A DENSITY-FUNCTIONAL TREATMENT OF ORGANOLITHIUM COMPOUNDS - COMPARISON TO AB-INITIO, SEMIEMPIRICAL, AND EXPERIMENTAL RESULTS

Density functional calculations on several classes of organolithium compounds are described. The compounds studied include lithium bonds to carbon, oxygen, and nitrogen and are representative of most types of organolithium compounds that have appeared in the recent literature. The computational results are compared to those using MNDO, which has been shown to have some serious deficiencies in compounds involving carbon-lithium bonds, and to PM3 results, which offer some improvement over MNDO for many organolithium compounds. Most of the density functional calculations with a large basis set are in good agreement with available ab initio and experimental data. Calculated carbon-lithium bond lengths were slightly shorter than those calculated by other ab initio methods and were substantially longer than those calculated by MNDO, which is known to underestimate carbon-lithium bond lengths severely. Dimerization energies of methyllithium, calculated by DMol, were also in good agreement with those of other ab initio calculations. Lithium-nitrogen bonds in lithium amides were calculated to be slightly shorter by DMol than by MNDO, although the two methods were in qualitative agreement for this type of compound. (C) 1995 by John Wiley & Sons, Inc.