Search results for "Bond length"
showing 10 items of 209 documents
Statics and Dynamics of Bidisperse Polymer Melts: A Monte Carlo Study of the Bond-Fluctuation Model
1998
As a first step toward the computer simulation of polydisperse polymeric melts, a lattice model containing two types of chains with lengths N1 = 20 − x and N2 = 20 + 4x (0 ≤ x ≤ 10 ) is studied. This variation of x, together with the fixed composition of 80% of short and 20% of long chains, leads to a polydispersity of 1 ≤ Nw/Nn ≤ 2 (Nw, Nn: weight-, number-average chain lengths). To represent dense melts, the bond-fluctuation model at a volume fraction, φ = 1/2, of occupied lattice sites is used. The simulation treats both the athermal case (chain connectivity and excluded volume interaction only) and a thermal case, where additionally a choice for the bond length and bond angle potential…
High-resolution stimulated Raman spectroscopy and analysis of the ν 1 , 2ν 1 -ν 1 , ν 2 , 2ν 2 , and 3ν 2 -ν 2 bands of CF4
2013
The spectra of the ν1, 2ν1–ν1, ν2, 2ν2, and 3ν2–ν2 bands of CF4 were obtained with a quasi-continuous wave stimulated Raman spectrometer. These five bands were studied at a temperature of 135 and 300 K (for the hot bands). The spectrum of ν1 was obtained at a sample pressure of 2 mbar. For the spectra of the other regions, which are much weaker, higher pressures were used. The analysis has been performed thanks to the xtds and spview softwares developed in Dijon for such highly symmetric molecules. Combining the present results with a previous infrared study, we could determine a very accurate value for the C–F equilibrium bond length, i.e. re = 1.31588(6) A. Copyright © 2013 John Wiley & S…
Density Functional Study of Spin State in CpM(NO)X2 (M = Mo, Cr; X = Cl, NH2, CH3): Spectrochemical and Nephelauxetic Effects in Organometallic Comp…
1998
International audience; The relationship between spin state and metal−ligand bonding interactions in CpM(NO)X2 species was investigated using density functional computational techniques. The geometries of CpM(NO)Cl2 (M = Cr, Mo), CpCr(NO)(NH2)X, and CpCr(NO)(CH3)X (X = Cl, CH3) were optimized at the DFT-B3LYP level for both the diamagnetic (S = 0) and paramagnetic (S = 1) electronic configurations. While the geometric parameters of the singlet compounds matched well with structures determined experimentally, the Cr−NO bond lengths in the triplet species exceeded the experimentally observed range by a significant margin, thereby indicating a propensity for nitrosyl-ligand dissociation from t…
Mössbauer investigation of the photoexcited spin states and crystal structure analysis of the spin-crossover dinuclear complex [{Fe(bt)(NCS)(2)}(2)bp…
2006
The crystal structure of the complex [{Fe(bt)(NCS)(2)}(2)bpym] (1) (bt=2,2'-bithiazoline, bpym=2,2'-bipyrimidine) has been solved at 293, 240, 175 and 30 K. At all four temperatures the crystal remains in the P space group with a=8.7601(17), b=9.450(2), c=12.089(3) A, alpha=72.77(2), beta=79.150(19), gamma=66.392(18) degrees , V=873.1(4) Angstrom(3) (data for 293 K structure). The structure consists of centrosymmetric dinuclear units in which each iron(II) atom is coordinated by two NCS(-) ions in the cis position and two nitrogen atoms of the bridging bpym ligand, with the remaining positions occupied by the peripheral bt ligand. The iron atom is in a severely distorted octahedral FeN(6) e…
Intermetallic compounds of the heaviest elements: the electronic structure and bonding of dimers of element 112 and its homolog Hg
2002
Abstract Fully relativistic (four-component) density-functional calculations were performed for the element 112 dimers (112)X (X = Pd, Cu, Ag and Au) and those of its lighter homolog, Hg. A relatively small decrease of about 15–20 kJ/mol in bonding was found from the HgX to (112)X compounds. Respectively, the bond lengths were increased by 0.06 A on the average. The Mulliken population analysis has shown this effect to be a result of a decreasing contribution of the relativistically stabilized 7s-AO of element 112 to bonding. The following trend in the binding energies was predicted for (112)X as a function of X: Pd >Cu>Au>Ag, exactly as the trend obtained experimentally for adsorption of H…
Synthesis and crystal structure of {Rh2(O2CCH3)4·P(o-CH3OH6H4)Ph2}2. A novel dirhodium(II) monoadduct with intermolecular μ-oxo interactions
1997
Abstract We have investigated the reaction of dirhodium tetraacetate with the phosphine P( o -CH 3 OH 6 H 4 )Ph 2 (P) under different experimental conditions. From these reactions we have been able to isolate the dirhodium tetraacetate phosphine mono-adduct. The crystal structure shows that in the solid state this compound forms a centrosymmetric dimer of the dimer, {Rh 2 (O 2 CCH 3 ) 4 ·P(0-CH 3 OC 6 H 4 )Ph 2 } 2 , in which we oxygen atom from one acetate group in one Rh 2 (O 2 CCH 3 ) 4 ·P unit is axially coordinating one Rh atom on another Rh 2 (O 2 CCH 3 ) 4 · P unit (Rh⋯) 2.347(3) A intermolecular versus Rh⋯O 2.455(3) A intermolecular), and vice versa. The RhRh bond distance is 2.414…
3-formylphenylboronic acid.
2004
The molecule of the title compound, C(7)H(7)BO(3), is planar, and the bond lengths and angles are typical. The formyl group is essentially coplanar with the benzene ring but does not influence significantly the distortion of the ring, although the formyl group does have a strong influence on the crystal packing. The geometry of the boronic acid group is typical. In the crystal structure, the molecules are linked by O-H...O hydrogen bonds.
Selective ortho-metallation reaction of the phosphine P(o-ClC6H4)Ph2. Synthesis and crystal structure of [Rh2(μ-O2CCH3)3(μ-(ClC6H3)PPh2(OH2)2]·CHCl3
1993
Abstract From the reaction of [Rh2(O2CCH3)4(MeOH)2] in hot acetic acid with P(o-ClC6H4)Ph2, two monometallated compounds [Rh2(O2CCH3)3(C6H4)P(o-ClC6H4)Ph(HO2CCH3)2] (1), already described, and [Rh2(O2CCH3)3{(ClC6H3)PPh2}(OH2)2] have been isolated. The new compound has been characterized by an X-ray study. It crystallizes in the triclinic space group P1. It contains three acetate groups bridging a Rh24+ unit that has a Rh-Rh bond distance of 2.426(1) A; the fourth bridging ligand is derived from one P(o-ClC6H4)Ph2 metallated in the halogenated ring. The two water molecules occupy the axial coordination sites.
Simultaneous substitution of bridging acetate groups and reversible RhC bond cleavage in [Rh2(O2CCH3)3-{(C6H4)PPh2}(HO2CCH3)2] in the presence of CF…
1993
Abstract The reaction of the monometallated compound [Rh2(O2CCH3)3 {(C6H4)PPh2}(HO2CCH3)2] (1) with CF3CO2H at room temperature yields [Rh2(O2CCF3)3{(C6H4)PPh2}(HO2CCF3)2] (3) as the only isolable product. Compound 3 has been characterized by X-ray methods. 3 crystallizes in the space group P21 / n. It contains three trifluoroacetate groups bridging a Rh4+2 unit with a RhRh bond distance of 2.438(1) Ă; the fourth bridging ligand is a triphenylphosphine metallated at one of the ortho positions. Two molecules of trifluoroacetic acid occupy the axial coordination positions. In addition to the substitution of acetate groups, reversible electrophilic RhC bond activation is observed.
Über polystannane
1985
Abstract The compound I(t-Bu2Sn)4I has been synthesized by controlled cleavage of the related cyclotetrastannane (t-Bu2Sn)4 with iodine in toluene. Both compounds have been investigated by mass, NMR and vibrational spectra. I(t-Bu2Sn)4I: δ(119Snterminal) 67.7, δ(Sncentral) 17.4 ppm; 1J(SnSn) 2199 (terminal-central) and 1575 (central-central), 2J(SnSn) 20 (terminal-central), 3J (SnSn) 307 Hz (terminal-terminal); ν(SnSn) 119, ν(SnI) 167 cm−1. (t-Bu2Sn)4: δ(Sn) 87.4 ppm; ν(SnSn) 125 cm−1. The crystal structure of I(t-Bu2Sn)4I has been determined (R = 0.071): bond lengths SnSn 289.5(1) (terminal-central) and 292.4(1) (central-central), SnI 275.3(1) pm. The conformation of the chain ISn…