Synthesis and structural characterization of [(μ-H)Ru3(CO)8{μ-S(CH2)3SH}(μ-dppe)] and [Ru3(CO)5{μ2-S(CH2)3S}2(η2-dppe)] (dppe=Ph2PCH2CH2PPh2)

The reaction of 1,3-propanedithiol with [Ru₃(CO)₁₀(μ-dppe)] (2) at 66°C afforded the thiolate complexes [(μ-H)Ru₃(CO)₈{μ-S(CH₂)₃SH}(μ-dppe)] (6) and [Ru₃(CO)₅{μ₂-S(CH₂)₃S}₂(η²-dppe)] (7) in 25 and 23% yields respectively. Compound 6 is formed by simple oxidative addition of one of the S–H bonds of 1,3-propanedithiol while the structurally unique 7 consists of an open triruthenium cluster with four terminal and one asymmetrically bridged carbonyl groups, two doubly bridged propanedithiolate ligands and a chelating dppe ligand.     

Synthesis,structure and calculated NLO properties of [(n-Bu)2Sn-μ-O-μ-OH-Sn(n-Bu)2(CH3CO2)]2 and its putative derivatives

Title compound[(n-Bu)₂Sn-μ-O-μ-OH-Sn(n-Bu)₂(CH₃CO₂)]₂ was obtained accidentally by the reaction of n-Bu₂SnCl₂ with the metalloligand K₂[Ni(CDC)₂] in ethanol - water mixture while synthesizing a heterobimetallic complex [n-Bu₂Sn Ni(CDC)₂]. This has been characterized by micro analysis, UV–Vis, ¹H, ¹³C and ¹¹⁹Sn NMR spectroscopy and the single crystal X-ray. The complex forms an interesting supramolecular architecture via (acetate)O?HO hydrogen bonding interactions which generates hydrophobic “pseudo-cage”. The electronic absorption bands of the title complex were assigned with the help of the time dependent density functional theory (TD-DFT) calculations. Density functional theory (DFT) calculations have been performed at the optimized molecular geometry of some of its putative derivatives e. g. trans p-amino cinnamic acid derivative 2; trans p-amino cinnamic acid and trans p-nitro cinnamic acid derivative 3; trans p-amino cinnamic acid and trans p-(N,N dimethylamino) cinnamic acid derivative 4. The first static hyperpolarizability (β) of the title compound and its derivatives were calculated with double numerical differentiation of total energies. The derivatives 3 and 4 showed three times and five times enhancement in the non-linear optical (NLO) responses than the standard p-nitroaniline (pNA).     

Phosphorus–carbon bond cleavage of Ph2PCH2PPh2 at a triruthenium center: synthesis and structural characterization of [Ru3(μ-CO)(CO)6(μ-PPh2)2(μ3-CH2PPh)]

The reaction of Ph₂PH with [Ru₃(CO)₁₀(μ-dppm)] (1) at 98°C gave [Ru₃(μ-CO)(CO)₆(μ-PPh₂)₂(μ₃-CH₂PPh)] (7) in 20% yield. Compound 7 was characterized by elemental analysis, ¹H and ³¹P{¹H} NMR and mass spectroscopic data and also by a single crystal structure determination. The compound is shown to consist of a triruthenium cluster with an unusual example of a triply bridging CH₂PPh ligand and two doubly bridging PPh₂ ligands.     

Unexpected fragmentation of the Fe3(CO)9(μ3-Se)(μ3-AsCH3) cluster core in the reaction with CpCo(CO)2: synthesis and structure of Fe3(CO)6(μ3-Se)(μ-AsCH3{CpFe(CO)2})2(μ-CO)

The [Fe₃(CO)₆(μ₃-Se)(μ-AsCH₃{CpFe(CO)₂})₂(μ-CO)] (Cp=η⁵-C₅H₅) cluster has been obtained by the reaction of [Fe₃(CO)₉(μ₃-Se)(μ₃-AsCH₃)] with [CpCo(CO)₂]. Its crystal and molecular structures have been determined by X-ray analysis.     

A 2D polymer constructed through bridging oxalato and 4,4′-bipyridine ligands: crystal structure and magnetic behavior of [Cu3(μ-ox)3(μ-4,4′-bpy)2(4,4′-bpy)2]n

The crystal structure of the compound [Cu₃(μ-ox)₃(μ-4,4^′-bpy)₂(4,4^′-bpy)₂]_n 1 (ox=oxalato, 4,4^′-bpy=4,4^′-bipyridine) is comprised of two-dimensional sheets in which copper(II)–oxalato chains are cross-linked by bridging bidentate 4,4^′-bpy ligands. Metal centers show a tetragonally elongated octahedral environment formed by four oxygen atoms from two asymmetrically coordinated oxalato ligands and two nitrogen atoms from two trans-coordinated 4,4^′-bpy molecules. The magnetic measurements show the occurrence of weak ferromagnetic couplings.     

A novel dirhenium(III) complex with bridging picolinate and methoxide ligands from the reaction between cis-Re2(μ-O2CCH3)2Cl4(H2O)2 and picolinic acid

The reaction of cis-Re₂(μ-O₂CCH₃)₂Cl₄(H₂O)₂ with picolinic acid (Hpic) affords either the diamagnetic, metal–metal bonded, dirhenium(III) complex Re₂(μ-OMe)(μ:η²-pic)(η²-pic)₃Cl (1) or the mononuclear rhenium(V) complex ReO(η²-pic)₂Cl (2), depending on whether mixed methanol/ethanol or acetone/ethanol solvent mixtures are used. The structures of 1 and 2 have been established by X-ray crystallography. Complex 1 is unusual in having a bridging methoxide and bridging picolinate ligand in an edge-sharing bioctahedral structure in which the Re–Re bond distance of 2.4588(4) Å is unusually short for what is a formal Re–Re double bond.     

Ring-opening polymerization of (CH3)2Si[CpMo(CO)3]2, a molecule with an –Si(CH3)2– bridge between two cyclopentadienyl ligands

The (CH₃)₂Si[CpMo(CO)₃]₂ complex (1) was synthesized and used to explore ring-opening polymerization (ROP) as a method to prepare high molecular weight polymers containing Mo–Mo bonds along their backbones. Attempts to initiate ROP of 1 using n-BuLi or PtCl₂ did not yield any polymers. The X-ray crystal structure of 1 shows that the Si center is not strained, and it is suggested that no ROP occurred because 1 is less strained than other organometallic ROP monomers, such as the silicon-bridged ferrocenophanes. Thermal ROP (TROP) of 1 was successful and yielded a polymer (M _w = 210,000 g mol⁻¹) containing both Mo–Mo single bonds and Mo≡Mo triple bonds. When CO_(g) is passed over the polymer in the solid state, the Mo≡Mo triple bonds are converted to Mo–Mo single bonds. Attempts to increase the yield of the TROP polymer by increasing the reaction times led to polymer decomposition. The decomposition is likely caused by the weakness of the Mo–Mo bond, cleavage of which causes the polymer to degrade.     

Semi-rigid N-para-ferrocenyl(benzoyl)amino-acid esters for biomaterials: synthesis and characterization of Fc-C6H4CONHCH(R)CO2Me where Fc = (η5-C5H5)Fe(η5-C5H4) and R=H,CH3,CH2CH(CH3)2,CH2C6H5 and the X-ray crystal structures of Fc-C6H4CO2Me and the l-alanine derivative Fc-C6H4CONHCH(CH3)CO2Me

A series of N-para-(ferrocenyl)benzoyl amino-acid esters, para-Fc(C₆H₄)CONHCH(R)CO₂CH₃ {Fc = (η⁵-C₅H₅)Fe(η⁵-C₅H₄); R = H, CH₃, CH₂CH(CH₃)₂, CH₂C₆H₅}, 3–6 have been prepared by coupling para-(ferrocenyl)benzoic acid to the amino-acid esters (gly, l-Ala, l-Leu, l-Phe) using the standard 1,3-dicyclohexylcarbodiimide (DCC), 1-hydroxybenzotriazole (HOBt) protocol. The compounds were fully characterized by a range of spectroscopic techniques including FAB-MS. The X-ray crystal structures of the parent para-(ferrocenyl)benzoyl methyl ester, Fc-C₆H₄CO₂Me, 1 and a chiral derivative N-{para-(ferrocenyl)benzoyl}-l-alanine methyl ester, Fc-C₆H₄CONHCH(CH₃)CO₂Me, 4 have been determined.     

(en)Mn2(V2O7): A 3D manganese vanadate built by Mn–O layers and two types of pillars of V2O7 and en bridges

An unexpected 3D manganese vanadate (en)Mn₂(V₂O₇) (1) (en = ethylenediamine) has been hydrothermally obtained by H₂E₂Ge₂O₃ (E = ? CH₂CH₂COO^?) ligands and well-prepared mixture of V–Mn-amine and characterized by IR spectroscopy, elemental analysis, thermal stability and powder X-ray diffraction. Single-crystal X-ray diffraction analysis reveals that the structure is a novel pillared-layer, in which MnO₅N octahedra are corner-linked to form an infinite sheet with 4-membered rings (MRs) and further condensed to the 3D framework. The most prominent feature of 1 is the connection between the sheets via double bridges, namely, inorganic V₂O₇ dimeric units and organic en molecules. It is noteworthy that inorganic and organic double bridges between sheets have not been seen in manganese vanadates.     

Synthesis and structure of an octanuclear oxothiomolybdenum(V) wheel with bridging hydrazine ligands encapsulating a central MoVIO4 tetrahedron, [MoV8S8O8(OH)7(N2H4)2MoVIO4]−

Reaction of hydrazine with the octanuclear mixed valence oxothioanion [Mo^V₈S₈O₈(OH)₈{HMo^VIO₅(H₂O)}]³⁻ has afforded the octanuclear anion [Mo^V₈S₈O₈(OH)₇(N₂H₄)₂{Mo^VIO₄}]⁻ as potassium salt. Its structure has been established by X-ray crystallography, showing that four of the hydroxo bridges have been replaced by μ₂-N₂H₄ ligands. Concomitantly the coordination of the central Mo^VI atom has changed from octahedral to tetrahedral. In the solid, the anionic rings are attached to double chains of potassium ions.     

Preparation of a new cobalt-containing diphosphine ligand and its reaction towards dicobalt octacarbonyl; X-ray crystal structure of [Co2(CO)4(μ-CO)2{μ-P,P-(μ-PPh2CCPPh2)Co2(CO)6}]

Consecutive reactions of bis(diphenylphosphino)acetylene with Co₂(CO)₈ resulted in an alkyne-bridged, diphosphine-chelated tetracobalt complex, [Co₂(CO)₄(μ-CO)₂{μ-P,P-(μ-PPh₂CCPPh₂)Co₂(CO)₆}] (2), which has been characterized by spectroscopic means as well as X-ray studies.     

[Ru(CO)(CH3CO2)(tpa)]ClO4·C6H5CH3 (tpa=tris(2-pyridylmethyl)amine), the first ruthenium carbonyl complex of tpa

The reaction of dodecacarbonyltriruthenium with tris(2-pyridylmethyl)ammonium perchlorate (tpa·3HClO₄), in the presence of acetic acid, afforded a new ruthenium complex of tpa, [Ru(CO)(CH₃CO₂)(tpa)]ClO₄·C₆H₅CH₃ (1). Compound 1 has been characterized by X-ray structural analysis, IR and ¹H NMR spectra.     

Ru4(μ-CO)(CO)9(η4-μ4-C6H4)(η2-μ1,μ4-PPhCH2CH2PPh2): an unusual pyrolysis product of Ru3(CO)10(dppe) containing a benzyne ligand

The thermal decomposition of Ru₃(CO)₁₀(dppe) in refluxing benzene gives, in contrast to the pyrolysis of the dppm analogue, the tetranuclear cluster Ru₄(μ-CO)(CO)₉(η⁴-μ₄-C₆H₄)(η²-μ₁,μ₄-PCH₂CH₂PPh₂) (1) along with Ru₃(CO)₉(η²-μ₁,μ₂-C₆H₅)(η³-μ₁,μ₂-PPhCH₂CH₂PPh₂) (2). The single-crystal structure analysis of 1 reveals a square-planar tetraruthenium skeleton containing a η⁴-μ₄-benzyne ligand as well as a η²-μ₁,μ₄-phosphinidene–phosphine ligand.     

Conversion of ethylene into ethylidyne on a mixed-metal cluster: synthesis and structure of IrRu4(CO)15(μ4-CCH3)

The thermal reaction of the tetranuclear cluster HIrRu₃(CO)₁₃ with ethylene in hexane (90°Cm 2bar) affords, in addition to H₃IrRu₃(CO)₁₂, the pentanuclear cluster HIrRu₄(CO)₁₅(μ₄-CCH₃) (1) in which the ethylidyne ligand is coordinated through a carbon atom to the four ruthenium atoms in the IrRu₄ core. In this reaction, the CH₂CH₂ molecule has been transformed into a CCH₃ moiety coordinated as a μ₄-ligand to the cluster.     

The first complex of the pentameric phosphazane macrocycle [{P(μ-NtBu)}2(μ-NH)]5 with a neutral molecular guest: Synthesis and structure of [{P(μ-NtBu)}2(μ-NH)]5(CH2Cl2)2

The reaction of [{P(μ-N^tBu)}₂(μ-NH)}₅I]⁻[Li(thf)₄]⁺([1 · I]⁻[Li(thf)₄]⁺) with NaOMe in CH₂Cl₂ gives the title compound [{P(μ-N^tBu)}₂(μ-NH)]₅(CH₂Cl₂)₂ [1 · (CH₂Cl₂)₂] the first adduct containing this type of macrocyclic phosph(III)azane host and a neutral guest.     

Two novel three-dimensional coordination polymers with [Ag(CN)2]− as bridging ligands: synthesis and structural characterization of {KMn[Ag(CN)2]3(H2O) }n and {Mn[Ag(CN)2]2(bpy)2}n (bpy=4,4′-bipyridine)

Two novel three-dimensional coordination polymers {KMn[Ag(CN)₂]₃(H₂O)}_n 1 and {Mn[Ag(CN)₂(bpy)]₂}_n 2 have been prepared and structurally as well as magnetically characterized. In both compounds, the three-dimensional networks are constructed entirely by coordinative linkages with all the CN⁻ anions of [Ag(CN)₂]⁻, bpy and water ligands involved in bridging and the novel 3-D structure of 1 is unprecedented.     

Variations in binding modes of 2-mercaptobenzoxazolates in the novel cyclic trinuclear complexes [Mn3(CO)10(μ-SCNOC6H4)3] and [Re3(CO)12(μ-SCNOC6H4)3]

From reactions of [M₂(CO)₈(MeCN)₂] (MMn, Re) with 2-mercaptobenzoxazol, trinuclear clusters [Mn₃(CO)₁₀(μ-SCNOC₆H₄)₃] and [Re₃(CO)₁₂(μ-SCNOC₆H₄)₃] have been isolated; the former contains 2-mercaptobenzoxazolate ligands in three different binding modes, while in the latter all three bridge rhenium centres by S,N-coordination, but the three rhenium atoms all have different coordination environments.     

Adsorption of Off‐Gases from Steam Methane Reforming (H2, CO2, CH4, CO and N2) on Activated Carbon

Abstract

Hydrogen is the energy carrier of the future and could be employed in stationary sources for energy production. Commercial sources of hydrogen are actually operating employing the steam reforming of hydrocarbons, normally methane. Separation of hydrogen from other gases is performed by Pressure Swing Adsorption (PSA) units where recovery of high‐purity hydrogen does not exceed 80%.

In this work we report adsorption equilibrium and kinetics of five pure gases present in off‐gases from steam reforming of methane for hydrogen production (H₂, CO₂, CH₄, CO and N₂). Adsorption equilibrium data were collected in activated carbon at 303, 323, and 343 K between 0‐22 bar and was fitted to a Virial isotherm model. Carbon dioxide is the most adsorbed gas followed by methane, carbon monoxide, nitrogen, and hydrogen. This adsorbent is suitable for selective removal of CO₂ and CH₄. Diffusion of all the gases studied was controlled by micropore resistances. Binary (H₂‐CO₂) and ternary (H₂‐CO₂‐CH₄) breakthrough curves are also reported to describe the behavior of the mixtures in a fixed‐bed column. With the data reported it is possible to completely design a PSA unit for hydrogen purification from steam reforming natural gas in a wide range of pressures.