Coordinate bond INDEX

My first incursion into organo-transition metal chemistry occurred because of my interest in chemical bonding. How did olefins with no lone pair of electrons form coordinate bonds to metal atoms The position in 1941 can be read in Keller s review on olefin complexes 54). During the war years I was able to assemble a card index of all references to olefin complexes and I convinced myself that they should be formulated as chelate complexes of, for example, structure (VII) for Zeise s ion if chlorine could bridge metal atoms why should it not bridge carbon to a metal Nature rejected my letter on this topic as being... 

Theoretical data supported quite well the vibrational IR and RAIRS data and allowed an interpretation of the energetic process of the complex-surface interaction. The variation observed in the Wiberg index values for the metal-ligand coordination bond suggests an important tc electronic redistribution around the cation by surface effect Table 14.7. 

In order to understand the behaviour of the valence transition and its (l/af dependence, we arran the different /bond index plot. For brevity the six equal 1/a values for R(l) are represented by a single lozen. We also give in this plot the /cf values (shaded squares) for the ionic radii of Pr(III) and Pr(IV) in the octahedral coordination (Shannon and Pretwitt 1969). We immediately see that at least four points of the gr h lie on a plateau. We draw a mean horizontal line passing through them. The points falling... 

There have been several reviews of mechanisms of photosubstitution in rhodium(III) complexes. Bond indexes for ground and excited states have been discussed in relation to D2h species. " The observation of stereospecificity has been discussed in relation to lifetimes for triplet singlet deactivation and geometric rearrangements. Direct evidence has been presented to support the intermediacy of, and role of rearrangement in, five-coordinate intermediates in ligand field irradiation experiments. Rhodium(III) has been discussed in relation to cobalt(III) and iridium(III), and to ruthenium(II) and ruthenium(III) as well. ... 

It is convenient to first establish some definitions, and these are listed in Table 6.2. As discussed in Chapter 5, as an adsorbate approaches a surface, changes occur in the potential energy of the system and one must relate this energy, Epot, to the distance, r, from the surface. It is certainly anticipated that the migration and dissociation of an adsorbate, X, on the surface involve changes in the coordination mode, Mn — X, and the M-X distance, r, where M is a metal atom and n is the coordination number. Assuming quasi-spherical interactions, a two-center M-A bond index, x, in the form of Pauling s bond order [23], is defined as... 

Here the sum is extended over the various coordination shells indexed by j, each containing Nj identical atoms at a distance Rj from the central one. The backscattering ampbtude and phase, A and bond length Rj (curved wave approximation). Typical k dependencies of Afk, Rj) and (p k, Rj) + 25c are shown in Figures 2-3(a) and (b), taking Ce as central atom and Ce or O as backscatterers. The functions were calculated from tabulated values (McKale, 1988). 

Wiberg bond Indexes (B,), % evolution through the reaction coordinate (%E ), average bond index variation (5Bav)< and synchronicity... 

The group-subgroup relation of the symmetry reduction from diamond to zinc blende is shown in Fig. 18.3. Some comments concerning the terminology have been included. In both structures the atoms have identical coordinates and site symmetries. The unit cell of diamond contains eight C atoms in symmetry-equivalent positions (Wyckoff position 8a). With the symmetry reduction the atomic positions split to two independent positions (4a and 4c) which are occupied in zinc blende by zinc and sulfur atoms. The space groups are translationengleiche the dimensions of the unit cells correspond to each other. The index of the symmetry reduction is 2 exactly half of all symmetry operations is lost. This includes the inversion centers which in diamond are present in the centers of the C-C bonds. 

Reed and Allen, using their bond polarity index, have assigned values of 0.000, 0.027, and 0.050, respectively (compared to H —0.032 and F 0.189) [108]. Without attempting to be too quantitative, convenient values of the core energies of hybrid atomic orbitals, in units, recognizing that changes in coordination number also occur, are approximately... 

---