New syntheses of platinum (IV) and platinum (VI) fluorides

γ-Ray and peroxide-initiated additions of dimethylether to F-cyclobutene, F-cyclopentene, and F-cyclohexene give mixtures of $\text{cis-}$ and $\text{trans-}$ adducts in each case, with a clear preference for $\text{trans}$-addition with F-cyclobutene. Selective bromination of the adducts occurs but the position of chlorination depends dramatically on solvent. Fluorination with cobalt trifluoride is very efficient.     

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).     

Pentamethylcyclopentadienylplatinum(IV) complexes

Reaction of dichloro(η⁴-pentamethylcyclopentadiene)platinum with bromine yields a η⁵-pentamethylcyclopentadienylplatinum(IV) complex which is formulated as [C₅Me₅PtBr₃PtC₅Me₅]Br₃.     

Cationic carbonyl complexes of manganese (I) with nitriles and dinitriles

The reaction of Mn(CO)₅OClO₃ with nitriles,L, and dinitriles,L-L, in a wide variety of conditions affords cationic pentacarbonyls, [Mn(CO)₅(L)] ClO₄ and [Mn (CO)₅(L-L)] ClO₄ and fac-tricarbonyls, [Mn (CO)₃ (L)₃] ClO₄ and [(CO) ₃Mn (μ L-L) ₃Mn (CO)₃] (ClO₄)₂     

Identification of Cu(II)/Cu(III) couples in binuclear copper(II) complexes

A new series of binuclear copper(II) complexes were synthesised and studied by magnetic, spectral, ESR and cyclic voltammetry methods. The μ_eff values per copper atom correspond to the values observed for mononuclear copper(II) complexes. ESR spectral data in solution indicate weak interactions resulting from the electron delocalisation through the ligand system. Two nearly reversible red-ox couples are identified at $\text{+}\text{?}$0.50 V and $\text{+}\text{?}$0.75 V vs SCE. They correspond to Cu(II)αCu(III) red-ox processes, successively occurring at the two copper sites in the binuclear complexes.     

Halide and complex halogeno anions as salts of oxinate chelates of titanium(IV)

(η⁵-Cyclopentadienyl)(η⁵-pyrrolyl)titanium(IV) dichloride, (η⁵-indenyl)-(η⁵-pyrrolyl)titanium(IV) dichloride and (η⁵-cyclopentadienyl)(η⁵-indenyl)-titanium(IV) dichloride, when treated with 8-hydroxyquinoline (oxine) in aqueous medium form ionic derivatives of the type, [(η⁵-R)(η⁵-R′)TiL]⁺ Cl^- (R = C₅H₅, C₉H₇, R′ = C₄H₄N; R = C₅H₅, R′ = C₉H₇; L is the conjugate base of (oxine). A number of halide and complex halogeno anions present in aqueous solution were isolated as salts of these ionic complexes giving derivatives of the type, [(η⁵-R)(η⁵-R′)TiL]⁺ X^- (X = Br^-, I^-, ZnCl₃(H₂O)^-, CdCl₄^2-, HgCl₃^-). Conductivity measurements in nitrobenzene solution indicate that these complexes are electrolytes. Both the IR and ¹H NMR spectral studies demonstrate that the ligand L is chelating. Consequently there is tetrahedral coordination about the titanium(IV) ion.     

Bis(indenyl)titanium(IV) and zirconium(IV) complexes of monofunctional bidentate salicylidimines

Dichlorobis(indenyl)-titanium(IV) and -zirconium(IV), (C₉H₇)₂TiCl₂ and (C₉H₇)₂ZrCl₂, react with bidentate Schiff bases such as salicylidene aniline, salicylidene-o-toluidine, salicylidene-m-toluidine and salicylidene-p-toluidine in a 1:1 molar ratio in refluxing tetrahydrofuran in the presence of triethylamine to yield complexes of the type (C₉H₇)₂Ti(SB)Cl and (C₉H₇)₂Zr(SB)Cl, respectively where SB is the anion of the corresponding Schiff base, SBH. The new derivatives have been characterised on the basis of their elemental analyses, conductance measurements and spectral (IR, ¹H NMR and electronic) studies.     

Monocyclopentadienyl titanium(IV) alkyl xanthate complexes

Titanium(IV) alkyl xanthates of the types CpTi(S₂COR)Cl₂, CpTi(S₂COR)₂Cl and CpTi(S₂COR)₃, where R = CH₃, C₂H₅, C₃H₇, C₄H₉ and C₅H₁₁, have been prepared by the reaction of monocyclopentadienyl titanium(IV) trichloride with potassium alkyl xanthates in anhydrous dichloromethane. Conductance and infrared studies suggest that these complexes are non-electrolytes in which all of the xanthate ligands are bidentate. Proton nmr spectra of these complexes indicate that there is rapid rotation of the cyclopentadienyl ring about the metal-ring axis and for the CpTi(S₂COR)₃ complexes non-equivalence of the alkylxanthate ligands was observed.     

Template reactions with polynuclear complexes. The reaction of octachlorodimolybdate(II) with 2-aminobenzaldehyde

The binuclear molybdenum(II) anion [Mo₂Cl₈]^4? acts as a template for the self-condensation of 2-aminobenzaldehyde. The dimolybdenum unit is retained in the molybdenum(IV) product, [Mo₂(A)₂(H₂O)⁴⁺.4Cl^?, where A is a macrocyclic tetradentate ligand containing two Schiff base nitrogen donors. The product forms as two isomers, whose ¹H nmr spectra are discussed.     

The pK(a), values of the conjugate acid of imidazole in water-ethanol mixtures

The pK(a) values of protonated imidazole in 10 different water-ethanol mixtures were determined at 25 degrees by potentiometric titration in a cell without liquid junction (glass and silver-silver bromide electrodes). The pK(a) values can be used in a standardization procedure that allows determination of pK(a) values for protonated organic nitrogen bases in aqueous ethanol.     

The formation of flouride complexes of titanium(IV)

The complex formation equilibria between titanium(IV) and fluoride ions have been studied at 25°C in 3 M(Na)Cl ionic medium by measuring, with an ion selective electrode for F^?, the free HF concentration in acid Ti(IV) solutions. The [H⁺] was kept within 0.25 and I M where the predominant form of uncomplexed metal is the dihydroxotitanium(IV) ion, Ti(OH)²⁺₂. The potentiometric data have been explained by assuming Ti(OH)₂F⁺, TiF₄ and HTiF^?₆, with equilibrium constants given in Table 3. Within the accuracy of the present e.m.f. study, ±0.2 mV, no evidence for intermediate complexes bearing 2, 3 and 5 F^? was found.From a special series of measurements, carried out by replacing a large part of the Cl^? with ClO^?₄, it is concluded that no appreciable amount of Ti(IV)Cl complexes is formed at the 3 M level employed as ionic medium.     

The infrared spectra of imidazole complexes of platinum(II) halides and nitrite

Summary The i.r. spectra (4000-90 cm^–1) of the [Pt(Him)₄]X₂ complexes (Him = imidazole, X = Cl, Br or I) andcis- andtrans-[Pt(Him)₂X₂] (X = Cl, Br, I or NO₂) and their D₃-labelled analogues have been determined. The distinction between the ring and C-H (or N-H) modes of imidazole is based on the relative shifts which these bands undergo on D₃-labelling. Assignments, based on the effects of imidazole deuteriation and halide substitution, are provided for the v(Pt-Him) and v(Pt-X) modes.     

Some mixed-ligand palladium(II) complexes and comparison of their photosensitizing ability with analogous platinum(II) complexes

Three new palladium(II) complexes of formula [Pd(bipy)(XX)] [where bipy is 2,2′-bipyridine and XX are dianions of catechol (CAT), 4-tert-butylcatechol (BCAT) and 3,4-dimercaptotoluene (DMT)] have been prepared and characterized by physical methods. A ligand-ligand charge-transfer band in each complex was observed between 16–21 kK (ε_max = 1500–2200 1 mol^?1 cm^?1) which is negatively solvochromic. These palladium(II) complexes in dimethylformamide photosensitize the formation of singlet oxygen and their ability to photosensitize triplet oxygen (³O₂) to singlet oxygen (¹O₂) are compared with analogous platinum(II) complexes. In addition, 2,2′-bipyridine-platinum(II) complex of 3,4-dimercaptotoluene also undergoes self-sensitized photooxidation.     

Hafnium(IV)-nitrilotriacetate and hafnium(IV)-fluoride complexes investigated using an ion-selective electrode

Models of plutonium solution chemistry in vivo require formation constants which are difficult to obtain but hafnium(IV) is biochemically similar t     

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.     

Binuclear complexes of silicon(IV) chloride with nickel(II) salicylaldoximates

Some binuclear complexes of silicon(IV) chloride and nickel(II) salicylaldoximates were synthesized and characterised by elemental analyses, conductivity measurements, magnetic and spectral data. The complexes were proved to be 1:1 SiCl₄ adducts. The resulting complexes were amorphous in nature and electrolytes in solution.     

Trans-bis(dimethylglyoximato) cobalt(III) complexes containing imidazole and thiocyanate as axial ligands

Imidazole(Im), benzimidazole(BzIm), morpholine (Morph) and their derivatives react with Co(CNS)₂ and dimethylglyoxime(DH₂) in ethanolic medium in presence of air to form a number of new cobalt(III) complexes of the type trans-[Co(DH)₂(L)(SCN)], which are characterised on the basis of electronic and IR spectra, NMR (¹H and ¹³C) and mass spectra as well as thermogravimetric (TG-DTA) and conductance measurements. The thiocyanate groups are S-bonded. The NMR observations suggest that in solution these compounds exist as mixtures of the neutral species [Co(DH)₂(L)(SCN)] and the salt [Co(DH)₂(SCN)₂]^? [Co(DH)₂(L)₂]⁺. The mass spectra does not show the molecular ion peak of the complex. The TG-DTA measurements show that the thermolysis of these complexes proceeds through polymeric intermediates giving CO₃O₄ as the end product.     

Polarographic study of mixed ligand complexes of Pb(II) with carboxylate ions and imidazole

Mixed complexes of Pb(II) with some carboxylate ions, viz. tartrate (tart^2?), malonate (mal^2?) and citrate (citr^3?); and imidazole (im) have been studied polarographically at 25°C and at constant ionic strength μ = 2.0 (NaNO₃) and at pH 6. The polarographic reduction of the complexes in each case is reversible and diffusion-controlled. Pb(II) forms a single mixed complex with tartrate and imidazole, viz [Pb(tart)(im)] with stability constant log β₁₁ = 4.19; with mal^2? and im, three mixed complexes, [Pb(mal)(im)], [Pb(mal)(im)₂] and [Pb(mal)₂(im)]^2? with stability constants log β₁₁ = 4.3, log β₁₂ = 7.3 and log β₂₁ = 5.5 respectively are formed. With citr^3? and im a single mixed species, [Pb(citr)(im)]^? with stability constant log β₁₁ = 8.0 is formed. Various equilibria involved in the mixed systems have been discussed.     

Thermal decomposition of oxovanadium(IV) complexes with substituted pyridines

The kinetics of decomposition of solid complexes of bis(dibenzoylmethanato) oxovanadium(IV) with pyridine and several methyl, dimethyl and aminopyridines has been studied using differential scanning calorimetry. Activation energies have been determined and, in general show an increase with increasing basicity of the ligands. A linear relationship exists between pK_b values of the bases and the temperatures for the decomposition, except for the complexes obtained with 4 aminopyridine and 4 methylpyridine. These complexes are less stable than expected from the basicity of the ligands. These observations are discussed in terms of the nature of the metalligand bond.     

Polarographic study of Sn(IV) chloride-pyridine N-oxide complexes in acetonitrile

Polarograms recorded of Sn(IV) chloride in acetonitrile in the presence of controlled quantities of each of nine substituted pyridine N-oxide ligands demonstrated the formation of stable and soluble complexes with a stoichiometry dependent upon the nature and position of the ring substituent. The polarographic data associated with each complex and the free ligands are used to substantiate a proposed bonding model which explains the dependency of the complex formula on the ligand structure. The salt SnCl₄·5H₂O was employed as a source of Sn(IV) and the complete polarographic behaviour of this salt in acetonitrile is described as a basis for the interpretation of complex reduction behaviour.