Coordinative bonding, energy

Continuity equation electrochemical reactor, 30 311 mass transport, 30 312 Continuous-flow stirred-tanlt reactor, 31 189 Continuous reactor, 33 4-5 Continuous stirred-tank reactor, 27 74-77 ControUed-atmosphere studies, choice of materials for construction, 31 188 Conversion theory, 27 50, 51 Coordinatimi number, platinum, 30 265 Coordinative bonding, energy of, 34 158 Coordinative chemisorption on silicon, 34 155-158... 

The electron acceptor numbers (AN) can be used as a measure solvent ability to take a share in the electron pairs from suitable donors. They are defined by means of a different experimental procedure on the basis of the NMR chemical shifts of phosphorous which are produced on transfer of EtsPO through solvents. AN values are scaled from an arbitrarily chosen value of zero for the shift produced by hexane (or 1,2-dichloroethane) to one hundred for the shift produced by the 1 1 EtsPO—SbCls adduct in 1,2-dichloroethane. An estimation of the coordinate bond energy is possible by making use of the formula after Gutmann [155]... 

Table 11. Coordinate bond energies (CBE)a), i.e. AH° of reactions MXn(g) Mn+(g) -nX (g), for halides at 25° C (heat). — Total ionization potentialsb) SIn, and hydration energiese), AH, for the acceptors tabulated (eV)...

We have assumed implicitly that Cr3+ ions will not occur in tetrahedral holes in an oxide lattice. Cr + is a species. In the crystal field theory, such ions lead to particularly good stabilization of octahedral coordination. For example, the coordinate bond energy of Cr(H20) + is 120 kcal, of which 9 represent crystal field stabilization energy (CFSE) (35). In fact, there are no known chromias with crystal struc-... 

Descriptors 1, Coordinate bond energy (eV) 2, negative of standard enthalpy of... 

Calculations of coordinate bond energies can be made using classical potential energy equations that take into account the attractive and repulsive interactions between charged particles (10) ... 

Much effort has been directed toward finding a universal softness parameter a. Pearson and Mawby (8) calculated the coordinate bond energy (CBE) for metal halides and defined a parameter [CBE(F ) — CBE(I )]/CBE(F ) which provides a measure of the softness of the acceptor (acid) within a charge group (e.g., M , M , M3 , etc). 

Accordingly, the energy required to separate Li from F at a bond distance of 2.88 au is 8.38 eV. This is called the coordinate-bond energy. However, we want to calculate the standard bond-dissociation energy, which refers to the process... 

The most commonly cited scale producing the most successful correlations (i.e., highest correlation coefficients, r) is the one computed by Pearson and Mawby (Pearson and Mawby 1967). This scale involves the so-called sofmess parameter (Op) defined for a metal ion in terms of the coordinate bond energies of its metal fluoride, CBE(F), and metal iodide, CBE(1). 

The fluoride ion is the least polarizable anion. It is small, having a diameter of 0.136 nm, 0.045 nm smaller than the chloride ion. The isoelectronic E and ions are the only anions of comparable size to many cations. These anions are about the same size as K" and Ba " and smaller than Rb" and Cs". The small size of E allows for high coordination numbers and leads to different crystal forms and solubiUties, and higher bond energies than are evidenced by the other haUdes. Bonds between fluorine and other elements are strong whereas the fluorine—fluorine bond is much weaker, 158.8 kj/mol (37.95 kcal/mol), than the chlorine—chlorine bond which is 242.58 kJ/mol (57.98 kcal/mol). This bond weakness relative to the second-row elements is also seen ia 0-0 and N—N single bonds and results from electronic repulsion. 

Element Electronegativity Covalent radius, pm Usual coordination number Bond with hydrogen Bond length, pm Bond energy, kj/mot ... 

N occupy an sp lone-pair in the plane of the ring (or the plane of the local PNP triangle) as in Fig. 12.26a. The situation at P is less clear mainly because of uncertainties concerning the d-orbital energies and the radial extent (size) of these orbitals in the bonding situation (as distinct from the free atom). In so far as symmetry is concerned, the sp lone-pair on each N can be involved in coordinate bonding in the jcy plane... 

It is claimed by Minchenko and Smirnov that a correlation should exist between bulk viscosity and the bonding energy between the associated species and the ions of the second coordination sphere. 

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