1. (a) Advanced Inorganic Chemistry, 5. Ed., Wiley, New York, 1988.
2. (b) in Comprehensive Coordination Chemistry, Vol. 3, (Ed.: ), Pergamon, Oxford, 1987, p. 183.
3. Theoretical studies on the stability of thallium-carbon .sigma.-bonds in aliphatic organothallium compounds
4. (b) and a series of heavy-element hydrides and halides ( J. Am. Chem. Soc., in press.) by pseudopotential calculations.
5. Full Hartree-Fock gradient geometry optimizations have been carried out with the Gaussian 90 program (Gaussian 90, Revision F, Gaussian, Inc., Pittsburgh, PA, 1990).