Binuclear trivalent and tetravalent uranium halides and cyanides supported by cyclooctatetraene ligands

Abstract

Although the first organoactinide chloride Cp 3 UCl (Cp = η 5 -C 5 H 5 ) was synthesized more than 50 years ago, binuclear uranium halides remain very rare in organoactinide chemistry. Herein, a series of binuclear trivalent and tetravalent uranium halides and cyanides with cyclooctatetraene ligands, (COT) 2 U 2 X n (COT = η 8 -C 8 H 8 ; X = F, Cl, CN; n = 2, 4), have been systematically studied using scalarrelativistic density functional theory (DFT). The structures with bridging halide or cyanide ligands were predicted to be the most stable complexes of (COT) 2 U 2 X n , and all the complexes show weak antiferromagnetic interactions between the uranium centers. However, for each species, there is no significant uranium-uranium bonding interaction. The bonding between the metal and the ligands shows some degree of covalent character, especially between the metal and terminal halide or cyanide ligands. The U-5f and 6d orbitals are predominantly involved in the metal-ligand bonding. All the (COT) 2 U 2 X n species were predicted to be more stable compared to the mononuclear half-sandwich complexes at room temperature in the gas phase such that (COT) 2 U 2 X 4 might be accessible through the known (COT) 2 U complex. The tetravalent derivatives (COT) 2 U 2 X 4 are more energetically favorable than the trivalent (COT) 2 U 2 X 2 analogs, which may be attributed to the greater number of strong metal-ligand bonds in the former complexes.

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

“…In addition, the B3LYP functional , can evaluate the U–E bonding character in the (CpSi­Me 3 ) 3 ­U-E­(NCH­Mes) 2 complexes, and the hybrid functionals can give more accurate energies than GGA ones . The uranium atom used the scalar-relativistic ECP60­MWB and the corresponding ECP60­MWB-SEG valence basis set, − which provides reliable calculations for actinide complexes. − The LANL­08d basis set with effective core potential was applied for Ge, Sn, and Pb. − And the basis set, 6-31G­(d), was applied for H, C, N, and Si atoms. To confirm the ground states of the (CpSi­Me 3 ) 3 ­U-E­(NCH­Mes) 2 complexes, four electronic states (2, 4, 6, 8) for each (CpSi­Me 3 ) 3 ­U-E­(NCH­Mes) 2 complex were considered and their electronic energies with PBE and B3LYP functionals are listed in Table S1.…”

Metal–Halide Covalency, Exchange Coupling, and Slow Magnetic Relaxation in Triangular (CpiPr5)3U3X6 (X = Cl, Br, I) Clusters

“…This result has been attributed to both the increasing U···U separation, as well as the decreasing electronegativity of the bridging halide, down the series. Similar trends have also been suggested from computational studies on hypothetical halide-bridged uranium(III) and uranium(IV) complexes …”

“…Similar trends have also been suggested from computational studies on hypothetical halide-bridged uranium(III) and uranium(IV) complexes. 120 Magnetic Hysteresis. A comparison of zero field-cooled and field-cooled dc magnetic susceptibility data collected for 1-Cl revealed a small divergence in the χ M T values below 3 K (Figures S51 and S56), indicative of the onset of magnetic blocking that is a hallmark of single-molecule magnetism.…”