Reactions of homobinuclear platinum and palladium complexes with carbon monoxide

The reactivity of homobimetallic complexes of platinum(II) and palladium(II) containing diethyl(diphenylphosphinomethyl)amine (ddpa = (C₆H₅)₂PCH₂N(C₂H₅)₂) as a bridging ligand has been investigated. Carbon monoxide reacts reversibly with these complexes. The species formed are binuclear carbonyl-bridged derivatives, which can isomerize to ionic terminal carbonyl complexes. Reaction of [PtCl₂(CO)]₂[(C₂H₅)₄N]₂ with ddpa in dichloromethane gives the ionic platinum(I) complex [Pt(ddpa)Cl₂]₂[(C₂H₅)₄N]₂, which reacts with carbon monoxide. Still, homobimetallic derivatives of palladium(I) are unstable, and none have been isolated.     

Thermal and chromatographic behaviour of metal complexes. Part III. Complexes of palladium(II) with iminodiacetic acid

A study of the thermal properties of the complexes formed between Pd(II) and iminodiacetic acid (IDA) and the chromatographic analysis of their thermal decomposition products have been carried out. The dehydration of the isolated compounds is detected above 100°C. The decarboxylation process of the COO^? groups takes place yielding CO₂ and CO simultaneously or consecutively if they are not coordinated, respectively. The formation of gases (methane, ethane, etc.) is also observed.     

Rhodium(I) phosphine complexes containing bidentate unsaturated thio ligands: II. Reactions with O2 and H2

The rhodium(I) complexes (Ph₃P)₂Rh[Me₂NC(S)NC(S)NMe₂], (Ph₃P)₂Rh[SC(S)NMe₂] and (Ph₃P)₂Rh[PhNC(S)NMe₂] react with O₂ to give 1/1 dioxygen adducts. In solution, trans-(Ph₃P)₂Rh(O₂)[Me₂NC(S)NC(S)NMe₂], cis- and trans-(Ph₃P)₂Rh(O₂)[SC(S)NMe₂] and cis- and trans-(Ph₃P)₂Rh(O₂)[PhNC(S)NMe₂] are observed. For (Ph₃P)₂Rh(O₂)[PhNC(S)NMe₂], there is a solvent effect on the initial cis—trans ratio and the rate of O=PPh₃ formation. In C₆H₆, O=PPh₃ formation from (Ph₃P)₂Rh(O₂)[PhNC(S)NMe₂] is inhibited by additional PPh₃.The reaction of (Ph₃P)₂Rh[Ph₂PC(S)NPh] with O₂ in the presence of additional PPh₃ gives O=PPh₃ and cis-(Ph₃P)₂Rh(O₂)[Ph₂P(O)C(S)NPh] as the only products. The same complex also can be prepared from (Ph₃P)₂Rh[Ph₂P(O)C(S)NPh] and O₂.Only (Ph₃P)₂Rh[PhNC(S)NMe₂] reacts with H₂ at room temperature to give (Ph₃P)₂RhH₂[PhNC(S)NMe₂], which is a catalyst for cyclohexene hydrogenation.     

Stability and thermodynamic parameters of thiopyrimidines, 2-thioxanthine and their complexes with Zn(II) and Cd(II)

The thermodynamic protonation constants of 4-amino-1,6-dihydro-2-methylthio-5-nitroso-6-oxo-pyrimidine (MTH), 4-amino-5-nitroso-6-oxo-1,2,3,6,-tetrahydro-2-thiopyrimidine (TANH) and 2-thioxanthine (TXH) in aqueous media at 25, 30, 40 and 50 ± 0.1°C, have been determined potentiometrically by Bjerrum and Robinson's methods. The ionic strength was maintained constant by using 0.1 M NaNO₃ as the supporting electrolyte.The stability constants and thermodynamic functions for Zn(II) and Cd(II) complexes of MTH and TXH, at different ionic strengths and temperatures, have been calculated.     

Thermal studies on purine complexes. I. Thermal behaviour of some xanthine complexes of cobalt(II), copper(II) and cadmium(II)

Cobalt, copper and cadmium xanthinate tetrahydrates have been prepared in aqueous medium, and characterized on the basis of elemental analysis, IR and ¹HNMR studies. The thermal behaviour of these compounds has been studied using TG, DTG and DSC techniques. Heats of dehydration have been calculated from DSC curves.     

Reactions of some electrophilic olefins with (carbonato)bis(triphenylphosphine)- and (carbonato)bis(triphenylarsine)-platinum complexes

Carbonato complexes L₂PtCO₃ (L = PPh₃ or AsPh₃) react with certain electrophilic olegins, such as 1,1-dicyanoolefins, under mild conditions to liberate CO₂. The reaction of L₂PtCO₃ with tetracyanoethylene at room temperature is solvent dependent, and in alcoholic solvents, in contrast to an earlier report, the dicyano complexes, L₂Pt(CN)₂, and tricyanoethenolato complexes, L₂Pt(CN) [OC(CN)C(CN)₂] have been isolated and identified.     

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.     

Extraction and determination of anionic surfactants with copper (II)-ethylenediamine derivative complexes

Anionic surfactants, S(-) [where S(-) is dodecyl sulphate (DS) or dodecylbenzenesulphonate (DBS)] were extracted with a series of copper (II)-ethylenediamine derivative complexes, CU(R-en)(2)(2+), where R-en is ethylenediamine (en), N,N'-dimethylethylenediainine (NN'Me(2)en), N,N-dimethylethylenediamine (NNMe(2)en), N,N-diethylethylenediamine (NNE(2)en) or 1,2-cyclohexanediamine (Cyen). The extraction constant of the ion-pair is K(ex) = [Cu(R-en)(2)(2+) . 2S(-)](0)/[Cu(R-en)(2)(2+)][S(-)](2). The constants for extraction of the DS complexes with en, NN'Me(2)en, NNMe(2)en, NNEt(2)en and Cyen into chloroform were found to be log K(ex) = 7.93, 9,19, 8.88, 8.74 and 11.45 (+/- 0.05 at 25 degrees C), respectively. The extractability of the ion-pair Cu(en)(2)(2+) . 2S(-) gave a linear correlation with the acidity of the solvent. The Cu(Cyen)(2)(2+) extraction system was applied to the determination of some anionic surfactants. With use of graphitefurnace atomic-absorption spectrophotometry, a limit of detection of 5mug l . was obtained with a 20-ml sample of river water or sea-water.     

Thermal and chromatographic behaviour of metal complexes. Part II. Complexes of platinum(II) with dipeptide ester

Experimental measurements of the rate of reduction of particles of Carol Lake and Kiruna ores have been made using pure hydrogen and pure carbon monoxide and mixtures of these two gases. The temperature range covered was 773–1143 K and throughout this range the reduction rate with hydrogen was greater than that with carbon monoxide. A retracting core model was found to best fit the experimental data even when granules of 9 × 10^?4 m diameter were used. Reduction with gas mixtures of hydrogen and carbon monoxide give rates intermediate between those of the pure gases.     

Thermal decomposition of mixed ligand complexes of cobalt(II), nickel(II), zinc(II) and cadmium(II) containing 1,3-diaminopropan-2-ol and oxalate

Non-isothermal kinetics of the thermal decomposition of mixed ligand complexes of cobalt(II), nickel(II), zinc(II) and cadmium(II) have been studied using thermogravimetry (TG) and differential scanning calorimetry (DSC). The reaction in which the complex loses one molecule of the ligand is found to be first order and the activation energy was calculated using established techniques. Using Dharwadkar and Karkhanavala's method, the values obtained were 25.65, 17.32, 25.22 and 20.95 kcal mole^?1, respectively. Infrared spectral studies of these complexes and intermediates provided information regarding the coordinating nature of the ligand 1,3-diaminopropan-2-ol in these complexes.     

π-Arene complexes of the main group elements. II. Complexes of cadmium(II) and zinc(II)

π-Arene complexes of cadmium(II) and zinc(II) have been prepared from the first time. The 1:1 complexes Cd(AsF₆)₂. Arene(Arene=hexaethylor hexamethylbenzene, pentamethylbenzene, durene, $\text{p}$-xylene or benzene), Cd(SbF₆)₂. Arene(Arene = hexamethylbenzene, toluene or benzene) and Zn(SbF₆)₂. Arene(Arene = hexamethylbenzene or pentamethylbenzene) are synthesized from the strong acid salt and arene in liquid sulfur dioxide. ¹H and ¹³C NMR spectra are consistent with localized bonding of the arene to the metal cation. Exchange-averaged vn]¹³C chemical shifts for the systems Cd(AsF₆)₂-arene-SO₂ confirm the 1:1 stoichiometry in solution and suggest that the stabilities of the complexes are in the approximate range 0.48 – 2.1 M^?1 for the series benzene-hexamethylbenzene. For the system Cd(AsF₆)₂-C₆Me₆-SO₂, a detailed ¹¹³Cd NMR study is consistent with the solution stoichiometry and stability determined from ¹³C NMR. In general, complexation to an arene produces deshielding of the ¹¹³Cd resonance of Cd(AsF₆)₂.     

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.     

Adducts of a palladium(II) derivatives containing a α-bonded α-diimino group with transition metals a new class of bimetallic complexes

The characterization of 1 : 1 adducts of [PdCl C(NC₂H₄OMe)(MeCNC, H₄OMe)(PPh₃)₂] and MCl₂ (M = Fe, Co, N₄, Cu and Zn) is described.     

π-Allymetal chemistry 8. Uncatalyzed cis-trans isomerization of n3-allyl (pentachloropehnyl) palladium (II) complex

Two geometrical isomers of an n³-crotyhlpalladium(II) complex, Pd(n³-crotyl)(C₆Cl₅)(PPh₃) have been found to undergo uncatalyzed mutual interconversion in benzene above room temperature. The rate constants of the isomerization have been determined by the ¹H NMR method at 45–67°C, and thermodynamic data calculated. The large decrease of the rate on adding free tripheylphosphine ligand is attributed to occurrence of a dissciative isomerization path involving a 3-coordinate intermediate. Reductive elimination of the complex takes place at much slower rates than the isomerization to afford MeCHCHCH₂C₆Cl₅ selectively.     

Reactions of hexamethyldilead with 7,7,8,8-tetracyanoquinodimethane (TCNQ) and tetracyanoethylene (TCNE)

Hexamethyldilead reacts with TCNQ to give Pb(TCNQ)₂ and tetramethyllead and with TCNE to give Pb(TCNE).     

Preparation and electronic spectra of some alkyl- and aryl(2,2′-bipyridine)platinum(II) complexes

A series of alkyl- and aryl-(2,2′-bipyridine)-platinum (II) complexes has been prepared by displacement of the diene ligand in the corresponding cyclooctadiene complexes with 2,2′-bipyridine. Dimethyl(1,10-phenanthroline)platinum(II) was prepared in an analogous way. The electronic spectra of the complexes contain metal to ligand charge transfer bands whose energy is dependent on the nature of the substituents on platinum and on the solvent. It is suggested that π-bonding is important in the phenyl—platinum bond.     

Spectroscopic and biological studies on palladium(II) complexes with N-ethyl and N-propylimidazole

Palladium(II) halide complexes with N-ethylimidazole (N-EtIm) and N- propylimidazole (N-PropIm) with general formulae Pd(L)₂X₂ and Pd(L)₄X₂ (X = Cl, Br, I) were prepared and characterized by spectroscopic methods and conductivity measurements. These complexes are diamagnetic and have square planar stereochemistry. The Pd(L₂)X₂ derivatives, are non-conductors, and have trans-structures except for the cis-Pd(N-EtIm)₂Br₂. The biological activity of water soluble Pd(II) compounds is also reported.     

Alkyl complexes of palladium(II) with trimethylphosphine and 1,2-bis-(dimethylphosphino)ethane ligands

A number of neutral, mononuclear dialkylpalladium(II) tertiary phosphine complexes of geneal formula cis or trans-PdR₂(PMe₃)₂ and cis-PdR₂ (dmpe) [dmpe = 1,2-bis(dimethylphosphino)ethane], R = Me, CH₂Ph, CH₂CMe₂Ph, CH₂SiMe₃ have been obtained by interaction of magnesium reagents with palladium(II) acetate or trans-Pd(O₂CMe)₂(PMe₃)₂.