Lithium clusters, chemical bonds

In order to discuss the valence electronic state and chemical bonding of lithium vanadium oxide we made calculations using cluster models. The density of states (DOS) and the partial density of states (PDOS) of Li1.1V0.9O2 are obtained by this study as shown in Figure 3.4. The filled band located from —8 to —3 eV is mainly composed of O 2p orbital. The partially filled band located around —2 to 4 eV is mainly composed of V 3d orbital. Unoccupied band located above 5 eV is... 

A few years later Arnold and co-workers also reported the synthesis of lithium complexes of the neutral and anionic salts of a tridentate amino bis-carbene ligand (Scheme 2).13 Treatment of the cationic amino bis-imida-zolium salt with three equivalents of //-butyl lithium affords the lithium amino bis-carbene chloride complex (5). Deprotonation with four equivalents of n-butyl lithium affords the lithium amide salt (6). Although the complexes were not characterised in the solid state, characteristic shifts in the multinuclear NMR spectra and elemental analysis are consistent with the lithium complexes being formed. NMR spectra of 5 suggest formation of a cluster of lithium chloride ions with lithium-NHC bonds (13C NMR NCN 203.9 ppm) and NH-chloride bonding interactions. Following further deprotonation to form 6 the complex also retains lithium chloride and exhibits a similar C2 chemical shift (13C NMR NCN 203.4 ppm). 

The obtained lithium salt can be widely functionalized by treatment with a whole range of electrophiles. Figure 22.3 shows the two possible pathways for substitution at both of the carbon atoms. One pathway (bottom) leads to a symmetrically substituted carborane, in which both substituents at the carbon atoms are introduced simultaneously after dilithiation of the carborane cluster. The other pathway (top) gives an unsymmetrically substituted carborane cluster. After selective mono-lithia-tion of one position and reaction of the lithium salt with an electrophile, the mono-substituted compound is obtained. It is then possible to use this compound as monodentate ligand or to introduce a second substituent. This can be achieved by lithiation of the hydrogen atom on the second carbon atom, followed by introduction of another electrophile. If a phosphorus substituent is introduced in the first step (R ), n-BuLi can cleave the P-C and the C-H bond in the next step [23]. It is therefore possible to form ligands in which R and R can differ dramatically from each other in chemical nature. 

---