A Very Short Uranium—Uranium Bond: The Predicted Metastable U₂²⁺.

Abstract

Quantum chemical calculations, based on multiconfigurational wave functions and including relativistic effects, show that the U 2 21 system has a large number of low-lying electronic states with S of 0 to 2 and K ranging from zero to ten. These states share a very small bond length of about 2.30 Å , compared to 2.43 Å in neutral U 2 . The Coulomb explosion to 2 U 1 lowers the energy by only 1.6 eV and is separated by a broad barrier.

Relativistic quantum chemical calculations show that the uranium molecule U2 has a quadruple bond

“…Irrespective of the active space models, distinctive features of the Ω = 9 g state in comparison to the Ω = 8 g state are its singly occupied orbitals of predominantly 5f δ -type and empty orbitals with mainly 5f π -character, originating from distinctively different leading determinants at the spin-free level. Table 2 summarizes 52 We have confirmed this picture in U 2+ 2 for our Ω = 1 g ground (Σ = −0.08) and Ω = 0 + g (Σ = 0.00) excited states whereas other electronically excited states shown in Supplementary Fig. 5 with Ω > 1 exhibit larger departures from integer Σ values.…”

Identification of a uranium–rhodium triple bond in a heterometallic cluster

“…For instance, the U-Rh bond is computed to be 3.01 Å (vs. 2.96 Å experimentally) and the U-Cl ones to be 2.73 and 2.81 (vs. 2.69 and 2.78 Å experimentally). At the NBO level, a σ U-Rh bond is found formed with an s/d/f hybrid orbital (17,39, and 44%) on uranium and a d orbital on Rh. At the second order no substantial donation from Rh to U is found, indicating that no more bonding interaction between U and Rh is present.…”

“…Therefore, it is understandable that the study of f-block metal-metal multiple bonds remains scarce, perhaps due to the extreme difficulty of their synthesis and structural characterization. More recent works have tried to explore the chemistry of actinide-metal multiple bonds through theoretical calculations (15)(16)(17)(18)(19)(20)(21)(22)(23)(24). Gagliardi and Roos (16), for example, theoretically predicted the quintuple-bond character in the uranium molecule U 2 in 2005.…”

Selective hydroboration of terminal alkynes catalyzed by heterometallic clusters with uranium–metal triple bonds

“…Recently, we identified a UhRh triple bond in a heterometallic cluster, which was authenticated by X-ray diffraction. 25 Although theoretical studies suggest that actinide-metal multiple bonding is quite common, [26][27][28][29][30][31][32][33][34][35][36][37][38] no structurally authenticated species with multiple bonding between U and first-row transition metals have been isolated. Information concerning the reactivity of actinide-metal bonds is limited and the catalysis by such species has not been reported to date.…”