Thermal Decompositions of the Molybdotellurates of Nickel(II) and Cobalt(II)

Molybdotellurates [M(H₂O)₆]₃·[TeMo₆O₂₄], with M=Ni(II) and Co(II), were synthesized and characterized by single-crystal X-ray diffraction for compound 1 and X-ray powder diffraction for compound 2, EDAX, IR, electronic spectra in the solid phase and in solution, and magnetic properties. Thermogravimetry and differential scanning calorimetry of both compounds revealed a loss of 11 water molecules through an endothermal process with ΔH=800 kJ mol⁻¹ for the nickel compound and ΔH=833 kJ mol⁻¹ for the cobalt compound. The residual compounds were characterized by chemical analysis, IR and XPS spectroscopy This revised version was published online in July 2006 with corrections to the Cover Date.     

Magnetic coupling through the carbon skeleton of malonate in two polymorphs of ([Cu(bpy)(H2O)][Cu(bpy)(mal)(H2O)])(ClO4)2 (H2mal = malonic acid; bpy = 2,2'-bipyridine)

Two polymorphic malonato-bridged copper(II) complexes of formula ([Cu(bpy)(H2O)][Cu(bpy)(mal)(H2O)])-(ClO4)2 (1 and 2) (bpy = 2,2'-bipyridine and mal = malonate dianion) have been prepared and their structures solved by X-ray diffraction methods. Compound 1 crystallizes in the monoclinic space group P2(1)/a, with a = 23.743(3) A, b = 9.7522(5) A, c = 27.731(2) A, beta = 114.580(10) degrees, and Z = 4. Compound 2 crystallizes in the orthorhombic space group Pbcn, with a = 23.700(5) A, b = 25.162(5) A, c = 9.693(5) A, and Z = 4. The structures of 1 and 2 are made up of uncoordinated perchlorate anions and malonate-bridged zigzag copper(II) chains grouped in an isosceles triangle running parallel to the b (1) and c (2) axes. These chains are built by a [Cu(bpy)(mal)(H2O)] unit acting as bis-monodentate ligand toward two [Cu(bpy)(H2O)] adjacent units through its OCCCO skeleton in an anti-anti conformation, whereas the OCO carboxylate bridges exhibit the anti-syn conformation. Compounds 1 and 2 contain four crystallographically independent copper(II) atoms, but the environment of all of them is distorted square pyramidal: the axial position is occupied by a water molecule, whereas the equatorial plane is formed by a chelating bpy and either a bidentate malonate or two carboxylate oxygens from two malonate groups. The equatorial Cu-O(mal) (1.911(4)-1.978(4) (1) and 1.897(5)-1.991(4) A (2)) and Cu-N(bpy) (1.983(4)-2.008(5) (1) and 1.971(6)-2.007(6) A (2)) bonds are somewhat shorter than the axial Cu-O(w) one (2.257(5)-2.524(5) (1) and 2.236(5)-2.505(6) A (2)). The angles subtended at the copper atom by the chelating bpy vary in the ranges 80.9(2)-81.8(2) degrees (1) and 80.4(2)-82.1(2) degrees (2), values which are somewhat smaller than those of the chelating malonate (80.4(2)-82.1(2) degrees (1) and 93.0(2)-93.6(2) degrees (2)). The intrachain copper-copper separations through the OCCCO fragment are 8.227(1) (1) and 8.206(2) A (2), whereas those through the OCO bridging unit are 4.579(1)-5.043(1) (1) and 4.572(2)-5.040(2) A (2). The magnetic behavior of 1 and 2 in the temperature range 2.0-290 K is very close, and it corresponds to an overall ferromagnetic coupling, the chi MT versus T curve exhibiting a maximum at 18 K. The analysis of the magnetic data through a numerical expression derived for the real topology of 1 and 2, that is, chains of isosceles triangles with two intrachain exchange pathways J1 (exchange coupling through the OCO carboxylate) and J2 (exchange coupling through the OCCCO malonate), indicates the occurrence of ferro- (J1 = +4.6 cm-1) and antiferromagnetic couplings (J2 = -4.2 cm-1). The magnetic coupling through these exchange pathways is further analyzed and substantiated by density functional theory calculations on a malonate-bridged trinuclear copper(II) model system.     

Tungstotellurates of the imidazolium and 4-methylimidazolium cations

Tungstotellurates of the organic imidazolium and 4-methyl-imidazolium cations have been prepared and characterized by X-ray diffraction and i.r. spectroscopy. The [TeW₆O₂₄]^6– anion is formed by close packing of oxygen atoms with Te and W atoms in distorted octahedral voids. In both compounds the organic cations are involved in hydrogen bonds, to the [TeW₆O₂₄]^6– anion in [H₂imz]₆[TeW₆O₂₄] · 2(Himz) (1) and to Te(OH)₆ units in [4-H₂-methyl-imz]₆[TeW₆O₂₄] · Te(OH)₆ (2). Solution studies of (1) and (2) by ¹H-, ¹⁸³W- and ¹²⁵Te-n.m.r. have been carried out. Thermogravimetric (t.g.) and calorimetric (d.s.c.) analyses were performed for both compounds.     

Synthesis of the water soluble ligands dmPTA and dmoPTA and the complex [RuClCp(HdmoPTA)(PPh(3))](OSO(2)CF(3)) (dmPTA = N,N'-Dimethyl-1,3,5-triaza-7-phosphaadamantane, dmoPTA = 3,7-Dimethyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane, HdmoPTA = 3,7-H-3,7-Dimethyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane)

The new water-soluble ligand dmPTA(OSO(2)CF(3))(2) (1) (dmPTA = N,N'-dimethyl-1,3,5-triaza-7-phosphaadamantane) has been synthesized by reaction of PTA with MeOSO(2)CF(3) in acetone (PTA = 1,3,5-triaza-7-phosphatricycle[3.3.1.1(3,7)]decane). The reaction of 1 with KOH gave rise to the new water-soluble ligand dmoPTA (3) (dmoPTA = 3,7-dimethyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane) by elimination of the -CH(2)- group located between both NCH(3) units. Compound dmPTA(BF(4))(2) (2) and complex [RuClCp(HdmoPTA)(PPh(3))](OSO(2)CF(3)) (4) have also been synthesized, while compounds HdmoPTA(BF(4)) (3a) and [RuClCp(dmPTA)(PPh(3))](OSO(2)CF(3)) (5) were characterized but not isolated. The new ligands and the complex have been fully characterized by NMR, IR, elemental analysis, and X-ray crystal structure determination (ligand 1 and complex 4). The synthetic processes for 3 and 4 were studied.     

Comparative study of [RuClCp(HdmoPTA-κP)(PPh3)][CF3SO3] and the heterobimetallic complexes [RuClCp(PPh3)-μ-dmoPTA-1κP:2κ2N,N'-M(acac-κ2O,O')2] (M=Co, Ni, Zn; dmoPTA=3,7-dimethyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane)

The synthesis of novel heterobimetallic derivatives of general formula [RuClCp(PPh(3))-μ-dmoPTA-1κP:2κ(2)N,N'-M(acac-κ(2)O,O')(2)] (M = Ni (3), Zn (4); dmoPTA = 3,7-dimethyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane) is described. The preparations of the ruthenium-cobalt analogue (M = Co (2)) and the starting compound [RuClCp(HdmoPTA-κP)(PPh(3))](CF(3)SO(3)) have been revised and their yield improved. Similar to 2, the solid state structures of 3 and 4 show that the dmoPTA-P and the dmoPTA-N(CH(3)) atoms are involved in the coordination to the {RuCpCl(PPh(3))} and {M(acac)(2)} moieties, respectively. The size of the diffusing units is almost the same for the three binuclear complexes, indicating that they exhibit similar solution structures. The diamagnetic ruthenium-zinc derivative was fully characterized in solution at 193 K by NMR as two diastereomeric pairs of enantiomers (R-Ru, Δ-Zn; R-Ru, Λ-Zn; S-Ru, Δ-Zn; S-Ru, Λ-Zn). Finally, the electrochemical properties of the complexes have been investigated by cyclic voltammetry.     

Inorganic-organic hybrids formed by P,P'-diphenylmethylenediphosphinate, pcp2-, with the Cu2+ ion. X-ray crystal structures of [Cu(pcp)(H2O)2] x H2O and [Cu(pcp)(bipy)(H2O)

Weakly coordinated [Cu(pcp)(H2O)n] complexes are formed in aqueous solution, at room temperature, by interaction of P,P'-diphenylmethylene diphosphinic acid (H2pcp) with copper(II) ions. However, heating of the solutions gives rise to the formation of two extended metal-oxygen networks of formulas [Cu(pcp)(H2O)2] x H2O, 1, and [Cu(pcp)(H2O)2], 2. In the presence of 2,2'-bipyridyl (bipy) the diamine derivative [Cu(pcp)(bipy)(H2O)], 4, has been isolated. Complex 1 easily loses water to form a monohydrated derivative [Cu(pcp)H2O], 3, whereas 2 is completely dehydrated after prolonged heating at 150 degrees C, under vacuum. The compounds 1 and 2 have substantially different solid-state structures as shown by X-ray powder diffraction spectra, IR spectra, and thermogravimetric analyses. Consistently, the two complexes cannot be directly interconverted and present different dehydration pathways. Rehydration of these materials in both cases allows quantitative formation of 1. X-ray analysis established that the structure of 1 consists of a corrugated two-dimensional layered polymeric array, where infinite zigzag chains of Cu centers and bridging phenylphosphinate ligands are linked together through strong hydrogen-bonding interactions; the structure of 4 consists of monodimensional polymers, where the hydrogen-bonding interactions play an essential bridging role in the extended architecture. In both structures the metal center displays a five-coordinate environment with approximate square pyramidal geometry, with the pcp ligand acting as bidentate and monodentate in 1 and solely as bidentate in 4. In 1 the coordination sphere is completed through water molecules; in 4, through water and diamine ligands. The thermogravimetric analyses of the complexes are compared with those of the related hybrids [M(pcp)(H2O)3] x H2O, where M = Mn, Co, or Ni, confirming that noncoordinated water molecules also play a basic role in determining the molecular packing.     

Water-soluble 3,7-dimethyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane (dmoPTA) as a polydentate ligand: synthesis of [RuClCp(PPh3)-mu-dmoPTA-1kappaP:2kappa2N,N'-Co(acac-kappa2O,O')2].H2O

The dinuclear complex [RuClCp(PPh3)-mu-dmoPTA-1kappa P:2kappa(2)N, N'-Co(acac-kappa(2)O, O') 2].H 2O (2; dmoPTA = 3,7-dimethyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane) has been synthesized by reaction of [RuClCp(HdmoPTA)(PPh3)](OSO2CF3) (1) with Co(acac)2 in methanol (HdmoPTA = 3,7-H-3,7-dimethyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane). Elemental analysis, IR, NMR, and single-crystal X-ray structure determination have characterized the new complex. This complex is active for the catalytic isomerization of but-1-en-3-ol in acetone better than 1.     

Synthesis,structural analysis,and thermal and spectroscopic studies of methylmalonate-containing zinc(II) complexes

The synthesis, crystal structure, thermal analysis and spectroscopic studies of five zinc(II) complexes of formulae [Zn(Memal)(H₂O)]_n (1) and [Zn₂(L)(Memal)₂(H₂O)₂]_n (2-5) [H₂Memal = methylmalonic acid, and L = 4,4′-bipyridine (4,4′-bpy) (2), 1,2-bis(4-pyridyl)ethylene (bpe) (3), 1,2-bis(4-pyridyl)ethane (bpa) (4) and 4,4′-azobispyridine (azpy) (5)] are presented here. The crystal structure of 1 is a three-dimensional arrangement of zinc(II) cations interconnected by methylmalonate groups adopting the μ₃-κ²O:κO’:κO”:κO”’ coordination mode to afford a rare (10,3)-d utp-network. The structures of the compounds 2-5 are also three-dimensional and they consist of corrugated square layers of methylmalonate-bridged zinc(II) ions which are pillared by bis-monodentate 4,4′-bpy (2), bpe (3), bpa (4) and azpy (5) ligands. The Memal ligand in 2-5 adopts the μ₃-κO:κO′:κO′′:κO′′′ coordination mode. Each zinc(II) ion in 1-5 is six-coordinated with five (1)/four (2-5) methylmalonate-oxygen atoms, a water molecule (1-5) and a nitrogen atom from a L ligand (2-5) building distorted octahedral environments. The rod-like L co-ligands in 2-5 appear as useful tools to control the interlayer metal-metal separation, which covers the range 8.4311(5) Å (2) – 9.644(3) Å (5). The influence of the co-ligand on the fluorescence properties of this series of compounds has been analyzed and discussed by steady-state and time resolved spectroscopy on all five compounds in the solid state.     

Molybdotellurates containing the 1-methyl-, 2-methyl- and 4-methyl imidazolium cations

Four molybdotellurates containing the 1-methylimidazolium, 2-methylimidazolium and 4-methylimidazolium cations have been synthesized and their structures: [2-H2-methyl-imz]6[TeMo6O24 ]·2H2O (2), [2-H2-methyl-imz]6[TeMo6O24 ]·2(2-H-methyl-imz)·2H2O (3) and [4-H2-methyl-imz]6[TeMo6O24 ]·Te(OH)6 (4) determined by X-ray diffraction methods. The protonated organic bases are bonded to the anion in the crystal by hydrogen bonds, except for (4) where the crystal structure consists of discrete [TeMo6O24]6– anions and Te(OH)6 units, both bonded to 4-methylimidazolium cations by hydrogen bonds. The hydrogen bonds were studied as a function of the unit charge of the oxygen atoms of the [TeMo6O24]6– anion. Distortions of the central octahedron of polyanions of formula [XMo6O24]n– (X=AlIII, MoVI, TeVI and IVII), and polyanions of formula [H6YMo6O24]n–, (Y=CoII, CuII, ZnII, CrIII, RhIII and PtIV) are discussed. 95Mo n.m.r spectroscopy of compounds [1-H2-methyl-imz]6[Te-Mo6O24]·Te(OH)6 (1), (2) and (4) indicates the existence of an octahedral oxygen atom arrangement around the molybdenum and a pH variation experiment, carried out with compound (1), confirmed the existence of hydrolytic processes of the compounds in aqueous solution. 125Te n.m.r. studies permitted identification of the Te atom in the [TeMo6O24]6– kernel in all compounds; the presence of two different Te(OH)6 moieties in compounds (1) and (4) was also detected. The similarity between the spectra of both compounds could indicate that (1) has the same structural arrangement as (4). Finally, the thermal behaviour and the thermal stabilities of the complexes as a function of the organic cation were studied.