A multiconfigurational approach to the electronic structure of electro-generated species of the Re2(μ- Ph2PCH2PPh2)(S2CNEt2)4 complex

Studies electronic structure of transition metal complexes containing metal-metal multiple bond offer insight into the nature of metal-metal bonding and facilitate predictions of the physical properties and the reactivities. In this computational study, we have explored the electronic structure of the neutral and two oxidized species of the Re2(μ-Ph2PCH2PPh2)(S2CNEt2)4 (10, 1+, and 12+) complex using state-of-the-art quantum chemical methodologies including DFT and CASSCF. In particular, we focused on the nature of the Re-Re bonding in those species. Our results show that the ground state electron configuration of the 10 is 𝜎"𝜋$𝛿"𝛿∗" with an effective bond order of 2.73 computed with CASSCF. The two oxidized processes of the 10 remove electrons from metal-based orbital as suggested by DFT to produce 1+ and 12+ with an effective bond order of 2.71 and 2.64, respectively, calculated by CASSCF. Those values very similar to that of the neutral molecule suggesting that the oxidation process has almost no effect on the Re-Re bond strength even though it remove electrons from metal-based orbitals. However, the wavefunction is different which explain the similarity of effective bond order of all three species. The electrons of the 𝛿 components of the Re-Re bond is localized on two Re ions in the 1+ and 12+ which are excluded from bond order evaluation. In another words, the 𝜎 and 𝜋 and their antibonding counterparts are determined the nature of the Re-Re bonding of the oxidized species (1+ and 12+).