Electronic Structure of Cyclopentadienylthallium(I)

An SCF calculation based on the recently developed theory of effective potentials has been carried out for gaseous cyclopentadienylthallium(I) in its experimental equilibrium conformation. In this compound, the thallium atom is found to be nearly neutral with an overall electron distribution of s1.75p0.45d0.71 as obtained from a Mulliken population analysis. The overlap population of 0.47 e between thallium and the cyclopentadienyl ring is about half of each C-C overlap in the ring. Bonding is principally due to the highest filled molecular orbital pair of E1 symmetry based primarily on pd2 of T1 and p of the C atoms interacting in π symmetry with respect to the C5 axis of the molecule. A lesser contributor is the second highest a1 orbital dominated by T1 sp interaction with the carbon p's that are again π with respect to the ring plane. The electronic basis for the half-sandwich structure of C5H5T1 is discussed.