and electronic spectral studies. All the complexes have been found to possess the composition M(ligand)2 and octahedral geometry.

Lanthanide chelates of fluorinated β-diketones. Part II magnetic moments and electronic spectra of lanthanide chelates of four fluorinated β-diketones and the crystal structure of [Er(m · MeC6H4CO=CHCOF3)3(H2O)2] · H2O

Abstract: Magnetic and spectral data are reported for the complexes Ln(RCO=CHCOCF3)3 ·nH 2O (Ln=lanthanide; R=p BrC6H4,m-MeC6H4,o-MeC6H4, Bu-t; n=2 or 3). An x-ray crystal structure determination of Er(m-MeC6H4CO=CH-COCF3)3 · 3 H2O showed that the complex is eight-coordinate with three bidentate β-diketonato and two aquo ligands; the third water molecule is hydrogen-bonded to one of the coordinated water molecules. The configuration about the erbium atom approximates to a square antiprism. The magnetic moments of the samarium and europium chelates are temperature-dependent, whereas those of the other paramagnetic lanthanides obey the Curie-Weiss law. The visible spectra of the chelates of Pr, Nd, Sin, Eu, Tb, Dy, Ho, Er, and Tm display line-like absorption bands typical of lanthanide ions. Hypersensitive transitions were observed for Nd, Sm, Eu, Dy, Ho, and Er.

Bivalent metal complexes ofp-methyl- andp-methoxybenzoylhydrazone oximes

Abstract: Bivalent metal complexes ofp-chloro-,p-methyl- andp-methoxybenzoylhydrazone oximes (H2BMCB, H2BMMB or H2BMTB=H2L), [M(H2L)Cl2]. nH2O (M=ZnII, CdII or HgII, n=0 or 1; [M(H2L)Cl2] (M=ZnII or CdII); [M(HL)2(H2O)n]. YH2O (M=CoII, CuII, ZnII or UVIO2, n=0–2); [Ni(H2BMCB)(H2O)3]Cl2, [Ni(BMMB)(H2O)]2 and [Ni(BMTB)(H2O)]2, were synthesized by conventional physical and chemical measurements. I.r. spectra show that the ligands are bidentate or tridentate. Spectral, magnetic and molecular weight measurements suggest that cobalt(II) and nickel(II) have monomeric octahedral geometry when derived from H2BMCB, a dimeric square planar geometry for nickel(II) and monomeric square planar geometry for cobalt(II) for those isolated from H2BMMB or H2BMTB. Also, a monomeric distorted octahedral structure is proposed for copper(II) complexes derived from the ligands under investigation.

N.m.r. studies of complexes of molybdenum(VI) with tartaric acid in aqueous solution

Abstract: Complex formation between molybdate ions and R,R-(+)-tartaric acid has been studied in aqueous solution, and to a limited extent in DMSO, over a range of concentrations and pH at 298K, using1H and13C n.m.r. techniques. Only four main species are evident; two, which have Mo: L ratios of 1∶1 and 1∶2, are bondedvia a carboxylic oxygen atom and an adjacent hydroxyl oxygen atom. The 1∶2 species forms stereospecifically. The other two main species contain bridging tartaric acid molecules, and a 2∶2 species, also formed stereo-specifically in solution, have been isolated and characterised in the solid state. A limited number of experiments with racemic acid and meso-tartaric acid indicate that only a few species are formed in these systems and with a good deal of stereospecificity also.

A convenient method of preparing nickel(II) thiocyanate and its use in synthesis

Abstract: A convenient method for preparing nickel(II) thiocyanate is described. Some new compounds containing nickel thiocyanate and ligands, such as OPPh3, OAsPh3, bipy, Me2NH, Et3N or N2H4 are reported, together with their structures and the nature of the bond between the thiocyanate and the metal, which has been determined by physical and chemical methods.

C-N Stretching Force Constants in Cyano Complexes' General Trends for Polycyano, Mixed-ligand and Cyano-bridged Complexes

Abstract: The study of the vibrational data for a large number of cyano-complexes of the transition metals within a factored force field scheme (also known as Cotton-Kraihanzel force field) shows that CN bond strengths in these complexes only depend, to a good degree of approximation, on the coordination number and oxidation state of the central metal cation. This is summarized in a linear equation which provides a rough estimate for the CN stretching frequencies of many cyanocomplexes not fully characterized. For mixed ligand cyanocomplexes, the observed trends are rationalized in terms of the π-acid properties of the hetero-ligand and a good correlation is found between the CN stretching force constant and the electronegativity of the hetero-ligand. When the cyano-group bridges two metal atoms in polynuclear complexes, a strengthening of the CN bond is apparent in the values of the force constants of the bridging groups, while the strength of the terminal cyano-group is not affected by the bridge formation.

Metal chelates of heterocyclic Nitrogen containing ketones. XV. Five-coordinate nickel(II) and copper(II) complexes with a sulphur-nitrogen tridentate schiff base

Abstract: Complexes of the Schiff base, 2-picolylphenylketone-hydrazine-S-benzyl dithiocarbazate, PPKBzTE, with nickel(II) and copper(II) halides have been prepared and characterized using spectral (1H n.m.r., i.r., uv-visible and e.s.r.) and magnetic measurements. A square pyramidal geometry is assumed for [Ni(PPKBzTE-H)X]2(X=Cl or. Br) and a square planar structure for [Ni(PPKBzTE-H)I]. The spectral studies in inert solvents show the presence of temperature dependent equilibria between tetrahedral and five-coordinate species in the chloro-and bromo-complexes. The interaction of nickel(II) complexes with various heterocyclic nitrogen Lewis bases yielded distorted octahedral 1∶2 adducts. Copper(II) complexes, [Cu3(PPKBzTE)(PPKBzTE-H)Cl5] and [Cu(PPKBzTE-H)Br]2 were separated and associated with a five-coordinate structure. Variable temperature magnetic susceptibility and the spectral studies showed that they are trimeric and dimeric, respectively.

Interaction of divalent metal ions with uracil III. Complexes of MnII, FeII, CoII, NiII and CuII with uracil acting as bidentate ligand

Abstract: Some novel nonelectrolytic complexes of uracil in its anionic form with divalent metal ions were synthesised by heating to reflux a methanolic solution of uracil and a metal salt at pHca. 7.5. The isolated complexes are formulated as [ML2(H2O)2] where M = Mn, Fe, Co, Ni, or Cu; L = C4H3N2O2 Electronic spectra indicate the hexacoordination of the metal ion in all the complexes and also the presence of a weak metal-oxygen interaction. The disappearance of the δ(NH) band and also the appreciable change both in intensity and position the characteristic bands of the 2-keto group of the uracil in the infrared spectra of all the complexes indicate the chelation of the uracil through C(2)=O and N(3).

Cobalt(II) Complexes of Creatinine

Abstract: Cobalt(II) complexes of creatinine [Co(creat)2X2] (X = Cl, Br, I or NCS) and [Co(creat)2X2(H2O)2] (X = HCO2, HOCH2CO2 or CNCH2CO2) have been prepared. Their i.r. spectra show an increase in ν(NH) of the cyclic secondary amine group, compared to free ligand (3300 cm−1), indicating that cyclic nitrogen is involved in coordination. The thiocyanate group coordinates through nitrogen and carboxylates coordinate as univalent unidentate ligands. The electronic spectra and magnetic moments suggest a d7 configuration for cobalt: a tetrahedral geometry (4.4 B.M.) for halide and thiocyanate complexes, and an octahedral geometry (5.0 B.M.) for the carboxylate complexes. On heating, the ligand moiety is lost and the respective cobalt halide or cobalt carboxylate is formed, which is converted finally into Co3O4. There is a correlation between the high intensity electronic transitions and the polarographic half-wave potentials.

Synthesis and X-ray crystal structure of tetraethylammonium bis[1,2-di(carbomethoxy)ethane-1,2-dithiolato]oxotechnetate(V)

Abstract: The (NEt4)+[TcO{SCH(CO2Me)CH(CO2Me)}2]− compound has been prepared from technetium(V) gluconate and characterized by single crystal x-ray structural analysis (R factor=0.065).

Reactions of TiX4 and VOCl3 with P=S ligands

Abstract: The reactions of TiX4 (X=Cl or Br) with the bidentate ligands, L, (Figure 1), yield hexacoordinate complexes TiX4·L, whereas similar reactions with VOCl3 lead to reduction of vanadium and give rise to vanadium(IV) pentacoordinate complexes, VOCl2·L. All the compounds have been characterized by elemental analyses, i.r., visible and e.p.r. spectra. The occupation of the sixth coordination position in pentacoordinate complexes, VOCl4·L, by different donor solvents, has been studied by means of visible and e.p.r. spectra.

Kinetic and spectroscopic intimations of intermediates in nucleophilic attack at diimine complexes of iron(II) and of molybdenum(O)

Abstract: Kinetics of nucleophilic substitution at a range of low-spin iron(II)diimine complexes have been examined in the presence of a variety of salts, to probe the role of hydroxide and cyanide as nucleophiles and of other ions in ion association equilibria. Equilibrium constants for interaction of hydroxide and of cyanide with many of these ligands, free or complexed with iron(II) or molybdenum(0), have been measured, in water and in binary aqueous solvent mixtures. Effects of solvent, temperature, and pressure on rate constants and on equilibrium constants have been monitored for selected systems. In the light of these results, and of ancillary qualitative observations, we discuss the role and nature of intermediates in nucleophilic substitution reactions of transition metaldiimine complexes.

A Chlorotitanocene Tetrachloroferrate Complex Stabilized by Acetonitrile Coordination

Abstract: Titanocene derivatives of the dichlorodicyclopentadienyltitanium type(1) are known to possess antineoplastic activity against Ehrlich ascites and other tumor systems in mice. Good solubility in water is generally a prerequisite for biomedical applications of this kind. A titanocene derivative possessing excellent cold water solubility (being converted into an aquated species in the process of dissolution) is the complex(2), acetonitrilechlorodicyclopentadienyltitanium tetrachloroferrate, readily obtained from(1) and iron(III) chloride in acetonitrile. Some spectroscopic properties of(2) are presented.

Metal complexes of sulphur-nitrogen chelating agents. Part 14. Nickel(II), palladium(II), copper(II), cobalt(II), and cobalt(III) complexes of the tetradentate schiff bases having ONNS donor sites

Abstract: Complexes of nickel(II), palladium(II), copper(II), cobalt(II), and cobalt(III) with methyl-2-(β-salicylaldiminoethyl)-cyclopent-1-en-dithiocarboxylate (H2L1) and methyl-2-(β-salicylaldiminoisopropyl)cyclopent-1-en-dithiocarboxylate (H2L2) have been prepared. They contain the donor sites ONNS. The metal(II) ions from neutral, monomeric square planar chelate complexes. The cobalt(III) complexes [CoL1-(H2O)2]X (X=Cl or ClO4) appear to betrans-diaqua-species. All compounds have been characterized by a number of physico-chemical methods.

Chloro(N-ethyl-1,3-imidazolidine-2-thione)gold(I): Spectroscopic studies and x-ray structure

Abstract: Chloro(N-ethyl-1,3-imidazolidine-2-thione)gold(II) crystallizes in the triclinic space group P¯I with cell dimensions:a=7.213(2)A,b=7.857(7)A,c=9.056(3)A, α=108.54°, β=100.06(3)°, γ=107.27(4)° and Z=2.,The structure was refined by a least squares method to a conventional R factor of 7.3%, using 2157 reflections. The metal atom is bonded through the sulfur atom of the ligand which is consistent with the13C n.m.r. spectra of the complexes in d6-acetone. The structure of the complex and coordination around metal are compared with other linear gold(I) complexes.

Order and disorder in mixed metal linear chains: The homo and heterobimetallic EDTA (M(H2O)4OIOII)[M′(EDTA)] · 6H2O complexes (M = Mg, Mn, Co, Zn and Ni; M′ = Co, Ni, Cu and Zn)

Abstract: Polymetallic solid solutions of the ethylenediaminetetracetic acid (EDTA) and six divalent metal ions exist in the range: MgαMnβCoγZnδNieCuτ(EDTA) · 6H2O where α + β + γ + δ + e + τ=2, 0⩽τ⩽1, 0⩽γ,e,δ⩽2, 0⩽α, β⩽1. This type of structure is characterized by the presence of two different octahedral carboxylate-bridged coordination sites forming infinite zig-zag chains. Visible and i.r. spectra and t.g.a. analysis show that there is occupational preference for the two coordination sites in the crystalline structure. Due to this preference, and also to the structural features, the heterobimetallic MM′(EDTA) · 6H2O compounds constitute a structurally new class of materials which can be described as ordered alternating-heterobimetallic polymeric coordination complexes.

Different chemoselectivities in cobalt(0)- and cobalt(I)-catalyzed cyclocotrimerization of C≡C and C≡N triple bonds

Abstract: A comparison between Co0 and CoI-catalyzed reactions of certain 1,6-diynes with monoalkynes or nitriles is reported. Different chemoselectivities are observed with two Co0 and CoI complexes. Co0 appears to be particularly sensitive to steric effects, nitriles being cotrimerized with C≡C bonds in good yields only when sterically demanding groups are present in the diyne. The CoCl2/Mn system exhibits a type of reactivity which is in accord with the formation of Co0.

Transfer chemical potentials for iron(II)-diimine complexes from water into aqueous methanol

Abstract: Solubilities of perchlorate and thiocyanate salts of several iron(II)-diimine complexes of Schiff base ligands in methanolwater mixtures are reported. From these results and published values for transfer chemical potentials of the perchlorate and thiocyanate anions, transfer chemical potentials for the complex cations are calculated. Trends with solvent composition suggest that preferential solvation varies from negligible to very strongly by methanol, depending on the size and hydrophilic-hydrophobic character of the complex.

Transfer Chemical Potentials for Cobalt(III) and Chromium(III) Complexes from Water into Aqueous Methanol; their Relevance to Reactivity Trends for Cobalt(III)-Chloride Aquation

Abstract: We report solubilities of a number of cobalt(III) and chromium(III) complex salts in methanol-water mixtures. From these, and published solubilities of salts of other complexes of these metals, we have calculated transfer chemical potentials from water into aqueous methanol for a variety of cationic and anionic complexes of cobalt(III) and chromium(III), using the assumption δmμ⊖(Ph4As+) + δmμ⊖(BPh 4 − ). The established trends are discussed in terms of electrostatic factors and of the hydrophilicity or hydrophobicity of the ligands present. The effects of single ion assumptions on conclusions of initial state-transition state analyses of solvent effects on reactivity are assessed with particular reference to aquation of thetrans-[Co(en)2Cl2]+ andtrans-[Co(py)4Cl2]+ cations.

Reactions of conjugated dienes with cobalt carbonyls under hydroformylation conditions. a high pressure i.r. spectroscopic study

Abstract: The chemistry of cobalt carbonyls in the presence of dienes and high pressure of synthesis gas was studied by online i.r. spectroscopy. Dicobalt octacarbonyl reacts with butadiene under 95 bar CO/H2 and 80°C to give [η3-C4H7Co(CO)3] (1) and [η4-C4H6)2Co2(CO)4] (2). Hydrogenation or hydroformylation are observed only with [HCo(CO)4] as the starting catalyst, and only at the beginning of the reaction. The results are explained by formation of an alkenyl complex, [σ-C4H7Co(CO)4], which either reacts with [HCo(CO)4] to give butene and [Co2(CO)8], or loses CO to give (1), depending on the [HCo(CO)4] concentration. The butene is hydroformylated. At temperatures >100°C (1) is transformed into a CO-free species, which catalyzes the oligomerisation of butadiene. Addition of tributylphosphine (L) leads to the formation of [η3-C4H7Co(CO)2L] (5) and [Co2(CO)6L2] (6). In (5) the π-allyl moiety is more labile than in (1) and a slow hydrogenation and hydroformylation of the butadiene is observed. In methanol solution the reaction of the cobalt carbonyls to give (1) is incomplete and the remaining H+ and [Co(CO)4]− catalyze the hydroformylation of butadiene. Isoprene is less reactive than butadiene but otherwise behaves similarly.

Complexes of aminobenzylamines. part II. Complexes ofo-aminobenzylamine with palladium(II) and platinum(II)

Abstract: The reactions of K2[MX4] (M = PdII or PtII and X = Cl or Br) witho-aminobenzylamine (o-aba) have been studied in neutral aqueous solutions. Two types of complexes were isolated from these studies: [MLX2] and [ML2]X2. Elemental analyses, conductivity measurements, i.r. and visible spectra suggest polymeric structures for [MLX2] with the ligand,o-aba = L, acting as a bridge, and/or mononuclear structures for [ML2]X2.

Structural and spectroscopic comparison of methylaminophenylcarbenepentacarbonyltungsten(0) with tungsten carbonyl carbene complexes lacking a heteroatom

Abstract: Crystallographic and Spectroscopic data for (CO)5− WC(NHCH3)C6H5 provide evidence that there is comparatively little metal-carbene π-bonding in this and other zero-valent tungsten carbonyl carbene complexes. The W-Ccar bond length of 2.19(2) A indicates that its bond order is significantly lower than 2.0. Resonances in the13C n.m.r. spectrum for CO w.r.t. tetramethylsilane at 195 and 215 ppm and an asymmetric CO stretching frequency of 2060 cm−1, in addition to structural similarities, imply analogous bonding in other zero-valent tungsten carbonyl carbene complexes, including those lacking a heteroatom bonded to the carbene carbon.

Synthesis and spectroscopic features of bis(tetramethylammonium) and bis(benzyltriethylammonium) salts possessing a μ-oxo-bis(trichloroferrate) anion structure

Abstract: The two μ-oxo-bis(trichloroferrate) salts (1) and (3) with diamagnetic ammonium cations are prepared as prototype compounds possessing an oxo-bridged dimer anion structure in which each iron(III) centre coordinates tetrahedrally to the three Cl ligands in addition to the bridging ligand. Antiferromagnetic coupling between the two iron centres in the anion complex is indicated by the low room-temperature effective magnetic moments (1.71–1.74 μB). The i.r. and electronic absorption spectra are in accord with the proposed anionic oxygen bridge structure.

Synthesis and characterization of complexes of PdII with 2-aminopyridine

Abstract: The synthesis and identification of the compoundstrans-bis(2-aminopyridine)dichloropalladium(II) and tetrakis(2-aminopyridine)palladium(II) chloride are described. The infrared spectra are discussed, particularly the metal-halogen and metal-ligand vibrations. Thermal decomposition was studied by differential thermal analysis (DTA) and thermogravimetry (TG).