Search results for " sphere"
showing 10 items of 404 documents
Rational design of aminoanthraquinones for colorimetric detection of heavy metal ions in aqueous solution
2011
A family of water-soluble colorimetric chemosensors incorporating an anthraquinone signalling subunit functionalized with a polyamine chain that bears hydrophilic diethoxyphosphoryl moieties was prepared with the aim of assaying metal cations. The outstanding UV-Vis absorption properties of the 1-aminoanthraquinone chromophore allowed the efficient visual detection and quantification of copper(II) ions by chelators L(1)-L(3) in buffered aqueous solution. Moreover, the visible response of L(2) is not interfered by addition of large excesses of 13 common metal ions, whereas chemosensor L(3) produces also a color change in the presence of equimolar amounts of lead(II). Considering the 134 nm g…
A Two-State Computational Investigation of Methane C-H and Ethane C-C Oxidative Addition to [CpM(PH3)]n+ (M=Co, Rh, Ir;n=0, 1)
2006
Reductive elimination of methane from methyl hydride half-sandwich phosphane complexes of the Group 9 metals has been investigated by DFT calculations on the model system [CpM(PH(3))(CH(3))(H)] (M = Co, Rh, Ir). For each metal, the unsaturated product has a triplet ground state; thus, spin crossover occurs during the reaction. All relevant stationary points on the two potential energy surfaces (PES) and the minimum energy crossing point (MECP) were optimized. Spin crossover occurs very near the sigma-CH(4) complex local minimum for the Co system, whereas the heavier Rh and Ir systems remain in the singlet state until the CH(4) molecule is almost completely expelled from the metal coordinati…
Copper(II) complexes of 1,4,5,8,9,12-hexaazatriphenylene with oxalate, squarate, perchlorate as auxiliary ligands or counter ion
2002
Abstract The crystal structures of [Cu(hat)(H2O)(ox)]·H2O (I), [Cu(hat)(H2O)3(sq)]·3H2O (II) and [Cu(hat)(H2O)2](ClO4)2·4H2O (III) have been determined from X-ray single crystal diffraction data (hat=1,4,5,8,9,12-hexaazatriphenylene, ox=oxalate, sq=squarate=dianion of 3,4-dihydroxy-cyclobut-3-ene-1,2-dione). Compound I crystallises in the triclinic system, space group P 1 with a=6.6626(10), b=9.2001(14), c=12.9954(19) A , α=103.301(15), β=91.414(21), γ=105.523(13)°, Z=2; compound II in the orthorhombic system, space group P212121 with a=6.9274(2), b=8.4327(3), c=34.0577(14) A , Z=4; and compound III in the monoclinic system, space group C2/c with a=22.6652(10), b=9.2220(10), c=16.1400(10) A…
Investigation into the reactivity of oxoniobocene complexes [Cp*2Nb(O)R] (Cp*=η5-C5Me5; R=H, OH, OMe) towards heterocumulenes: formation of carbamat…
2001
Abstract The reaction of [Cp*2NbCl2] (Cp*=η5-C5Me5) with KOH or Ba(OH)2·8H2O in THF was investigated under slightly modified conditions. In addition to the known complex [Cp*2Nb(O)H] (1), the new compound [Cp*2Nb(O)OH] (2) was formed. The reaction of 2 with PhNCS gave yellow [Cp*2Nb(O){SC(O)NHPh}] (3), while PhNCO formed yellow [Cp*2Nb(O){OC(O)NHPh}] (4). Complexes 3 and 4 were analytically and spectroscopically characterized. X-ray diffraction analyses of both compounds show that they contain either η1-S-thiocarbamato (3) or η1-O-carbamato ligand (4) along with a terminal NbO group. The reaction of 1 with one equivalent of PhNCO mainly gave orange [Cp*2NbH{OC(O)NPh}] (5) along with so…
Crystal structure of the coordination polymer [FeIII2{PtII(CN)4}3]
2015
[EN] The title complex, poly[dodeca--cyanido-diiron(III)triplatinum(II)], [FeIII2{PtII(CN)4}3], has a three-dimensional polymeric structure. It is built-up from square-planar [PtII(CN)4] 2 anions (point group symmetry 2/m) bridging cationic [FeIIIPtII(CN)4] + 1 layers extending in the bc plane. The FeII atoms of the layers are located on inversion centres and exhibit an octahedral coordination sphere defined by six N atoms of cyanide ligands, while the PtII atoms are located on twofold rotation axes and are surrounded by four C atoms of the cyanide ligands in a square-planar coordination. The geometrical preferences of the two cations for octahedral and square-planar coordination, respectiv…
Structural and Electrochemical Studies of Copper(I) Complexes with Diethoxyphosphoryl-1,10-phenanthrolines
2014
Two series of copper(I) complexes with diethoxyphosphoryl-substituted 1,10-phenanthroline ligands were synthesized and characterized in the solid state and in solution. The first comprised mixed-ligand CuI complexes with phenanthroline and triphenylphosphine. The second series includes bis-chelates with two phenanthroline ligands. According to the X-ray data for the six complexes, the ditopic phenanthroline ligands exhibit bidentate coordination to the copper(I) atom through two nitrogen atoms in both series. Solution equilibria involving different phenanthroline copper(I) species were studied by 1H and 31P NMR spectroscopy, electrochemistry, and spectroelectrochemistry. The solution specia…
Multidentate Tetrahydrofurfuryloxide Ligand in a Ziegler−Natta Catalyst Studied by Molecular Modeling
2008
The transition from a generation III Ziegler-Natta catalyst with a monodentate Lewis base to a more modem generation 1V/V system, containing a tetrahydrofuran derivative, the tetrahydrofurturyloxide C 4 H 7 O-CH 2 O - bidentate ligand (THFFO), was studied by means of molecular modeling and DFT calculations. This particular ligand was carefully chosen so that it remained in the titanium coordination sphere in the model active site. With such a constraint, the dual role of tetrahydrofurfuryloxide was identified: it was demonstrated how the presence of this ligand limits the number of isomeric active sites as well as enhances the selectivity of the species that can still exist. The results ind…
Exceptionally long-lived light-emitting electrochemical cells: multiple intra-cation π-stacking interactions in [Ir(C^N)2(N^N)][PF6] emitters
2015
A series of cyclometalated iridium(iii) complexes [Ir(C^N)2(N^N)][PF6] (N^N = 2,2′-bipyridine (1), 6-phenyl-2,2′-bipyridine (2), 4,4′-di-tert-butyl-2,2′-bipyridine (3), 4,4′-di-tert-butyl-6-phenyl-2,2′-bipyridine (4); HC^N = 2-(3-phenyl)phenylpyridine (HPhppy) or 2-(3,5-diphenyl)phenylpyridine (HPh2ppy)) are reported. They have been synthesized using solvento precursors so as to avoid the use of chlorido-dimer intermediates, chloride ion contaminant being detrimental to the performance of [Ir(C^N)2(N^N)][PF6] emitters in light-electrochemical cell (LEC) devices. Single crystal structure determinations and variable temperature solution 1H NMR spectroscopic data confirm that the pendant pheny…
C−C Cross-Couplings from a Cyclometalated Au(III) C∧ N Complex: Mechanistic Insights and Synthetic Developments
2021
Abstract In recent years, the reactivity of gold complexes was shown to extend well beyond π‐activation and to hold promises to achieve selective cross‐couplings in several C−C and C−E (E=heteroatom) bond forming reactions. Here, with the aim of exploiting new organometallic species for cross‐coupling reactions, we report on the Au(III)‐mediated C(sp2)−C(sp) occurring upon reaction of the cyclometalated complex [Au(CCH2N)Cl2] (1, CCH2N=2‐benzylpyridine) with AgPhCC. The reaction progress has been monitored by NMR spectroscopy, demonstrating the involvement of a number of key intermediates, whose structures have been unambiguously ascertained through 1D and 2D NMR analyses (1H, 13C, 1H‐1H CO…
Outer and inner coordination sphere chemistry of polyazacyclophane platinum(II) complexes. Crystal structure of [PtBr4]2(H4L1) · H2O (L1 = 2,6,9,13-t…
1997
Abstract The interaction of PtCl42− with the new azaparacyclophane 2,5,8,11-tetraaza[12]paracyclophane (L2) has been studied by 1H, 13C and 195Pt NMR spectroscopy. Three different complexes are detected as a function of pH, all of them presenting cis-arrangement of nitrogen donors and chloride anions. In the first one, formed at acidic pH, the central nitrogen atoms of the macrocyclic are coordinating to Pt(II) while the benzylic nitrogens remain protonated. Deprotonation of these nitrogens brings about a reorganisation of the complex, and the platinum is then coordinated by one benzylic nitrogen and the consecutive nitrogen in the macrocycle. This process can be monitored by NMR. Finally, …