Synthesis and characterization of diethylphosphino Ga(III) and In(III) complexes with covalent metal-phosphorus bonds

The covalent derivatives [Et₂M-PEt₂]₃ (M = Ga, In) have been prepared from Lewis acid-base complexes, R₃M.PHEt₂, by alkane elimination and characterized by elemental analyses, IR, ¹H and ³¹P NMR spectroscopy. Features of the mass spectra reveal a trimeric form and the strength of the [M-P]_n ring. For the compound [ClMeGa-PEt₂]_n, spectral data are consistent with a weakening of the [Ga-P]_n chain, in good agreement with the pyrolysis results.     

Synthesis,physicochemical properties and voltammetric characterization of some new Fe(III) complexes with semicarbazone-based ligands

Several bis(ligand) octahedral complexes of iron(III) with salicylaldehyde semi-, thiosemi-, and S-methylthiosemi- carbazones have been synthesized and characterized by elemental analysis, conductivity and magnetic measurements, electronic and IR spectra, as well as by linear sweep and cyclic voltammetry. General procedures for the syntheses of all types of complexes have been established, giving better defined reaction conditions. Physicochemical properties of the novel complexes have been related to those of the already known compounds of the same type.     

Allyl complexes of dicyclopentadienyl-niobium(III) and -tantalum(III)

The synthesis and the properties of the complexes Cp₂TaCl₂, Cp₂M(allyl), Cp₂M(1-methylallyl) and Cp₂M(2-methylallyl) with M  Nb, Ta are described. The complex Cp₂TaCl₂ has one unpaired electron per tantalum atom, while the allyl complexes are diamagnetic. The IR and PMR spectra indicate that the allyl group is π-bonded to the metal. The mass spectra of the complexes are discussed; the thermal stability of the Cp₂Nb- and Cp₂Ta-(allyl) complexes was investigated by differential thermal analysis. The properties of the niobium and tantalum complexes are compared with those of the corresponding titanium complexes.     

Synthesis and characterization of triorganoantimony(V) complexes with bidentate ligands

Monochelated organoantimony(V) complexes of the type R₃Sb(OMe)L, where R = Me or Ph, and L is the anion of acetylacetone, 8-hydroxyquinoline, salicylaldehyde, o-hydroxyacetophenone or 2-hydroxy-1-naphthaldehyde have been obtained from triorganoantimony(V) dibromide and the sodium derivative of the ligands in a benzene-methanol mixture. Molecular weight determination in benzene reveals the monomeric nature of these complexes. IR and NMR data suggest that L acts as a bidentate ligand giving an octahedral environment for the antimony atom.     

Synthesis and characterization of two Ni(II) complexes with furfural s-methylthiosemicarbazone

Synthesis of two Ni(II) complexes with furfural S-methylthiosemicarbazone (HL) of the formula [Ni(HL)₂(H₂O)₂](ClO₄)₂ (A) and [Ni(HL)₂(ClO₄)₂] (B) are reported. Compound A was obtained from an ethanolic solution of Ni(ClO₄)₂·6H₂O and HL, whilst compound B was produced by heating compound A to 378 K. An X-ray analysis of the complex A showed that it has a trans(H₂O)-trans(HL) octahedral configuration in which HL behaves as a bidentate (NN) ligand. On the basis of the IR and electronic spectra as well as the magnetism, it was found that the compound B has also an octahedral configuration in which, HL and ClO₄ groups, are coordinated.     

Cationic dihydridoiridium(III) complexes of nitriles

The reaction of [IrL(CO)(PPh₃)₂]ClO₄ (PPh₃ = triphenylphosphine) with H₂ produces new cationic dihydridoiridium(III) complexes of nitriles (L), [Ir(H)₂L(CO)(PPh₃)₂]ClO₄ [L = CH₃CN (1), CH₃CH₂CN (2), CH₃CH₂CH₂CN (3) and C₆H₅CN (4)], where nitriles are coordinated through the nitrogen atom. Proton NMR spectral data for complexes 1–4 suggest that the two hydrides in each complex are cis to each other and trans to CO and nitrogen (nitrile), and the two PPh₃ are trans to each other.     

A binuclear tantalum(III) complex with a bridging carboxylato ligand

Ta₂Cl₆(SMe₂)₃ reacts with one equivalent of C₄H₉CO₂Li to give a complex with a bridging carboxylate ligand, Ta₂Cl₅(O₂CC₄H₉)(SMe₂)(THF)₂. The product was isolated in two crystalline forms, 1 and 2, from a THF/hexane and benzene/hexane solvent mixture, respectively. The following are the unit cell parameters, for 1: monoclinic (P2₁/n), a = 10.537(5) Å, b = 22.015(4) Å, c = 11.663(4) Å, β = 107.80(3)°, V = 2576(3) ų, and Z = 4; for 2: monoclinic (P2₁/c), a = 15.584(4) Å, b = 15.647(4) Å, c = 11.275(3) Å, β = 106.04(5)°, V = 2642(3) ų and Z = 4. The complex is a dimer with a distorted octahedra-sharing-an-edge geometry. The TaTa distances in 1 and 2 were 2.766(1) Å and 2.779(1) Å, respectively, which is somewhat longer than in previously reported Nb(III) and Ta(III) dinuclear compounds. Diamagnetism of the complex is shown by NMR. Fenske—Hall calculations, which correctly predict an electronic transition at about 16,000 cm^?1, indicate a double TaTa bond. The observed elongation of the metalmetal bond is attributed mainly to steric crowding. The complex is the first proven low-valent Ta species with a coordinated carboxylate ion.     

Copper(II) and nickel(II) complexes of a neutral pentadentate Schiff base

A new pentadentate Schiff base 2,6,10-triaza-1,11-bis(2′-aminophenyl)-undeca-1,10-diene, abaDPT, and its complexes of general formula M(abaDPT)X₂ where M = Cu(II), Ni(II), X = Cl, Br, I, NO₃ and ClO₄, have been prepared. The complexes have been characterized by electronic and IR spectra, EPR, magnetic moments, molar conductances, and elemental analysis. IR data show an interaction between halide anion of the outer coordination sphere and the complexed amino group. EPR and spectrophotometric data of most of the copper compounds are consistent with a distorted square pyramidal geometry. Single crystal EPR studies of Cu(abaDPT)(NO₃)₂ and Cu(abaDPT)Br₂ revealed that copper atoms in the former compound occupy two magnetically inequivalent places in the lattice while copper atoms in the latter compound take identical sites. Principal g tensor axes of the two compounds have been determined.     

Comparative study of hydroxo-fluoro and hydroxo-sulphido mixed ligand complexes of aluminum(III) and gallium(III)

The mixed ligand complex formation had been studied in the aluminate-fluoride, gallate-fluoride, aluminate-sulphide and gallate-sulphide systems by spectrophotometric as well as potentiometric methods using glass and sulphide selective electrodes. The formation of the species Al(OH)₃F^? and Ga(OH)₂S^? has been demonstrated and the equilibrium constants have been determined. Similar interaction could not be detected in the aluminate-sulphide and gallate-fluoride systems.The differences in behaviour of the metal ions to the characteristically hard fluoride and soft sulphide ligands can be interpreted in that the Ga³⁺ ion may form complexes with charged soft ligands too, its behaviour then differing from that of the typically hard Al³⁺ ion.     

Thiosemicarbazide complexes of antimony(III) halides

Some hitherto unknown complexes of thiosermicarbazide (Htsc) and antimony(III) halides have been synthesized in 1,4-dioxane. The elemental analyses have indicated that these compounds are of the type Sb(CH₅N₃S)Cl₃ and Sb(CH₅N₃S)X₃.C₄H₈O₂, where X = Br or I. The electronic and vibration spectral analyses have shown that Htsc acts as a bidentate ligand in these complexes, linking through sulphur and “the hydrazine terminal nitrogen” to Sb(III).     

Linkage isomerism of the oximato group: The characterization of some mono- and binuclear square planar nickel(II) complexes of vicinal oxime-imine ligands

The reactions of the Schiff-base N,N-ethylenebis-(isonitrosoacetylacetoneimine), (H₂L), with Ni(II) acetate led to the formation of the yellow-orange complex LNi (I) in water and the red complex LNi (II) in ethanol. Both oximato groups in I are coordinated to the metal through the oximino-oxygen whereas in II one group is similarly coordinated while the other is coordinated through the oximino-nitrogen. Complex I was converted to complex II by boiling in chloroform and the conversion was reversed by reacting complex II with either piperidine or ethylenediamine. H₂L neutralized by ammonia reacted with Ni(II) chloride (1:1) and the complex formed was characterized as the red square planar bis-(4-iminopentane-2,3-dione 3-oximato)Ni(II);(III). This trans complex reacted with piperidine (1:4) to produce its cis configuration (IV). Complex III reacted with ethylenediamine (2:1) and 1,3-diaminopropane (1:1) to produce complexes II and V respectively of the identical structure. Attempted similar reaction (1:1) with either 1,4-diaminobutane or 1,5-diaminopentane led to the formation of the binuclear complexes VI and VII in which two molecules of complex III are linked together by -(CH₂)₄- and -(CH₂)₅-Moieties respectively. The suggested structures of the square planar Ni(II) complexes are based on analytical, spectral and magnetic moment evidence.     

Metal template synthesis of chromium(III) complexes

Chromium(III) complexes of Schiff bases resulting from the condensation of one mole of diacetyl with two moles of ethylene-diamine or 1,3 diaminopropane has been isolated by metal template reaction. The isolated complexes have been assigned cis configurations.     

(1,4,7,10-Tetraazacyclododecane) (diamine or alanine)-Cobalt(III) complexes

(1,4,7,10-Tetraazacyclododecane) [diamine or (S)-alanine]-cobalt(III) complexes [diamine = ethylenediamine, 2-(aminomethyl)pyridine, (R)-1,2-propanediamine, (R,R)-1,2-diaminocyclohexane, trimethylenediamine and 2-methyl-1,3-diaminopropane] are prepared and characterized spectroscopically. The ligand field transitions occur at lower energies than those of the corresponding tetraamine analogues. Severe distortions caused by the too small size of the cyclic ligand are one of the origins. The distortions also exert influence upon circular dichroism spectra.     

Catalytic activity of binuclear planar copper(II) complexes for the decomposition of hydrogen peroxide

Planar binuclear copper(II) complexes generally showed high catalytic activities for the decomposition of hydrogen peroxide compared with the relevant planar mononuclear copper(II) complexes. This result was explained on the assumption that the two-electron transfer occurs between H₂O₂ molecules via an intervening binuclear copper(II) complex.     

New biimidazole and bibenzimidazole derivatives: mono and binuclear palladium(II) or platinum(II) complexes and heterobinuclear palladium(II)-rhodium(I) or platinum(II)-rhodium(I) complexes

Novel neutral biimidazolate or bibenzimidazolate palladium(II) and platinum(II) complexes of the type M(NN)₂(dpe) [M = Pd, Pt; (NN)₂^2? = BiIm^2?, BiBzIm^2?. dpe = 1,2-bis(diphenylphosphino) ethane] have been obtained by reacting MCl₂(dpe) with TI₂(NN)₂. Complexes M(NN)₂(dpe) which are Lewis bases react with HClO₄ or [M(dpe)(Me₂CO)₂](ClO₄)₂ to yield, respectively, mononuclear cationic complexes of general formula [M{H₂(NN)₂](dpe) (M = Pd, Pt; H₂(NN)₂ = H₂BiIm, H₂BiBzIm) and homobinuclear palladium(II) or platinum(II) cationic complexes of the type [M₂{μ - (NN)₂}(dpe)₂](ClO₄)₂. Reactions of M(BiBzIm)(dpe) with [Rh(COD) (Me₂CO)_X](ClO₄) render similar heterobinuclear palladium(II)-rhodium(I) and platinum(II)-rhodium(I) cationic complexes, of general formula [(dpe)M(μ-BiBzIm)Rh(COD)](ClO₄) (M = Pd, Pt; COD = 1,5-cyclooctadiene). Di- and mono-carbonyl derivatives [(dpe)M(μ-BiBzIm)Rh(CO)L](ClO₄) (M = Pd, Pt; L = CO, PPh₃) have also been prepared. The structures of the resulting complexes have been elucidated by conductance studies and IR spectroscopy.     

μ-Peroxodicobalt(III) complexes containing aromatic ligands

A series of new μ-peroxodicobalt(III) complexes have been prepared and characterized. Studies of the chemical and physical properties of these complexes were carried out using IR, electronic and NMR spectroscopy along with conductivity, magnetic susceptibility and thermogravimetric measurements. The complexes [Co₂(dpk·dien)₂ (dpk·H₂O)O₂] (ClO₄)₄·H₂O, [Co₂(dpk)₄(py)₂O₂](ClO₄)₄·4H₂O, [Co₂(dpk·H₂O₄(py)₂O₂] (ClO₄)₄, and [Co₂(dpk)₂(terpy)₂O₂](ClO₄)₄ were prepared by bubbling oxygen through a solution containing Co(NO₃)₂, NaClO₄, and the appropriate ligand mixture. Electronic spectral studies are consistent with the formulation as binuclear peroxo complexes. Thermogravimetric studies reveal the stoichiometric loss of O₂ and H₂O below 100°C. The auxiliary ligands, pyridine (py), diethylenetriamine (dien) and terpyridine (terpy) are lost at higher temperatures. Molar conductance of these complexes is indicative of a 4:1 electrolyte while magnetic susceptibility measurements indicate the diamagnetic character of the above four complexes. Three additional complexes of Co(II) containing di-2-pyridyl ketone (dpk) and terpy were prepared to compare spectral changes upon oxygenation.     

Mechanistic aspects of (CC) isomerization in vinylic rhodium(III) complexes

Observations concerning the (CC) isomerization of several vinylic Rh^III complexes suggest an intramolecular pathway; isomerization occurs at a rate which is affected by the backbonding ability of the metal and the π-acidity of the vinylic ligand in the complex.     

Formation of Cu(II)—dicyandiamide complexes in neutral and acidic aqueous solutions

This work presents spectroscopic studies and electrochemical characterization of Cu(II)—dicyandiamide (DCDA) complex formation. The range of conditions leading to the precipitation of the complex is significantly larger than that presented in the literature. In all cases the stoichiometry of the compound is: [Cu(DCDA)₂(SO₄)(H₂O)₅). The spectroscopic data suggest that DCDA is a monodentate ligand forming a bond with Cu²⁺ via the nitryl nitrogen. Electroreduction of this complex is a two-step process occurring through a Cu(I)—DCDA intermediate.     

Synthesis,characterisation and reactions of pentacoordinated iridium(I) complexes

Stable, pentacoordinated iridium(I) complexes have been synthesised by the replacement of the chlorine in IrCO(PPh₃)₂Cl by bidentate chelating ligands such as β-diketones, N-benzoyl-N-phenyl hydroxylamine, salicylaldehyde, 8-hydroxyquinoline, 2-hydroxybenzophenone and 2-hydroxy 4-methoxybenzophenone. Most of them gave stable oxygen adducts IrCO(PPh₃)₂(L)O₂ and all of them underwent oxidative addition with bromine in methylene chloride giving IrCO(PPh₃)₂(L)Br₂. These chelated iridium(I) compounds reacted with liquid sulphur dioxide to produce two types of SO₂ insertion products.     

Chemistry of iron complexes—III. X-ray diffraction,ESR and other spectral studies of new iron(II) and iron(III) complexes with tri-p-tolylarsine oxide

Reactions of iron(II) and iron(III) salts with tri-p-tolylarsine oxide(L) in suitable organic solvents yield complexes of formulas: (i) [FeL₂Cl₂(OH₂)₂] [FeCl₄].2H₂O, [FeL₂Br₂] [FeBr₄].2H₂O; (ii) [Fe(NCS)₃L₂].H₂O; (iii) [FeL(O₂ClO₂)₂(OH₂)] (ClO₄).0.25C₆H₆; (iv) [FeL₃I] [FeI₃].H₂O and (v) [Fe(CO)₃LI]I. Characterization has been done through elemental analyses, IR, far IR, ESR, and reflectance spectra, molar conductance, magnetic moments, t.g.a. and X-ray diffraction (powder) data. The species [FeL₂Cl₂(OH₂)₂]⁺, [FeL₂Br₂]⁺, [Fe(NCS)₃L₂], [FeL(O₂ClO₂)₂OH₂]⁺, [FeL₃I]⁺ and [Fe(CO)₃LI]⁺ have been assigned trans-octahedral, trans-square planar, trans-trigonal bipyramid, trans-octahedral, tetrahedral and cis-trigonal bipyramid structures respectively.