Chiral biscyclopentadienylniobium(III) complexes

Summary Bimetallic chiral complexes [(⁵-C₅H₄CHMePh)(⁵-C₅H₅) Nb(CO)ML _n ] with ML _n =Co(CO)₄ and HFe(CO)₄ have been prepared and characterized. The lability of the metal-metal bond explains the lack of stereostability of these complexes. The two diastereoisomeric forms of polymetallic chiral complexes [(⁵- C₅H₅CHMePh)(⁵-C₅H₅)Nb(CO)[HFe₃(CO)₁₁] have been synthetized, separated and their stereostability has been investigated. All the complexes were characterized by elemental analysis i.r. and¹H n.m.r. spectroscopy.     

Metal ion catalysed aquation of carboxylatoamine cobalt(III) complexes. Kinetics of copper(II) catalysed aquation ofcis(diformato)bis(ethylenediamine)cobalt(III) ion

Summary The aquation ofcis-[(en)₂Co(CO₂H)₂]⁺ tocis-[(en)₂Co(OH₂)(CO₂H)]²⁺ is catalysed by Cu²⁺ and the rate equation, –d[complex]_t/dt=(k_Cu[Cu²⁺]+k_H [H⁺]) [complex)_T is valid at [Cu²⁺]_T=0.01–0.1, I=0.5 and [HClO₄]=0.005 mol dm^–3. The rate measurements are reported at 30, 35, 40 and 45°C and the rate and activation parameters for the Cu²⁺ and H⁺-catalysed paths are: k_H(35°C)=(2.44±0.09)×10^–2 dm³ mol^–1 s^–1, H=83±13 kJ mol^–1, S=–8±42 JK^–1 mol^–1, k _Cu (35°C)=(3.30±0.09)×10^–3 dm³ mol^–1 s^–1, H=73.2±6.1 kJ mol^–1, S=–55±20 JK^–1 mol^–1. The formate-bridged innersphere binuclear complex,cis-[(en)₂Co{(O₂CH)₂Cu}]³⁺ may be involved as the catalytically active intermediate in the copper(II)-catalysed path, just as the corresponding H⁺-bridged species presumed to be present in the acidcatalysed path.     

Fluxional nickel(II)- and palladium (II)-triazenido (C5H5)(L)(RN3R)M complexes; Evidence for a triplet-state intermediate

Summary The (⁵-C₅H₅)(L)(RN₃R)Ni and (⁵-C₅H₅)(PPh₃)(RN₃R)Pd compounds, with L = PPh₃, CO, CNR, and RN₃R = diaryltriazenido anion, were prepared. The bonding mode of the triazenido ligand is monodentate in the (⁵-C₅H₅)(PPh₃)(RN₃R)M phosphine compounds. The carbonyl and isonitrile groups are inserted into the nickel-nitrogen bond and a five-membered heteronuclear ring is formed in (⁵-C₅-C₅H₅)(L)(RN₃R)Ni, when L= CO and CNR.Most compounds are fluxional, involving site exchange of the triazenidoaryl-groupsvia intermediates with a chelating bonding mode of the triazenido ligand. The (⁵-C₅H₅)(PPh₃)(RN₃R)Ni compound shows anomalous solution paramagnetism, that is correlated with the fluxional mechanism. The temperature dependence of contact shifts in the n.m.r. spectrum was determined and E-values were calculated.     

Kinetics of the Electron-Transfer Reactions between (Ethylenediaminetetraacetato) Cobaltate (III) and (4-Aminopyridine)Pentacyanoferrate (II) Complexes

Kinetic measurements for the forward reaction Fe(CN)₅4-AmPy^3? + Co(edta)^? ? Fe(CN)₅s4-AmPy^2? + Co(edta)^2? have been carried out; the rate constant is 2.72 ± 0.07 M^?1s^?1, at pH = 8, μ = 0.10 M LiClO₄, and T = 25°C. The activation parameters of the reaction were also studied with and . The mechanism of the reaction is discussed in the context of the Marcus cross relation for an outer-sphere process.     

Crystal and molecular structure of trans-diiodobis-(1-methyl-5-nitroimidazole)platinum(II)

Summary A new platinum complex of 1-methyl-5-nitroimidazole has been obtained and characterized by elemental analysis, i.r. and n.m.r. spectroscopy. The structure of [PtI₂-(C₄ H₅N₃O₂)₂] has been determined by single-crystal X-ray diffraction. The crystals are triclinic: P1, a = 15.640(3), b = 12.617(2), c = 6.701(1) , = 102.77(5), = 101.15(5), = 100.71(5)°, V = 1228.6(3) ³, Z = 3, D_x = 2.851(6) Mg m^–3, (MoK ) = 0.71069 , = 12.85 mm^–, F(000) = 948, final R = 0.038 for 2859 reflections. The complex consists of monomeric PtI₂(1-methyl-5-nitroimidazole)₂ units. The coordination geometry is square-planar. The two 1-methyl-5-nitroimidazole ligands are trans coordinated to platinum.     

Reactions of Tin and Lead with Tricarbonylcyclopentadienylmolybdenum(II) and Tricarbonylcyclopentadienyltungsten(II) Chlorides

Tin was oxidized with tricarbonylcyclopentadienylmolybdenum and tricarbonylcyclopentadienyltungsten chlorides to obtain polynuclear organometallic compounds [⁵-C₅H₅M(CO)₃]₂SnCl₂ (M = Mo, W). The reactions of the above-mentioned oxidants with lead gave lead chloride and [⁵-C₅H₅M(CO)₃]₂ dimers. Formal-kinetic regularities of tin oxidation with tricarbonylcyclopentadienylmolybdenum chloride in N,N-dimethylformamide were found. Thermodynamic parameters of adsorption of the reagent on the metal surface were determined.     

Isolation of dithiocarbazate salts as oxinato-complexes of titanium(IV), zirconium(IV) and hafnium(IV)

Summary Ionic chelate complexes of the type, [(⁵-R)₂ML][dtz] [R=cyclopentadienyl (Cp) or indenyl (C₉H₇); M=Ti^IV, Zr^IV or Hf^IV; HL=oxine; dtz=phenyldithiocarbazate (PhNHNHCS₂)] have been synthesised and characterised. Conductance measurements indicate that the complexes are 11 electrolytes. From i.r. and u.v. spectral studies we conclude that the oxinato-group is chelating. Consequently there is tetrahedral coordination around the metal ion.¹H and¹³C N.m.r. studies are consistent with the stoichiometries. X-ray powder diffraction studies have been made for [(⁵-Cp)₂ZrL][dtz]. For [(⁵-Cp)₂TiL][dtz] and [(⁵-Cp)₂ZrL][dtz] thermal (t.g. and d.t.a.) and mass spectral studies have been carried out.     

Structural studies of 3-amino-4-(substituted arylazo)-5-(1H)pyrazolone compounds

Summary Transition metal complexes of cobalt(II), nickel(II), copper(II) and palladium(II) with 3-amino-4-(arylazo)-5-(1H)pyrazolones (Aryl=Ph, 4-C₆H₄CO₂H, 4-C₆H₄-OMe, 3-C₆H₄Cl, 3-C₆H₄CO₂H, 3-C₆H₄NO₂, 3-C₆H₄-Me, 3-C₆H₄OH and 2-C₆H₄CO₂H) are discussed. The stoichiometry of the complexes is: 11, 23 Co^II; 11 Ni^II; 11, 21 Cu^II and 12 Pd^II. The investigations suggest rhombic symmetry with 4- or 5-coordinate Co^II, square planar and tetrahedral configuration for Ni^II, tetrahedral Cu^II and square planar for Pd^II complexes. The complexes contain no anions.     

Reaction of Indium with Tricarbonylcyclopentadienyl-molybdenum(II) and -tungsten(II) Chlorides

The reactions of indium with tricarbonylcyclopentadienyl-molybdenum(II) and -tungsten(II) chlorides in donor solvents result in formation of compounds containing Mo-In and W-In bonds. The formalkinetic features of the metal oxidation with ⁵-C₅H₅Mo(CO)₃Cl in dimethylformamide were studied.     

Extraktiv-photometrische Eisenbestimmung als Tris-(Dibenzylsulfoxid) Eisen(III)-rhodanid

Zusammenfassung Die Extraktion des Eisens aus 0,5-n salzsaurer Lösung, die 3% Kaliumrhodanid enthält, in 8%ige Lösung von Dibenzylsulfoxid in Methylenchlorid ermöglicht bei 500 nm die extraktiv-photometrische Bestimmung von 5 bis 100g Fe³⁺ als [Fe(CNS)₃(OS{CH₂C₆H₅}₂)₃]. Es werden neben Bi³⁺, Cr³⁺, Mg²⁺, Zn²⁺ Spezifitäten Fe³⁺: Fremdion = 110⁴, neben Al³⁺, Ca²⁺, Cd²⁺, Co²⁺, Hg²⁺, Mn²⁺, Ni²⁺, VO²⁺, Zr⁴⁺ solche von 110⁵ und darüber erreicht. An verschiedenartigen Beispielen wird die Anwendbarkeit des Verfahrens ausgewiesen.

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Extractive-photometric iron determination as tris(dibenzylsulfoxide) iron(III)-thiocyanate

Summary The extraction of iron from 0.5N hydrochloric acid solution, that contains 3% potassium thiocyanate, into 8% solution of dibenzylsulfoxide in methylene chloride makes possible the extractive-photometric determination at 500 nm of 5–100g of Fe³⁺ as [Fe(CNS)₃(OS{CH₂C₆H₅}₂)₃]. Specifities for Fe³⁺: foreign ion = 110⁴ are attained in the presence of Bi³⁺, Mg²⁺, Zn²⁺, and specificities of 110⁵ and above have been reached in the presence of Al³⁺, Ca²⁺, Cd²⁺, Co²⁺, Hg²⁺, Mn²⁺, Ni²⁺, VO²⁺, Zr⁴⁺. The applicability of the procedure has been demonstrated on various specimens.

     

Über die oxidative Fluorierung von (CF3)(R) (R = CF3, Cl) und die Kristallstruktur von (CF3)(Cl)F+ AsF6−

Oxidative Fluorination of (CF₃)(R) (R = CF₃, Cl) and the Crystal Structure of (CF₃)(Cl) F⁺ AsF₆^? Oxidative fluorination of (CF₃)(R) (R = CF₃, Cl) with XeF⁺MF₆^? (M = As, Sb) in anhydrous HF results in formation of monofluorsulfonium hexafluorometalates. The salts are characterized by vibrational, NMR, and mass spectra. (CF₃)(Cl)F⁺ AsF₆^? crystallizes in the monoclinic space group P2₁/c with a = 9.955(10) Å, b = 11.050(5) Å, c = 12.733(15) Å, β = 97.77(5)°, and Z = 4.     

Polymerization Reactions in an Al(OBus)3-(COOH)2 System

Reactions in an Al(OBu^s)₃-(COOH)₂ (OA)-tetrahydrofuran (THF)/(CD₃)₂SO (DMSO-d₆) system (Al(OBu^s)₃: THF : DMSO-d₆: OA = 1 : 5 : 5 : x, x = 0.01 –3) were studied, without the addition of water and the process was monitored by NMR. When x 0.3, homogeneous solutions were obtained, whereas white precipitates formed with x 0.7. The formation of sec-butyl alcohol was evident with x 0.6, indicating that oxalate groups coordinate to aluminum to release sec-butyl alcohol. ¹³C NMR spectra of the solutions after 1 day suggest the presence of polymeric species if 0.03 x 0.6. The addition of a small amount of water resulted in the formation of a white precipitate (Al(OBu^s)₃: THF : DMSO-d₆ : OA : H₂O = 1 : 5 : 5 : 0.3 : y,y = 0.03–0.3), indicating that water, possibly formed by esterification in the Al(OBu^s)₃-OA-THF/DMSO-d₆ system, does not take a major role in the present system.     

Halogenation of π-cyclopentadienyltricarbonylrhenium and π-cyclopentadienyl(triphenylphosphine)dicarbonylrhenium

Conclusions The following previously unknown rhenium semicoordinaticn compounds were synthesized: [-C₅H₅Re(CO)₂PPh₃Cl]⁺Cl^–, [-C₅H₅Re(CO)₃Cl]⁺Cl^–, [-C₅-H₅Re(CO)₂PPh₃Cl]⁺Be₄, [-C₅H₅Re(CO)Cl₂]⁺ [Re(CO)₄Cl₂]^–, and -C₅H₅Re(CO)₂I₂, the latter of which was separated into the cis and trans isomers.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimlcheskaya, No. 2, pp. 408–413, February, 1981.The authors express their gratitude to V. F. Sizom, P. V. Petrovskii, and B. V. Lokshin for taking the mass, IR, and PMR spectra.     

Thermal Studies of Cobalt(II), Nickel(II) and Copper(II) Complexes of 4-(Sulfonylazido Phenylazo) Pyrazolones

The thermal decompositions of cobalt(II), nickel(II) and copper(II) complexes of4-(3'-sulfonylazido-6'-methoxyphenylazo)-1-phenyl-3-methyl-2-pyrazolin-5-one H(D¹–SO₂N₃) and 4-(4'-sulfonylazido phenylazo)-3-phenyl-3-methyl-2-pyrazolin-5-one H(D²–SO₂N₃) were studied by thermogravimetry. The decomposition in all cases takes place along two stages. The first stage is due to the elimination of water and nitrogen molecules with the formation of tetracoordinate complexes containing nitrene reactive species[M(DSO₂N:)₂]. The second stage represents the decomposition of the material to the metal oxide. The kinetics of the decomposition were examined by using Coats–Redfern, the decomposition in all complexes was found to be first order for the first and second stages. The activation energies and other activation parameters (H^* and S^* and G^*) were computed and related to the bonding and stereochemistry of the complexes.This revised version was published online in November 2005 with corrections to the Cover Date.     

Solvent and Temperature Dependence of 59Co NMR Chemical Shifts of Tris(acetylacetonato)cobaIt(III) and Tris(dipivaloylmethanato)cobalt(III)

Cobalt-59 NMR chemical shifts of Co(acac)₃, and Co(dpm)₃ (acac^– = acetylacetonate ion and dpm^– = dipivaloylmethanate ion) in 14 organic solvents, C₆H₁₄, C₆H₆, CH₂Cl₂, CHCl₃, CCl₄, CH₃CN, CH₃OH, C₂H₅OH, CH₃CH(OH)CH₃, (C₂H₅)₂O, (CH₃)₂CO, (CH₃)₂SO, (CH₃)₂NCHO and C₆H₅NO₂, were measured at five temperatures ranging from 289 to 329 K. The observed chemical shift (_obs) was linearly correlated to the maximum absorption wavelength in the visible spectra (_max) corresponding to the d-d electronic transition energy between the ground ¹A_1g and excited ¹T_1g states. The _obs-_max relation was explained by the ligand field theory. The temperature coefficients of _obs, of each complex showed a negative correlation with _obs. The _obs, of Co(acac)₃ decreased with the increasing electrophilic ability of the solvent (Mayer's acceptor number), whereas no tendency was observed in the case of Co(dpm)₃.     

Synthesis and magnetic properties of novel copper(II)-lanthanoid(III) heterobinuclear oxamido bridged complexes

Summary Seven novel -oxamido hetero-metal binuclear complexes have been prepared and characterized, namely [Cu(oxae)-Ln(NO₂-phen)₂ (ClO₄)](ClO₄)₂, where oxae denotes the N,N-bis(2-aminoethyl)oxamido dianion, NO₂-phen denotes 5-nitro-1,10-phenanthroline and Ln is Nd, Eu, Gd, Tb, Dy, Ho or Er. The magnetic susceptibility of [Cu(oxae)Gd(NO₂-phen)₂(ClO₄)](ClO₄)₂ was measured over a 4–300 K temperature range and the observed data were successfully simulated by an equation based on the spin Hamiltonian operator = -2J ₁·₂, giving the exchange integral for Gd^III J _(Cu-Gd) = -1.52cm^-1. This indicated a weak antiferromagnetic interaction between the Cu^II and Cd^III ions.Visiting scholar: Qufu Normal University.Visiting scholar: Tianjin Second Medical College.     

Synthetic and kinetic studies on copper(II), nickel(II) and cobalt(III) complexes of 1,4,7,10,13-pentaazacyclohexadecane ([16]aneN5)

Summary The pentadentate macrocycle 1,4,7,10,13-penta-azacyclo-hexadecane [16]aneN₅=(3)=L} has been prepared and a variety of copper(II), nickel(II) and cobalt(III) complexes of the ligand characterised. The copper complex [CuL](ClO₄)₂, on the basis of its d-d spectrum, appears to be square pyramidal, while [NiL(H₂O)](ClO₄)₂ is octahedral. The copper(II) and nickel(II) complexes dissociate readily in acidic solution and these reactions have been studied kinetically. For the copper(II) complex, rate=k_H[complex][H⁺]² with k_H =4.8 dm⁶ mol^–2s^–1 at 25 °C and I=1.0 mol dm^–3 (NaClO₄) with H=43 kJ mol^–1 and S ₂₉₈ =–89 JK^–1 mol^–1. Dissociation rates of the copper(II) complexes increase with ring size in the order: [15]aneN₅ < [16]aneN₅ < [17]aneN₅. For the dissociation of the nickel(II) complex, rate=k_H[Complex][H⁺] with k_H=9.4×10^–3 dm³mol^–1 s^–1 at 25 °C and I =1.0 mol dm^–3 (NaClO₄) with H=71 kJ mol^–1 and S ₂₉₈ =–47 JK^–1mol^–1.The cobalt(III) complexes, [CoLCl](ClO₄)₂, [CoL(H₂O)]-(ClO₄)₃, [CoL(NO₂)](ClO₄)₂, [CoL(DMF)](ClO₄)₃ (DMF=dimethylformamide) and [CoL(O₂CH)](ClO₄)₂ have been characterised. The chloropentamine [CoCl([16]aneN₅)]²⁺ undergoes rapid base hydrolysis with k_OH=1.1× 10⁵dm³ mol^–1s^–1 at 25°C and I=0.1 mol dm^–3 (H=73 kJ mol^–1 and S ₂₉₈ =98 JK^–1 mol^–1). Rapid base hydrolysis of [CoL(NO₂)]²⁺ is also observed and the origins of these effects are considered in detail.     

Palladium(II) iminophosphine complexes

New complexes of general formula [PdCl₂(NP)] (NP = o-Ph₂PC₆H₄-CH=N-R; R = Me, ⁱ Pr, ^t Bu, NH-Me) and [Pd(NP)₂](ClO₄)₂ (NP = o-Ph₂PC₆H₄-CH=N-R; R = Me, ⁱ Pr) have been prepared by directly reacting the precursor PdCl₂(PhCN)₂ with iminophosphines (NP) in 1:1 and 1:2 molar ratios respectively. When the chloro-complex [PdCl₂(o-Ph₂PC₆H₄-CH=N ⁱ -Pr)] was treated with CF₃SO₃Ag in MeCN, the labile complex [Pd(o-Ph₂PC₆H₄-CH=N ⁱ -Pr)(MeCN)₂](CF₃SO₃)₂ was obtained in good yield. The reactivity of the new precursor towards a variety of neutral N- and P-donor ligands (py, PMe₂Ph, PMePh₂, PEt₃, bipy, dppe, 2-thpy) has been studied. The new complexes were characterized by partial elemental analyses and by spectroscopy (i.r., ¹H- and ³¹P-n.m.r.). The molecular structure of the aquo-complex [Pd(NP)(2-thpy)(H₂O)](CF₃SO₃)₂ has been determined by a single-crystal diffraction study, showing that the iminophosphine acts as a chelating ligand with coordination around the palladium atom slightly distorted from square-planar geometry.     

Alkynyl Ti-M complexes based on M(CO)4 and MO2 building blocks (M = Mo, W)

The synthesis and properties of heterobimetallic Ti-M complexes of type {[[Ti](μ-η¹:η²-CCSiMe₃)][M(μ-η¹:η²-CCSiMe₃)(CO)₄]} (M = Mo: 5, [Ti] = (η⁵-C₅H₅)₂Ti; 6, [Ti] = (η⁵-C₅H₄SiMe₃)₂Ti; M = W: 7, [Ti] = (η⁵-C₅H₅)₂Ti; 8, [Ti] = (η⁵-C₅H₄SiMe₃)₂Ti) and {[Ti](μ-η¹:η²-CCSiMe₃)₂}MO₂ (M = Mo: 13, [Ti] = (η⁵-C₅H₅)₂Ti; 14, [Ti] = (η⁵-C₅H₄SiMe₃)₂Ti). M = W: 15, [Ti] = (η⁵-C₅H₅)₂Ti; 16, [Ti] = (η⁵-C₅H₄SiMe₃)₂Ti) are reported. Compounds 5-8 were accessible by treatment of [Ti](CCSiMe₃)₂ (1, [Ti] = (η⁵-C₅H₅)₂Ti; 2, [Ti] = (η⁵-C₅H₄SiMe₃)₂Ti) with [M(CO)₅(thf)] (3, M = Mo; 4, M = W) or [M(CO)₄(nbd)] (9, M = Mo; 10, M = W; nbd = bicyclo[2.2.1]hepta-2,5-diene), while 13-16 could be obtained either by the subsequent reaction of 1 and 2 with [M(CO)₃(MeCN)₃] (11, M = Mo; 12, M = W) and oxygen, or directly by oxidation of 5-8 with air. A mechanism for the formation of 5-8 is postulated based on the in-situ generation of [Ti](CCSiMe₃)((η²-CCSiMe₃)M(CO)₅), {[Ti](μ-η¹:η²-CCSiMe₃)₂}-M(CO)₄, and [Ti](μ-η¹:η²-CCSiMe₃)((μ-CCSiMe₃)M(CO)₄) as a result of the chelating effect exerted by the bis(alkynyl) titanocene fragment and the steric constraints imposed by the M(CO)₄ entity.The molecular structure of 5 in the solid state were determined by single crystal X-ray diffraction analysis. In doubly alkynyl-bridged 5 the alkynides are bridging the metals Ti and Mo as a σ-donor to one metal and as a π-donor to the other with the [Ti](CCSiMe₃)₂Mo core being planar.     

Solvatochromism of Heteroaromatic Compounds: XIII. Methyl(aroyloxymethyl)fluorosilanes and (Aroyloxymethyl)trifluorosilanes

The UV spectra of heptane solutions of methyl(aroyloxymethyl)fluorosilanes and (aroyloxymethyl)trifluorosilanes of the general formula 4-RC₆H₄COOCH₂Si(Me)_{3 - 4n} F _n (n = 1-3; R = H, F, Cl, Me, MeO, O2N) were studied. The intramolecular coordination bond Oarr;Si causes a bathochromic shift of the second -* transition, because the energy gap between the ground electronic and Franck-Condon excited states decreases owing to additional stabilization of the latter. The spectral shifts correspond to stabilization of the five-coordinate state of the silicon atom in (aroyloxymethyl)trifluorosilanes by 5-6 kcal mol^{- 1}.