Showing papers in "Transition Metal Chemistry in 1986"

Nickel(II) complexes of a thiosemicarbazone prepared from 2-Acetylpyridine

Abstract: The ligand 3-azabicyclo[3.2.2]nonane-3-thiocarboxylic acid 2-[1-(2-pyridinyl)ethylidene]hydrazide (HL), which is observed in an unusual tautomeric form in the solid state, and its selenium analogue (HLSe) have been used to prepare a series of nickel(II) complexes. Compounds of the general formula [NiLX] (X=Cl, Br, NCS, N3, NO2 or NCSe) as well as [Ni(LSe)Cl] have been found to be diamagnetic, planar complexes. A single crystal study of [NiL(NCS)] shows the deprotonated ligand bound in a tridentate mannervia its pyridyl nitrogen, imine nitrogen and the thione sulphur atom with the nitrogen atom of the thiocyanato-ligand occupying the fourth coordination position. The solids prepared from the nickel(II) salts having tetrafluoroborate, nitrate and iodide ions approximate to octahedral symmetry and have neutral HL ligands coordinated in a bidentate fashionvia the pyridine and imine nitrogens with the remaining coordination sites being occupied by the anions or water molecules. The [NiL2] solid is also octahedral with the two deprotonated ligands bonding as tridentate groupsvia the same atoms as in the [NiLX] complexes.

Transition metal ion complexes of thiosemicarbazones derived from 2-acetylpyridineN-oxide. I. The 4-methyl derivative

Abstract: TheN-methyl-2-[1-(2-pyridinyl-1-oxide)ethylidene]hydrazinecarbothioamide, HLO4M, has been used to prepare a series of CoIII, NiII and CuII complexes. Species with two deprotonated LO4M ligands, one LO4M and one HLO4M ligand, two HLO4M ligands and one HLO4M ligand with two small anionic ligands have been isolated. The deprotonated LO4M bonds as a tridentate ligandvia theN-oxide oxygen, the imine nitrogen (N1 and the sulphur while the HLO4M ligand coordinates primarily as a bidentate ligandvia only the first two atoms listed above. I.r., electronic, mass and e.s.r. spectra have been used to determine the nature of these complexes. One of the more striking differences between these compounds and those prepared with other thiosemicarbazones of 2-acetylpyridine and 2-acetylpyridineN-oxide is that tetrahedral yellow [Ni(HL)X2] rather than planar brown [NiLX] (X=Cl or Br) solids have been isolated with this ligand. Other differences in the nature of the coordination spheres of the various metal ions occur with this particular ligand when compared to previously studied thiosemicarbazone complexes.

The kinetics of oxidation of simple aliphatic sulphur compounds by potassium ferrate

Abstract: Potassium ferrate (K2FeO4) is highly soluble in water and a very strong oxidizing agent(1, 2). Other properties include a strong bacteriacidal action which has been documented by Murmann and Robinson(1). These characteristics, and others, suggest that potassium ferrate would be useful in the advanced treatment of municipal waste water. The efficiency of oxidation of various organic compounds by potassium ferrate must be investigated before conclusions can be drawn.

The Crystal Structure of Tetraphenylarsonium Tricyanooxopyridine-2- Carboxylatotungstate(IV) Dihydrate

Abstract: The structure of (AsPh4)2[WO(CN)3(Pic)] · 2H2O has been determined from three dimensional x-ray data. The cell dimensions are:a=17.699(8),b=13.546(6),c= 13.590(6) A, α=117.39(8), β = 71.54(7) and γ = 115.04(8)°, space group P¯1, Z = 2, The structure was solved from 5279 observed reflections. The anisotropic refinement converged to R = 0.060. The [WO(CN)3(Pic)]2−-ion is a distorted octahedron. The structure indicates that the aqua group in [WO(CN)4(H2O)]2− was displaced by an oxygen atom of the carboxylate of 2-picolinate, while a cyanide ligand was substituted by the pyridine nitrogen atom. Themer-arrangement of the three cyanide ligands has two normaltrans W-Cav = 2.17(2) A bond distances and a significant shorter W-C = 2.042(18) A bond trans to the W-N [2.188(18) A] bond. The W=O and W-O bond lengths are 1.676(9)A and 2.171 A, respectively.

Iron(III) complexes of 2-acetylpyridine-4-phenyl-3-thiosemicarbazones: Magnetic, E.s.r. and spectral studies

Abstract: Iron(III) complexes of 2-acetylpyridine-4-phenyl-3-thiosemicarbazone (LH) with the general formulae FeLX2 (X = Cl, Br, NO3 or SCN) and FeLSO4 have been prepared and characterised by elemental analysis and by magnetic measurements in the polycrystalline state in the 77–298 K range and by electronic, i.r. and e.s.r. spectra. The FeLX2 species (X = Cl, NCS or NO3) are square pyramidal of intermediate spin-state (S=3/2) with an4A2 ground state. The magnetic behaviour of FeLSO4 is commensurate with high order effects coupled with antiferromagnetic exchange interactions. FeLBr2 is a spin-free dimer involving bromine bridging between two FeLBr2 square pyramids. However, the low-spin species [FeL(DMF)3]2+ exists in dimethylformamide solution.

Effect of substituents on the structure of dioxouranium(VI) complexes of 7-carboxaldehyde-8-hydroxyquinoline and some of its Schiff bases

Abstract: A series of dioxouranium(VI) complexes with 7-carboxaldehyde-8hydroxyquinoline (oxine) and with some of its Schiff bases, LH, have been prepared and characterized by elemental analyses, electronic and vibrational spectral studies. All complexes except those of the oxine have the [UO2L2] · EtOH, stoichiometry (n=0, 1, 2 or 4). The uranyl complexes of the oxine have the formula [UO2L2(LH)]. The i.r. spectra reveal all ligands to be monobasic bidentate chelating agents coordinated to the uranium(VI)via the enolized phenolic OH and aldehydic oxygen or azomethine nitrogen atom. The force constant fU-o (mdyn A) and the bond length rU-o (A) of the U-O bond are also calculated and related to the electronic properties of thep-substituents.

Ligand influence on the redox properties of some copper(II) complexes with schiff bases derived from bromosalicylaldehydes and methyl or chloro-substituted anilines

Abstract: The synthesis, characterization and electrochemical behaviour of a new series of copper(II) complexes derivated from substituted anilines and bromosalicylaldehydes have been studied.

Cyclometallation, part II. I.r. and1H N.m.r. studies of palladium(II) compounds with substitutedN-(benzylidene)amines

Abstract: New cyclometallated complexes of palladium containing substitutedN-(benzylidene)amines have been prepared and characterized. Palladium(II) acetate is used to make the acetato-bridged dimers, which undergo metathetical reactions to give the halo-bridged dimers. These when treated with PPh3 or P(C6H11)3 in a 1∶2 molar ratio yield the phosphine monomers. I.r. and1H n.m.r. studies show that palladium is coordinated through nitrogen, and also reveal the disposition of the halogen and phosphine ligands in the monomeric complexes.

Nickel(II) and cobalt(II) complexes of the hydrazide of 1-naphthylacetic acid

Abstract: The hydrazide of 1-naphthylacetic acid forms both bis- and tris-(ligand) high-spin nickel(II) and cobalt(II) complexes possessing an octahedral configuration. The compositions of the complexes are influenced not only by the metal-ligand stoichiometry but also by the nature of the inorganic anion. A physico-chemical investigation showed that the ligand is neutral and bidentate, coordinated through amido-nitrogen and carbonyl oxygen. The compounds were characterized by elemental analysis, magnetic measurements, i.r. and diffuse-reflection spectra and molar conductivity.

Magnetic and spectral properties of the coligand isomer pair: Cu{N(CN)2}2(pyrazole)2 and Cu{pyrazole · N(CN)2}2

Abstract: New coligand isomers of composition Cu{N(CN)2}2(pz)2 and Cu{pz · N(CN)2}2 (pz = pyrazole) were prepared and studied by measuring their magnetic susceptibilities up to 4.2K and by aid of their e.s.r., ligand field and i.r. spectra. The susceptibility data have been analysed with various models for the exchange-coupled copper(II) polymers. It is shown that the resultant exchange coupling is ferromagnetic for Cu{N(CN)2}2(pz)2 (J ∼ 1.1 - 1.4 cm−1) but antiferromagnetic for Cu{pz · N(CN)2}2 (J ≈ −0.4 cm−1). A polymeric chain structure is proposed for Cu{N(CN)2}2(pz)2 havingpseudo-octahedrally coordinated copper(II) and CN-bridging dicyanamide ligands. Its coligand isomer contains anionic chelate ligands, formed by nucleophilic addition between N(CN)2 and pz in the copper(II) coordination sphere, and giving with this central atom a square-planar system. Definite, but slight axial interaction takes place between these structure units.

Hydrido-silyl complexes, Part VIII. Photochemical reaction of [Fe(CO)3H(PR′3)SiR3] with silanes, HSiR3: Influence of PR′3 and SiR3 on formation and structures of bis-silyl complexes [Fe(CO)3(PR′3)(SiR3)2]

Abstract: Upon u.v. irradiation of [Fe(CO)4(PR 3 ′ )] with HSiR3 (HSiR3 = HSiMePh2, PR′3 = PPh3; HSiR3 = HSiMe2Cl, PR′3 = PPh3 or PMe2Ph; HSiR3 = HSiMeCl2, PR′3 = PPh3, PMePh2, PMe2Ph or PMe3; HSiR3 = HSiCl3, PR′3 = PPh3, PMePh2, PMe2Ph, PMe3 or PBu 3 n ) the corresponding hydridosilyl complexes [Fe(CO)3H(PR′3)SiR3] are formed. The complexes have themer configuration with acis disposition of the hydride and the silyl ligands. Prolonged irradiation with an excess of silane results in the formation of bis-silyl complexes [Fe(CO)3(PR3)(SiR3)2], if electron density at the metal is not too high. Thus, [Fe(CO)3H(PPh3)SiMePh2] and [Fe(CO)3-H(PMe2Ph)SiMe2Cl] can be obtained but not the corresponding bis-silyl complexes. Most bis-silyl complexes are obtained asmer-isomers with acis-arrangement of the silyl ligands. Only for [Fe(CO)3(PR′3)(SiCl3)2] with small phosphine ligands (PR′3 = PMe3 or PMe2Ph) is thefac-isomer formed.

Synthesis, structure and bonding of 2-aminopyridinium heptamolybdate trihydrate

Abstract: 2-aminopyridinium heptamolybdate trihydrate crystallizes in the monoclinic system with space group P21/n and Z=4 (R=0.030). The unit cell dimensions area=14.8161(4) A,b=17.5073(4) A,c=20.8492(6) A, β=107.503(2)°, V=5157.7(2) A3. The [Mo7O24]6− anions in the 2-aminopyridinium, ammonium(4), guanidium(2), propyl- and isopropyl-ammonium(1) molybdates, while similar, show slightly differences in several bond lengths and angles. The distinguishing features of 2-aminopyridinium heptamolybdate trihydrate structure is its extensive hydrogen bonding. The planar cations and the water molecules are positioned so as to be able to form hydrogen bonds with either molybdate oxygen atoms or water oxygen atoms. Four different types of hydrogen bonds have been found-: N-H... O (mono- and bifurcated), N-H... Ow (monofurcated), Ow-Hw... O (mono- and bi-furcated) and Ow-Hw...OW (monofurcated). The closest approach distances associated with 27 of these potential hydrogen bonds vary from 2.67 to 3.24 A(7,8)). The proposed strong hydrogen bonding interactions appear to stabilize the structure and explain the way of three water molecules are lost upon heating. Some of these hydrogen bonds can play an important role in the possible photochromism of this compound.

The kinetics of oxidation of low molecular weight aldehydes by potassium ferrate

Abstract: Oxidation of simple aldehydes is shown to follow a mixed order rate equation(1), which contains three terms: the first, first order in the concentration of potassium ferrate (K2FeO4); the second, second order in K2FeO4; and the third contains the conditional rate constants which are substrate (aldehyde) concentration dependent. The third term is first order dependent on (K2FeO4). Aldehydes studied included chloral, acetaldehyde, and trimethylacetaldehyde.

Compounds of tungsten(VI) with citric acid: A spectrophotometric, polarimetric and hydrogen-1, carbon-13 N.M.R. study of the formation and interconversion equilibria in aqueous solution

Abstract: Tungsten(VI)-citrate complexes, which occur in aqueous solution, were studied by polarimetric and absorbance measurements. The pH of the medium is the principal variable controlling complex formation and interconversion equilibria. At high pH (>6), the stable complexes are monomers with 1∶2 and 1∶1 stoichiometry, depending on the tungsten(VI)-citrate ratio, while at lower pH two different dinuclear complexes are formed. The intervals of existence of these species with the pH, the number of equivalents of acid necessary for their formation, as well as the conditional stability constant, have also been calculated. The structure of these compounds have been investigated by1H and13C-n.m.r. spectroscopy. The n.m.r. results indicate the existence in all these species of strong, covalent metal-toligand oxygen bondingvia the carboxylic oxygen atom and the adjacent hydroxylic oxygen.

The crystal and molecular structure of a dinuclear copper(II) complex of a Robson-type macrocycle, [Cu2(C26H30N4O2)(H2O)2](BF4)2

Abstract: The crystal structure of the dinuclear complex [Cu2(C26H30-N4O2)(H2O)2](BF4)2 was determined by x-ray crystallography. The crystals are triclinic, P¯1, witha = 10.945(5),b = 8.703(5),c = 8.495(5) A, α = 103.86(3)°, β = 105.73(3)°, γ = 85.77(3)°, V = 756 A3 Dc = 1.65 g cm−3 for Z = 1. The copper(II) atoms are 5-coordinate and square-pyramidal. Selected bond distances are: Cu-N, 1.91 A (mean); Cu-O(base) = 1.90(1) and 1.91(1) A; Cu-O(apical) = 2.47(1) A; There are O(water)-H ... F interionic hydrogen bonds in the structure. The Cu .. Cu distance is 2.847 A.

Carbon-13 N.m.r. and I.r. Studies of copper(I) complexes of the — NHCS group in five- and six-membered heterocyclic rings

Abstract: Crystalline copper(I) complexes of the general formula [LCuCl] and [L2CuCl] were prepared for imidazolidine-2-thiones and 1,3-diazinane-2-thiones by the reduction of copper(II) halides with an excess of the ligands. The13C n.m.r. and i.r. spectra of these complexes are consistent with thione sulphur (ligand) donation in all cases. The magnitude of the high-field shift in the13C resonance of the thioureide carbon in the complexes as compared with that of the free ligands is interpreted in terms of coordination geometry around the metal atoms. A comparison of the chemical shifts for gold(I), silver(I) and copper(I) revealed a displacement ofca. 6–8 ppm for the mono- and 2–4 ppm for the bis-complexes, respectively.

Synthesis and characterization of new dioxomolybdenum(VI) complexes of ONS donor Schiff bases derived from thiosemicarbazide,S-methyldithiocarbazate,S-benzyldithiocarbazate ando-hydroxy-aromatic aldehydes/ketones

Abstract: Syntheses of several new dioxomolybdenum(VI) complexes with composition MoO2L · MeOH (where LH2 = Schiff base derived from salicylaldehyde, 2-hydroxy-1-naphthaldehyde,o-hydroxyacetophenone,o-hydroxybenzophenone, pyridoxal and thiosemicarbazide,S-methyldithiocarbazate orS-benzyldithiocarbazate) are reported. The complexes have been characterized by elemental analysis, i.r., n.m.r. and electronic spectra, conductance, molecular weight and magnetic susceptibility measurements. The complexes are monomers, nonelectrolytes, diamagnetic and six-coordinated. The Schiff bases behave as dibasic tridentate ligands and coordinate through phenolic oxygen, thioenolic sulphur and azomethine nitrogen atoms. The complexes have acis-O=Mo=O structure as evidenced by the presence of two strong bands at 880–915 and 925–955 cm−1. All of the complexes exhibit a band atca. 25000 cm−1 due to the ligand to metal charge transfer transition.

Ruthenium complexes with diazadienes, Part V(1).Cis-Dicarbonyl-1,4-diaza-1,3-diene-trans-diiodoruthenium Complexes; synthesis, properties and the crystal structure of [(DAD)Ru(CO)2I2] · DAD (DAD=p-tolyl-N=CMe-CMe=N-p-tolyl)

Abstract: Diazadienes (DAD) (RN=CR′CR′=NR with R′=H or Me and R=n-,i- ort-alkyl, aryl oro,o′-substituted aryl) easily form the thermally inert title compounds [(DAD)-Ru(CO)2I2] (2). Their stereochemistry is unambiguously derived from1H-n.m.r. and i.r. data. One of the complexes (2h) cocrystallizes with the free diazadiene (1h) in a 1∶1 molar ratio. An x-ray diffraction study, which allows a comparison of the free and bound diazadiene. was performed with the monoclinic crystal and gave the following cell parameters: space group C 2/c, a=2237.0(5), b=1017.4(3) and c=1824.9(4) pm, β=105.13(2)°, Z=4. From 2781 observed reflections 293 parameters were refined, leading to a final R-value of 0.0346 (Rw=0.0340). The tilting of thep-tolyl group is a consequence of an intra-ligand repulsion R/R′, the R-conformation being almost equal in the (E,E,E)-shaped molecule (1h) (68°) and the (E,Z,E)-chelate in (2h) (72°). Complexes (2) are photolabile (with loss of CO), and on reduction they lose iodide, thus offering selective ways for the exchange of π-acceptor or σ-donor ligands for precatalyst formation.

The crystal structure of a Di(tetramethylammonium)-bis[R,R-tartrato(2-)]-cis-dioxomolybdate(VI), (NMe4)2[MoO2(C4H4O6)2] · EtOH · 1.5 H2O, with comments on tartrate coordination

Abstract: In the salt (NMe4[MoO2(H2tart)2] · EtOH · 1.5 H2O (H4tart = R,R-(+)-tartaric acid) the tartrato-ligands are linked to molybdenum through a carboxyl oxygen and the vicinal deprotonated hydroxyl oxygen atom, with carboxyl oxygentrans to terminal oxygen of the MoO2 cis-dioxo core. The configuration about Mo is A. The C-C-C-C torsion angles of the ligands are almost 180°. This enables inter-ligand H-bonding from the uncoordinated hydroxyl groups. The five skeletal atoms from the uncoordinated section of a ligand are nearly co-planar. The probable strong preference fortrans coordination of carboxyl must limit the range of dissolved molybdenum(VI)-tartrate species.

Studies ono-hydroxyacetophenone-2-furoylhydrazone complexes of some 3d-bivalent metal ions

Abstract: Complexes ofo-hydroxyacetophenone-2-furoylhydrazone, H2L, of the types M(H2L)C12 · nH2O [Mn = CoII, n=0; NiII, n=2]; Cu(HL)Cl, M(HL)2 [M = VIVO, CoII, NiII or CuII] and M(L)(H2O)n [M = CoII or NiII, n=2; M = CuII, n=0] have been prepared and characterized by elemental analyses, molar conductance, magnetic susceptibility, visible, e.s.r. and i.r. spectral studies. The different modes of ligand chelation and the stereochemistry around the metal ions are discussed.

Kinetics of the substitution of the β-diketonate ligand in β-diketonatocyclo-octadienerhodium(I) complexes by phenanthroline

Abstract: The reaction between [Rh(β-diketonate)(COD)] and phenanthroline in a methanol medium to give [Rh(phen)(COD)]+ was studied for various β-diketones at different temperatures. The rate law is R = k[Phen][Rh(β-diketonate)(COD)]. The order of the effect of the β-diketonate on the reactivity of the complexes is acac < BA < DBM ≪ TFAA < TFBA ≪ HFAA indicating that electronegative substituents of the β-diketone increase the reactivity of the complexes towards substitution reactions. The values of the second-order rate constants at 25°C are 2.90×101, 5.12×101, 6.14×101, 1.33×103, 2.42×l03 and 2.76×105 dm3 mol−1 s−1 for the acac, BA, DBM, TFAA, TFBA and HFAA complexes, respectively. A good linear free energy relationship was obtained. The slope of the plot of log kvs pKa of the β-diketones is −0.8.

Preparation and x-ray crystal structure of a seven-coordinate cobalt(II) complex with 2,6-diacetylpyridine bis(2-picolinoylhydrazone)

Abstract: A new seven-coordinate cobalt(II) complex has been synthesized with 2,6-diacetylpyridine bis(2-picolinoylhydrazone) (H2dappc) and its crystal and molecular structure has been determined by x-ray diffraction methods from counter data and refined toR 0.0449 for 2128 observed reflections. The complex crystallizes in a triclinic cell, space group P¯1, with dimensions:a=13.759(8),b=7.685(3),c=13.816(7) A, α=86.50(5), β=66.48(5), γ=85.28(5)° andZ=2. The complete structure consists of [Co(H2dappc)(OH2)2] cations, chloride anions and solvating H2O molecules, interlinked by hydrogen bonds. The geometry around the cobalt is that of a distorted pentagonal bipyramid with the H2dappc ligand forming the equatorial plane and two H2O molecules occupying the axial positions.

Chemistry of dithiocarbamate derivatives of amino acids. Part II. Complexes of nickel(II) with derivatives of branched and cyclic amino acids

Abstract: Barium salts of the dithiocarbamate derivates of the amino acids: DL-valine, L-valine, DL-leucine, DL-isoleucine and L-proline have been synthesized. The anions have been used to obtain the corresponding nickel(II) complexes in acid form. The complexes are diamagnetic, and coordination takes place in a near-square planar geometry around the nickel(II) ion through the sulphur atoms of the dithiocarbamate moiety, the structure being confirmed by i.r.,1H n.m.r., u.v.-vis spectros copies and by chemical analysis.

Synthesis, characterisation and solid state thermal behaviour of nickel(II) diamine complexes

Abstract: [NiL2X2] (L =N,N′-dimethyl-1,2-ethanediamine; X = Cl−, CF3CO2−, CC13CO2− and CBr3CO2−), [NiL2C2O4] · H2O and [NiL2X2] · 2 H2O (X = Br−, 0.5 SO42− and 0.5 SeO4−) have been synthesised and their thermal studies carried out. Thermally induced phase transition phenomena are noticed in [NiL2X2] (X = CF3CO2− and CCl3CO2−) and their probable mechanisms are described. [NiL2X2] (X = Br−, 0.5 SO42− and 0.5 SeO42−) and [NiLX2] (X = Cl−, 0.5 C2O42− and 0.5 SO42−) have been prepared by solid state pyrolysis from the respective parent diamine complexes. [NiL2X2] have been made in solid state by temperature arrest technique from [NiL2(CX3CO2)2] (X = Cl− and Br−).

Cobalt(II), nickel(II), copper(II), zinc(II) and uranyl(VI) complexes of acetylacetone bis(4-phenylthiosemicarbazone)

Abstract: Reaction of one mole of acetylacetone with two moles of 4-phenylthiosemicarbazide yields the unusual Schiff base, MeC(=N-NHCSNHPh)CH2C(=NNHCSNHPh)Me. APT = H2L) acetylacetone bis(4-phenylthiosemicarbazone). The complexes of CoII, NiII, CuII, ZnII and UVIO2 have been prepared and characterized by analytical, i.r., electronic spectral and magnetic measurements. The CoII, NiII and CuII complexes have been assigned square-planar stereochemistry on the basis of magnetic and spectroscopic studies. The ligand is a neutral or dibasic quadridentate SNNS donor as revealed by i.r. spectral studies.

Mono- and bi-metallic complexes based on redox-active tris(3,5-dimethylpyrazolyl)borato-molybdenum nitrosyls, part III. (1) Complexes containing meta-substituted benzene- and naphthalenediols or -diamines

Abstract: The complexes [MoL*(NO)Cl(YC6H4YH-m)] (Y = O or NH), [MoL*(NO)Cl(YC10H6YH-1,5)], (Y = O or NH), [MoL*(NO)Cl(OC10H6OH-2,7)], [{MoL*(NO)Cl}2(XC6H4Y-m)] (X=Y=O, NH or S; X=O, Y=NH), [{MoL*(NO)-C1}2(YC10H6Y-1,5)] (Y=O or NH) and [{MoL*(NO)Cl2-(OC10H6-2,7)] have been prepared and studied by cyclic voltammetry. The monometallic species undergo a reversible oneelectron reduction, whereas the bimetallics undergo two oneelectron reductions. A comparison of ΔE1/2 (E1/2(1)-E1/2(2)) values for those new species with those obtained frompara- substituted analogues and bimetallics containing extended bridges YC6H4ZC6H4Y (e.g. Z = S or CH2CH2) established that the interaction between the redox centres in these new species is intermediate (YC6H4Y-m; NHC10H6NH-1,5) or weak (OC10H6O).

Synthesis, structural and spectral investigations of new types of dioxovanadium (V) complexes with S-methylthiosemicarbazones derived from salicyl and 2,4-dihydroxybenzaldehydes. X-ray structure of ammonium (salicylaldehyde S-methylthiosemicarbazonato)-dioxovanadate (V) monohydrate

Abstract: The x-ray crystal structure of [VO2(HL1)] (where L1 denotes the dianion of theS-methylthiosemicarbazone of salicylaldehyde) has been determined and refined to R=0.058 (Rw=0.063) for 3377 observed reflections. There are two symmetrically independent molecules in the asymmetric unit, showing no significant differences in their geometries. The vanadium atom is pentacoordinated in a distorted square-pyramidal arrangement. Absorption spectra of [VO2(HL1)] and [VO2(HL2)], in the 10000–45000 cm−1 range, were calculated from the measured reflectance spectra, applying Kubelka-Munk's theory. The extinction coefficients were determined from the absorption spectra of the solutions of these complexes in methanol. The observed maxima are interpreted on the basis of intraligand transition and charge-transfer spectra on the basis of the presence of approximate groupC 2v for both complexes.

Kinetics of anation of hexaaquachromium(III) ion by aspartic acid: mechanism and activation parameters

Abstract: The kinetics of the reaction of hexaaquachromium(III) ion with aspartic acid in aqueous-acidic medium have been investigated spectrophotometrically at [H+]=1×10−4 – 10× 10−4mol dm−3, t=35–45 °C and μ=1.0 mol dm−3 (KNO3). The results are in accord with a mechanism involving a fast 1∶1 outer-sphere association between hexaaquachromium(III) ion and the substrate species, followed by their transformation into the product by the process where the incoming ligand is appreciably bounded to the metal ion in the transition state. The rate law consistant with the mechanism is as follows: $$\begin{gathered} k_{obs} = \frac{{\left( {k_1 K_{IP} K_2 + k_2 K'_{IP} \left[ {H^ + } \right]} \right)\left[ A \right]_T }}{{\left( {{{\left[ {H^ + } \right]^2 } \mathord{\left/ {\vphantom {{\left[ {H^ + } \right]^2 } {K_1 }}} \right. \kern- ulldelimiterspace} {K_1 }}} \right) + \left[ {H^ + } \right] + K_2 + \left( {K_{IP} K_2 + K'_{IP} \left[ {H^ + } \right]} \right)\left[ A \right]_T }} \hfill \\ A = Aspartic acid \hfill \\ \end{gathered} $$ The rate parameters were evaluated and associated activation parameters calculated using the Eyring equation. Enthalpy and entropy terms for the rate constants:viz. ΔH≠(k1)=+81±1 kJ mol−1, ΔH≠(k2)=+50±1 and ΔS≠(k1)=−54±3 JK−1 mol−1, ΔS≠(k2)=−157±2 JK−1 mol−1 are indicative of an (Ia) mechanism. Comparison of the results with published data on this metal ion also provide evidence of an associative interchange mechanism.

Reactions ofN-ethoxycarbonyltoluene-4-thiocarboxamide (ETTH),N-ethoxycarbonylpyrrole-2-thiocarboxamide (ETH), 2-thiopyrrole-1,2-dicarboximide (TPH) andN-carbamoylpyrrole-2-thiocarboxamide (CPTH) with [CuI(MPh3)3X] [M = P or As; X = Cl, Br or I] and AgI, CdII, HgII or PbII ions

Abstract: Reactions of [Cu(MPh3)3X] with the title ligands yield [Cu(MPh3)2(LH)X] (LH = ETTH, ETH, TPH and CPTH). Twenty-four complexes have been characterized on the basis of analytical, i.r., electronic and n.m.r. spectral and magnetic measurements studies. These complexes are unique examples of tetrahedral coordination with the aromatic ligand bonded to copper(I) through sulphur. Reaction with AgI, CdII, HgII or PbII results in abstraction of sulphur from ETTH to give the corresponding sulphides and an oxygenated form of the ligand.

Mono and dinuclear copper (II) complexes of 2,4,6-tris (2-pyridyl)-1,3,5-triazine and halide or pseudohalide ions: synthesis and spectral studies

Abstract: By inhibiting the copper(II) assisted TPT (TPT = 2,4,6-tris(2-pyridyl)-1,3,5-triazine) hydrolysis, monomeric and dimeric copper(II) complexes having as general formulae Cu(TPT)X, · nH2O (X = Cl, Br, NCS, NCO or N3) and [Cu(TPT)X]2(PF6)2 · nH2O (X = Cl, Br, NCS or N3) have been synthesized and characterized by i.r., electronic and e.p.r. spectra, x-ray powder diffraction and analytical data. Spectroscopic results indicate five-coordinate geometry around the copper(II) ion, intermediate between trigonal-bipyramid and square-pyramid structures. The half-field absorption in the ΔMS = 2 region of powdered X-band e.p.r. spectra has been observed for the dimeric species.