Search results for "Denticity"
showing 10 items of 376 documents
Bridging vs. Chelating Coordination Modes of Vinylsilanes in CuIπ-Complexes: Structure and Stability
2013
Two new copper(I) olefin complexes, [Cu6Cl6(MTrVS)2] (1) and [Cu2Cl2(DMVSP)2] (2), of tridentate bridging methyltrivinylsilane (MTrVS) and bidentate chelating 2-[dimethyl(vinyl)silyl]pyridine (DMVSP) have been synthesized and characterized by single-crystal X-ray structure analysis, IR and 1H NMR spectroscopy. It has been shown that using the alkenylsilanes with required electronic properties, molecular symmetry and conformational flexibility, it is possible to control the formation of optimal copper(I) halide oligomers. The obtained results, together with relevant literature data, also illustrate how the coordination mode of vinylsilanes is related to Cu–(C=C) bond strengthening and, conse…
Carbon–Phosphorus Coupling from C^N Cyclometalated Au III Complexes
2020
Abstract With the aim of exploiting new organometallic species for cross‐coupling reactions, we report here on the AuIII‐mediated Caryl−P bond formation occurring upon reaction of C^N cyclometalated AuIII complexes with phosphines. The [Au(C^N)Cl2] complex 1 featuring the bidentate 2‐benzoylpyridine (CCON) scaffold was found to react with PTA (1,3,5‐triaza‐7‐phosphaadamantane) under mild conditions, including in water, to afford the corresponding phosphonium 5 through C−P reductive elimination. A mechanism is proposed for the title reaction based on in situ 31P{1H} NMR and HR‐ESI‐MS analyses combined with DFT calculations. The C−P coupling has been generalized to other C^N cyclometalated Au…
ChemInform Abstract: X-Ray Powder Structure Determination and Thermal Behavior of a New Modification of Pb(II) Selenite.
2010
The crystal structure of a new polymorphic form of lead(II) selenite (PbSeO3) was solved directly from conventional X-ray powder diffraction data. Direct methods and Rietveld refinement techniques were used for the structure determination. The compound crystallizes in the monoclinic space group P21/c (no. 14) with cell dimensions a = 9.1587(1) A, b = 8.0902(1) A, c = 8.7932(1) A, β = 103.032(1)°, and V = 634.76(2) A3. The final refinement gave background excluded Rp = 6.22%, Rwp = 8.81%, and RB = 2.16% by using 45 structural and 15 profile parameters with 10 atoms in an asymmetric unit. The three-dimensional structure consists of 9-coordinated lead atoms, which are linked by three bidentate…
Computational modeling of single-versus double-anchoring modes in di-branched organic sensitizers on TiO2 surfaces: structural and electronic propert…
2014
We present a first-principles DFT investigation of the adsorption geometry on the anatase (101) surface of a prototypical di-branched organic dye based on the extended tetrathiafulvalene moiety, incorporating two anchoring cyanoacrylic acid units. Reduced model systems with one and two anchoring groups have been initially studied to investigate the vibrational frequencies related to TiO2 dye adsorption. Our calculations confirm that the reduced systems can be used as reliable models to study the anchoring modes and that the conclusions extracted from the reduced systems can be extrapolated to the entire molecule. A series of molecular structures have been investigated to simulate the anchor…
DNA Oxidation Photoinduced by Norharmane Rhenium(I) Polypyridyl Complexes: Effect of the Bidentate N,N′-Ligands on the Damage Profile
2018
Re(I)--polypyridyl complexes have interesting and distinctive photochemical and photosensitizing properties. This work describes the capability to induce (or photoinduce) DNA damage of three Re(I)-complexes with a naturally occurring alkaloid called norharmane (nHo) as ligand: [Re(CO)₃ (nHo)(L)]CF₃ SO₃ where L=2,2'-bipyridine (ReBpy), phenanthroline (RePhen) or dipyrido[3,2-a:2',3'-c]phenazine (ReDppz). The interaction of the complexes with DNA was investigated by steady-state and time-resolved spectroscopy. Data show that the mode and strength of interaction depend on the chemical structure of the bidentate ligand. The complexes show a major static contribution to the overall interaction, …
Tuning the nuclearity of iron(iii) polynuclear clusters by using tetradentate Schiff-base ligands
2014
Three novel octanuclear, hexanuclear and tetranuclear complexes of high-spin Fe(III) ions were obtained by the reaction of the N,N′-bis-(1R-imidazol-4-ylmethylene)-ethane-1,2-diamine ligand (R = H, CH3) and its derivatives with Fe(ClO4)3·6H2O and KSCN. The tetradentate Schiff-base ligand acts as a bis(bidentate) chelating bridge between two adjacent high-spin Fe(III) centers. The presence of a methyl group in the imidazolyl substituent, the change of counterions or the replacement of imidazole by pyridine has a drastic effect on the nuclearity of the cluster. The magnetic properties of all compounds exhibit antiferromagnetic interactions via μ-oxo or μ-hydroxo pathways in Fe(III) dimers.
Coordination versatility of 1,5-bis(salicylidene)carbohydrazide in Ni(II) complexes
2014
Abstract Versatile coordination behavior of a polydentate Schiff base ligand 1,5-bis(salicylidene)carbohydrazide (H3bsc) has been explored in Ni(II) complexes. [Ni(H3bsc)2](ClO4)2 (1)·H2O·3CH3CN is a bis chelate mononuclear complex of H3bsc in keto form, and [Ni4(H0.5bsc)2(O2CCMe3)3(CH3OH)4](2)·2H2O·2CH3OH is a tetranuclear complex of H3bsc with an unusual coordination. In 2, one phenolate group of the ligand coordinates in a monodentate way and the other coordinates in a μ2-bridging mode to the Ni(II) center. This unusual coordination mode of the ligand stabilizes the Ni(II) complex in a tetranuclear form where the carbonyl oxygen of the ligand exists in between keto and enol form of bond …
Synthesis, properties and X-ray crystal structure of schiff base organoimido complexes of rhenium(V)
1984
Abstract Re(NR)Cl 3 (PPh 3 )( 2 (R = p-CH 3 C 6 H 4 , CH 3 ) react with polydentate ligands (LH = N-methyl-, N-phenyl-, N-tolyl-salicylideneimine, half, N,N′-ethylenebis-, half N,N′-propylenebis-(salicylideneimine), 8-hydroxyquinoline and LH 2 = N-2-hydroxyphenylsalicylideneimine) to yield complexes of the type Re(NR)Cl 2- (L)PPh 3 . With 8-hydroxyquinoline the bisubstituted Re(NR)Cl(L) 2 complexes are also obtained. The compounds were characterized by elemental analysis, molecular weight, and i.r. spectra. The crystal and molecular structures of two arylimido complexes, Re(p-CH 3 C 6 H 4 N)Cl 2 )RNCHC 6 H 4 O)PPh 3 with R = C 6 H 5 or CH 3 , were determined from X-ray crystallography base…
Bis (μ-tetrazolato-NN′) bridged dinuclear nickel(II) Schiff base complexes: Tandem synthesis, structure and self assembly
2015
Abstract Two new bis(μ-tetrazolato-NN′) bridged dinuclear nickel(II) Schiff base complexes [Ni2L12(PTZ)2]·2(CH3)2SO·2.69H2O (1) and 2[Ni2L22(PTZ)2]·3H2O (2) (HL1 and HL2 are Schiff bases, HL1 = 2-((2-(dimethylamino)ethylimino)methyl)phenol, HL2 = 2-((2-(methylamino)ethylimino)methyl)-6-methoxyphenol and HPTZ is 5-pyrazinyltetrazole) have been synthesized via [3+2] cyclo-addition of 2-cyanopyrazine and sodium azide in presence of nickel(II) acetate tetrahydrate and the respective Schiff bases. The structures of the complexes are confirmed by single crystal X-ray diffraction analysis. Both complexes show fluorescence. The change in the denticity of the Schiff base blocking ligand is shown to …
Synthesis and characterization of a new family of bi-, tri-, tetra-, and pentanuclear ferric complexes.
2004
Nine members of a new family of polynuclear ferric complexes have been synthesized and characterized. The reaction of Fe(O(2)CMe)(2) with polydentate Schiff base proligands (H(2)L) derived from salicylidene-2-ethanolamine, followed in some cases by reaction with carboxylic acids, has afforded new complexes of general formulas [Fe(2)(pic)(2)(L)(2)] (where pic(-) is the anion of 2-picolinic acid), [Fe(3)(O(2)CMe)(3)(L)(3)], [Fe(4)(OR)(2)(O(2)CMe)(2)(L)(4)], and [Fe(5)O(OH)(O(2)CR)(4)(L)(4)]. The tri-, tetra-, and pentanuclear complexes all possess unusual structures and novel core topologies. Mössbauer spectroscopy confirms the presence of high-spin ferric centers in the tri- and pentanuclear…