Photoluminescence of [Pt(C3Ph3)Ln]PF6 with L = phenylphosphine ligands. Emission from a (Pt0 to C3Ph3+) MLCT triplet

The complex cations [Pt⁰(C₃Ph₃)(PPh₃)₂]⁺ and [Pt⁰(C₃Ph₃)(tripod)]⁺ with tripod = CH₃C(CH₂PPh₂)₃ contain the smallest Hückel aromat C₃R₃⁺ (with n = 0) as ligand. Since this cation is a CT acceptor, the complexes are characterized by low-energy (Pt⁰ to C₃Ph₃⁺) MLCT states. The complexes show a photoluminescence which originates from the lowest MLCT triplet.     

Preparation,Crystal Structure,Thermal Decomposition,and Explosive Properties of [Cd(en)(N3)2]n

A new multi‐ligand coordination polymer of cadmium(II) ethylenediamine azide, [Cd(en)(N₃)₂]_n (en=ethylenediamine), was synthesized and characterized by using elemental analysis and FT‐IR spectrum. Its crystal structure was determined by means of X‐ray single crystal diffraction. The obtained results show that this crystal belongs to monoclinic, P2₁/n space group, a=0.6548(1) nm, b=1.0170(2) nm, c=1.2246(2) nm, β=90.23(1)°, V=0.8156(2) nm³, D_c=2.090 g⋅cm⁻³, Z=4, R₁=0.024, wR₂ (I>2σ(I))=0.0416 and S=0.998. The Cd(II) ion is six‐coordinated with four azido ligands by μ‐1, 1 azido bridges, and two ethylenediamine molecules which serve as bidentate ligands through the nitrogen atoms. The thermal decomposition mechanism of the title complex was studied by using differential scanning calorimetry (DSC) and thermogravimetry‐differential thermogravimetry (TG–DTG) techniques. Under nitrogen atmosphere with a heating rate of 10 K⋅min⁻¹, the thermal decomposition of the complex contains two main successive exothermic processes between 519 and 701 K in the DSC curve, and the final decomposed residue at 725 K is Cd. The non‐isothermal kinetics parameters were calculated by using the Kissinger's method, Ozawa–Doyle's method, pervasive integration method, and differential method, respectively. The sensitivity properties of [Cd(en)(N₃)₂]_n were also determined with standard methods.     

Reduction of n-C5H11N3 Catalyzed by [Mo2Fe6S8(OMe)3(SC6H4-p-n-C8H17)6]3– in an Aqueous Micellar Solution

Reduction of n-C₅H₁₁N₃ by Na₂S₂O₄ was performed in the presence of (n-Bu₄N)₃ [Mo₂Fe₆S₈(OMe)₃(SC₆H4-p-n-C₈H₁₇)₆] ((n-Bu₄N)₃ [Mo-Fe]) as a catalyst in aqueous Triton X-100 micellar solutions. The rate of the reduction is enhanced efficiently by the addition of methyl viologen (MV²⁺). The methyl viologen radical cation (MV⁺) produced by the reaction of MV²⁺ with Na₂S₂O₄ undergoes a disproportionation reaction to afford MV²⁺ and MV° in the micellar solution. The resultant MV° formed in the micelle transfers two electrons to [Mo-Fe]³⁻ effectively to give [Mo-Fe]⁵⁻, which reduces n-C₅H₁₁N₃ with two electrons to produce n-C₅H₁₁NH₂ and N₂.     

Decavanadate with a novel coordination complex: Synthesis and characterization of (NH4)2[Ni(H2O)5(NH3)]2(V10O28)·4H2O

A new compound (NH₄)₂[Ni(H₂O)₅(NH₃)]₂[V₁₀O₂₈]·4H₂O (1) containing a {V₁₀O₂₈} ⁶⁻ anionic cluster and a novel complex cation, [Ni(H₂O)₅(NH₃)]^2 +, has been synthesized and fully characterized by single crystal X-ray crystallography, spectroscopy and thermogravimetric analysis. The presence of the ammonia ligand in the complex cation in 1 was established unambiguously by X-ray crystallography and variable temperature (200–400 °C) thermogravimetric analyses in combination with FTIR spectroscopic studies. The formation of the novel complex species {Ni(H₂O)₅(NH₃)}^2 + during the synthesis of 1 can be rationalized in terms of ligand substitution involving {Ni(H₂O)₆}^2 +.     

[Fe(SCN)2(bipy)2]·2(S8): A two-dimensional coordination polymer intercalating the S8 molecules

A new coordination polymer compound [Fe(SCN)₂(bipy)₂]·2(S₈) (1) (bipy = 4,4′-bipyridine) has been synthesized by the reaction of the bifunctional ligand bipy, Fe(SCN)₂ and sulfur powder under hydrothermal conditions. The compound has been characterized by single and powder X-ray diffraction analysis, infrared spectroscopy and elemental analysis. Compound 1 features a two-dimensional layered structure with neutral S₈ molecules confined in between layers. The magnetic property studies of 1 indicated antiferromagnetic interactions.     

Synthesis, Characterization and Thermogravimetric Analysis of Two Dicyclohexyl-18-crown-6 Pd, Pt Isomaleonitriledithiolate Complexes

Two organic–inorganic hybrid dicyclohexyl-18-crown-6 complexes, [K(DC18C6-B)]₂[Pd(i-mnt)₂] (1) and [K(DC18C6-A)]₂[Pt(i-mnt)₂] (2) (DC18C6-A=cis-syn-cis-dicyclohexyl-18-crown-6, A isomer; DC18C6-B = cis-anti-cis-dicyclohexyl-18-crown-6, B isomer; i-mnt=1,1-dicyanoethene-2,2-dithiolate, isomaleonitriledithiolate), were synthesized by the reaction of dicyclohexyl-18-crown-6 with K₂(i-mnt) and PdCl₂ or K₂PtCl₄ respectively. These were characterized by elemental analysis, FT–IR, UV–Vis spectroscopy and single crystal X-ray diffraction. In complex 1, two [K(DC18C6-B)]⁺ complex cations and one [Pd(i-mnt)₂]²⁻ complex anion formed a neutral molecule through two K–N coordination bonds. The resulting molecule adopted a 1D chain arrangement via K N weak interactions. Complex 2 showed a 1D chain-like structure that was assembled by two [K(DC18C6-A)]⁺ complex cations and one [Pt(i-mnt)₂]²⁻ complex anion through N–K–N interactions. An erratum to this article can be found at     

A new polymeric chain in the dihydrogendecavanadate(V)–decavanadate(V) [NH2(CH2)4]5[V10O28H2]0.5[V10O28]0.5 obtained by in situ synthesis of the organic cation

A new polymeric compound, [NH₂(CH₂)₄]₅[V₁₀O₂₈H₂]_0.5[V₁₀O₂₈]_0.5, was obtained by in situ synthesis of the organic cation from an aqueous solution of V₂O₅–HCl–NH₂(CH₂)₄NH₂. The crystal structure was solved by single-crystal X-ray diffraction. [NH₂(CH₂)₄]₅[V₁₀O₂₈H₂]_0.5[V₁₀O₂₈]_0.5 consists of dihydrogendecavanadate(V), [H₂V₁₀O₂₈]^4?, and decavanadate(V), [V₁₀O₂₈]^6?, units assembled in one-dimensional arrays by interanionic hydrogen bonds O–H?O and cation-anion N–H?O interactions. The latter involve pyrrolidinium cations, which were obtained in the compound instead of the starting butane-1,4-diamine. Pyrrolidinium cations further connect the polymeric chains into a three-dimensional network. The presence of the two types of units, [H_nV₁₀O₂₈]^(6?n)? with n = 0 and n = 2, in one compound was not yet observed and is herein reported for the first time.     

WGSR catalyzed by cis-[Rh(CO)2(amine)2]PF6 heterogenised on poly(4-vinylpyridine)

This paper describes catalytic activation studies of the water–gas shift reaction by cis-[Rh(CO)₂(amine)₂]PF₆ (amine = 4-picoline, 3-picoline, 2-picoline, pyridine, or 2,6-lutidine) heterogenised on poly(4-vinylpyridine) in aqueous 2-ethoxyethanol. The effect of varying the nature of the amine was investigated. The rhodium complexes bearing 4-picoline (4-pic) ligands proved to be most active among those surveyed, and displaying turnover frequencies for hydrogen production of 8.9 mol of H₂ per mole of Rh per day for 9.4x10^-5 mol cis-[Rh(CO)₂(4-pic)₂]PF₆/1.00 g poly(4-vinylpyridine), P(CO) = 0.9 atm at 100°C. This revised version was published online in July 2006 with corrections to the Cover Date.     

Synthesis,crystal structure and water-induced reversible crystal-to-amorphous transformation property of [Co2(2,4-pydc)2(bpa)(H2O)6](H2O)2

The dinuclear Co^II coordination compound with empirical formula [Co₂(2,4-pydc)₂(bpa)(H₂O)₆](H₂O)₂ (1); bpa = 1,2-bis(2,4-pyridyl)ethane, 2,4-pydc = 2,4-pyridinedicarboxylate anion, has been synthesized and õcharacterized by elemental analysis, single crystal X-ray diffraction, IR and UV–vis spectra, TGA and XRPD. Compound 1 is a symmetry-related dinuclear compound consisting of two six coordinated cobalt atoms, one bpa ligand, two 2,4-pydc ligands and two lattice water molecules. Each Co^II ion is coordinated by one oxygen atom and one nitrogen atom from 2,4-pydc bidentate chelate ligand, one nitrogen atom of bpa bidentate bridging ligand and three water molecules, giving a distorted octahedral geometry with CoN₂O₄ chromophore. The crystal packing of this compound reveals a novel 3D supramolecular network, formed by hydrogen-bonding and C–H⋯π interactions. Investigations of the dynamic structural transformation behavior demonstrate that the title compound exhibits a solvent-induced reversible crystal-to-amorphous transformation with chromotropism when exposed to water vapor. This indicates that the dehydrated amorphous form, Co₂(2,4-pydc)₂(bpa)(H₂O)₂ (1A), may be utilized as an indicator for humidity.     

A new 2D HgII coordination polymer containing novel coordination mode of 2,5-bis(4-pyridyl)-1,3,4-oxadiazole (bpo) ligand, [Hg(μ-bpo)2(N3)2]n: Spectroscopic,thermal, fluorescence and structural studies

A new two-dimensional Hg^II coordination polymer containing 2,5-bis(4-pyridyl)-1,3,4-oxadiazole (bpo) and azide anions, [Hg(μ-bpo)₂(N₃)₂]_n, has been synthesized and characterized by elemental analysis, IR-, ¹H NMR-, ¹³C NMR spectroscopy and structurally determined by X-ray single-crystal diffraction. The thermal stability of compound [Hg(μ-bpo)₂(N₃)₂]_n was studied by thermal gravimetric (TG) and differential thermal analyses (DTA). The single-crystal X-ray data shows that ligand bpo is bridged via one pyridyl nitrogen and one oxadiazole nitrogen atom, as a novel coordination mode of the ligand bpo. Furthermore, the ligand and complex are luminescent in the solid state, with emission maxima in the visible light region (λ_max = 470 nm for both bpo and [Hg(μ-bpo)₂(N₃)₂]_n).     

An unprecedented mixed valence cobalt(III)/cobalt(II) ion-pair complex ([CoCO3(bipy)2]2[Co(DCA)2]⋅16H2O) with two novel water tapes

An unprecedented mixed valence cobalt(III)/cobalt(II) ion-pair complex, [CoCO₃(bipy)₂]₂[Co(DCA)₂]⋅16H₂O (1) [bipy = 2,2′-bipyridine, DCA = demethylcantharidate, exo-1,4-epoxy-cyclohexyl-2,3-dicarboxylate group, (C₈H₈O₅)^2 −], has been synthesized and characterized by elemental analysis, IR, UV–vis, Thermogravimetric analysis (TGA) and single crystal X-ray diffraction. The crystal structure of 1 consists of three independent molecular moieties: [CoCO₃(bipy)₂]⁺, [Co(DCA)₂]^2–, and water molecules of crystallization. Interestingly, two novel water tapes, one comprises of alternate cyclic water tetramer and octamer, the other is constructed by alternate cyclic water hexamer and carboxylate–water hybrid octamer [(H₂O)₂(COO)₂]^2 −, have been detected for the first time in the host framework of 1. The two novel water tapes are linked together by the DCA and carbonate ligands via hydrogen bonds into a 2D water layer, and then the water layers assemble complex ions ([CoCO₃(bipy)₂]⁺ and [Co(DCA)₂]^2 −) through hydrogen bonds, π–π interactions and electrostatic interactions to form the overall 3D metal–organic framework structure.     

Synthesis of palladium clusters with surface initiator for polymerization of 2-methyl-2-oxazoline

Summary Palladium clusters were synthesized by reduction of palladium(II) acetate in the presence of a bipyridyl ligand (1) with an initiator for polymerization of 2-methyl-2-oxazoline. The 1-protected palladium clusters were soluble in CHCl₃ and CH₂Cl₂. The 1-protected palladium clusters were combined with 2-methyl-2-oxazoline in chloroform. After polymerization, the reacted bipyridyl ligand was removed from the palladium cluster by suspending the obtained palladium clusters with pyridine. The ¹H NMR measurement indicated that the reacted bipyridyl ligand was formed via surface polymerization of 2-methyl-2-oxazoline. Received: 19 April 2001/Accepted: 2 May 2001     

Observation of [Al(OH) n (H2O)6-n ] n (MoO4) in hydrotreating catalyst precursors by solid-state27 Al NMR

A previously unobserved octahedral²⁷Al MAS NMR resonance has been detected in rehydrated calcined Mo/Al₂O₃ hydrotreating catalyst precursors. This resonance is attributed to the presence of hydrated forms of aluminum molybdate such as [Al(OH) _n (H₂O)_6-n ] _n (MoO₄) (n = 1 or 2). The cross-polarization relaxation parameters, obtained from variable contact time experiments, yielded information on the relative sizes of the [Al(OH) _n (H₂O)_6-n ] _n (MoO₄) domains in the catalysts with different molybdenum loadings. Analysis of the²⁷A1 MAS NMR spectra of P-Mo(8)/Al₂O₃ and P-Mo(12)/Al₂O₃ (wt%P = 0.0–12.0) shows that a function of the phosphate in the 12 wt% Mo catalyst is to prevent the re-hydration of the molybdate phases on the calcined catalysts.     

Co-polymerization of propylene oxide and CO2 using early transition metal (groups IV and V) metallocalix[n]arenes (n = 4, 6, 8)

A number of metallocalix[n]arenes, where n = 4, 6, or 8, of titanium and vanadium have been screened for their ability to act as catalysts for the co-polymerization of propylene oxide and CO₂ to form cyclic/polycarbonates. The vanadium-containing catalysts, namely [VO(L¹Me)] (1), [(VO₂)L²H₆] (2), [Na(NCMe)₆]₂[(Na[VO]₄L²)(Na(NCMe))₃]₂ (3), [VO(μ-OH)L^3/H₂]₂∙6CH₂Cl₂ (4), {[VO]₂(μ-O)L⁴[Na(NCMe)₂]₂} (5), {[V(Np-tolyl)]₂L⁴} (6) and [V(Np-RC₆H₄)Cl₃] (R = Cl (7), OMe (8), CF₃ (9)), where L¹H₃ = methylether-p-tert-butylcalix[4]areneH₃, L²H₈ = p-tert-butylcalix[8]areneH₈, L³H₄ = p-tert-butylthiacalix[4]areneH₄, L⁴H₆ = p-tert-butyltetrahomodioxacalix[6]areneH₆, performed poorly, affording, in the majority of cases, TONs less than 1 at 90°C over 6 h and low molecular weight oligomeric products (M_n ≤ 1665). In the case of the titanocalix[8]arenes, {(TiX)₂[TiX(NCMe)]₂(μ₃-O)₂(L²)} (X = Cl (10), Br (11), I (12)), which all adopt a similar, ladder-type structure, the activity under the same conditions is somewhat higher (TONs >6) and follows the trend Cl > Br > I; by comparison the non-calixarene species [TiCl₄(THF)₂] was virtually inactive. In the case of 10, it was observed that the use of PPNCl (bis[triphenylphosphine]iminium chloride) as co-catalyst significantly improved both the polymer yield and molecular weight (M_n 3515). The molecular structures of the complexes [HNEt₃]₂[VO(μ-O)L³H₂]₂∙3CH₂Cl₂ (4∙3CH₂Cl₂), [VO(μ-OH)L^3/H₂]₂∙6CH₂Cl₂ (4^/) (where L^3/H₂ is a partially oxidized form of L³H₄) and {(TiCl)₂[TiCl(NCMe)]₂(μ₃-O)₂(L²)}·6.5MeCN (10·6.5MeCN) are reported.     

Synthesis, characterization and crystal structure of cis,mer-[ReH(CO)2{PPh(OMe)2}3]

The dicarbonylhydride complex cis,mer-[ReH(CO)₂{PPh(OMe)₂}₃] (1) was serendipitously obtained when, in an attempt to replace a CO ligand by the phosphonite ligand PPh(OMe)₂ in [ReH(CO)₃(L)] (L = PPh₂OCH₂CH₂OPPh₂), this complex was treated with PPh(OMe)₂ under UV irradiation. The complex 1 was characterized by IR, ¹H and ³¹P{¹H} NMR spectroscopy and by crystal structure determination. The spectroscopic features are consequent with the cis,mer configuration showed by the X-ray crystallographic analysis of the complex. The environment of the metal centre is a distorted octahedron.     

Interfacial tension between aluminum and cryolite melts during electrolysis of the systems Na3AlF6–AlF3 (NaF)–Al2O3

The interfacial tension between aluminum and cryolite melts containing different salt additions has been measured by the capillary depression method. The technique is based on the measurement of the capillary depression occurring when the capillary, which is moved vertically down through the molten salt layer, passes through the salt/metal interface. The depression is measured by simultaneous video recording of the immersion height of the alumina capillary. The interfacial tension was found to be strongly dependent on the n(NaF)/n(AlF₃) ratio (cryolite ratio, CR). At the cryolite ratio 2.28 (80 wt.% Na₃AlF₆ + 10 wt.% AlF₃ + 10 wt.% Al₂O₃ // Al, t = 1000 °C) the interfacial tension was 546 mN m⁻¹, while it was 450 mN m⁻¹ at the cryolite ratio 4.43 (80 wt.% Na₃AlF₆ + 10 wt.% NaF + 10 wt.% Al₂O₃ // Al, t = 1000 °C). Experiments under current flow conditions were also performed. During the electrolysis the interfacial tension at n(NaF)/n(AlF₃) ratio 2.28 decreased from 546 mN m⁻¹ at zero current to 518 mN m⁻¹ at 0.112 A cm⁻². The same trend was observed in the system with a cryolite ratio 4.43. The interfacial tension decreased from 450 mN m⁻¹ at zero current to 400 mN m⁻¹ at 0.112 A cm⁻². The consequent increase in interfacial tension of these systems caused by interruption of electrolysis was observed. Electrolysis of the system 25 wt.% NaF + 75 wt.% NaCl (eutectic mixture)/Al indicated no influence of applied current on the interfacial tension at 850 °C.     

Synthesis of aromatic carboxyl functionalized polymers by atom transfer radical polymerization

The synthesis of aromatic carboxyl functionalized polymers by atom transfer radical polymerization is described. The α‐bromo‐p‐toluic acid ( 1 ) initiated polymerization of styrene in the presence of copper(I) bromide and 2,2′‐bipyridyl affords quantitative yields of the corresponding aromatic carboxyl functionalized polystyrene ( 2 ). Polymerization proceeded via a controlled free radical process to afford quantitative yields of the corresponding aromatic carboxyl functionalized polymers with predictable molecular weights (M_n = 1600–25 900 g mol⁻¹), narrow molecular weight distribution (M_w /M_n = 1.1–1.40) and an initiator efficiency above 0.87. The polymerization process was monitored by gas chromatographic analysis. The functionalized polymers were characterized by thin layer chromatography, size exclusion chromatography, spectroscopy, potentiometry and elemental analysis. © 2000 Society of Chemical Industry     

An unprecedented 2D isopolymolybdate with (3·4)(3·5·8)(3·4·5·6·8)(3·4·5·6) topology

A novel two-dimensional molybdenum oxide polymer, [Mo₄O₁₃]_n · 2nH₃O, has been prepared under specific hydrothermal conditions and characterized by IR spectroscopy and TG analysis. Single-crystal X-ray diffraction analysis reveals that compound 1 exhibits a (3, 4, 5, 6)-connected 2D layer structure with (3²·4)(3²·5³·8)(3·4²·5⁴·6·8²)(3⁴·4³·5⁴·6⁴) topology, which is constructed by two parallel molybdenum oxide dimeric chains (Mo₂O₁₀)_n bound together by the dimer of Mo₂O₉ subunits via the sharing of corners. Additionally, the electrochemistry activity of compound 1 is also reported.     

Synthesis,spectral and antibacterial studies on Ni(II) and Zn(II) complexes involving N-furfuryl-N-isopropyldithiocarbamate (f iprdtc) and Lewis bases: X-ray structure of [Ni(f iprdtc)(NCS)(PPh3)]

[Ni(fⁱprdtc)₂] (1), [Ni(fⁱprdtc)(PPh₃)(NCS)] (2), [Ni(fⁱprdtc)(PPh₃)₂]ClO₄ (3), [Zn(fⁱprdtc)₂] (4), [Zn(fⁱprdtc)₂(1,10-phen)] (5) and [Zn(fⁱprdtc)₂(2,2′-bipy)] (6) (f ⁱprdtc=N-furfuryl-N-isopropyldithio- carbamate, 1,10-phen=1,10-phenanthroline and 2,2′-bipy=2,2′-bipyridine) complexes were prepared and characterized by elemental analysis, electronic, IR and NMR spectra and the structure of 2 was determined by single-crystal X-ray crystallography. UV–Vis spectral data of 1–3 are consistent with the formation of square planar complexes. IR spectra of the complexes show the contribution of the thioureide form to the structure. A single-crystal X-ray structural analysis of 2 proved four-coordinated nickel in a distorted square planar arrangement with a S₂PN donor set. Significant asymmetry in Ni–S bond distances was observed in [Ni? S1=2.1655(8); Ni? S2=2.2120(8) Å]. This observation clearly supports the less effective trans of SCN^? over PPh₃. The observed shielding in N¹³CS₂ chemical shifts of heteroleptic nickel complexes 2 and 3 when compared with homoleptic nickel complex 1 indicates the effect of PPh₃ on the mesomeric drift of electron density toward nickel through the thioureide C? N bond. The N¹³CS₂ chemical shift of 5 and 6 are additionally deshielded compared with 4 owing to the increase in coordination number. Complexes were screened for in vitro antibacterial activity and significant activity has been found.