Bidentate Bridging Ligand Research Articles

Synthesis and characterization of mercury(II) mixed ligands complexes derived from 5-(4-pyridyl)-1,3,4-oxadiazole-2-thione with tertiary phosphines ligands

Many new mixed ligand mercury complexes have been synthesized with LH = 5(4-pyridyl)-1,3,4-oxadiazole-2-thione and tertiary phosphines as co-ligands. The compounds have been characterized by elemental analyses, IR, molar conductivity, and NMR spectroscopy. In the binuclear complexes (2-5), both Hg atoms have tetrahedral geometry, the Hg atom bonded to three halide ions and one thione ligand (LH) through the sulfur atom. The complex (6) show that thionlate ligand(L) is coordinated as monodentate through the sulfur atom. The bis(diphenylphosphino)methane (dppm) behave as bidentate bridging ligand to bonded two Hg(II) ions in the complex (7), Whereas in the complexes (7-10), the thionlate ligand bonded as a monodentate fashion via the sulfur atom, while the diphosphines ligands coordinated as bidentate chelating ligands, and the geometry around the Hg center ion is tetrahedral. And in the complexes (11 and 12), the phosphine bonded as monodentate ligand, and the thionlate bonded via the sulfur atom as monodentate to give tetrahedral complexes.

Solvothermal Syntheses, Crystal Structures and Optical Properties of New Members of Transition Metal Complexes Based on Hexaselenidobistannate Ligand

Two zinc binuclear complexes based on a hexaselenidobistannate bridging ligand, [{Zn(tren)}2(μ-Sn2Se6)] (1) and [{Zn(tepa)}2(μ-Sn2Se6)] (2) were prepared by solvothermal reactions of Zn, Sn, and Se in tris(2-aminoethyl)amine (tren) and tetraethylenepentamine (tepa) solvents, respectively. Compound 1 crystallizes in monoclinic space group C2/c, while 2 in tetragonal I4 1 /a. Acting as a bidentate bridging ligand, the bimeric [Sn2Se6]4− anion joins two [Zn(tren]2+ or two [Zn(tepa]2+ units via two trans terminal Se atoms to form the binuclear complexes 1 and 2, respectively. The Zn2+ ion is in a trigonal bipyramidal environment in 1 and in an octahedral environment in 2. Compounds 1 and 2 show well-defined absorption edges with band gaps of 2.38 and 2.31 eV at room temperature. New transition metal complexes base on hexaselenidobistannate ligand, [{Zn(tren)}2(μ-Sn2Se6)] and [{Zn(tepa)}2(μ-Sn2Se6)] were solvothermaly synthesized in tren and tepa (tren = tris(2-aminoethyl)amine, tepa = tetraethylenepentamine) solvents, respectively.

NEW SELENATO TRIPHENYLTIN (IV) AND TRIMETHYLTIN (IV) DERIVATIVES: SYNTHESIS, INFRARED AND NMR STUDIES

Five derivatives of general formulae [cation] [SeO4SnR3] (R = Ph, Me) have been studied by infrared (IR) and nuclear magnetic resonance (NMR) spectroscopy. The suggested structures are infinite chains or oligomers, the environment around the tin centre being trans trigonal bipyramidal, the phenyl and methyl substituants occupying equatorial positions, the selenate anion behaving as a bridging bidentate ligand and occupying the apical positions. When cations are involved, supramolecular architectures may be obtained.

Synthesis, structure, and luminescence of Cd-MOF based on 5-(4-(1-Imidazolyl)phenyl)pyrimidine and cadmium silicofluoride

ABSTRACTA novel Cd-Metal-organic frameworks (MOF) was generated based on asymmetric ligand 5-(4-(1-imidazolyl)phenyl)pyrimidine (L) with CdSiF6. The crystal belongs to the orthorhombic system, space group Pnna with a = 15.429(3), b = 16.683(3), and c = 12.703(3) Å, C26H20CdF6N8Si. L acts as a bridging bidentate ligand to link Cd(II) centers to generate a (4, 4) net architecture, further linked by fluosilicate anions resulting in a 3D network with fluosilicate anions encapsulated in channels. In addition, the luminescent properties of L and Cd-MOF were investigated primarily in the solid state.

Lanthanide(III) complexes with μ-SnSe4 and μ-Sn2Se6 linkers: solvothermal syntheses and properties of new Ln(III) selenidostannates decorated with linear polyamine

Abstract New lanthanide-selenidostannate complexes [{La(peha)(Cl)}{La(peha)(NO3)}(μ-1κ2:2κ2-SnSe4)] (1), [H2trien][{La(trien)2}2(μ-1κ:2κ-Sn2Se6)][Sn2Se6]·H2O (2) and [{Ln(tepa)(μ-OH)}2(μ-1κ:2κ-Sn2Se6)] n ·nH2O (Ln=Sm(3), Eu(4)) were prepared by solvothermal methods in pentaethylenehexamine (peha), triethylenetetramine (trien) and tetraethylenepentamine (tepa), respectively. Acting as a tetradentate chelating and bridging ligand, μ-1κ2:2κ2-SnSe4, the tetrahedral SnSe4 unit joins {La(peha)(Cl)}2+ and {La(peha)(NO3)}2+ complex fragments to generate the neutral coordination compound 1. The tetradentate μ-1κ2:2κ2 bridge in 1 represents a new coordination mode for the SnSe4 tetrahedron. In 2, dinuclear [Sn2Se6]4− anions are formed of SnSe4 tetrahedra via edge-sharing. One [Sn2Se6]4− anion acts as a bidentate bridging ligand in a μ-1κ:2κ coordination mode to join two {La(trien)2}3+ units, and the other [Sn2Se6]4− anion exists as a free charge compensating ion. In 3 and 4, the [Sn2Se6]4− anion connects binuclear [{Ln(tepa)(μ-OH)}2]2+ (Ln=Sm, Eu) units with a bidentate μ-1κ:2κ mode, giving neutral coordination polymers [{Ln(tepa)(μ-OH)}2(μ-1κ:2κ-Sn2Se6)] n . The La(2)3+ ion in 1 is in a 10-fold coordination environment of LaN6O2Se2, whereas the La(1)3+ ions in 1 and 2 are in 9-fold coordinated environments forming polyhedra LaN6ClSe2 and LaN8Se, respectively. The Sm3+ and Eu3+ ions in 3 and 4 are both in an 8-fold coordination environment of LnN5O2Se. Compounds 1−4 exhibit optical band gaps between 2.21 and 2.42 eV. Their thermal stabilities were investigated by thermogravimetric analyses.

Lanthanide contraction effect on the crystal structures of 2D lanthanide coordination polymers based on 2-(trifluoromethyl)-1H-imidazole-4,5-dicarboxylic acid

A series of new two-dimensional (2D) lanthanide(III) coordination polymers, namely {[Ln2(μ 2-HTFMIDC)3(DMA)4] · 2H2O} n [Ln = Pr (1); Nd (2); Sm (3); Eu (4); H3TFMIDC = 2-(trifluoromethyl)-1H-imidazole-4,5-dicarboxylic acid, DMA = N,N′-dimethylacetamide] for type I and {[Ln2(μ 2-HTFMIDC)3(DMA)2(H2O)2] · DMA} n [Ln = Eu (5); Gd (6)] for type II, have been successfully prepared under solvothermal conditions and structurally characterized for the first time. Both two types of structures exhibit similar 2D honeycomb-like networks, which are constructed by the linkages of μ 2-HTFMIDC2− bis-(bidentate) bridging ligands and Ln(III) metal centers. However, slightly different ABAB stacking fashions of the 2D layers and distinctly different hydrogen bonding interactions between the neighboring 2D layers are observed in crystal structures of type I and type II, which may be attributed to the lanthanide contraction effect. Meanwhile, the solid-state luminescent properties of 4 and 5 have been also investigated.

Synthesis, characterization, thermal behavior and antimicrobial activity of 3-methyl benzoate complexes of transition metal with hydrazine

Reaction of the ligands, 3-methyl benzoic acid (mbH) and hydrazine with transition metal ions form the complexes of formulae, [M(N 2 H 4 ) 2 (mb) 2 ].H 2 O where M = Co(II) and Zn(II) at pH = 5-6, [M(N 2 H 4 ) n (mb) 2 ].xH 2 O where M = Ni(II), n = 2, x = 0 at pH = 5 and M = Cd, n = 1, x = 1 at pH = 6. The same acid also forms metal carboxylates with zinc and copper of formula, [Zn(mb) 2 H 2 O].H 2 O at pH = 6 and [Cu(mb) 2 ].H 2 O at pH = 5, respectively. The IR spectra of the complexes show that hydrazine is present as bridging bidentate ligand and the carboxylic acid as monodentate bridging carboxylate anion. The electronic spectra, magnetic moments and ESR spectral data suggest the coordination number. Thermal studies show that cobalt, zinc and nickel complexes containing hydrazine, and carboxylates of copper, zinc on their thermal decomposition form the corresponding metal oxides in nano size in the temperature range 755-815 °C. The antibacterial and antifungal activity show that both activities of the complexes are higher than that of the acid and among the complexes, cadmium compound shows more antimicrobial activity towards bacteria and fungi. KEY WORDS : Hydrazinium complexes, 3-Methyl benzoic acid, Thermal analysis, IR, Electronic spectra, Biological activity Bull. Chem. Soc. Ethiop. 2016 , 30(2), 241-252. DOI: http://dx.doi.org/10.4314/bcse.v30i2.8

Cycloplatinated(II) complexes containing bridging bis(diphenylphosphino)acetylene: Photophysical study

Reaction of the known cycloplatinated (II) complexes [PtAr(C^N)(SMe2)], in which Ar=p–MeC6H4 or p–MeOC6H4 and C^N= 2-phenylpyridinate (ppy) or benzo[h]quinolinate (bhq), with 0.5 equivalent of the bidentate phosphine ligand 1,1′–bis(diphenylphosphino)acetylene, dppac, in acetone at room temperature gave the symmetrical binuclear cycloplatinated(II) complexes [Pt2Ar2(C^N)2(μ–dppac)], 1–4, in which dppac acts as a bridging bidentate ligand. All the complexes were fully characterized using multinuclear (1H, 31P and 195Pt) NMR spectroscopy and the complex [Pt2(p–MeC6H4)2(ppy)2(μ–dppac)], 1, was further identified by single crystal X-ray structure determination. Additional information about the geometries and electronic spectra of these cycloplatinated (II) complexes are discussed. Effects of aryl and C^N ligands on the luminescent properties of the complexes were also investigated that are complying well with the related DFT/TD-DFT calculations.

Metal-organic frameworks in cadmium(II) complexes with 5-methoxyindole-2-carboxylic acid: structure, vibrational spectra and DFT calculations

Two new complexes of Cd(II) with an O-deprotonated anion of 5-methoxyindole-2-carboxylic acid (5-MeOI2CA), of the formulas [Cd(5-MeOI2CA)2(H2O)2]n (1) and [Cd3(5-MeOI2CA)6(H2O)4(DMSO)4]⋅2DMSO (2) were synthesized. In the polymeric complex 1, the 5-MeOI2CA anion acts as a bidentate bridging ligand and the coordination environment around the Cd(II) ion can be described as a distorted octahedron. Single crystal X-ray diffraction analysis of 2 has revealed that this complex is a trimer and it crystallizes in the monoclinic system (space group P21/c with a = 20.3403(4), b = 14.3079(2), c = 15.0603(3) Å, β = 92.4341(17)°, V = 4379.00(14) Å3 and Z = 2). In 2, the 5-MeOI2CA anions act as bidentate bridging and bidentate chelating ligands. The asymmetric unit of 2 contains two crystallographically independent Cd(II) cations. One of the cations is coordinated to six oxygen atoms and shows an octahedral geometry with a rhombic deformation. The other Cd(II) cation adopts a distorted seven-coordinate pentagonal-bipyramidal geometry involving seven oxygen atoms. In 2, the DMSO solvent molecules play a key role in the formation of metal-organic frameworks by filling voids, which are created by the bridging and chelating 5-MeOI2CA anions, the cadmium cations and the other DMSO molecules coordinated to cadmium. Comprehensive theoretical calculations (including the optimized structural parameters, harmonic frequencies and vibrational intensities) were performed for 2 using the B3LYP method with the 6–311++G(d,p)/LanL2DZ basis sets. The infrared and Ramana spectra were measured and a detailed assignment of the experimental spectra of 2 was performed. All cadmium-oxygen stretching vibrations occur in the range below 400 cm−1.

Syntheses, structures and properties of zinc(II) and cadmium(II) coordination polymers with mixed organic ligands

Three new coordination polymers [Zn(tib)(BPDS)] (1), [Zn(tib) (BPDS) (H2O)]·6H2O (2) and [Zn2(tib) (TPDC-4CH3)2]·DMF·10H2O (3) (DMF = N, N-dimethylformamide), and a previously reported one [Cd(tib)2]·2NO3·4DMF (4) were synthesized by hydro/solvothermal reactions of corresponding metal salt with mixed organic ligands of 1, 3, 5-tris(1-imidazolyl)benzene (tib) and 4, 4'-biphenyldisulfonic acid (H2BPDS)/2′, 3′, 5′, 6′-tetramethylterphenyl-4, 4″-dicarboxylic acid (H2TPDC-4CH3). The complexes were characterized by elemental, thermogravimetric analyses, IR, single crystal and powder X-ray diffractions. 1 and 2 are 2D networks with {4·82} and {63} topologies, which are further assembled into 3D architectures through hydrogen bonding interactions. In 3, both tib and TPDC-4CH32− act as bidentate bridging ligands and link Zn(II) centers to form a 3-fold interpenetrating 3D framework, while 4 is a (3, 6)-connected binodal 3D net with the Schläfli symbol of {4·62}2{42·610·83}. Gas and dye sorption and photoluminescence properties of the complexes were investigated.

Crystal structure, microbiological activity and theoretical studies of Ag(I) and Cu(I) coordination polymers with 1,1′-(butane-1,4-diyl)bis(3-methylimidazoline-2-thione) ligand

Reaction of 1,1′-(butane-1,4-diyl)bis(3-methylimidazoline-2-thione) (bbit) with appropriate silver(I) and copper(I) salts at room temperature leads to the formation of {[Ag(μ2-bbit)](BF4)}n (1) and {[Cu2(μ-bbit)3](PF6)2}n (2) coordination polymers. These compounds have been fully characterized by using the single crystal X-ray diffraction, XRPD, TGA, elemental analysis, infrared spectroscopy, antibacterial activity and molecular docking studies. Crystal structure of (bbit) shows that the molecule has a center of symmetry lies at the mid-point of the (CH2)4 spacer between the two imidazole-2-thione rings. In the cationic 3D structure of 1, silver atom has a distorted tetrahedral coordination geometry and each of the centrosymmetric μ2-bbit ligands with an anticonformation bridging two crystallographically related silver atoms to form a double-bridged Ag(μ2-S)2Ag core as a basic building block. Coordination mode of the bbit ligands and geometry around the metal ions in polymers 1 and 2 are different. Each of the copper atoms in 2 has a trigonal planar CuS3 environment and μ-bbit act as a bridging bidentate ligand, so that two of the CuS3 motifs are interconnected by a pair of μ-bbit ligands through the thione sulfur atoms to generate a 22-membered [Cu2(μ-bbit)2]2+ ring. The adjacent [Cu2(μ-bbit)2]2+ cores are linked by a single μ-bbit ligand to form a 1D chain structure. Additionally, the adjacent 1D chains are extended into a non-covalent 3D network structure by the intermolecular PF…H hydrogen bonds. The in vitro antibacterial studies of bbit, polymers 1 and 2 showed that, polymer 1 was able to inhibit growth of the tested bacteria, whereas the bbit ligand has a weak and polymer 2 showed no antibacterial activity against these bacteria.

Copper inorganic-organic hybrid coordination compound as a novel L-cysteine electrochemical sensor: Synthesis, characterization, spectroscopy and crystal structure

Dinuclear coordination compound of Cu(II), namely, [Cu2(pydc)2(pz)(H2O)2] ⋅2H2O, where pydc = pyridine-2,6-dicarboxylic acid (dipicolinic acid) and pz = pyrazine has been synthesized and characterized by elemental analysis, spectra (IR, UV-Vis), thermal (TG/DTG) analysis, magnetic measurements and single crystal X-ray diffraction. In the dimeric structure, the planar tridentate pyridine-2,6-dicarboxylic acid dianion coordinates to a Cu(II) ion in a meridional fashion and defines the basal plane of the complex. The fourth equatorial coordination site is then occupied by a pyrazine molecule that functions as a linear bidentate ligand bridging two Cu(II) complexes to form a dimer. The axial positions of each Cu(II) complex are occupied by one water molecule to form a distorted square pyramidal geometry. The complicated hydrogen bonding network accompanied with C–O ⋯π and C–H ⋯π stacking interactions assemble the crystal structure of 1 into a fascinating supramolecular architecture. Electrochemical behavior of [Cu2(pydc)2(pz)(H2O)2] (Cu-PDAP) on the surface of carbon nanotube (CNTs) glassy carbon electrode (GCE) is described. Oxidation of cysteine on the surface of modified electrode was investigated with cyclic voltammetry and electrochemical impedance spectroscopy (EIS). The results show that the Cu-PDAP/CNTs film displays excellent electrochemical catalytic activities towards L-cysteine oxidation. Dinuclear coordination compound of Cu(II), namely, [Cu2(pydc)2(pz)(H2O)2].2H2O, has been synthesized and characterized by elemental analysis, spectral (IR, UV-Vis), thermal (TG/DTG) analysis as well as single crystal X-ray diffraction. Electrochemical behavior of [Cu2(pydc)2(pz)(H2O)2] on the surface of carbon nanotube (CNTs) glassy carbon electrode (GCE) was described and oxidation of cysteine on the surface of modified electrode was investigated.

Cr-Cr Quintuple Bonds: Ligand Topology and Interplay Between Metal-Metal and Metal-Ligand Bonding.

Chromium-chromium quintuple bonds seem to be approaching the lower limit for their bond distances, and this computational density functional theory study tries to explore the geometrical and electronic factors that determine that distance and to find ways to fine-tune it via the ligand choice. While for monodentate ligands the Cr-Cr distance is predicted to shorten as the Cr-Cr-L bond angle increases, with bridging bidentate ligands the trend is the opposite, since those ligands with a larger number of spacers between the donor atoms favor larger bond angles and longer bond distances. Compared to Cr-Cr quadruple bonds, the quintuple bonding in Cr2L2 compounds (with L a bridging bidentate N-donor ligand) involves a sophisticated mechanism that comprises a positive pyramidality effect for the σ and one π bond, but a negative effect for one of the δ bonds. Moreover, the shorter Cr-Cr distances produce a mismatch of the bridging ligand lone pairs and the metal acceptor orbitals, which results in a negative correlation of the Cr-Cr and Cr-N bond distances in both experimental and calculated structures.

Investigating the effect of anion substitutions on the structure of silver-based coordination polymers

Five silver(I) compounds namely, [Ag(tdmpp)(NO3)]n (1), [Ag2(SeCN)2(tdmpp)]n (2), [Ag(tdmpp)]PF6 (3), [WS4Ag3Cl (tdmpp)1.5]·2CH3CN (4) and [WS4Ag4I2(tdmpp)]1.5CH3CN (5) were prepared by the reactions of 1,1,3,3-tetrakis(3,5-dimethyl-1-pyrazolyl)propane (tdmpp) with various silver(I) salts in order to investigate the impact of the variation of the inorganic anions on the structure of these complexes. In the chain structures of 1 and 2, each tdmpp ligand acts as a bridge between a pair of adjacent silver(I) centers. In the structure of 1, the nitrate ion act as a terminal, monodentate ligand, while in compound 2 the SeCN anion functions as bidentate-bridging ligand between two neighboring Ag(I) centers. The parallel adjacent chains in 1 and 2 are linked together by means of non-covalent interactions to generate two-dimensional structures. In contrast to the distorted AgN4O square–pyramidal structure of 1, in the structure of 2 each of the silver ions possesses a distorted tetrahedral with an AgN3Se coordination geometry. Crystals of compounds 3–5 were not suitable for X-ray diffraction studies.

Rheological behavior, molecular structure of precursor and evolution mechanism: zirconia fibers from polyaceticzirconium precursors

Polycrystalline zirconia fibers with dense surface and good flexibility were achieved from polyaceticzirconium (abbreviated as PEZ) precursor fibers followed by steam pretreatment and post-calcination. PEZ was synthesized via a one-pot solid–liquid reaction between basic zirconium carbonate and glacial acetic acid in methanol. Rheological behavior of the precursor sol with different concentrations was investigated, the power law model was used to describe the rheological behavior more accurately, and the relationship between the rheology and the spinnability of sol was discussed particularly. For the polymeric structure of PEZ, acetic acid was used as chelating agent and the carboxyl group was acted as a bidentate bridging ligand, which was speculated by FT-IR analysis. The effect of the pretreatment atmosphere on the evolution of the precursor fibers and the microstructure of the final fibers was discussed. The acetate group was removed in the form of molecules, and the final fibers preheated under steam atmosphere had better densification and flexibility than those were not. In addition, crystallization process, phase composition and thermal decomposition were investigated by XRD, Raman spectra and TG/DSC. The preheated atmosphere exerts an important influence on the densification and flexibility of zirconia fibers. Under steam atmosphere, acetate group in the precursor fibers is removed in the form of molecules and zirconia fibers sintered at 1050 °C for 2 h have a dense surface. However, zirconia fibers not subjected to the steam pretreatment have a large number of voids on the surface due to the decomposition of the organics. Furthermore, the fibers preheated under steam atmosphere have better flexibility than those were not. Therefore, pretreatment under steam atmosphere is essential for the preparation of the dense and flexible fibers.

Methanolothermal Syntheses, Crystal Structures and Optical Properties of Binuclear Transition Metal Complexes Involving the Bidentate S-Donor Ligand μ-Sn2S6

New binuclear transition metal complexes concerning the bidentate S-donor ligand μ-Sn2S6, [{Mn(tren)}2(μ-Sn2S6)] (1), [{Zn(tren)}2(μ-Sn2S6)] (2), and [{Mn(tepa)}2(μ-Sn2S6)] (3) [tren = tris(2-aminoethyl)amine, tepa = tetraethylenepentamine] were prepared under methanolothermal conditions. The Mn2+ and Zn2+ ions are coordinated by a tren ligand, forming [TM(tren)]2+ (TM = Mn, Zn) units. As a bidentate bridging ligand, the hexathiobistannate [Sn2S6]4− anion joins two [TM(tren)]2+ units via trans terminal S atoms to form neutral complexes 1 and 2. Both Mn2+ and Zn2+ ions are in a trigonal bipyramidal environment. In 3, the Mn2+ ion binds a pentadentate tepa ligand to give a [Mn(tepa)]2+ unit. Two [Mn(tepa)]2+ units are connected by a μ-Sn2S6 bridging ligand, forming neutral complex [{Mn(tepa)}2(μ-Sn2S6)], in which the Mn2+ ion is in an octahedral environment. Intermolecular N–H···S H-bonding interactions connect 1–3 into layered structures, while 3 forms a three-dimensional network via the N–H···S H-bonds. 1–3 exhibit possible semiconducting properties with the band gaps at 2.3, 2.7 and 2.4 eV, respectively. Transition metal complexes concerning the bidentate S-donor ligand μ-Sn2S6, [{Mn(tren)}2(μ-Sn2S6)], [{Zn(tren)}2(μ-Sn2S6)], and [{Mn(tepa)}2(μ-Sn2S6)] were respectively synthesized using tris(2-aminoethyl)amine (tren) and tetraethylenepentamine (tepa) as second ligands under mild methanolothermal conditions.

Chelating and Linking S4O13(2-) Anions: Synthesis and Characterization of the Bis-(tetrasulfato) Palladates M2[Pd(S4O13)2] (M = NH4, Rb, NO) and the Sodium Palladium Tetrasulfate Na2Pd(S4O13)2.

The reaction of SO3 with either the palladium chlorides M2PdCl6 (M = Rb, NH4) or the nitrato-palladate (NO)2[Pd(NO3)4] at elevated temperature led to yellow single crystals of the complex palladates M2[Pd(S4O13)2] (M = NH4: triclinic, P1̅, a = 7.3882(3) Å, b = 8.5223(3) Å, c = 9.2712(4) Å, α = 71.945(2)°, β = 88.910(2)°, γ = 72.603(2)°, V = 527.88(4) Å3; M = NO: triclinic, P1̅, a = 7.2881(3) Å, b = 8.9125(2) Å, c = 8.9220(4) Å, α = 75.546(2)°, β = 89.151(2)°, γ = 69.516(2)°, V = 524.02(4) Å3; M = Rb: triclinic, P1̅, a = 7.4468(4) Å, b = 8.5066(4) Å, c = 9.2477(4) Å, α = 72.321(2)°, β = 88.512(2)°, γ = 72.128(2)°, V = 529.75(4) Å3). In the isotypic compounds, the Pd atom is in square planar oxygen coordination, achieved by two bidentate-chelating tetrasulfate anions. The reaction of Na2PdCl6 with neat SO3 afforded yellow crystals of Na2Pd(S4O13)2 (monoclinic, P21/c, a = 6.9953(4) Å, b = 15.9420(9) Å, c = 9.2299(5) Å, β = 100.235(2)°, V = 1012.45(1) Å3). The structure exhibits no palladate complexes but an anionic two-dimensional network, according to ∞2[Pd(S4O13)(4/2)]2–. The latter shows the tetrasulfate anions acting as bidentate-bridging ligands. The tetrasulfato-palladates were studied in more detail by means of thermal analyses and infrared (IR) spectroscopy. The observed IR bands were assigned according to quantum chemical calculations performed on the anion [Pd(S4O13)2]2–.

Syntheses and crystal structures of copper(II), zinc(II) and cadmium(II) complexes containing pyridine, quinoline and 2-methylquinoline

Nine new complexes, Cu(L1)2(py)2·H2O (1) [L1=3-(4-methoxyphenyl)acrylate, py=pyridine], Cd(L2)2(py)3 (2) [L2=2-methyl-2-phenoxypropionate], Cd(L3)2(mql)2 (3) [L3=3,4-(methylenedioxy)benzoate, mql=2-methylquinoline], Cu(py)2(L4)2·H2O (4) [L4=2-chloronicotinate], Zn(L5)0.5(py) (5) [L5=butane-1,2,3,4-tetracarboxylate], [Zn(L6)2(ql)]2 (6) [ql=quinoline, L6=(4-chloro-phenoxy)-acetate], [Zn(L7)2(H2O)2](mql)2 (7) [L7=2-hydroxy-5-(phenyldiazenyl)benzoate], [Cd(L7)2(H2O)2](mql)2 (8) and [Zn(ql)2(H2O)4]·(L8)·(H2O)2 (9) [L8=naphthalene-1,5-disulfonate], have been synthesized from an alcohol solution at room temperature and characterized by EA, IR, TGA and single-crystal X-ray diffraction. X-ray crystallographic studies show that these complexes display mononuclear, dinuclear to polymeric chain structures with an octahedral arrangement around the cadmium ions, square-pyramidal coordination geometry around the Cu ion and square-pyramidal/octahedral coordination for the Zn ions. In 1, 4 and 8, the carboxylates are monodentate ligands, while in 2 the carboxylate groups functioned as both monodentate and chelating bidentate ligands. In 3 and 7 the carboxylates are chelating bidentate ligands, the carboxylates in 5 act as a tetra-chelating bidentate ligand and the carboxylates in 6 function as a bridging bidentate ligand. The anions in 9 act as a counter ion. Rich intra- and inter-molecular weak interactions, such as classical hydrogen bonds, CH–Cl, C–H⋯O, CH2⋯O, CH3–O, Cl–O, Cl–π, C–H⋯π, CH3–π and π–π interactions, have been analyzed.

Complexes of selected transition metal ions with 4-oxo-4-{[3-(trifluoromethyl)phenyl]amino}but-2-enoic acid: Synthesis, structure and magnetic properties

The new complexes of 4-oxo-4-{[3-(trifluoromethyl)phenyl]amino}but-2-enoic acid, HL anion with Mn(II), Co(II), Ni(II), Cu(II) and Pr(III), Nd(III), Sm(III), Gd(III), Dy(III), Ho(III), Er(III), Y(III) were synthesized and some of their physico-chemical properties investigated. The complexes form hydrates with two or three molecules of water. The carboxylate groups act as a bidentate bridging or chelating ligand. The compounds of Pr(III), Nd(III), Sm(III), Gd(III), Dy(III), Ho(III), Er(III) and Y(III) are amorphous solids while those of Cu(II), Co(II), Ni(II) and Mn(II) crystalline ones that crystallize in monoclinic system. Complex of Cu(II) is the centrosymmetric dinuclear compound. Around both Cu(II) cations the tetragonal pyramide is formed. Being heated in air at 293–1173K the complexes are decomposed in three steps. The oxides of appropriate metals are the final products of complex decomposition. All analysed compounds obey Curie–Weiss law. They show the paramagnetic properties with the ferromagnetic interactions between molecular centres.

Rearrangement of a Krebs-type polyoxometalate upon coordination of N,O-bis(bidentate) ligands.

Selective coordination of 2,3-pyzdc to the Krebs-type [{Ni(H2O)3}2(WO2)2(SbW9O33)2](10-) anion promotes a skeletal rearrangement that results in the [(2,3-pyzdc)2{NaNi2(H2O)4Sb2W20O70}2](22-) (Ni4) hybrid dimer showing a novel dinickel containing a 20-tungsto-2-antimonate(III) framework stabilized by N,O-bis(bidentate) bridging ligands. The solution stability and magnetism of Ni4 is discussed.