[Cu12S6(PnPr3)8] and [Cu20S10(PnBu1Bu2)8]: Two sulfur bridged copper clusters with Cu-s cluster cores of known compositions but new structures

The synthesis and X-ray determination of two sulfur bridged copper clusters with the known compositions of [Cu₁₂S₆(PⁿPr₃)₈] and [Cu₂₀S₁₀(PⁿBu¹Bu₂)₈] but new molecular structures allow a comparison of these isomeric copper sulfide clusters. The Cu-S frameworks of the clusters with twelve copper atoms are highly topologically related and can both be derived flom a hypothetical naked [Cu₁₂,S₆] cluster that results from theoretical investigations. More dificult is the comparison of the two clusters containing 20 metal atoms. The two cluster types can be called either a prolate or an oblate isomer of [Cu₂₀S₁₀(pR₃)₈].     

Preparation of Porous Cordierite with Thermally Stable Pore Structure

A cordierite ceramic with a thermally stable pore structure was prepared by a simple modification of a sol-gel reaction of alkoxide precursors, synthesized from Mg metal or Mg acetate, Al(i-OPr)₃, and partially prehydrolyzed Si(OEt)₄. For aging and drying, wet cordierite gel was treated with water vapor at 150°C to strengthen the gel network through enhanced hydrolysis and condensation reactions. The cordierite xerogels showed BET surface areas between 220–410 m²/g, depending on the catalyst and treatment conditions used. In particular, water vapor treated xerogel displayed comparatively thermally stable pore characteristics, which exhibited only a 4–17% decrease in BET surface area up to 700°C, while samples prepared using the conventional sol-gel method showed a 55–91% reduction. Both the DTA and XRD patterns showed that crystallization began at 900°C leading to the -Cordierite phase and the subsequent phase transition to -cordierite at temperatures between 1050 to 1250°C.     

X-Ray Diffraction Study of Piperidine Octamolybdate

Piperidine octamolybdate [C₅H₅NH₂]₄[Mo₈O₂₆]·4H₂O (I) has been synthesized and characterized by X-ray diffraction analysis. Crystals I are monoclinic, space group P2₁/n, a=12.892(3), b=9.283(2), c=19.184(4) , =92.50(3)°, V=2293.7(9) ³, Z=2,_calc = 2.317 g/cm³.     

In vitro and in vivo antitumour studies of a new thiosemicarbazide derivative and its complexes with 3d-metal ions

A new ligand, 1-(2-furanthiocarbo)-3-thiosemicarbazide (H₂ftsc), prepared from thiosemicarbazide and carboxymethyl-2-furandithioate, forms complexes [Mn(ftsc)(H₂O)₂], [Pd(ftsc)] · 2H₂O, [M(Hftsc)(acac)₂] (M=Co^III or Cr^III), [M(Hftsc)₂(acac)] (M=Mn^III or Fe^III) and [Zn(Hftsc)₂] · 2H₂O, which were characterized by elemental analyses, magnetic susceptibility, i.r., electronic and n.m.r. spectral data. The Mössbauer spectra of [Fe(Hftsc)₂(acac)] at 298K and 80K suggest the presence of high-spin iron(III) with an S=5/2 state. In vivo and in vitro antitumour activity of the ligand and the complexes have been screened towards several tumour cell-lines.     

Heterodinuclear PtRh and PtIr complexes with phosphinite groups as bridging ligands

Compounds of the general formula [Pt(²-L) {P(O)Ph2}- {P(OH)Ph₂}], where ²-L={²-S₂P(OEt)₂}^- (1) and {²-S₂CNEt₂}^- (2), react in THF solution with the dinuclear complex [{(cod)M(-OMe)}₂] (M = Rh^I or Ir^I) to give new heterodinuclear compounds of the type [(²-L)Pt{-P(O)Ph₂}₂M(cod)], where ²-L={²-S₂P- (OEt)₂}^-;; M=Rh^I (3), Ir^I (4) and ²-L = {²-S₂C-NEt₂}^-; M=Rh^I (5) and Ir^I (6). Compounds (3) and (4) react with an excess of CO, leading to displacement of the coordinated -diolefin (cod) and the formation of the dicarbonyl derivatives [{²-S₂P(OEt)₂}Pt{-P(O)-Ph₂}₂]M(CO)₂] [M=Rh^I (7), Ir^I (8)].All products were characterized by carbon and hydrogen microanalysis and by i.r. and n.m.r. spectroscopy {¹H and³¹ P(¹H)}.     

Photometric detection of cyclodextrins in liquid chromatography by using iodine generated electrochemically in-situ

A method has been developed for photometric detection of cyclodextrins (CD) in liquid chromatography using iodine (I₂) generated electrochemically in-situ. Iodide ion in the mobile phase was electrochemically oxidized to I₂ which was subsequently reacted with I^–, in an electrochemical flow cell, forming I₃^–. The absorbance of I₃^– was found to be greatly enhanced when CD were present in the mobile phase. The absorbance enhancement was caused by the change in the mole fraction of I₃^–, because of the inclusion reaction of I₃^– with CD. On the basis of this phenomenon, CD were detected by means of a photodiode-array UV–visible detector positioned downstream of the electrochemical flow cell. The signals were found to be linearly dependent on CD concentration. Because the formation constants of I₃^– with CD decrease in the order -CD>-CD>-CD, -CD was most detectable by the method. Detection limits were 1.0 mol L^–1 for -CD, 65 mol L^–1 for monoG1--CD, 100 mol L^–1 for -CD, and 200 mol L^–1 for -CD.     

The hydrolysis and fluoride complexation behavior of Fe(III) at 25°C and 0.68 molal ionic strength

Fe(III) hydrolysis and fluoride complexation behavior was examined in 0.68 molal sodium perchlorate at 25°C. Our assessment of the complexation of Fe(III) by fluoride ions produced the following results: log_F1 = 5.15₅, log_F2 = 9.10₇, log_F3 = 11.96, log_F4 = 13.7₅, where log_Fn = 5.15₅=[FeF _n ^(3-n)+ ][Fe³⁺]^–1[F^–]^–n. The stepwise fluoride complexation constants,FK _n+1, obtained in our work (where log_F K _n+1 =log_Fn) indicate that K _n+1/K _n =0.072±0.01. Formation constants for equilibria, Fe³⁺+nH₂OFe(OH) _n ^(3–n)+ +nH⁺, expressed in the form _n ^* [Fe(OH) _n ^(3-n)+ ][H⁺]ⁿ ,[Fe ³⁺]^-1, were estimated as ₁ ^* = –2.754, and ₂ ^* –7. Our study indicates that the results of previous hydrolysis investigations include very large overestimates of Fe(OH) ₂ ⁺ formation constants.     

Self-Assembly of d10 Metal Adduct Polymers Bridged by Bipyridyl-Based Ligands

Four d¹⁰ metal polymers, cluster [AgI₂(bpe)] _n (1), complexes [Zn(tmp)I₂] _n (2), [Cd(tmp)I₂] _n (3), and [Hg(tmp)Br₂] _n (4) (bpe=1,2-bis(4-pyridyl)ethane, tmp=4,4-trimethylene dipyridine) have been synthesized and structurally characterized by elemental analysis, IR spectroscopy and X-ray single-crystal diffraction. 1 is a cluster polymer, and exhibits a two-dimensional open structure consisting of the staircase clusters connected by regular bpe bridges. While complexes 2, 3, and 4 are one-dimensional wave-shaped coordination polymers. In contrast, 3 also displays a 2D structure with large supramolecular cavities. The diverse coordination properties of d¹⁰ metals make them good building blocks for the construction of coordination polymers with diverse architectures, which is dependent on both the rigidity and length of the bifunctional ligand and the coordination geometry of the metal ions.     

Metal-betaine interactions. Part 17: A study of intradimer Cu · · · Cu distance variation in copper(II) betaine complexes containing [Cu2 (carboxylato-O,O′)4L2]n+ species

Four copper(II) complexes of betaines, [Cu₂(BET)₄Cl₂][Cu(BET)₂Cl₂]Cl₂ (2), [Cu₂(pyBET)₄Cl₂]₃[CuCl₄]₂Cl₂ (3), [Cu, (pyBET)₄ (H₂O)₂] (NO₃)₄ · 2H₂O (4), and [Cu₂(ppBET)₄(H₂O)₂](ClO₄)₄ · 4H₂O (5), (BET = Me₃N⁺CH₂COO^–; pyBET = C₅H₅N⁺CH₂COO^–; ppBET=C₅H₅N⁺CH₂CH₂COO^–), have been prepared and characterized by X-ray crystallography. These complexes all contain dimeric [Cu₂ (carboxylato-O,O)₄L₂] structures [basal Cu-O=1.955(4) 1.991(2), Cu Cu=2.602(1) 2.759(1) Å] with the apical ligand L=Cl^– in (2) and (3) [Cu-Cl=2.415(1) 2.436(3) Å] and L = H₂O in (4) and (5) [Cu-OH₂=2.158(4) 2.192(3) Å]; also present are a discrete [Cu(BET)₂Cl₂] molecule with a compressed tetrahedral CuO₂Cl₂ chromophore involving two unidentate carboxylate ligands [Cu-O=1.916(2), Cu-Cl=2.254(1) Å] in (2), and a discrete C_3v [CuCl₄]^2– anion in (3). Generally the intradimer Cu Cu distance may be correlated to the electronic repulsion of the metal-ligand bonds in the CuO₄L chromophore, as well as the steric interaction between the carboxylate moieties and the apical ligand.     

Violurato complexes of nickel(II). Formation equilibria. Deprotonation equilibria of the coordinated ligands and related stereochemical changes

Summary The formation equilibria of nickel(II) violurato-complexes in water and dimethylsulphoxide-water (8020) as well as deprotonation of the coordinated ligands and related stereochemical changes are reported. The stability constants of the Ni²⁺-H₂V^– complexes log₁=5.06, Iog₂=9.38, log₃=12.98 as well as the acidity constants of the [Ni(H₂V)₃]^– complex, log_j1= 8.37, log_j2=15.76, log_j3=22.37 are determined at 25 °C and 0.1M NaClO₄. A new violurato-complex of Ni²⁺, Na₄[Ni(HV)₃]5H₂O, is isolated and characterized.     

The reductive dimerization of [W(NCMe)(MeC2Me)2(η-C5H5)]+: Synthesis and X-ray structure of the novel bis(metallacyclopentadiene) complex [W2(μ-σ,σ,η2,η2-C4Me4)2(η-C5H5)2]

Treatment of [W(CO)(MeC₂Me)₂(-C₅H₅)][PF₆] with ONMe₃ in acetonitrile yields [W(NCMe)(MeC₂Me)₂(-C₅H₅)][PF₆] which undergoes irreversible reduction at a Pt electrode in THF. Sodium amalgam reduction of [W(NCMe) (MeC₂Me)₂(-C₅H₅)][PF₆] gives orange crystals of [W₂(µ-,, ², ²-C₄Me₄)₂ (-C₅H₅)₂] X-ray studies on which reveal pairwise alkyne coupling and a novel bis(metallacyclopentadiene) structure.Dedicated to Professor L. F. Dahl on the occasion of his 65th birthday.     

Isocyanide complexes of rhodium,part 41,2). η5-pentamethylcyclopentadienyl-rhodium (III) compounds

Summary The complexes Rh(⁵-C₅Me₅)(CNR)Cl₂, [Rh(⁵ - C₅Me₅)(CNR)₂Cl][PF₆], (R = Me, Et, i-Pr, t-Bu, C₆H₁₁, , p-CIC6H4 and 1-naphthyl), and [Rh(⁵-C⁵Me⁵)(CNR)₃][PF₆] (R = Et, i-Pr and t-Bu)] have been prepared by treatment of [Rh(⁵-C₅Me₅)Cl₂]₂ with RNC in the presence of [PF₆]^– (as appropriate). These complexes do not react with alcohols or amines to yield carbenes, but withm-MeC₆H₄SNa and NaS₂CNR₂, the species Rh(⁵-C₅H₅)(CNEt)(SC₆M₄Me-m)₂ and [Rh(⁵-C₅Me₅)(CNR)(S₂CNR₂)][PF₆] (R = Me, R¹ = Me or Et; R =p-ClC₆H₄, R¹ = Me) are formed. Treatment of [Rh(⁵-C₅H₅)(CNR)₂Cl][PF₆] with NaBH₄ gave low yields of compounds tentatively formulated as [Rh(⁵-C₅Me₅)(CNR)₂(BH₄)][PF₆] (R = Me or Et).Reprints of this article are not available.     

Copper(I) hexafluorosilicateπ-complexes with allylammonium salts. Synthesis and crystal structure of [CuOOCH·C3H5NH3]2SiF6 and [Cu2Cl3·2C3H5NH3]2SiF6

Two novel copper (I) -complexes containing the SiF ₆ ^2– anion have been synthesized and studied by X-ray structure analysis. The crystals of the first title compound (A) are monoclinic, space group P2₁/b with a=13.039(5), b=10.586(4), c=6.072(2) Å, =100.23(2)°, and Z=2. The crystals of the second title compound (B) are triclinic, space group with a=14.495(5), b=7.633(2), c=6.429(8) Å, =90.67(8), =81.80(8), =94.05(3)°, and Z=1. In structure A, the copper cations and the bridge formiate anions form infinite [Cu(HCOO)]_n spirals, which are cross-linked due to the -interaction between copper and the double bond AA and the strong hydrogen bonds N–H... F(SiF ₆ ^2– ) to form a three-dimensional framework. In structure B, allylammonium similarly acts as a bridge linking the SiF ₆ ^2– and Cu₄Cl ₆ ^2– anions into layers.Lvov State University. Institute of Physical Chemistry, Ukrainian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 34, No. 4, pp. 141–148, July–August, 1993.Translated by T. Yudanova     

C-C bond formation at polynuclear metal centers

Studies on C-C bond formation between simple hydrocarbon species such as CH₂, C=CH₂, CH=CH₂, CH₂=CH₂, CH₂=C=CH₂ and CHCH at a diruthenium center suggest that the process is promoted when the dimetal center can readily compensate for the two electrons lost in the formation of the new C-C bond. Thus, whereas -CH₂ and ethene combine only under forcing conditions, the combination of -CH₂ with allene or ethyne, which have additional -electrons available for coordination, occurs readily at room temperature. Likewise, the availability of uncoordinated -electrons in -C=CH₂ allows vinylidene to link rapidly with ethene at room temperature. Alkyne complexes [Ru₂(CO)(-RCCR)(-C₅H₅)₂] (R=CF₃ or Ph) react only under vigorous conditions with additional alkyne to give [Ru₂(CO)(-C₄R₄) (-C₅H₅)₂], but give these same species at room temperature in the presence of acid, shown to be due to the intermediacy of highly reactive 30-electron -vinyl cations. Thermally, alkyne linking proceedsvia three-alkyne species [Ru₂(-C₆R₆)(-C₅H₅)₂] to a four-alkyne complex [Ru₂(-C₈R₈)(-C₅H₅)₂], containing an unprecedented C₈ ligand composed of a C₆ ring with a C₂ tail. Treatment of [Ru₂(CO)(-RCCR)(-C₅H₅)₂] with unsaturated metal fragments gives trimetal complexes such as [Ru₃(CO)₅(₃-CF₃CCCF₃) (-C₅H₅)₂]. The MeCN derivative of this species undergoes unusual linking processes on reaction with additional alkyne to giveinter alia [Ru₃(CO)₃(₃-CCF₃){₃-C₃(CF₃)₃}(-C₅H₅)₂], arising from alkyne cleavage, and [Ru₃(CO)₃{₃-C₄(CF₃)₂(CO₂Me)₂}(-C₅H₅)₂], a closo-pentagonal bipyramidal Ru₃C₄ cluster.     

Complex formation equilibria in iron(III)-L-alanine system

Summary Complex formation in iron(III)-L-alanine solutions was studied by emf glass electrode and spectrophotometric measurements, in 0.5 mol dm ^–3 (Na)NO₃ medium, at 25 ° C. In the concentration range 0.5 [Fe]₀ 20.0, 5.0 [Ala]₀ 1000.0 (mmol dm^–3) and 1.0 -log [H⁺] 3.5; {[Ala]/[Fe] = 10:1-100:1| the equilibria in the title system were explained by the model including the species FeHL, FeL, Fe(OH)L, Fe₂(OH)₂L₂ (where HL denotes L-alanine) and several hydrolytic products. The stability constants of complexes are given. The mechanism of formation and structure of complexes in solution is proposed.Abbreviations Ala alaninate ion - HAla alanine (zwitterion) - AlaH alanine (neutral) - H₂Ala⁺ alanine cation     

Mixed ligand palladium(II) complexes of oxalate and malonate with vitamin-B6 molecules: synthesis,crystal structure and kinetics

The synthesis of six mononuclear palladium complexes of general formula [Pd(ox)/(mal)L₂] and [Pd(ox)/(mal)L] (ox = oxalate, mal = malonate, both L and L are vitamin-B₆ molecules (I), L = pyridoxine, pyridoxal and L = pyridoxamine) has been achieved. The structures of these compounds were established by elemental analysis, i.r. and ¹³C-n.m.r. [Pd(oxalate)(pyridoxine)₂] was analyzed by single crystal X-ray diffraction. It exhibits square planar coordination with bond lengths 2.015 (2) Å for Pd—N and 2.010 (2) Å for Pd—O. The interaction of [Pd(ox)₂]^2– and [Pd(mal)₂]^2– with L has been followed kinetically in order to look into the nature of products and the mechanism of formation under the conditions [Pd^II-chelate] [L] and [L].     

α- andβ-Tri-ferricononatungstosilicate isomers

Summary Eight new compounds of the- and- M_aH_b[SiW₉Fe₃ (H₂O)₃O₃₇]·xH₂O type, where M = K, Me₄N, Et₄N or Na n-Bu₄N, and a + b = 7, have been synthesized from trivacant heteropoly tungstate- and- [SiW₉O₃₄]^10– precursors, and characterized by i.r., u.v., x-ray photoelectron (x.p.e.) and Mössbauer spectroscopy, and polarography, and by their magnetic moments and thermal behavior. The i.r. and u.v. spectra confirm that the-and- [SiW₉Fe₃(H₂O)₃O₃₇]^7– isomers possess the Keggin structure. The main i.r. bands shift regularly with the changes of cation-size. The charge transfer energies of the easily reduced-isomers are lower than those of the-isomers. The x.p.e. results indicate-bond back-donation between iron and oxygen. The Mössbauer parameters obtained for the-isomer show that the three iron atoms in the polyanion are of two types; the lower magnetic moments suggest the presence of anti-parallel coupling via iron d-orbitals overlap with the p-orbitals of the bridging oxygens. All compounds decompose atca. 600°C.     

Mixed complex formation of copper(II) with 2,2′, 2″-terpyridine and some tridentate ligands in aqueous solution

Summary The formation of copper(II) ternary complexes [Cu(tpy)(L)] (tpy = 2,2,2-terpyridine; L = oxydiacetate, thiodiacetate, iminodiacetate or dipicolinate) has been studied by potentiometric measurements in aqueous solution at 25° and I = 0.1 mol dm^–3 (NaNO₃ or NaClO₄). All the systems investigated also form protonated species of the [Cu(tpy)(L)H]⁺ type. The effect of the different heteroatoms (donor atoms) in the ligands L (i.e. O, S or N), other than oxygens of the carboxylic groups, on the stability of the mixed complexes has been evaluated and compared with the trends observed for the analogous complexes of copper(II) with 2,2-bipyridine (bpy).The stabilization of ternary complexes of copper(II) with respect to the different coordination levels is also discussed.     

Reactions of the dinitrogen complextrans-[ReCl(N2)(dppe)2] with thiolate compounds and with carbon bisulphide

Summary The complextrans-[ReCl(N₂)(dppe)₂], (1) reacts with the thiolate salts Li[SC₆H₄Me-4], Tl[SC₆H₄Me-4] and [Pb(SBu-t)₂] to yield [ReCl(SC₆H₄Me-4)(dppe)₂], [Re(SC₆H₄Me-4) (dppe)₂] and [{ReO(dppe)}₂(-Cl)(-S)(-SBu-t)] (tentative formulation), respectively. The [ReCl(²-CS₂)(dppe)₂] complex appears to be formed by reaction of (1) with CS₂.     

Synthesis,Structure, and Conduction of Trisubstituted Cesium and Rubidium Salts of Trimesic Acid

Salts of trimesic (1,3,5-benzenetricarboxylic) acid generally formulated as ₃[C₆H₃(COO)₃] · 5H₂O, where Me = Rb and Cs, are synthesized and their structure and conductivity are examined. Both salts are ionic conductors with conductivities of 4.6 × 10^–7 and 2.2 × 10^{–9 –1} cm^–1 at 298 K and activation energies of conduction equal to (1.09 ± 0.02) and (1.07 ± 0.01) eV, respectively.