Three one-dimensional nickel coordination polymers (CPs) based on P,P'-diphenylethylenediphosphinic acid and three different bis-pyridine coligands, namely, 4,4'-bipyridine (bipy), 1,2-bis(4-pyridyl)ethane (bpy-ane), and 1,2-bis(4-pyridyl)ethylene (bpy-ene), were prepared in mild hydrothermal conditions from water solutions containing the dissolved reagents. The CPs have the formula [Ni(H2O)(4)(bipy)center dot pc(2)p](n) (1), [Ni(H2O)(4)(bpy-ane)center dot pc(2)p](n) (2), and [Ni(H2O)(4)(bpy-ene)center dot pc(2)p](n) (3), and their structural features were investigated by single crystal X-ray diffraction, UVvis, Fourier transform infrared spectroscopies, and magnetic measurements. They are constituted of infinite Ni(H2O)(4)(bis-pyridine) one-dimensional rows connected, through hydrogen bonds, with the phosphinic acids placed among adjacent rows. Although the formulas and the structural topologies of the three compounds are almost identical, they behave in different manners upon heating. Compound 1 yields an amorphous phase when water molecules are thermally removed, whereas compound 3 undergoes interesting phase transformations derived from the connection of Ni atoms with the phosphinates oxygen atoms, increasing the dimensionality to three-dimensional and maintaining crystallinity. The behavior of compound 2 has some analogies to that of 3, although a complete structural characterization was not performed because of a significant crystallinity loss of the heated phase. The structural features were studied by means of a combination of variable temperature single crystal and powder X-ray diffraction and thermogravimetric analysis. The reason for these different behaviors was ascribed to both the length and the flexibility degree of the nitrogenated coligands.

Three 1D nickel coordination polymers (CPs) based on P,P’-diphenylethylenediphosphinic acid and three different bis-pyridine co-ligands, namely 4,4’-bipyridine (bipy), 1,2-bis(4-pyridyl)ethane (bpyane) and 1,2-bis(4-pyridyl)ethane (bpy-ene), were prepared in mild hydrothermal conditions from water solutions containing the dissolved reagents. The CPs have formula [Ni(H2O)4(bipy)·pc2p]n (1),[Ni(H2O)4(bpy-ane)·pc2p]n (2), and [Ni(H2O)4(bpy-ene)·pc2p]n (3) and their structures were characterized by single crystal X-ray diffraction. They are constituted of infinite Ni(H2O)4(bis-pyridine) 1D rows connected, through hydrogen bonds, with the phosphinic acids placed among adjacent rows. Although the formulas and the structural topologies of the three compounds are almost identical, they behave in different manners upon heating. Compound 1 yields an amorphous phase when water molecules are thermally removed, whereas compound 3 undergoes interesting phase transformations derived from the connection of Ni atoms with the phosphinates oxygen atoms, increasing the dimensionality to 3D and maintaining crystallinity. The behavior of compound 2 has some analogies to that of 3 although a complete structural characterization was not performed because of a significant crystallinity loss of the heated phase. The structural features were studied by means of combination of variable temperature (VT) single crystal and powder X-ray diffraction and thermogravimetric analysis.

We have reported several 1D, 2D and 3D coordination polymers based on diphosphinic acid (pcp= P,P'diphenylmethylenediphosphate or pc2p= P,P'-diphenylethylenediphosphate) and in some cases we have described crystalcrystal transformation induced by temperature and by water [1].For instance the Metal Organic NanoTube (MONT) [[Cu2(bpye) (pcp)2] 2.5H2O]n (bpye = 1,2-bis(4-pyridyl)ethane)) is converted in the 1D slab[Cu2(bpye)(pc2p)2](H2O)]n in water while the isostructural MONT [[Cu2(bipy)(pcp)2] 5H2O]n (bipy = (4, 4' bi-pyridine)) remain unaltered.[2]In this work, we report the different behaviour, under heating, of three 1D coordination polymers, namely [Ni(H2O)4(bipy)•pc2p]n, 1, [Ni(H2O)4(bpye)•pc2p]n, 2, and [Ni(H2O)4(bpe)•pc2p]n, 3 (bpe = 1,2-bis(4-pyridyl)ethene)).For 1, only an amorphous phase was obtained, while in case of 2 an anhydrous crystalline 3D coordination polymer was detected.Finally for 3, we have obtained a monohydrated [Ni(H2O)(bpe)pc2p]n and an anhydrous [Ni(bpe)pc2p]n phase.An interpretation based on the length of the bipyridine as well as on the role of supramolecular interactions will be given.

Given the ability of forming homomeric amide(...)amide dimer by iso-nicotinamide (nda), we postulate the existence of a hydrogen bond equivalent of the iso-reticular metal organic nanotubes (MONT) built by using copper, p,p-diphenylmethylene-diphosphinate (pcp), and bipyridine. We obtained the desired primary arrangement of Cu/pcp/nda consisting of a 1-D chain. Instead of the expected amide/amide dimer, the NH2 groups were engaged in H-bonding networks with the phosphinate ligands in a series of 2-D slabs. The differences and the similarities of the Cu/pcp chains in known MONTs and in the reported structure are also highlighted.

The impregnation of Ketjen Black (C) with iron and cobalt phthalocyanines (MPc) taken one by one or as a 1:1 stoichiometric mixture, followed by heat treatment at 600 degrees C under inert atmosphere, gave materials containing arrays of single metal ions coordinated by four nitrogen atoms (M-N-4 units). Increasing the pyrolysis temperature to 800 degrees resulted in the formation of carbon-supported, nanosized metal particles. A key role of the carbon support in determining the material structure at either temperature investigated was demonstrated by TPD, EXAFS, XANES and XRPD studies. These also showed that a Fe-Co alloy is obtained at 800 degrees C when the impregnation of Ketjen Black involves a mixture of FePc and CoPc. Electrodes coated with the different Fe, Co and Fe-Co materials, containing ca. 3 wt% metal loadings, were scrutinized for the oxygen reduction reaction (ORR) in alkaline media by linear sweep voltammetry. For comparative purposes, two Pt electrocatalysts containing 3 and 20 wt% metal were investigated. The electrochemical activity of all materials was analyzed by Tafel and Koutecky-Levich plots as well as chronopotentiometry. The Fe-containing electrocatalysts have been found to be highly active for the ORR in alkaline media with convective limiting currents as high as 600 A g Fe-1 at room temperature and onset potentials as high as 1.02 V vs. RHE. It has been found that (i) the ORR mass activity of the Pc-derived electrocatalysts is superior to that of the Pt catalysts investigated; (ii) the activity of FePc and FePc-CoPc/C, heat treated at either 600 or 800 degrees C, is superior to that of the corresponding Co materials; (iii) the electrocatalysts obtained at 600 degrees C are fairly more active than those obtained at 800 degrees C. (C) 2010 Elsevier B.V. All rights reserved.

The selective production of chemicals from biomasses with contemporaneous release of energy can be accomplished for a variety of renewable alcohols by means of direct fuel cells in alkaline environment In such devices, on anode electrocatalyst based on nanosized Pd particles, alone or promoted by Ni-Zn phases, promotes the partial oxidation of the alcohol to the corresponding carboxylate The direct alcohol fuel cells described in this report are able to provide power densities up to 60 mW cm(-2) at room temperature and up to 160 mW cm(-2) at 80 degrees C.

The catalytic hydrogenation of 1,10-phenanthroline (Phen) or 2,9-dimethyl-1,10-phenanthroline (DMPhen) has been achieved using silica-supported palladium nanoparticles (Pd/SiO2) with metal contents of 1.98 or 9.95wt%. With either catalyst, the hydrogenation regiochemistry has been effectively controlled by the reaction temperature. The catalyst with the higher metal content was selective for the hydrogenation of one heterocyclic ring of either substrate at 80°C and for both external rings at 130°C for Phen and at 160°C for DMPhen. The catalyst with the lower metal content was more active and exhibited comparable selectivity.

The complex [Rh(cod)(dppp)]OTf (Rh(cod)) has been immobilized onto silica-supported palladium nanoparticles (Pd/SiO2) via a dual H-bond/ionic interaction (dppp = 1,3-bis(diphenylphosphino)propane; cod = cycloocta-1,5-diene). The product obtained, Rh(cod)-Pd/SiO2, has been employed to catalyze the hydrogenation of benzene to cyclohexane, showing much higher activity as compared to Pd/SiO2, while Rh(cod) grafted on, bare silica (Rh(cod)/SiO2) is totally inactive. The catalyst generated by Rh(cod)-Pd/SiO2 exhibits a remarkable stability and can be recycled several times with no loss of activity, even if exposed to air. In situ and ex situ EXAFS and DRIFTS measurements, batch catalytic reactions under different conditions, deuterium labeling experiments, and model organometallic studies, taken altogether, have provided valuable mechanistic information. The reduction of benzene to cyclohexa-1,3-diene occurs with the cooperation of the two metals, while the rhodium single sites are more effective than the palladium nanoparticles in the hydrogenation of cyclohexa-1,3-diene to cyclohexane.

The complex Rh(cod)(sulfos) (Rh(I); sulfos = (-)O(3)S(C(6)H(4))CH(2)C(CH(2)PPh(2))(3); cod = cycloocta-1,5-diene), either free or supported on silica, does not catalyze the hydrogenation of benzene in either homogeneous or heterogeneous phase. However, when silica contains supported Pd metal nanoparticles (Pd(0)/SiO(2)), a hybrid catalyst (Rh(I)-Pd(0)/SiO(2)) is formed that hydrogenates benzene 4 times faster than does Pd(0)/SiO(2) alone. EXAFS and DRIFT measurements of in situ and ex situ prepared samples, batch catalytic reactions under different conditions, deuterium labeling experiments, and model organometallic studies, taken together, have shown that the rhodium single sites and the palladium nanoparticles cooperate with each other in promoting the hydrogenation of benzene through the formation of a unique entity throughout the catalytic cycle. Besides decreasing the extent of cyclohexa-1,3-diene disproportionation at palladium, the combined action of the two metals activates the arene so as to allow the rhodium sites to enter the catalytic cycle and speed up the overall hydrogenation process by rapidly reducing benzene to cyclohexa-1,3-diene.

In this work are described the syntheses of several new dppp-like ligands (dppp = 1,3-bis(diphenylphosphino)propane) bearing different substituents on the carbon backbone and of their palladium (II) complexes with acetate or trifluoroacetate coligands (L). The complexes exhibit the general formula Pd(P-P)(L)(2) and have been employed as catalyst precursors for the copolymerization of ethene and carbon monoxide in MeOH under experimental conditions that are comparable to those reported in the relevant literature and patents for dppp-based Pd(II) copolymerization catalysts. It has been found that the introduction of alkyl substituents in the 2-position of the carbon backbone of dppp does not significantly improve the performance of the corresponding catalyst precursors (highest productivity value 6.2 kg of copolymer (g of Pd h)(-1) vs 5.4 kg of copolymer (g of Pd h)(-1) for Pd(dppp)(L)(2)). In contrast, the productivity increases remarkably when methyl groups are introduced in both 1-positions of the diphosphine ligand, particularly with R,S (S,R) stereochemistry as in meso-CH2(CH3CHPPh2)(2) (productivity of 8.0 kg of copolymer (g of Pd h)(-1)). On the basis of NMR and cyclic voltammetric studies of the catalyst precursors, it is suggested that the increased productivity provided by the C-1-substituted ligands is both electronic and steric in nature. In situ high-pressure NMR experiments in sapphire tubes equipped with Ti alloy valves showed that the only phosphorus-containing species visible on the NMR time scale in effective copolymerization conditions are Pd(II) complexes with the formula Pd(diphosphine)X-2 (X = p-toluene-sulfonate, trifluoroacetate, or MeOH). It has been proposed that these Pd(II) complexes act as a reservoir of [Pd(diphosphine)](2+) moieties which may either be delivered into the catalysis cycle by action of various reagents (MeOH, H+, H2O, H-2) or be withdrawn after the termination step and watched over deactivation paths.

The novel Ir(III) nonclassical tetrahydrido complex [(triphos)Ir(H(2))(H)(2)]BPh(4) (4BPh(4)) has been prepared by hydrogenation of the ethene dihydride complex [(triphos)Ir(C(2)H(4))(H)(2)]BPh(4) in either the solid state (P(H)()2 >/= 1 atm) or CH(2)Cl(2) solution (P(H)()2 >/= 3 atm) [triphos = MeC(CH(2)PPh(2))(3)]. Complex 4BPh(4)()()is very labile in solution and can be isolated in the solid state exclusively from solid-gas reactions. Characterization of 4BPh(4) in solution can be achieved( )()by high-pressure NMR and IR spectroscopies, however. Various deuterated isotopomers of [(triphos)Ir(H(2))(H)(2)](+) have been obtained in CD(2)Cl(2) solution at low temperature by treatment of the trihydride [(triphos)IrH(3)] with DOSO(2)CF(3). On the basis of a variety of NMR experiments, the complex cation [(triphos)Ir(H(2))(H)(2)](+) is assigned an octahedral structure where two terminal hydride ligands and a dihydrogen molecule are trans to the phosphorus atoms of a facial triphos ligand. Complex 4BPh(4)()()dissolves in THF at room temperature yielding [(triphos)IrH(3)], BPh(3), and benzene; a similar reaction occurs in acetone, whereas in CH(2)Cl(2) the complex loses H(2) converting to the dimers cis- and trans-[(triphos)IrH(&mgr;-H)(2)HIr(triphos)](BPh(4))(2).

The novel Ir(III) nonclassical tetrahydrido complex [(triphos)Ir(H(2))(H)(2)]BPh(4) (4BPh(4)) has been prepared by hydrogenation of the ethene dihydride complex [(triphos)Ir(C(2)H(4))(H)(2)]BPh(4) in either the solid state (P(H)()2 >/= 1 atm) or CH(2)Cl(2) solution (P(H)()2 >/= 3 atm) [triphos = MeC(CH(2)PPh(2))(3)]. Complex 4BPh(4)()()is very labile in solution and can be isolated in the solid state exclusively from solid-gas reactions. Characterization of 4BPh(4) in solution can be achieved( )()by high-pressure NMR and IR spectroscopies, however. Various deuterated isotopomers of [(triphos)Ir(H(2))(H)(2)](+) have been obtained in CD(2)Cl(2) solution at low temperature by treatment of the trihydride [(triphos)IrH(3)] with DOSO(2)CF(3). On the basis of a variety of NMR experiments, the complex cation [(triphos)Ir(H(2))(H)(2)](+) is assigned an octahedral structure where two terminal hydride ligands and a dihydrogen molecule are trans to the phosphorus atoms of a facial triphos ligand. Complex 4BPh(4)()()dissolves in THF at room temperature yielding [(triphos)IrH(3)], BPh(3), and benzene; a similar reaction occurs in acetone, whereas in CH(2)Cl(2) the complex loses H(2) converting to the dimers cis- and trans-[(triphos)IrH(&mgr;-H)(2)HIr(triphos)](BPh(4))(2).

Der zweikernige Komplex 1 ist die unmittelbar vor der hydrierenden Entschwefelung von Benzo[b]thiophen auftretende Verbindung. Die Rh‐Komponente sorgt zunächst für den C‐S‐Bindungsbruch und die W‐Komponente nach Zugabe von Wasserstoff für die Entschwefelung.magnified image

The synthesis, characterization and reactivity of some square-planar rhodium(I) complexes with new bidentate ligands o-Ph2PC6H4CH=NR (R = Et, Pr(n), Pr(i) or Bu(t)) having NP donor atoms have been investigated. Depending on the steric crowding of the ligands the complexes can reversibly form dioxygen adducts, in organic solvent solutions at room temperature. The oxygenation-deoxygenation cycles, which have been monitored by P-31 NMR spectroscopy, can be repeated several times with minor loss in the starting material. A reversible adduct is similarly obtained by reaction with CO. The reaction of the dioxygen adduct with SO2 allows the formation of a sulfate derivative. The molecular structure of the dioxygen complex [Rh(o-Ph2PC6H4CH=NPri)2(O2)] BPh4 has been determined by a single-crystal diffraction study: triclinic, space group P1BAR, a = 17.450(7), b = 16.518(7), c = 9.624(5) angstrom, alpha = 92.79(6), beta = 92.52(7), gamma = 92.69(7)-degrees, Z = 2, R = 0.057. The co-ordination of the metal may be alternatively described as distorted trigonal bipyramidal or distorted octahedral, according to whether the dioxygen molecule is treated as occupying one or two equatorial sites respectively. The two oxygen atoms, which are equidistant from the metal, are 1.436(9) angstrom apart.

The tripod-like ligand N(CH2CH2PPh2)3(tdpea) forms the palladium(0) trigonal complex [Pd(tdpea)]·0.5Me2CO, (1), in which the apical nitrogen atom of the phosphine is unco-ordinated. This unsaturated species undergoes both addition (CO, SO2) and oxidative-addition reactions (alkyl halides) to form respectively tetrahedral and trigonal bipyramidal complexes. The latter contain quadridentate tdpea. Complex (1) reacts with CO2 or CS2 in the presence of O2 to form a square planar carbonate or dithiocarbonate derivative, with oxidation of a terminal PPh2 group to OPPh2. Crystal data for (1) are: a= 10.827(8)Å, α= 108.82(9)°, space group R3, and Z= 1. In the molecule the metal atom displays an unprecedented out-of-plane trigonal co-ordination. Crystal data for [Pd(tdpea)Me]I are: a= 10.570(7)Å, α= 106.10(7)°, space group R3, and Z= 1. The geometry of the [Pd(tdpea) Me]+ cation is trigonal bipyramidal, with the three-fold crystallographic axis passing through the nitrogen, the palladium, and the carbon atom.

The Pd(0) trico-ordinate out-of-plane (np3)Pd,[np3= N(CH2CH2 PPh3)3], and the Pt(0) pseudotetrahedral (np3)Pt(PPh3) complexes react, under mild conditions, with CH2Cl2 yielding (M–CH2–Cl) complexes; [(np3)Pt(CH2Cl)]BPh4·CH2Cl2 has been structurally characterised by X-ray analysis: variable temperature 31P{1H} n.m.r. spectroscopy measurements have shown that the eighteen electron complex (np3)Pt(PPh3) can dissociate in solution, giving the strong nucleophilic species (np3)Pt.