Lithium molecular orbital model

Spherical-domain models of three-center bonds in localized-molecular-orbital models of a nonclassical carbonium ion, B4CI4, and TaeClfJ have been described 49,52) a drawing of a spherical-domain model of the methyl lithium tetramer, (LiCH, is shown in Fig. 31. Large, outer circles represent domains of electron-pairs of C—H bonds. Solid circles represent domains of Li+ ions. Shaded circles represent 4-center lithium-lithium-lithium-carbon bonds — i.e., electron-pair domains that touch, simultaneously, three lithium ions and the kernel of a carbon atom. The... 

In this chapter we shall use lithium hydride, LiH, to discuss the application of the molecular orbital model to a heteronuclear diatomic molecule, and begin by outlining a very simple computational procedure that yields an approximate description of the molecular orbital containing the two valence electrons. We then go on to outline the application of Hartree-Fock (HF) calculations based on a wavefuntion for both the two valence and the two inner-shell electrons. The wavefunction obtained by such calculations indicate that the bonding molecular orbital must be written as a linear combination of the H I5 with both 2s and 2pa atomic orbitals on the Li atom. 

Molecular orbital modeling of the reaction of organolithium compounds with carbonyl groups has examined the interaction of formaldehyde with the dimer of methyllithium. The reaction is predicted to proceed by initial complexation of the carbonyl group at lithium, followed by a rate-determining step involving formation of the new carbon-carbon bond. The cluster then reorganizes to incorporate the newly formed alkoxide ion. ... 

The effecfs of boron addition were also calculated based on a semiempiri-cal molecular-orbital model. Results show that the introduction of boron is favorable for lithium intercalation. When a layer of BQ is coated onto the surface of natural graphite, the performance improves considerably. In contradiction, another theoretical study based also on a semiempirical molecular orbital method concludes that the substitution of the carbon by boron is not effective for lithium storage. This illustrates the complexity of the carbon structure. These results suggest that the exact bonding states of boron may markedly influence the properties of the carbon materials. 

In 1998, Hasanayn and Streitwieser reported the kinetics and isotope effects of the Aldol-Tishchenko reaction . They studied the reaction between lithium enolates of isobu-tyrophenone and two molecule of beuzaldehyde, which results iu the formation of a 1,3-diol monoester after protonation (Figure 28). They analyzed several aspects of this mechanism experimentally. Ab initio molecular orbital calculatious ou models are used to study the equilibrium and transition state structures. The spectroscopic properties of the lithium enolate of p-(phenylsulfonyl) isobutyrophenone (LiSIBP) have allowed kinetic study of the reaction. The computed equilibrium and transition state structures for the compounds in the sequence of reactions in Figure 28 are given along with the computed reaction barriers and energy in Figure 29 and Table 6. 

Lithium clusters have been a popular model for the calculation of metal properties because of their low atomic number. Lasarov and Markov (49) used a Hiickel procedure to determine the properties of a 48-atom Li crystal. They found a transition to metal properties with the binding energy per atom approaching 1.8 eV at 30 atoms. The ionization potential approached the bulk value since some electrons occupy antibonding molecular orbitals, as observed for Ag clusters. The calculated properties of the largest cluster were not those of a bulk metal. 

The reaction of [tris(3-p-tolylpyrazolyl)hydroborate)]MgMe with H2S produces the monomeric hydrosulfido complex [tris(3-p-tolylpyrazolyl)hydroborate)]MgSH, which has been structurally authenticated the Mg—S bond length is 2.35 A.Other monodentate sulfur ligands include 2-(l-methylethyl)-l,3-dimethyl-l,3,2-diazaphosphorinane 2-sulfide, whose lithium complex has been modeled with molecular orbital calculations, l,3-dimethyl-2-benzylide- 2-thioxo-1,3,2-diazaphosphorinane-S,S), and A-diisopropoxythiophosporylthiobenzamine. ... 

The modeling of monomeric (,R,S)-2 [B3LYP/6-31+G(d)] indicates that the highest occupied molecular orbital (HOMO) is chiefly located at the metalated carbon center and the aromatic ring system (Fig. 5). It can be deduced from the calculated orbital coefficients that both inversion and retention of configuration are almost equally likely to result from electrophilic attack. Only the fact that the site opposite the lithium center is sterically accessible to attack by electrophiles (the coordination polymer of the solid-state structure should be broken up in solution) makes it possible for (R,S)-2 to react selectively with inversion of configuration at C(3) under kinetic control in nonpolar solvents. 

Lithium Battery Electrolyte Stability and Performance from Molecular Modeling and Simulations provide an example of the power of this experimental technique. Molecular orbital calculations have proven useful and have the... 

The primary molecular modeling methods that have been extensively applied to lithium battery electrolytes and electrode/electrolyte interfaces are molecular orbital calculations and molecular dynamics simulations. The former involves ab initio and density functional methods and will be referred to quanmm chemistry or QC... 

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