RESUMO
The recognition and in-depth understanding of inverse trans influence (ITI) have successfully guided the synthesis of novel actinide complexes and enriched actinide chemistry. Those complexes, however, are mainly limited to the involvement of high-valence actinide and/or metal-ligand multiple bonds. Examples containing both low oxidation state actinide and metal-metal single bond remain rare. Herein, more than 20 actinide-transition metal (An-TM) complexes of phosphinoaryl oxide ligands have been designed in accordance with several experimentally known analogs, by changing the metal atoms (An = Th, Pa, U, Np, and Pu; and TM = Ni, Pd, and Pt), actinide oxidation states (IV and III) and metal-metal axial donor ligands (X = Me3SiO, F, Cl, Br, and I). The relativistic density functional theory study of structural (trans-An-X and cis-An-O toward An-TM), bonding (topological electron/energy density), and electronic properties reveals the order of the ITI stabilizing actinide-metal bond. Computed electron affinity (EA) values, related to the electrochemical reduction, linearly correlate with experimentally measured reduction potentials. Although the same ITI order for the ligand donors was shown as in a previous study, the correlation between electrochemical reduction and the ITI was found to be weak when the actinide atoms were changed. For most complexes, the reduction is primarily of an actinide-based mechanism with minor participation of transition metal and phosphinoaryl oxide, whereas that of thorium-nickel complexes is different.
RESUMO
Heterobimetallic uranium-transition metal (U-TM) complexes have abundant active centers (two metals and several ancillary ligands with various donor atoms) and possible metal-metal bonding interaction, leading to diversified electronic structures and rather complicated electronic transition types. In this regard, a comprehensive and systematic theoretical study is highly desired although challenging. In the work, density functional theory (DFT) was utilized to examine a series of uranium-group 10 metal complexes supported by bidentate phosphinoaryl oxide ligands (labeled as L). TM (Ni, Pd, and Pt), uranium oxidation state (IV and III) and axial donor (I, Br, Cl, F, Me3SiO, and vacant) were varied. Calculations demonstrate an intrinsic TM â U dative bond. The order of bond strength of U-Ni > U-Pt > U-Pd is suggested by the formal shortness ratios, quantum theory of atoms in molecule (QTAIM) data, interaction energy ( Eint), and bond orders calculated at various levels of theory. It is further evidenced by relativistic effects of heavy metal, natural orbital population and electronic spectroscopy. Regarding U-Ni complexes with different axial donors, metal-metal distances are found to be linearly correlated with QTAIM data/ Eint/bond orders. Experimental UV-vis-NIR spectra were well reproduced by time-dependent DFT calculations. Complicated visible-light absorption bands, whose understanding remains unclear for many experimentally known heterobimetallic complexes, were rationalized in the work, along with NIR bands assigned as 5f â 5f transitions.
