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Donor Atoms (donor + atom)
Kinds of Donor Atoms Selected AbstractsSingle-Atom O -Bridged Urea in a Dinickel(II) Complex together with NiII4, CuII2 and CuII4 Complexes of a Pentadentate Phenol-Containing Schiff Base with (O,N,O,N,O)-Donor AtomsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 5 2003Soumen Mukherjee Abstract A pentadentate phenol-containing ligand (H3L) with N2O3 donor atoms yields NiII2 (1), NiII4 (2), CuII2 (3) and CuII4 (4) complexes, which have been structurally characterized by X-ray diffraction. Complex 1 contains a single-atom O -bridged urea. The compounds were characterized by IR, UV/Vis, mass spectrometry, electrochemistry and variable-temperature (2,295 K) magnetic susceptibility measurements. Analysis of the susceptibility data shows antiferromagnetic interactions between the metal centers indicating a diamagnetic ground state for complexes 1, 3 and 4, whereas complex 2, a tetranuclear NiII cubane, has a complicated low-lying magnetic structure with a non-diamagnetic ground state. A plot of J vs. Ni,O,Ni angles for all structurally characterized Ni4O4 cubane cores, including 2, irrespective of their symmetry exhibits a large variation of J values within a small range of Ni,O,Ni angles. The electrochemistry of all complexes was investigated in detail and the ligand-centered oxidation to a radical-ligand is inferred from the occurrence of oxidation processes at potentials which are similar. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] Control of Intramolecular Ether-Oxygen Coordination in the Crystal Structure of Copper(II) Complexes With Dipicolylamine-Based LigandsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 8 2007Yuji Mikata Abstract Thirteen crystal structures of copper(II) complexes with a series of dipicolylamine (DPA)-derived ligands, N -(2-methoxyethyl)- N,N -bis(2-pyridylmethyl)amine (L1), N -[2-(2-hydroxyethyloxy)ethyl]- N,N -bis(2-pyridylmethyl)amine (L2) and N -(3-methoxypropyl)- N,N -bis(2-pyridylmethyl)amine (L3), have been determined and the factors that control the coordination of the ether-oxygen atom of these ligands to the copper centre are discussed. Complexes that have +1 or +2 charges exhibit coordination of the ether-oxygen atom, whereas neutral complexes in which two anions are bound to the copper(II) centre tend to lose the oxygen coordination. Upon chelation of the oxygen atom, L3 forms a six-membered chelate ring with respect to the 3-aminopropyl ether moiety whereas L1 and L2 form a five-membered chelate. This difference, especially in the nitrate and bromide complexes, determines whether the ether-oxygen atom chelates to the metal centre to give a monocationic complex, or the second anion coordinates to the metal centre to form the ether-free, neutral complex. The terminal anchor hydroxy group of L2 facilitates the ether-oxygen coordination via a hydrogen bond interaction to the donor atom located trans to the aliphatic nitrogen atom in the basal plane. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Asymmetrical Schiff Bases as Carriers in PVC Membrane Electrodes for Cadmium (II) IonsELECTROANALYSIS, Issue 8 2005Hossein Mashhadizadeh, Mohammad Abstract 5-[((4-Methyl phenyl) azo)- N -(6-amino-2-pyridin) salicylaldimine] (S1), and 5-[((4-methyl phenyl) azo)- N -(2-diamino-2-cyano-1-ethyl cyanide) salicylaldehyde] (S2) with N and O donor atoms are effective ionophores to make Cd2+ -selective membrane electrodes. The electrodes based on S1 and S2 exhibits a Nernstian or near-Nernstian response for cadmium ion over a wide concentration range 1.5×10,1,7.5×10,7 with a slope of 28 and 2.0×10,1,4.0×10,7 with a slope of 22, respectively. They have quick response and can be used for three or four months without any divergence in potential. The proposed sensors show fairly good selectivity over some alkali, alkaline earth, transition and heavy metal ions. The electrodes based on S1 and S2 can be used in the pH range 3.5,9. These electrodes were used as an indicator electrode in potentiometric titration of cadmium ion with EDTA and in the direct determination of cadmium ion in aqueous solutions. [source] A ,3 -Alkoxo-Bridged Tetranuclear [Cu4L2] Copper(II) Complex of a Hexadentate N2O4 Donor Ligand with a [6 + 0] Cu4O4 Cubane Core: Synthesis, Crystal Structure, and Magnetic PropertiesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 22 2010Dipankar Maity Abstract A novel hexacoordinating non-Schiff base ligand (H4L) with N2O4 donor atoms has been synthesized by simple Mannich reactions. The use of this ligand with Cu(ClO4)2·6H2O in different molar ratios as well as pH leads to the formation of a mononuclear species and a tetranuclear CuII complex possessing a cubane [Cu4L2] core with almost equal Cu···Cu separation. In the presence of an excess amount of copper(II) ions and triethylamine at reflux, the mononuclear [CuH2L] species can be converted into the tetranuclear one, whereas the reverse process was not observed even after prolonged reaction time. Both the complexes have been characterized by single-crystal X-ray diffraction and magnetic measurements. Magnetic studies reveal that complex 1 displays a paramagnetic Curie-type behavior whereas 2 displays a singlet-spin ground state induced by strong intramolecular antiferromagnetic interactions. [source] Solid-State and Solution Structure of Lanthanide(III) Complexes with a Flexible Py-N6 Macrocyclic LigandEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 8 2009Cristina Núñez Abstract Lanthanide complexes of a hexaaza macrocyclic ligand containing a pyridine head unit (L) were synthesized (Ln = La,Lu, except Pm). The solid-state structures of the corresponding La, Ce, Pr, Nd, and Lu complexes were determined by single-crystal X-ray crystallography, and they reveal the presence of three different mononuclear complexes with three different conformations of the macrocycle and coordination environments around the metal ions. In all complexes the lanthanide ion is coordinated in an endomacrocyclic manner to the six nitrogen donor atoms of the ligand. In the La, Ce, and Pr complexes the metal ions show a 12-coordinate mononuclear environment in which 3 nitrate anions coordinate in a bidentate fashion. However, in the Nd analogue the metal ion displays a 10-coordinated environment with the coordination of 2 bidentate nitrate groups, whereas Lu shows a 9-coordinate environment interacting with 2 nitrate ligands, one of them acting as bidentate and the second one coordinating in a monodentate fashion. The 1H and 13C NMR spectra of the complexes recorded in CD3CN suggest that the complexes adopt in solution a similar structure to that observed for the Nd complex in the solid state. The [Ln(L)(NO3)3] and [Ln(L)(NO3)2]+ complexes were characterized by density functional theory (DFT) calculations (B3LYP model). The structures obtained from these calculations for La, Ce, Pr, and Nd are in good agreement with the experimental solid-state structures. The relative stabilities of the [Ln(L)(NO3)2]+ complexes with respect to the [Ln(L)(NO3)3] ones (Ln = La, Nd, Gd, Ho, or Lu) were studied both in vacuo and in acetonitrile solution (PCM model) at the same computational level. Our calculations indicate that in solution the [Ln(L)(NO3)2]+ species is the most stable one along the whole lanthanide series, in agreement with the NMR spectroscopic data.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Toward an Allosteric Metallated ContainerEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 2 2009Helga Szelke Abstract Polytopic ligands L1 and L2 in which three 2,2,-bipyridine units are linked to a central tris(pyrid-2-yl)amine (L1) or tris(pyrid-2-yl)methanol (L2) moiety by alkyl spacers were prepared by multistep organic syntheses. The parent tris(pyrid-2-yl)-type ligands were shown to be modest-to-good chelators for Zn2+ and Cu2+ ions in solution, and bi- and tridentate N-coordination was confirmed by crystal structures of CuII and RuII complexes, respectively. FeII and RuII smoothly form stable, cage-like 1:1 complexes with L1 and L2, in which the metal ion is coordinated to the tris(bpy) site of the ligands. The vacant tris(pyrid-2-yl) site of these complexes is, however, a poor donor site for Zn2+ and Cu2+ ions. In addition, FeII modulates the coordination behaviour of the tris(pyrid-2-yl) site toward Zn2+: Whereas tris(5-methylpyrid-2-yl)amine forms a 2:1 complex with Zn2+ in CH2Cl2, [Fe(L1)]2+ forms a 1:1 Zn complex. Spectrophotometric titrations suggest that [Fe(L2)]2+ forms a polynuclear Zn2+ complex in CH2Cl2, possibly involving bridging coordination of the alcohol OH group, which contrasts the smooth formation of a 2:1 complex of the parent tris(pyrid-2-yl)-type ligand with Zn. FeII might therefore be considered as an allosteric effector, which modulates the metal binding properties of the second tris(pyrid-2-yl) site of L1 and L2. Contrary to expectation, Zn2+ and Cu2+ appear to associate weakly with donor atoms directed toward the exterior of the cage-like complexes [Fe(Ln)]2+ and [Ru(L1)]2+, rather than locating in the interior of the container by tripodal coordination to the tris(pyrid-2-yl) site.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Fine-Tuning Ligands for Catalysis Using Supramolecular StrategiesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 29 2007Vincent F. Slagt Abstract Coordinative bonds have been used to prepare supramolecular ligands leading to well-defined catalysts formed by assembly. The construction of these ligands is based on selective metal,ligand interactions between nitrogen donor atoms of phosphorus-nitrogen building blocks and various zinc(II) porphyrins. The major advantage of this supramolecular approach of catalyst preparation is the simplification of ligand variation enabling straightforward modification of steric, electronic and chiral properties of the supramolecular ligand. A large number of new ligands becomes accessible by this modular variation of the building blocks. The ligand assembly based on pyridyl phosphites and zinc(II) porphyrin with electron-withdrawing substituents led to a twelve-fold increase in activity and an increase in enantioselectivity from 17 to 50,% in the rhodium-catalyzed hydrogenation of dimethyl itaconate. The first examples of assemblies based on non-chiral ligands and chiral zinc(II) porphyrin template molecules show, as proof of principle, an enantiomeric excess up to 18,% in the asymmetric palladium-catalyzed allylic alkylation. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] A Magnetostructural and Electrochemical Study of CuII and FeIII Complexes Containing a Tetradentate Aminebis(phenolate) Ligand with a Pendent Tetrahydrofuran GroupEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 16 2007Elham Safaei Abstract Ligating properties of a tetradentate ligand 2-{bis[(3,5-di- tert -butyl-2-hydroxybenzyl)amino]methyl}tetrahydrofuran,H2L, with [O,O,N,O]-donor atoms towards CuII and FeIII are described. The ligand H2L yields both mononuclear LFeIII(acac) (1) and dinuclear [L2FeIII2(,-OCH3)-(,-OH)] (2), [L2FeIII2(,-C2O4)] (3) and [L2CuII2] (4) complexes, which were characterized by various physical techniques, including X-ray diffraction, Mössbauer, electrochemical and magnetic susceptibility (2,290 K) measurements. That the electrochemical oxidations are ligand-centered, i.e. formation of phenoxyl radicals from the coordinated phenolates, have been shown by voltammetric methods. Complexes 2,4 display antiferromagnetic exchange coupling of the neighbouring metal centers. Comparison of the evaluated weak exchange coupling constants (J) with the literature values leads to the conclusion that the angle Cu,O,Cu, is not the only determinant for the nature of the exchange coupling and the capability of the bridging ligands as mediators for spin coupling in case of FeIII follows the order phenoxide , methoxide > hydroxide. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Receptor versus Counterion: Capability of N,N, -Bis(2-aminobenzyl)-diazacrowns for Giving Endo- and/or Exocyclic Coordination of ZnIIEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 13 2007Lea Vaiana Abstract The structure of ZnII complexes with receptors L1 and L2[L1 = N,N, -bis(2-aminobenzyl)-1,10-diaza-15-crown-5 and L2 = N,N, -bis(2-aminobenzyl)-4,13-diaza-18-crown-6] was studied both in the solid state and in acetonitrile solution. Both receptors form mononuclear ZnII complexes in this solvent, while no evidence for the formation of dinuclear complexes was obtained. This is in contrast with previous investigations that demonstrated the formation of dinuclear complexes of L2 with first-row transition metals such as NiII, CoII and CuII. Compounds of formula [Zn(L1)](ClO4)2 (1), [Zn(L1)](NO3)2·2CH3CN (2), [Zn(L2)](ClO4)2 (3) and [Zn(L2)(NO3)2] (4) were isolated and structurally characterised by X-ray diffraction analyses. L1 forms seven-coordinate ZnII complexes in the presence of both nitrate and perchlorate anions, as a consequence of the good fit between the macrocyclic cavity and the ionic radius of the metal ion. The ZnII ion is deeply buried into the receptor cavity and the anions are forced to remain out of the metal coordination sphere. The cation [Zn(L1)]2+ present in 1 and 2 is one of the very few examples of seven-coordinate Zn complexes. Receptor L2 provides a very rare example of a macrocyclic receptor allowing endocyclic and exocyclic coordination on the same guest cation, depending on the nature of the anion present. Thus, in 3 the ZnII ion is endocyclically coordinated, placed inside the crown hole coordinated to four donor atoms of the ligand in a distorted tetrahedral environment, whereas in 4, the presence of a strongly coordinating anion such as nitrate results in an exocyclic coordination of ZnII, which is directly bound only to the two primarily amine groups of L2 and two nitrate ligands. Spectrophotometric titrations of [Zn(L2)]2+ with tetrabutylammonium nitrate in acetonitrile solution demonstrate the stepwise formation of 1:1 and 1:2 adducts with this anion in acetonitrile solution. The [Zn(L1)]2+, [Zn(L2)]2+ and [Zn(L2)(NO3)2] systems were characterised by means of DFT calculations (B3LYP model). The calculated geometries show an excellent agreement with the experimental structures obtained from X-ray diffraction analyses. Calculated binding energies of the macrocyclic ligands to ZnII are also consistent with the experimental data.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Synthesis, Structure and Magnetic Properties of a Tetranuclear Copper(II) Complex on the Basis of a 2-Substituted Glucopyranoside Schiff Base Ligand,EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 17 2006Anja Burkhardt Abstract Condensation of a derivatized 2-aminoglucose fragment with salicylaldehyde affords the new sugar-based Schiff base ligand benzyl 4,6- O -benzylidene-2-deoxy-2-salicylideneamino-,- D -glucopyranoside (H2L). The reaction of the dibasic ligand H2L with [Cu(CH3COO)2]·H2O leads to the formation of the tetranuclear copper(II) complex [{Cu(L)}4] (3) by a self-assembly process. The X-ray structural analysis of complex 3 which crystallizes together with two molecules of chloroform and one molecule of ethanol in the space group P212121 revealed for all copper atoms a NO3 coordination environment with a square-planar geometry. The tetranuclear molecule 3 consists of four chiral building blocks {Cu(L)} with the rare 2,3-coordination of the trans -configured donor atoms of the sugar backbone. The observed coordination mode of the building blocks exemplifies how chitosan-derived polysaccharide ligands can act as a chiral support for transition-metal complexes. The C-3 alcoholate oxygen atoms of the carbohydrate unit is bridging adjacent {Cu(L)} moieties resulting in an eight-membered Cu4O4 ring with a boat-like conformation. Temperature-dependent magnetic measurements of 3 indicate moderate antiferromagnetic interactions between the four copper(II) ions with a coupling constant of J = ,130 cm,1.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Chiral Half-Sandwich Ruthenium(II) Complexes as Catalysts in 1,3-Dipolar Cycloaddition Reactions of Nitrones with Methacrolein,EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 16 2006Daniel Carmona Abstract Ruthenium complexes of formula [(,6 -arene)Ru(LL*)(H2O)][SbF6]2 (arene = C6H6, p -MeC6H4iPr, C6Me6; LL* = bidentate chelate chiral ligand with PN, PP or NN donor atoms) have been tested as catalyst precursors for the asymmetric 1,3-dipolar cycloaddition of nitrones to methacrolein. The reaction occurs quantitatively with perfect endo selectivity and moderate enantioselectivity (up to 74,% ee). The ruthenium aqua complexes can be prepared from the corresponding chlorides, [(,6 -arene)RuCl(LL*)][SbF6]. Dipolarophile intermediates [(,6 -arene)Ru(PNiPr)(methacrolein)][SbF6]2 {PNiPr = (4S)-2-(2-diphenylphosphanylphenyl)-4-isopropyl-1,3-oxazoline} as well as nitrone-containing complexes [(p -MeC6H4iPr)Ru(PNiPr)(nitrone)][SbF6]2 (nitrone = N -benzylidenephenylamine N -oxide, N -benzylidenemethylamine N -oxide, 3,4-dihydroisoquinoline N -oxide) have been also isolated and characterised. The crystal structures of the chlorides (RRu)-[(,6 -C6Me6)RuCl(PNiPr)][SbF6], (RRu)-[(,6 -C6H6)RuCl(PNInd)][SbF6] {PNInd = (3aR,8aS)-2-[2-(diphenylphosphanyl)phenyl]-3a,8a-dihydroindane[1,2- d]oxazole} and those of the aqua solvates (RRu)-[(,6 -arene)Ru(PNiPr)(H2O)][SbF6]2 (arene = C6H6, C6Me6) were determined by X-ray diffraction methods. (© 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 CompoundsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 24 2005Eugenio 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] Mono- and Dinuclear CuII and ZnII Complexes of Cyclen-Based Bis(macrocycles) Containing Two Aminoalkyl Pendant Arms of Different LengthsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 11 2005Carmen Anda Abstract The basicity and coordination properties towards CuII and ZnII of the bis(macrocycles) L1, L2 and L3 have been investigated by means of potentiometric, 1H NMR and UV/Vis spectroscopic titrations in aqueous solutions. The synthesis of L1 and L3 is also described. The three ligands are composed of two [12]aneN4 units separated by a p- phenylene spacer and differ in the length of the aminoalkyl pendant arms linked to each macrocyclic unit. L1,L3 form mono- and dinuclear complexes in aqueous solutions; in the dinuclear species each metal ion is coordinated by one of the two identical [12]aneN4 ligand moieties, as shown by the crystal structures of the complexes [Cu2L1]Cl4·8H2O, [Zn2L2](ClO4)4 and [Zn2L3](ClO4)4·H2O. In all structures the metal ion is pentacoordinate, and is bound to the four nitrogen donors of the cyclic unit and to the amine group of the side arm. The stability of both the [ML]2+ and [M2L]4+ complexes in aqueous solution decreases in the order L1 > L2 > L3. At the same time, both the [Cu2L]4+ and [Zn2L]4+ complexes show a different ability in proton binding among the three ligands, with the [M2L1]4+ complexes displaying the highest basicity. These results are explained in terms of the decreasing number of nitrogen donors involved in CuII or ZnII binding on passing from L1 to L3; in other words, while in the L1 dinuclear complexes each metal ion is coordinated to the four amine groups of a [12]aneN4 moiety and to the amine group of the side arm, in the L3 ones the metal cations are bound only to the four donor atoms of a cyclic moiety, the aminobutyl group not being coordinated. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Structure Comparison of Early and Late Lanthanide(III) Homodinuclear Macrocyclic Complexes with the Polyamine Polycarboxylic Ligand H8OHECEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 19 2004Ulrike A. Böttger Abstract The solid-state structures of two new homodinuclear chelate complexes with the late lanthanide(III) ions Yb and Lu, [Na2(Yb2OHEC)].14.5H2O (1), and [Na2(Lu2OHEC)].14.5H2O (2) (H8OHEC = 1,4,7,10,14,17,20,23-octaazacyclohexacosane- 1,4,7,10,14,17,20,23-octaacetic acid), have been determined by X-ray crystal structure analysis. Each lanthanide(III) ion is coordinated by eight donor atoms of the ligand and the geometry of the coordination polyhedron approaches a bicapped trigonal prism. These structures are compared with those of the homodinuclear chelate complexes with the same ligand and the mid to early lanthanide(III) ions Gd, Eu, La and also Y. A distinctive structural change occurs across the lanthanide series. The centrosymmetric mid to early lanthanide(III) complexes are all ninefold-coordinated in a capped square antiprismatic arrangement with a water molecule coordinated in a prismatic position. This structure is maintained in aqueous solution, together with an asymmetric minor isomer. The late lanthanide(III) OHEC complexes not only lack the inner-sphere water, but the change of coordination sphere also results in a loss of symmetry of the whole complex molecule. The observed change of coordination mode and number of the lanthanide ion may offer a geometric model for the isomerization process in eight- and ninefold-coordinated complex species that are isomers in a possible coordination equilibrium observed by NMR in aqueous solution. This model may also explain the intramolecular rearrangements necessary during water exchange in the inner coordination sphere of the complex [(Gd2OHEC)(H2O)2]2, through a slow dissociative mechanism. Protonation constants of the H8OHEC ligand and complex formation constants of this ligand with GdIII, CaII, CuII and ZnII have been determined by solution thermodynamic studies. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Towards Cationic Gallium Derivatives: Metallacycles from the Reactions of Organogallium Compounds with Tetraorganodichalcogenoimidodiphosphinates and a New N -(Diphenylthiophosphinyl)thioureato LigandEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 18 2004Virginia Montiel-Palma Abstract The organometallic complexes of general formulae [Me2Ga{,2 - E,E, -[R2P(E)NP(E,)R,2]}] [R = R, = Ph, E = E, = O (1); R = R, = Ph, E = E, = S (2); R = R, = Ph, E = E, = Se (3); R = R, = Ph, E = O, E, = S (4); R = Me, R, = Ph, E = S, E, = O (5)] and [Me2Ga{,2 - S,S, -[Ph2P(S)NC(S)(C9H10N)]}] (6) were obtained by facile methane elimination reactions from GaMe3 and the acidic ligands L1H [(XPPh2)2NH (X = O, S, Se), (OPPh2)(SPPh2)NH, and (OPMe2)(SPPh2)NH] and L2H [Ph2P(S)NHC(S)(C9H10N)] in toluene. Replacement of one phosphorus atom by a carbon atom in the ligand skeleton of L1H gave the new ligand L2H, which, upon reaction with GaMe3, gave compound 6, which shows no significant structural differences with respect to 1,5. Therefore, L2H does not induce partial planarity in the six-membered ring, indicating the necessity for replacing both phosphorus atoms of the ligand by carbon atoms, as in the ,-diketonate-type derivatives, in order to impose ring planarity. Thus, despite originating from a variety of ligands with differing donor atoms and substituents at the phosphorus atoms, all complexes show little structural differences. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Synthesis and Luminescence Properties of New Dinuclear Complexes of Lanthanide(III) IonsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 11 2004Violetta Patroniak Abstract As a result of coordination of the ligand L, containing two tridentate binding units, to samarium(III), europium(III), terbium(III), and dysprosium(III) ions, new dinuclear architectures containing two ions with coordination number 9 were formed. The structures of the complexes have been assigned on the basis of their solution spectroscopic and microanalytical data, and confirmed by X-ray crystallography in the case of the europium(III) complex 2. The structural analysis of the dinuclear complex 2 showed the presence of two europium centers [Eu(1) and Eu(2)] and four ligands L. Each europium ion is coordinated by 9 donor atoms with typical Eu,N and Eu,O distances. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Configuration of Octahedral Metal Compounds , Equilibrium, Crystal and Molecular Structure of Nickel(II) Complexes of Linear N2O4, N4S2 or N6 Donors Set Atoms LigandsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 6 2004Aminou Mohamadou Abstract Two new nickel(II) complexes of symmetric hexadentate mixed-ligand N,O [1,12-bis(2-pyridyl)-5,8-dioxa-2,11-diazadodecane (pydado)] and N,S [1,12-bis(2-pyridyl)-5,8-dithia-2,11-diazadodecane (pydadt)] donor atoms have been synthesised as perchlorate salts and characterised by X-ray crystallography and ligand-field spectroscopy. In both complexes the Ni2+ ion is hexacoordinate. The cation [Ni(pydado)]2+ is pseudo-octahedral with the two pyridyl groups in trans position; all Ni,N and Ni,O bond lengths are practically equivalent. In [Ni(pydadt)]2+ complex, however, the size of the thioether sulfur atoms imposes a C2v symmetry; the pyridyl groups and the sulfur atoms are in trans positions and all Ni,N bond lengths are equivalent. The comparison of these structures with those of octahedral cobalt, copper and zinc complexes with the same ligands shows that their configurations depend not only on the nature of the two central donor atoms of the ligand, but also on the nature of the metallic ion. In aqueous solution, the stability constants of the NiII chelates with these two ligands, determined by potentiometry, show the formation of [Ni(LH)]3+ and [NiL]2+ species in all cases. The chelating power of the pydadt ligand is slightly greater than that of pydado. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Metal-Controlled Stereoselectivity in Complex Formation: Assembly of Tetranuclear Copper(I) Complexes with Four Stereogenic Nitrogen Donor Functions in all-(R) and all-(S) ConfigurationsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 9 2003Jörg Schneider Abstract The reaction of N,N, -dialkyl-3,7-diazanonane-1,9-dithiolate (NR2S2) ligands (R = Me, Et) with monovalent copper resulted in the formation of the chiral complexes [Cu4(NMe2S2)2] (1) and [Cu4(NEt2S2)2] (2) which were characterised by means of X-ray diffraction and spectroscopic techniques. They contain copper atoms in both linear {S,Cu,S} fragments, which act as linkers between mononuclear [Cu(NR2S2)], subsites, and in {CuS2N2} units within these building blocks, which can be described as incomplete coordination octahedra of unusual design. Due to favourable interplay between the spatial demands of the ligand system and the electronic requirements of the copper atom, the nitrogen donor atoms within the [Cu(NR2S2)], metallo ligands are restricted to identical absolute configurations. The combination of two [Cu(NR2S2)], metallo ligands with two further CuI ions to give the tetranuclear complexes 1 or 2 via S,Cu,S bridges underlies stereochemical control, resulting in optically active systems with (R,R,R,R) and (S,S,S,S) configurations. Consequently, metallo ligands in their enantiomeric forms cannot combine via S,Cu,S bridges to form optically inactive meso complexes with the (R,R,S,S) configuration. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] Studies of Pyridinyl-Containing 14-Membered Macrocyclic Copper(II) ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 7 2003Sabrina Autzen Abstract Six copper(II) complexes of tetracoordinating, pyridinyl-containing 14-membered macrocycles with varying ratios of nitrogen and oxygen donor atoms were prepared and characterized by IR, UV/Vis, and EPR spectroscopy and cyclic voltammetry. A distorted tetragonal coordination of the copper center in the solid-state was established by X-ray crystallography for the tetraazamacrocyclic complex Cu-3 carrying a methoxybenzyl pendent arm and the trioxaaza complex Cu-6. The superoxide dismutase-like activity of the CuII complexes was investigated by inhibition of NADH oxidation. Although the UV/Vis and EPR spectra of the complexes were strongly affected when the coordinating nitrogen atoms were successively replaced by oxygen atoms, no significant change in their reactivity towards superoxide was observed. In all cases a 1:1 or 1:2 stoichiometry for the reaction with superoxide was found, with the exception of the methoxybenzyl-substituted tetraaza complex, which showed a low catalytic activity with a turnover number of about 10. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] Organic Ligands Made Porous: Magnetic and Catalytic Properties of Transition Metals Coordinated to the Surfaces of Mesoporous OrganosilicaADVANCED FUNCTIONAL MATERIALS, Issue 7 2010Andreas Kuschel Abstract Inorganic solids with porosity on the mesoscale possess a high internal surface area and a well-accessible pore system. Therefore, it is a relevant task to equip the surfaces of such materials with a maximum density of various organic functional groups. Among these functions it is the capability of coordinating to metal species as a ligand that is of extraordinary importance in many areas, for example, in catalysis. This paper describes how prominent ligands containing donor functions such as carboxylic, thio, chelating, or amine groups can be obtained in the form of nanoporous organosilica materials. The coordination of metal centers such as CoII, MnII, VIV, or PtIV is studied in detail. The magnetic properties of the corresponding materials and some applications in catalysis are reported. A quantitative determination of the surface density of donor atoms by distance measurements using EPR spectroscopy is shown. [source] Synthesis, characterization, and in vitro antimicrobial activities of organotin(IV) complexes of Schiff bases with ONO-type donor atomsHETEROATOM CHEMISTRY, Issue 6 2010Gülgün Yeni, ehirli A new series of diorganotin complexes of the type R2SnL (L1: N -(2-hydroxy-5-chlorophenyl)- 3-ethoxysalicylideneimine, R = Me, (Me2SnL1), R = n -Bu, (n -Bu2SnL1), R = Ph, (Ph2SnL1), L2: N -(2-hydroxy-4-nitro-5-chlorophenyl)-3-ethoxysalicylideneimine, R = Ph, Ph2SnL2, L3: N -(2-hydroxy-4-nitrophenyl)-3-methoxysalicylideneimine, R = Me, (Me2SnL3), R = n -Bu, (n -Bu2SnL3), L4: N -(2-hydroxy-4-nitrophenyl)-3-ethoxysalicylideneimine, R = Me, (Me2SnL4), R = n -Bu, (n -Bu2SnL4)) were synthesized and characterized by elemental analysis, infrared (IR), 1H, and 13C NMR mass spectroscopic techniques, and electrochemical measurements. Ph2SnL1 and Ph2SnL2 were also characterized by X-ray diffraction analysis and were found to show a fivefold C2NO2 coordination geometry nearly halfway between a trigonal bipyramidal and distorted square pyramidal arrangement. The CSnC angles in the complexes were calculated using Lockhart's equations with the 1J(117/119Sn- 13C) and 2J(117/119Sn- 1H) values from the 1H NMR and 13C NMR spectra. Biocidal activity tests against several micro-organisms and some fungi indicate that all the complexes are mildly active against Gram (+) bacteria and the fungi, A. niger and inactive against Gram (,) bacteria. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 21:373,385, 2010; View this article online at wileyonlinelibrary.com. DOI 10.1002/hc.20628 [source] Low- and high-spin iron (II) complexes studied by effective crystal field method combined with molecular mechanicsJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 14 2003M. B. Darkhovskii Abstract A computational method targeted to Werner-type complexes is developed on the basis of quantum mechanical effective Hamiltonian crystal field (EHCF) methodology (previously proposed for describing electronic structure of transition metal complexes) combined with the Gillespie,Kepert version of molecular mechanics (MM). It is a special version of the hybrid quantum/MM approach. The MM part is responsible for representing the whole molecule, including ligand atoms and metal ion coordination sphere, but leaving out the effects of the d -shell. The quantum mechanical EHCF part is limited to the metal ion d -shell. The method reproduces with reasonable accuracy geometry and spin states of the Fe(II) complexes with monodentate and polydentate aromatic ligands with nitrogen donor atoms. In this setting a single set of MM parameters set is shown to be sufficient for handling all spin states of the complexes under consideration. © 2003 Wiley Periodicals, Inc. J Comput Chem 14: 1703,1719, 2003 [source] 15N NMR coordination shifts in Pd(II), Pt(II), Au(III), Co(III), Rh(III), Ir(III), Pd(IV), and Pt(IV) complexes with pyridine, 2,2,-bipyridine, 1,10-phenanthroline, quinoline, isoquinoline, 2,2,-biquinoline, 2,2,:6,, 2,-terpyridine and their alkyl or aryl derivativesMAGNETIC RESONANCE IN CHEMISTRY, Issue S1 2008Leszek Pazderski Abstract The 15N NMR data for 105 complexes of Pd(II), Pt(II), Au(III), Co(III), Rh(III), Ir(III), Pd(IV), and Pt(IV) complexes with simple azines such as pyridine, 2,2,-bipyridine, 1,10-phenanthroline, quinoline, isoquinoline, 2,2,-biquinoline, 2,2':6', 2"-terpyridine and their alkyl or aryl derivatives have been reviewed. The 15N NMR coordination shifts, i.e. the differences between the 15N chemical shifts of the same nitrogen in the molecules of the complex and the ligand (,15Ncoord = ,15Ncompl , ,15Nlig), have been related to some structural features of the reviewed coordination compounds, like the type of the central ion and the character of auxiliary ligands (mainly in trans position). These ,15Ncoord parameters are negative, their absolute magnitudes (ca 30,150 ppm) generally increasing in the metal order Au(III) < Pd(II) < Pt(II) and Rh(III) < Co(III) < Pt(IV) < Ir(III), as well as with the enhanced trans influence of the other donor atoms (H, C , Cl < N). Copyright © 2008 John Wiley & Sons, Ltd. [source] A three-dimensional pyrazine-2,5-dicarboxylate CdII coordination framework with new (4,4,4)-connected three-nodal topologyACTA CRYSTALLOGRAPHICA SECTION C, Issue 1 2009Ping Yang Poly[(,4 -pyrazine-2,5-dicarboxylato)cadmium(II)], [Cd(C6H2N2O4)]n or [Cd(pzdc)]n (pzdc is the pyrazine-2,5-dicarboxylate dianion), has been synthesized hydrothermally. The asymmetric unit consists of a CdII atom and two independent halves of pzdc ligands that can be expanded via inversion through the centres of the ligands so that each ligand binds to four CdII atoms with the same binding mode using six donor atoms. The CdII centre is in a distorted octahedral coordination geometry with four O- and two N-atom donors from four pzdc ligands. The infinite linkage of the metal atoms and ligands forms a three-dimensional framework with a rectangular channel which is so narrow that there is no measurable void space in the overall structure. This coordination polymer represents the first example of (4,4,4)-connected three-nodal framework. [source] The new three-dimensional supramolecule bis{,-2-[(4-hydroxybenzoyl)hydrazonomethyl]phenolato}bis[aquacopper(II)] dinitrateACTA CRYSTALLOGRAPHICA SECTION C, Issue 10 2008Hua Yin In the title centrosymmetric binuclear complex, [Cu2(C14H11N2O3)2(H2O)2](NO3)2, the two metal centres are bridged by the phenolate O atoms of the ligand, forming a Cu2O2 quadrangle. Each Cu atom has a distorted square-pyramidal geometry, with the basal donor atoms coming from the O,N,O,-tridentate ligand and a symmetry-related phenolate O atom. The more weakly bound apical donor O atom is supplied by a coordinated water molecule. When a further weak Cu...O interaction with the 4-hydroxy O atom of a neighbouring cation is considered, the extended coordination sphere of the Cu atom can be described as distorted octahedral. This interaction leads to two-dimensional layers, which extend parallel to the (100) direction. The two-dimensional polymeric structure contrasts with other reported structures involving salicylaldehyde benzoylhydrazone ligands, which are usually discrete mono- or dinuclear Cu complexes. The nitrate anions are involved in a three-dimensional hydrogen-bonding network, featuring intermolecular N,H...O and O,H...O hydrogen bonds. [source] catena -Poly[[(trifluoromethanesulfonato-,O)silver(I)]-,-di-2-pyridylamine-,2N2:N2,], a chain polymer with short Ag,C contactsACTA CRYSTALLOGRAPHICA SECTION C, Issue 9 2006Peter G. Jones The title compound, [Ag(CF3O3S)(C10H9N3)]n, is a chain polymer in which neighbouring monomeric units are related by a glide plane. The silver centre is four-coordinate; the donor atoms are one trifluoromethanesulfonate O atom and one pyridine N atom from each of two symmetry-related dipyridylamines, and an additional and unexpected Ag,C contact [2.6464,(16),Å] is observed to a pyridine C atom. The chains are reinforced by one classical N,H,O and two `weak' C,H,O hydrogen bonds. [source] Dihalodimethyltin(IV) complexes of 2-(pyrazol-1-ylmethyl)pyridineAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 9 2003Pedro Álvarez-Boo Abstract Reaction of dichloro- and dibromodimethyltin(IV) with 2-(pyrazol-1-ylmethyl)pyridine (PMP) afforded [SnMe2Cl2(PMP)] and [SnMe2Br2(PMP)] respectively. The new complexes were characterized by elemental analysis and mass spectrometry and by IR, Raman and NMR (1H, 13C) spectroscopies. Structural studies by X-ray diffraction techniques show that the compounds consist of discrete units with the tin atom octahedrally coordinated to the carbon atoms of the two methyl groups in a trans disposition (SnC = 2.097(5), 2.120(5) Å and 2.110(6), 2.121(6) Å in the chloro and in the bromo compounds respectively), two cis halogen atoms (SnCl = 2.4908(16), 2.5447(17) Å; SnBr = 2.6875(11), 2.7464(9) Å) and the two donor atoms of the ligand (SnN = 2.407(4), 2.471(4) Å and 2.360(5), 2.455(5) Å). In both cases, the SnN(pyridine) bond length is markedly longer than the SnN(pyrazole) distance. Copyright © 2003 John Wiley & Sons, Ltd. [source] Lanthanide(III) Complexes of 4,10-Bis(phosphonomethyl)-1,4,7,10-tetraazacyclododecane-1,7-diacetic acid (trans -H6do2a2p) in Solution and in the Solid State: Structural Studies Along the SeriesCHEMISTRY - A EUROPEAN JOURNAL, Issue 28 2010M. Paula Abstract Complexes of 4,10-bis(phosphonomethyl)-1,4,7,10-tetraazacyclododecane-1,7-diacetic acid (trans -H6do2a2p, H6L) with transition metal and lanthanide(III) ions were investigated. The stability constant values of the divalent and trivalent metal-ion complexes are between the corresponding values of H4dota and H8dotp complexes, as a consequence of the ligand basicity. The solid-state structures of the ligand and of nine lanthanide(III) complexes were determined by X-ray diffraction. All the complexes are present as twisted-square-antiprismatic isomers and their structures can be divided into two series. The first one involves nona-coordinated complexes of the large lanthanide(III) ions (Ce, Nd, Sm) with a coordinated water molecule. In the series of Sm, Eu, Tb, Dy, Er, Yb, the complexes are octa-coordinated only by the ligand donor atoms and their coordination cages are more irregular. The formation kinetics and the acid-assisted dissociation of several LnIII,H6L complexes were investigated at different temperatures and compared with analogous data for complexes of other dota-like ligands. The [Ce(L)(H2O)]3, complex is the most kinetically inert among complexes of the investigated lanthanide(III) ions (Ce, Eu, Gd, Yb). Among mixed phosphonate,acetate dota analogues, kinetic inertness of the cerium(III) complexes is increased with a higher number of phosphonate arms in the ligand, whereas the opposite is true for europium(III) complexes. According to the 1H,NMR spectroscopic pseudo-contact shifts for the Ce,Eu and Tb,Yb series, the solution structures of the complexes reflect the structures of the [Ce(HL)(H2O)]2, and [Yb(HL)]2, anions, respectively, found in the solid state. However, these solution NMR spectroscopic studies showed that there is no unambiguous relation between 31P/1H lanthanide-induced shift (LIS) values and coordination of water in the complexes; the values rather express a relative position of the central ions between the N4 and O4 planes. [source] | ||||||||||