Fragment Orbital Analysis

The lesson to draw from these experiences is that the use of localized orbitals may be an adequate tool to separate the regions of strong (covalent) interactions of the fragments from the set of orbitals involved only in weak (non-covalent) interactions, governing the chemical event under study. 

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The ionization potential in a simple one-electron approximation measures the energy of the highest occupied molecular orbital (HOMO). This orbital is only one of an entire manifold of levels which contribute to the bonding characteristics and total stability of the cluster. Frontier fragment-orbital analysis in organometallic reactivity studies has provided a clear indication... 

The interacting fragment orbital analysis can be put on more quantitative terms by performing explicit energy decomposition analysis of FIF or DFT wave functions. The extended transition state (ETS) approach decomposes the energy change into four... 

A series of papers by Shustorovi ch(63) and/or Baetzo1d(64) summarized in a recent article(65) have addressed the problem of chemisorption on metal surfaces in terms of electron accepting and donating interactions. Saillard and Hoffmann (66) developed qualitatively identical pictures of these interactions but starting from fragment orbital type analysis. These papers are only a few of the theoretical discussions that consider hydrogen activation, however we will use their approach because it address the problem in a fashion that can interpolate between the organometallic cluster and the bulk. 

Scheme 6 Extended Htickel fragment analysis of the interaction between the partially occupied Cp2M and occupied dithiolene fragment orbitals in d1 [Cp2M(dt)]+ complexes, M = Mo, W (adapted from [69])...

Molecular orbital analysis of diatomic and triatomic fragments... 

Since the COs have been written as a linear combination of BOs associated with the different AOs of the unit cell, the DOS curves can be analyzed in terms of contributions per AO of the unit cell. In other words, once the DOS plot has been calcnlated, we can project the contribution of certain AOs or fragment orbitals of interest for the analysis. In order to iUnstrate the process let ns consider the two-center MO... 

A molecular orbital analysis of the bonding capabilities of carbon disulfide toward transition metal fragments, using the extended Hiickel method, was carried out by Hoffmann et al. The thiaferracyclopropane 73 is a starting... 

The following very useful approach for the analysis of photochemical reactions is due to Dauben, Salem, and Turro [13]. A bond, a—b, made from fragment orbitals and of molecular fragments, a and b, is broken in the process under consideration. The relationship to the orbital interaction diagram is transparent (see Figure 15.3). The orbitals... 

To quantify our perturbational picture of the TM-H bond, we performed Density Functional calculations for a variety of complexes. For the optimized molecular geometries, we did a fragment molecular orbital analysis, as outlined in Scheme 1. The HOMO energies E, for the L M fragment, as well as the nd -IJj overlap terms S are displayed in Figure 2. 

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