A Theoretical Study on Divalent Heavier Group 14 Complexes as Promising Donor Ligands for Building Uranium-Metal Bonds

The study of metalmetal bonds is one of the important challenges in organometallic chemistry and of great significance in applied and structural chemistry. We built a series of potential complexes (CpSiMe3)(3)U-E(NCHMes)(2) (E = Si, Ge, Sn, Pb) by constructing two neutral fragments [(CpSiMe3)(3)U] and [E(NCHMes)(2)] and investigated their structures with scalar-relativistic theoretical calculations. U-E bonds possess highly polarized U-E interactions and also strong donor-acceptor interactions according to the analyses of MO (molecular orbital), natural charge, QTAIM (quantum theory of atoms in molecules), and ELF (electron localization function). Particularly, the four U-E bonds are mainly composed of U 6d orbitals and E ns orbital, which lead to the nature of donor-acceptor interaction between U and E atoms. These bonds are significantly different from the general uranium-transition-metal and uranium-main-group bonds, Moreover, the U-E bond strengths in the (CpSiMe3)(3)U-E(NCHMes)(2) complexes follow the trend of U-Si > U-Sn > U-Ge > U-Pb according to the results of bond orders and EDA (energy decomposed analysis). The binding energies suggest that the four (CpSiMe3)(3)U-E(NCHMes)(2) complexes are thermodynamically accessible. This work indicates that the divalent heavier group 14 complexes are promising donor ligands for building unsupported uranium-metal bonds.