A THEORETICAL-STUDY OF SOME POSSIBLE ALKYLLITHIUM HEXAMERS

Using ab initio SCF calculations we optimized three possible structure s of hexameric methyl-lithium each having a near octahedral geometry o f lithium atoms with capping methyl groups. The isomer in which the va cant faces of the octahedron are trans to each other is the most stabl e. The alternative structure with the vacant faces in apical contact i s 8.8 kcal/mol (6-31G//4-31G) higher in energy while the edge contact isomer is 26.3 kcal/mol more energetic than the trans structure. The methyl groups were found not to be faced centered. These results are r ationalized electrostatically.