1208 J. Org. Chem., Vol. 53, No. 6, 1988 of d orbitals, impart anionic character to the neighboring carbon due to the positive nature of the metals, and produce stable compounds having the metal-lithium bond, in which the group IV atoms behave as nucleophiles. However, there are still many reactions in which a large difference is observed between these two metal compounds. Citing a few examples, the stannyllithium is much more ...