Single-bond Radii Research Articles

Mixed Ligand Palladium(II) Complex with NS‐Bidentate S‐Allyldithiocarbazate Schiff Base: Synthesis, Spectral Characterization, Crystal Structure and Decoding Intermolecular Interactions with Hirshfeld Surface Analysis

AbstractA new mixed ligand palladium(II) complex with bidentate NS‐donor chelate, [PdCl(PPh3)L] (L: S‐allyl β‐N‐(benzylidene)dithiocarbazate), has been prepared and characterized using single crystal X‐ray diffraction and spectroscopic (electronic, IR, 1H NMR and 13C NMR) techniques. The shorter PdP bond distance, 2.255(7) Å, than the sum of the single bond radii for palladium and phosphorus (2.41 Å), showed partial double bond character. Visualizing and exploring the crystal structure using Hirshfeld surface analysis showed the presence of π··· π, N··· π, CH··· π, Cl···H and weak CH···S interactions as most important intermolecular interactions in the crystal lattice, which are responsible to extension of the supramolecular network of the compound and stabilization of the crystal structure.

Valence bond structure of Ta-W alloys

The valence bond structure of substitutional BCC based Ta-W alloys is studied using characteristic crystal (CC) theory. This theory is based on cluster statistics of random alloys. By studying the correlativity between energy and volume of the CC in Ta- W alloys, the valence bond structure of CC is determined by the energy and shape method. Then, following additive law of CC, the valence bond structure of Ta-W alloys is calculated. It is found that the outer shell valence electronic distribution of Ta-W alloys shows a continuous change in the whole composition range. The covalent electrons ec (dc, sc, and pc) increase, whereas near free electrons ef decrease with increasing W concentration. The bond length and single-bond radius decrease, whereas bond energy and bond valence increase with increasing W concentration. The mechanism of solid solution strengthening of Ta-W alloys is analyzed based on their valence bond structure.

BOND-VALENCE PARAMETERS OF Sc AND Y METALS

Based on the energy and shape (ES) method, the bond-valence (BV) parameters of Sc and Y are determined. It gives the single-bond radius, the categories and magnitude of valence electron and bond properties including bond length, bond energy and bond valence. The single-bond radius values are 1.3257 and 1.4628 Å for Sc and Y . Their valence parameters are [Formula: see text] and [Formula: see text] respectively. The electric conductivity of Sc and Y metals was qualitatively explained by their valence parameters. Bond-valence parameters of Sc and Y metals are more refined and reliable than Pauling's and Brewer's.

Influence of pressure on the valence bond structure of tungsten

The valence bond structure of tungsten is redetermined at ambient pressure and calculated for pressures up to 300 GPa using the energy and shape method. The outer shell valence electronic distribution of tungsten at ambient pressure is e c 3.7408 ( d c 2.9268+ S c 0.2040 p c 0.6100) e f 2.2592. The value of the single-bond radius is 1.2532 Å. Under pressure, the covalent electrons e c ( d c, s c and p c) increase while near free electrons e f decreases with increasing pressure. The number of covalent electrons e c is 3.7408 under ambient conditions and 5.0321 at 300 GPa and the number of near free electrons e f changes from 2.2592 at ambient pressure to 0.9679 at 300 GPa. The bond length and single-bond radius decrease while bond valence increases with increasing pressure. These results indicate that the electron distributions are more localized and the bonding character of metal becomes more covalent bonding with increasing pressure.

Temperature-dependent valence bond structure study of tantalum

Based on energy and shape method for determining the VB structures of crystal, the valence bond structure of tantalum is redetermined at room temperature and extended to the whole temperature range. The outer shell valence electronic distribution of Ta at room temperature is e c 2.9011 (d c 2.2711+s c 0.1580+p c 0.4720) e f 2.0989 in crystal. The single-bond radius value is 1.2812 Å. The temperature-dependent valence structure of tantalum is not a drastic change. The bond length and single-bond radius increases while the bond energy and bond valence decreases with increasing temperature. The valence electrons e c (d c, s c and p c) decrease while e f increases with increasing temperature.

Structure and bonding in square-planar chalcogen rings

The molecular structures of square-planar X42+, X4+, and X4 (X = S, Se, Te) have been calculated using the effective core potential model. For X42+ the agreement between experimental and calculated values is excellent provided that d orbitals are included in the basis set. For the hypothetical molecules X4+ and X4 the bond lengths are found to increase dramatically as one and, subsequently, two electrons are added to the systems. Extensive population analysis shows that this increase is almost exclusively due to loss of bonding in the π system, whereas the bonding in the σ system remains relatively unaltered. These results make it possible to predict covalent single bond radii for S, Se, and Te for which the influence of π repulsion is removed. From the calculated variation of bond lengths with atomic charge, bond lengths are predicted for a series of planar disulphide rings. Keywords: structure, bonding, chalcogen, theoretical, ECP.

GENERAL EQUATION OF SINGLE BOND RADII R(1) OF ACTINIDES——NECESSARY PARAMETERS FOR THE EXTENSION OF THE EMPIRICAL ELECTRON THEORY OF SOLIDS AND MOLECULES TO THE 7TH PERIOD IN THE PERIODIC TABLE

Ⅰ. INTRODUCTION The well-known Pauling's electron theory for metals and alloys established the empirical general equation of the single bond radii R(1) for transition elements to the 4th, 5th and 6th periods in the periodic table. Yu Ruihuang first utilizes the form of Pauling's R(1) equation but changes the physical meaning and thereby the real physical nature of the

A revised set of values of single-bond radii derived from the observed interatomic distances in metals by correction for bond number and resonance energy

An earlier discussion [Pauling, L. (1947) J. Am. Chem. Soc. 69, 542] of observed bond lengths in elemental metals with correction for bond number and resonance energy led to a set of single-bond metallic radii with values usually somewhat less than the corresponding values obtained from molecules and complex ions. A theory of resonating covalent bonds has now been developed that permits calculation of the number of resonance structures per atom and of the effective resonance energy per bond. With this refined method of correcting the observed bond lengths for the effect of resonance energy, a new set of single-bond covalent radii, in better agreement with values from molecules and complex ions, has been constructed.

Carbonyl-eisen-komplexe von pentafulvenen

The structures and spectroscopic properties (IR, NMR) of coordination compounds formed by the reaction of diphenylfulvene, dimethylfulvene and diethylfulvene with Fe 2(CO) 9 are reported. Single-crystal X-ray diffraction studies of bis(dimethylfulvene)pentacarbonyldiiron and diphenylfulvenepentacarbonyldiiron have been made. The covalent single-bond radius of iron in the η-cyclopentadienyldicarbonyliron and η-allyltricarbonyliron group has been found to be 1.38 Å. Chemical bonding in diphenylfulvenepentacarbonyldiiron and 6-dimethylaminofulvenylfulvenepentacarbonyldiiron has been studied using the simple HMO-model.

Crystal structure of protactinium tetrabromide

The crystal structure parameters for PaBr4(isostructural with ThCl4) have been determined from quantitative X-ray powder data and refined to R 0·123. The Pa–Br bond distances are 2·77 and 3·07 Å; a value of 1·63 Å is deduced for the covalent single-bond radius of PaIV.

Lattice-parameter relationships in transition-metal laves phases

The application of the Pauling equation for atomic radii, r(1)− r( n)=0.3 log n, to transition-metal AB 2 Laves phases (where Zr, Hf, and Ti constitute the “A” atoms) yields the same apparent valencies of “A” and “B” from crystallographic data, irrespective of whether the cubic or hexagonal allotropic modifications are considered. This enables the lattice parameters of one allotropic form to be calculated from the parameters of the other form to within about 0.2% of experimental values. The lattice parameters of Zr, Hf, and Ti Laves phases have been calculated for hitherto undiscovered allotropes where parameters of the other form are available. It is suggested that the observed smooth variation across the Periodic Table of the apparent valency for both A and B atoms might be attributed to varying amounts of electron transfer from B atoms to A atoms, or to a smooth change in the single-bond radii with increasing d-orbital contributions.

Single bond radius of trigonal nitrogen and the C(sp2)—N(sp2) single bond

Estimation of p-π character in nitrogen–carbon bonding is dependent on a knowledge of the trigonal nitrogen – trigonal carbon single bond length. Recent experimental results indicate a value of 1.470 ± 0.005 Å for this bond distance and a value of 0.720 ± 0.010 Å for the trigonal nitrogen single bond radius; these values are suggested as criteria for estimating p-π character in trigonal N – aromatic C bonds.

Rare Earths in Covalent Semiconductors: the Thulium-Gallium Arsenide System

Solutions containing radioactive 170Tm were applied to the surface of GaAs wafers that were heated to 800°, 900°, or 1000°C for times up to 100 h. The solubilities and diffusion coefficients were obtained by fitting the experimental data with complementary error functions. The resulting surface concentration (cm−3) was taken as the equilibrium saturation solubility and is represented below the eutectic temperature of 1150°C by 6.7×1025 exp (−2.3 eV/kT), which gives Cmax=4×1017 cm−3. The atom size, defined as the single-bond radius, was found to be the dominant factor in limiting the solid-solution solubility of the rare earths in GaAs. Diffusion was faster at lower temperatures, and the diffusion coefficient D (cm2/sec) was 2.3×10−16 exp (1.0 eV/kT). This inverse temperature dependence of the diffusion coefficient may be explained by the effective D derived from the concept of simultaneous diffusion and chemical reaction. The resulting diffusion coefficient in intrinsic material is Dei=DiCii+/Cs0, where Di is the interstitial diffusion coefficient and Cii+/Cs0 is the ratio of singly ionized interstitial concentration to neutral substitutional concentration. The inverse temperature dependence of D may be ascribed to the more rapid increase of Cs0 with temperature than that of DiCii+.

INTERNUCLEAR DISTANCES IN HYDRIDES*

Metal-hydrogen internuclear distances in substantially all the known binary metallic and saline hydrides may be rationalized equally well on the basis of an ionic model or on the basis of a model utilizing delocalized covalent bonding. In the former the anionic radius (CN = 4) of hydrogen is 1.29 A; the cation radius is for the ion of maximum normal oxidation number. The internuclear distances in the Group I saline hydrides are shown to be increased by the anion-repulsion factor of Pauling. The covalent model is that suggested by Pauling for application to metals and employs a single-bond radius of 0.37 A for hydrogen. Both models are applicable to saline as well as to metallic binary hydride s. (auth)

An Electron Diffraction Investigation of Dimethyl Selenide

The results of an electron diffraction investigation of (CH_3)_2Se arc C-H/Se-C, 1.09/1.97 ( assumed); Se-C, 1.977 ± 0.012 A.; Se•••H, 2.571 ± 0.034 A.; C•••C, 2.98 ± 0.23 A.; ∠C-Se-C, 98 ± 10°; and ∠Se-C-H, 110.5 ± 3.5°. The selenium-carbon distance of 1.98 A. leads to a single-bond radius for selenium of 1.22 A., which is considerably larger than the value 1.17 A. chosen by Pauling.