Search results for "AH"
showing 10 items of 6917 documents
Atomic structure solution of the complex quasicrystal approximant Al77Rh15Ru8 from electron diffraction data
2014
The crystal structure of the novel Al77Rh15Ru8phase (which is an approximant of decagonal quasicrystals) was determined using modern direct methods (MDM) applied to automated electron diffraction tomography (ADT) data. The Al77Rh15Ru8E-phase is orthorhombic [Pbma,a= 23.40 (5),b= 16.20 (4) andc= 20.00 (5) Å] and has one of the most complicated intermetallic structures solved solely by electron diffraction methods. Its structural model consists of 78 unique atomic positions in the unit cell (19 Rh/Ru and 59 Al). Precession electron diffraction (PED) patterns and high-resolution electron microscopy (HRTEM) images were used for the validation of the proposed atomic model. The structure of the E…
Anion ordering and defect structure in Ruddlesden-Popper strontium niobium oxynitrides
2004
The crystal structure of the n = 1 member of the Ruddlesden-Popper family (SrO)(SrNbO(2)N)(n) was refined by the Rietveld method using neutron powder diffraction data. This complex crystallizes in the I4/mmm space group with cell parameters a = 4.0506(2) and c = 12.5936(9) angstroms. The refined composition was Sr(2)NbO(3.28)N(0.72), which corresponds to a formal oxidation state for Nb of +4.72, meaning 72% Nb(V) and 28% Nb(IV). The nitrogen atoms order in the equatorial sites of the niobium octahedra according to Pauling's second crystal rule as the more charged anion occupies the site showing the larger bond strength sums. Pauling's second crystal rule is shown to be able to predict the d…
Synthesis and mössbauer studies of some aquo complexes of tin(IV) with crown ethers
1984
Abstract The preparation, characterization, and 119Sn Mossbauer spectra of a number of tin(IV) complexes with cyclic polyethers are presented. With tin(IV) chloride and methyltin(IV) trichloride, 1:1 and 2:1 metal-to-crown-ether complexes are formed, while dimethyltin(IV) dichloride forms only 2:1 complexes; in every case, two water molecules are present in the solid state structure. An octahedral coordination geometry around the tin(IV) center is proposed on the basis of Mossbauer and IR spectra.
Syntheses, Structure, and Reactivity of Chiral Titanium Compounds: Procatalysts for Olefin Polymerization
2001
Titanium complexes with chelating alkoxo ligands have been synthesised with the aim to investigate titanium active centres in catalytic ethylene polymerisation. The titanium complexes cis-[TiCl2(η2-maltolato)2] (1, 89 %), and cis-[TiCl2(η2-guaiacolato)2] (2, 80 %) were prepared by direct reaction of TiCl4 with maltol and guaiacol in toluene. The addition of maltol to [Ti(OiPr)4] in THF results in the formation of species [Ti(OiPr)2(maltolato)2] (3, 82 %). The titanium compound cis-[Ti(OEt)2(η2-maltolato)2] (4, 74 %) was obtained by the transesterification reaction of species 3 with CH3CO2Et. When compound 4 is dissolved in THF a dinuclear species [Ti2(μ-OEt)2(OEt)4(η2-maltolato)2] (5, 45 %)…
Synthesis, spectroscopic and structural characterization of [Cu(phen)(C5O5)(H2O)]·H2O, [Ni(terpy)(C5O5)(H2O)]·H2O and [Ni(terpy)2](NO3)2·0.5H2O
2005
Abstract The new mononuclear complexes [Cu(phen)(C5O5)(H2O)]·H2O (1), [Ni(terpy)(C5O5)(H2O)]·H2O (2) and [Ni(terpy)2](NO3)2·0.5H2O (3) [phen=1,10-phenanthroline, C 5 O 5 2 − =dianion of the 4,5-dihydroxycyclopent-4-ene-1,2,3-trione and terpy=2,2′:6′,2″-terpyridine] have been synthesized and characterized by single-crystal X-ray diffraction. The copper atom of 1 has a distorted square pyramidal environment with two phen-nitrogen and two croconate-oxygen atoms building the equatorial plane and a water molecule in the apical position. The nickel atom of 2 exhibits a distorted NiN3O3 octahedral coordination, which may be described either as tetragonally compressed or as skewed trapezoidal bipyr…
Squarate and croconate in designing one- and two-dimensional oxamidato-bridged copper(II) complexes: synthesis, crystal structures and magnetic prope…
2001
Abstract The reaction of squarate (C4O42–, dianion of 3,4-dihydroxycyclobut-3-ene-1,2-dione) and croconate (C5O52–, dianion of 4,5-dihydroxycyclopent-4-ene-1,2,3-trione) with the dinuclear 〚Cu2(apox)〛2+ copper(II) complex 〚H2apox = N,N’-bis(3-aminopropyl)oxamide〛 in aqueous solution affords the compounds of formula 〚Cu2(apox)(C4O4)(H2O)2〛n·n H2O (1) and 〚Cu4(apox)2(C5O5)2〛·6 H2O (2). Crystals of 1 are monoclinic, space group C2/c, with a = 12.5527(9), b = 7.4161(6), c = 18.5198(12) A, β = 100.578(6)° and Z = 4. Crystals of 2 are triclinic, space group P 1 with a = 9.732(5), b = 9.795(2), c = 10.285(3) A, α = 84.95(2), β = 77.30(3), γ = 85.61(3)° and Z = 1. The structure of complex 1 consist…
Synthesis, crystal structure and magnetic properties of the chiral iron(II) chain [Fe(bpym)(NCS)2]n (bpym = 2,2′-bipyrimidine)
1996
Abstract The iron(II) compound of formula [Fe(bpym)(NCS)2]n (bpym = 2,2′-bipyrimidine) has been synthesized and its crystal structure determined by X-ray diffraction methods. It crystallizes in the tetragonal P41 (No. 76) and P43 space groups, a = 8.849(2), c=16.486(3) A , V=1290.9(5) A 3 , Z=4, D c =1.699 g cm −3 , M r =330.2, F(000)=664, λ( Mo K α)=0.71073 A , μ( Mo K α)=14.8 cm −1 and T=295 K. A total of 2449 reflections was collected over the range 3≤2ϑ≤55°; of these, 1657 were unique and 1321 were considered as observed (13σ(I)) and used in the structural analysis. The final R and Rw residuals were 0.027 and 0.026, respectively. The structure is made up of chiral (Δ and Λ enantiomers c…
Organotin(IV) chloride complexes with phosphocholine and dimyristoyl-L-?-phosphatidylcholine
2000
Several complexes of R n SnCl 4-n (R = Me, Ph, n = 1-3; R = nBu, n = 2, 3) with phosphocholine and dimyristoyl-L-α-phosphatidylcholine (phospholipid) have been synthesized and characterized by means of Mossbauer spectroscopy and NMR. Triorganotin chlorides form complexes of (R 3 SnCl) 2 .L stoichiometry with a trigonal bipyramidal pentacoordinate tin environment, while the others form 1:1 complexes with an octahedral hexacoordinate tin environment, with the ligands coordinating through anionic phosphodiester moieties in all cases.
Self-Assembly of the Hexabromorhenate(IV) Anion with Protonated Benzotriazoles: X-ray Structure and Magnetic Properties
2014
Two novel ReIV compounds of formulas [HBTA]2[ReIVBr6] (1) and [HMEBTA]2[ReIVBr6] (2) [BTA = 1H-benzotriazole and MEBTA = 1-(methoxymethyl)-1H-benzotriazole] have been synthesized and magneto-structurally characterized. 1 and 2 crystallize in the triclinic system with space group P1̅. In both compounds, the rhenium ion is six-coordinate, bonded to six bromo ligands in a regular octahedral geometry. Short ReIV–Br···Br–ReIV contacts, π–π stacking, and H-bonding interactions occur in the crystal lattice of both 1 and 2, generating novel supramolecular structures based on the ReIV. The different dispositions of the cations and the intermolecular Br···Br contacts in 1 and 2 play an important stru…
Synthesis, structural analysis, and thermal and spectroscopic studies of methylmalonate-containing zinc(II) complexes
2012
The synthesis, crystal structure, thermal analysis and spectroscopic studies of five zinc(II) complexes of formulae [Zn(Memal)(H2O)]n (1) and [Zn2(L)(Memal)2(H2O)2]n (2-5) [H2Memal = methylmalonic acid, and L = 4,4′-bipyridine (4,4′-bpy) (2), 1,2-bis(4-pyridyl)ethylene (bpe) (3), 1,2-bis(4-pyridyl)ethane (bpa) (4) and 4,4′-azobispyridine (azpy) (5)] are presented here. The crystal structure of 1 is a three-dimensional arrangement of zinc(II) cations interconnected by methylmalonate groups adopting the μ3-κ2O:κO’:κO”:κO”’ coordination mode to afford a rare (10,3)-d utp-network. The structures of the compounds 2-5 are also three-dimensional and they consist of corrugated square layers of meth…