Density Functional Theoretical Studies of the Re−Xe Bonds in Re(Cp)(CO)(PF3)Xe and Re(Cp)(CO)2Xe

Abstract

Density functional calculations have been used to probe the electronic structures of Re(Cp)(CO)2Xe and Re(Cp)(CO)(PF3)Xe. The calculated CO stretching frequencies compare favorably with those determined experimentally. Our calculations of δXe and 3JXe-F for Re(Cp)(CO)(PF3)Xe represent the first for a well-characterized transition metal−noble gas compound and demonstrate that DFT using the BP86 and SAOP functionals reproduces these parameters to within 1% and 8% of their experimentally determined values. The calculated Re−Xe bond dissociation energies for Re(Cp)(CO)2Xe (12.3 kcal mol-1) and Re(Cp)(CO)(PF3)Xe (11.9 kcal mol-1) are also in excellent agreement with the lower limits for these energies estimated from the activation parameters for the reaction of the complexes with CO in supercritical Xe. A topological analysis of the electron density in Re(Cp)(CO)2Xe and Re(Cp)(CO)(PF3)Xe reveals positive ∇2ρ(r) at the critical points (∇2ρ(rc) = 0.1310 and 0.1396 e Å5 for Re(Cp)(CO)2Xe and Re(Cp)(CO)(PF3)Xe, respectively, indicating that the Re−Xe interaction is essentially closed-shell in both complexes. Fragment and overlap density of states analyses show that the orbital interactions in these compounds is dominated by overlap involving the Xe p orbitals and the orbitals of the Cp, CO, and/or PF3 ligands; the Re d orbitals appear to contribute little to the orbital interactions between the Re(Cp)(CO)2 and Re(Cp)(CO)(PF3), and Xe fragments.