Structure, bonding, and solvation of lithium vinylcarbenoids.

[reaction: see text] Molecular modeling was used to determine the structure of lithium vinylcarbenoids in the gas phase and in THF solution. Solvent effects were modeled by microsolvation with explicit THF ligands on each of the lithium atoms. The carbenoid geometries are dependent on the heteroatom and on solvation. The calculations predict 1-chlorovinyllithium and 1-bromovinyllithium to be a mixture of monomer and dimer at 200 K and mostly monomer at higher temperatures, whereas the 1-fluoro-, 1-methoxy-, and 1-dimethylaminovinyllithium are predicted to be dimeric in solution.