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Donor Set (donor + set)

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Oxovanadium(IV) Complexes with Pyrazinecarboxylic Acids:The Coordinating Properties of Ligands with the (Naromatic, COO,) Donor Set

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 13 2006
Eugenio Garribba
Abstract Complex formation between the VIVO ion and four pyrazine derivatives, 2-pyrazinecarboxylic acid (pzc), 5-methyl-2-pyrazinecarboxylic acid (5-Mepzc), 2,3-pyrazinedicarboxylic acid (3-COOHpzc) and 5-hydroxy-2-pyrazinecarboxylic acid (5-OHpzc), was studied in aqueous solution and in the solid state through the combined application of potentiometric and spectroscopic (EPR and FT-IR) techniques. The results indicate that in acidic and neutral aqueous solution all theligands form mono(chelated), bis(chelated) and dinuclear species of composition VOL, VOL2 and (VO)2L2H,2. Hexacoordinated VOL2 complexes are characterised by a cis/trans isomerism, where cis and trans are the species with a water molecule bound in the cis or trans position with respect to the V=O group. The trans arrangement is favoured over the cis arrangement. Three solid derivatives, [VO(5-Mepzc)2] (1), cis -[VO(pzc)2(H2O)] (2) and cis -[VO(3-COOHpzc)2(H2O)] (3), were isolated and characterised. Based on the experimental results and on the data in the literature, the stability of cis and trans isomers in aqueous solution and in the solid state has been discussed, showing that with ligands of comparable basicity and size of the chelate ring the hydrophilicity favours the cis species and determines the relative amount of the two isomers. The analysis of the magnetic properties of the hydroxo-bridged VIVO dimers suggests that for the (VO)2L2H,2 species the anti -coplanar arrangement is realised. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]

Binding of Oxovanadium(IV) to Tripeptides Containing Histidine and Cysteine Residues and Its Biological Implication in the Transport of Vanadium and Insulin-Mimetic Compounds

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 24 2005
Eugenio Garribba
Abstract The complexation of VIVO ion with three tripeptides of biological importance containing L -histidine or L -cysteine (HisGlyGly, GlyGlyHis and GlyGlyCys) has been studied. This study was performed in aqueous solution by the combined application of potentiometric and spectroscopic (electronic absorption and EPR) techniques. The results indicate that these oligopeptides, if a ligand-to-metal molar ratio of 10 or 15 is used, can keep VIVO ion in solution until the deprotonation of the amide group with the donor set (NH2, CO, Nimax) for HisGlyGly or (COO,, CO) for GlyGlyHis and GlyGlyCys. In all the systems, at pH values around neutrality, a VOLH,2 species is formed with an (NH2, N,, N,, COO,) donor set for HisGlyGly, (NH2, N,, N,, Nim) for GlyGlyHis and (NH2, N,,N,, S,) for GlyGlyCys. These species, and those with onedeprotonated amide group coordinated to the VIVO ion, can be detected by EPR spectroscopy. The N,(amide) contribution to the hyperfine coupling constant along the z axis, Az, depends on the total charge of the donor atoms in the equatorial plane. The participation of albumin in the transport of vanadium and insulin-mimetic VIVO compounds is reconsidered based on these results. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source]

One-Dimensional Oxalato-Bridged Metal(II) Complexes with 4 - Amino-1,2,4-triazole as Apical Ligand

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 21 2005
Urko García-Couceiro
Abstract The synthesis, chemical characterization, thermal behavior and magnetic properties of six new one-dimensional oxalato-bridged metal(II) complexes of formula [M(,-ox)(4atr)2]n [MII = Cu (1), Ni (2), Co (3), Zn (4), Fe(5)] and [Cd(,-ox)(4atr)2(H2O)]n (6) (ox = oxalato dianion, 4atr = 4-amino-1,2,4-triazole) are reported. The crystal structures of 1 and 6 have been solved by single-crystal X-ray diffraction, whereas the remaining compounds have been studied by means of X-ray powder diffraction methods. Compounds 1,5 are isomorphous and crystallize in the triclinic space group P1¯ with unit cell parameters for 1 of a = 5.538(1) Å, b = 7.663(1) Å, c = 7.711(2) Å, , = 62.21(1)°, , = 73.91(1)°, , = 86.11(1)°, and Z = 1. The crystal structures are comprised of one-dimensional linear chains in which the trans -[M(4atr)2]2+ units are sequentially bridged by bis(bidentate) oxalato ligands, resulting in an octahedral O4N2 donor set. Cryomagnetic susceptibility measurements show the occurrence of antiferromagnetic intrachain interactions for 2, 3, and 5, whereas compound 1 exhibits a weak ferromagnetic coupling in agreement with the out-of-plane exchange pathway involved. The magnetic behavior of 1 and 2 is analyzed and discussed in the light of the available magneto-structural data for analogous systems. CdII complex crystallizes in the monoclinic space group C2/c with unit cell parameters of a = 16.128(2) Å, b = 6.757(1) Å, c = 11.580(2) Å, , = 104.46(1)°, and Z = 4. Its crystal structure contains one-dimensional chains in which metal centers are heptacoodinated to four oxygen atoms from two symmetry-related bis(bidentate) oxalato bridges, two endocyclic nitrogen atoms of trans -coordinated triazole ligands and one water molecule, to give a CdO4OwN2 pentagonal-bipyramidal geometry. Thermoanalytical and variable-temperature X-ray powder diffraction analyzes show that compound 6 undergoes a reversible dehydration,hydration process in which the anhydrous residue crystallizes with a different crystal lattice retaining the dimensionality of the oxalato,metal framework. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source]

Crystallographic report: (2,9-Dimethyl-1,10-phenanthroline)bis-(N,N -pyrrolidinedithiocarbamato)zinc(II) chloroform hemihydrate

APPLIED ORGANOMETALLIC CHEMISTRY, Issue 4 2003
Chian Sing Lai
Abstract The mononuclear structure of Zn(S2C(N(CH2)2)4)2(2,9-Me2 -1,10-phen) shows monodentate coordination by the dithiocarbamate ligands and a distorted tetrahedral geometry for zinc, defined by an N2S2 donor set, results. Copyright © 2003 John Wiley & Sons, Ltd. [source]

[N,N,-Bis(5-bromo­salicyl­idene)-1,3-di­amino­propane]­nickel(II) and [N,N,-­bis(5-chloro­salicyl­idene)-1,3-­di­amino­propane]copper(II)

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 11 2000
Ayhan Elmali
The title compounds, {4,4,-di­bromo-2,2,-[1,3-propane­diyl­bis(nitrilo­methyl­idyne- N)]­diphenolato- O,O,}nickel(II), [Ni(C17­H14­Br2­N2O2)], and {4,4,-di­chloro-2,2,-[1,3-pro­pane­diyl­bis­(ni­trilo­methyl­idyne- N)]­di­phen­ol­ato- O,O,}­copper(II), [Cu­(C17­H14­Cl2­N2O2)], lie on crystallographic twofold axes. In both structures, the metal coordination sphere is a tetrahedrally distorted square plane formed by the four-coordinate N2O2 donor set of the Schiff base imine,phenol ligands. In the Ni compound, the Ni,O and Ni,N distances are 1.908,(3) and 1.959,(4),Å, respectively, while in the Cu compound, the Cu,O and Cu,N distances are 1.907,(2) and 1.960,(2),Å, respectively. The two Schiff base moieties, which themselves are nearly planar, are inclined at an angle of 29.26,(7)° for the Ni compound and 29.26,(5)° for the Cu compound. [source]

Iron(II) Complexes with Bio-Inspired N,N,O Ligands as Oxidation Catalysts: Olefin Epoxidation and cis -Dihydroxylation

CHEMISTRY - A EUROPEAN JOURNAL, Issue 4 2008
Pieter
Abstract The Rieske dioxygenases are a group of non-heme iron enzymes, which catalyze the stereospecific cis -dihydroxylation of its substrates. Herein, we report the iron(II) coordination chemistry of the ligands 3,3-bis(1-methylimidazol-2-yl)propionate (L1) and its neutral propyl ester analogue propyl 3,3-bis(1-methylimidazol-2-yl)propionate (PrL1). The molecular structures of two iron(II) complexes with PrL1 were determined and two different coordination modes of the ligand were observed. In [FeII(PrL1)2](BPh4)2 (3) the ligand is facially coordinated to the metal with an N,N,O donor set, whereas in [FeII(PrL1)2(MeOH)2](OTf)2 (4) a bidentate N,N binding mode is found. In 4, the solvent molecules are in a cis arrangement with respect to each other. Complex 4 is a close structural mimic of the crystallographically characterized non-heme iron(II) enzyme apocarotenoid-15,15,-oxygenase (APO). The mechanistic features of APO are thought to be similar to those of the Rieske oxygenases, the original inspiration for this work. The non-heme iron complexes [FeII(PrL1)2](OTf)2 (2) and [FeII(PrL1)2](BPh4)2 (3) were tested in olefin oxidation reactions with H2O2 as the terminal oxidant. Whereas 2 was an active catalyst and both epoxide and cis -dihydroxylation products were observed, 3 showed negligible activity under the same conditions, illustrating the importance of the anion in the reaction. [source]

Influence of solvent on the structures of two one-dimensional cobalt(II) coordination polymers with tetrachloroterephthalate

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 2 2009
Yong-Qin Fang
The title cobalt coordination polymers, catena -poly[[[aquatripyridinecobalt(II)]-,-tetrachloroterephthalato] pyridine solvate], {[Co(C8Cl4O4)(C5H5N)3(H2O)]·C5H5N}n, (I), and catena -poly[[[diaquadipyridinecobalt(II)]-,-tetrachloroterephthalato] 1,4-dioxane trihydrate], {[Co(C8Cl4O4)(C5H5N)2(H2O)2]·C4H8O2·3H2O}n, (II), have been prepared with tetrachloroterephthalic acid (H2BDC-Cl4) under different solvent media. Both complexes form infinite cobalt(II),tetrachloroterephthalate polymeric chains. In (I), two independent CoII ions are six-coordinated through N3O3 donor sets in slightly distorted octahedral geometries provided by two carboxylate and three pyridine ligands, and one water molecule. The structure of (II) contains two independent CoII atoms, each lying on a twofold axis, which adopt a tetragonally distorted N2O4 octahedral geometry via two carboxylate groups, two pyridine ligands and two water molecules. The different stoichiometry of coordinated and solvent guest molecules leads to different two-dimensional supramolecular networks, with (I) utilizing C,H..., and weak ,,, interactions and (II) utilizing mainly conventional hydrogen bonding. [source]

A novel cobalt(II) coordination polymer with an unusual four-connected 42.63.8 topology

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 7 2008
Guo-Hua Wei
In the cobalt(II) coordination polymer poly[[(,2 -benzene-1,3-dicarboxylato){,2 -1,1,-[2,2,-oxybis(ethane-2,1-diyl)]di-1H -imidazole}cobalt(II)] monohydrate], {[Co(C10H14N4O)(C8H4O4)]·H2O}n, two crystallographically distinct CoII cations are four-coordinated by N2O2 donor sets in distorted tetrahedral geometries. The CoII centers are connected by benzene-1,3-dicarboxylate (m -BDC) anions, giving two types of linear chains, which are further joined via meso -helical 1,1,-[2,2,-oxybis(ethane-2,1-diyl)]di-1H -imidazole ligands to yield a thick two-dimensional slab. The compound displays a two-dimensional four-connected 42.63.8 topology, which is unprecedented in coordination polymers. [source]