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

Density functional calculations have been used to probe the electronic structures of Re(Cp)(CO) 2 Xe and Re(Cp)(CO)(PF 3 )Xe. The calculated CO stretching frequencies compare favorably with those determined experimentally. Our calculations of δ Xe and 3 J Xe - F for Re(Cp)(CO)(PF 3 )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) 2 Xe (12.3 kcal mol - 1 ) and Re(Cp)(CO)(PF 3 )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) 2 Xe and Re(Cp)(CO)(PF 3 )Xe reveals positive ∇ 2 ρ( r ) at the critical points (∇ 2 ρ( r c ) = 0.1310 and 0.1396 e Å 5 for Re(Cp)(CO) 2 Xe and Re(Cp)(CO)(PF 3 )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 PF 3 ligands; the Re d orbitals appear to contribute little to the orbital interactions between the Re(Cp)(CO) 2 and Re(Cp)(CO)(PF 3 ), and Xe fragments.