Post Hartree-Fock calculations of pnictogen-uranium bonding in EUF3 (E = N-Bi)

Photoelectron velocity map imaging spectroscopy of group 14 elements and iron tetracarbonyl anionic clusters MFe(CO)4- (M = Si, Ge, Sn)

The heteronuclear group 14 M-iron tetracarbonyl clusters MFe(CO)4- (M = Si, Ge, Sn) anions have been generated in the gas phase by laser ablation of M-Fe alloys and detected by mass and photoelectron spectroscopy. With the support of quantum chemical calculations, the geometric and electronic structures of MFe(CO)4- (M = Si, Ge, Sn) are elucidated, which shows that all the MFe(CO)4- clusters have the M-Fe bonded, iron-centered, and carbonyl-terminal M-Fe(CO)4 structure with the C2v symmetry and a 2B2 ground state. The M-Fe bond can be considered a double bond, which includes one σ electron sharing bond and one π dative bond. The C-O bonds in those anionic clusters are calculated to be elongated to different extents, and in particular, the C-O bonds in SiFe(CO)4- are elongated more. The Si-Fe alloy thus turns out to be a better collocation to activate the C-O bonds in the gas phase among group 14. The present findings have important implications for the rational development of high-performance catalysts with isolated metal atoms/clusters dispersed on supports.

Ligands enhanced the Ac[triple bond, length as m-dash]Ac triple bond

The multiple bonds between actinide atoms and their derivatives are computationally investigated extensively and compounds with an unsupported actinide-actinide bond, especially in low oxidation states, have attracted great attention. Herein, high level relativistic quantum chemical methods are used to probe the Ac-Ac bonding in compounds with a general formula LAcAcL (L = AsH3, PH3, NH3, H, CO, NO) at both scalar and spin-orbit coupling relativistic levels. H3AsAcAcAsH3, H3PAcAcPH3 and OCAcAcCO compounds show a type of zero valence Ac[triple bond, length as m-dash]Ac triple bond with a 1σ2g1π4u configuration, and H3AsAcAcAsH3 has been found to have the shortest Ac-Ac bond length of 3.012 Å reported so far. The Ac2 unit is very sensitive to the σ donor ligands and can form triple, double and even single bonds when suitable ligands are introduced, up to 3.652 Å with an Ac-Ac single bond in H3NAcAcNH3.

Synthesis, structure, and reactivity of uranium(vi) nitrides

Uranium nitride compounds are important molecular analogues of uranium nitride materials such as UN and UN2 which are effective catalysts in the Haber-Bosch synthesis of ammonia, but the synthesis of molecular nitrides remains a challenge and studies of the reactivity and of the nature of the bonding are poorly developed. Here we report the synthesis of the first nitride bridged uranium complexes containing U(vi) and provide a unique comparison of reactivity and bonding in U(vi)/U(vi), U(vi)/U(v) and U(v)/U(v) systems. Oxidation of the U(v)/U(v) bis-nitride [K2{U(OSi(O t Bu)3)3(μ-N)}2], 1, with mild oxidants yields the U(v)/U(vi) complexes [K{U(OSi(O t Bu)3)3(μ-N)}2], 2 and [K2{U(OSi(O t Bu)3)3}2(μ-N)2(μ-I)], 3 while oxidation with a stronger oxidant ("magic blue") yields the U(vi)/U(vi) complex [{U(OSi(O t Bu)3)3}2(μ-N)2(μ-thf)], 4. The three complexes show very different stability and reactivity, with N2 release observed for complex 4. Complex 2 undergoes hydrogenolysis to yield imido bridged [K2{U(OSi(O t Bu)3)3(μ-NH)}2], 6 and rare amido bridged U(iv)/U(iv) complexes [{U(OSi(O t Bu)3)3}2(μ-NH2)2(μ-thf)], 7 while no hydrogenolysis could be observed for 4. Both complexes 2 and 4 react with H+ to yield quantitatively NH4Cl, but only complex 2 reacts with CO and H2. Differences in reactivity can be related to significant differences in the U-N bonding. Computational studies show a delocalised bond across the U-N-U for 1 and 2, but an asymmetric bonding scheme is found for the U(vi)/U(vi) complex 4 which shows a U-N σ orbital well localised to U[triple bond, length as m-dash]N and π orbitals which partially delocalise to form the U-N single bond with the other uranium.

Electronic structures and bonding of the actinide halides An(TRENTIPS)X (An = Th-Pu; X = F-I): a theoretical perspective

To evaluate how halogen and actinide atoms affect the electronic structures and bonding nature, we have theoretically investigated a series of the actinide halides An(TRENTIPS)X (An = Th-Pu; X = F-I); several of them have been synthesized by Liddle's group. The An-X bond distances decrease from An = Th to Pu for the same halides, and the harmonic vibrational frequencies for the An-X bonds are more susceptible to being affected by the halogen atoms. The analyses of bonding nature reveal that the An-X bonds have a certain covalency with a polarized character, and the σ-bonding component in the total orbital contribution is greatly larger than the corresponding π-bonding ones based on the analysis of the NOCVs (the natural orbitals for chemical valence). Furthermore, the electronic structures of the thorium complexes are obviously different from those of the uranium and transuranic analogues due to more valence electrons in Th 6d orbitals. In addition, thermodynamic results suggest that the U(TRENTIPS)Br complex is the most stable and U(TRENTIPS)Cl has the highest reactivity based on the halide exchange reaction of U(TRENTIPS)X complexes using Me3SiX. The reduction ability of the tetravalent An(TRENTIPS)X is sensitive to halogen atoms according to the calculated electron affinity of the An(TRENTIPS)X and the reactions An(TRENTIPS)X + K → An(TRENTIPS) + KX. This work presents the effect of the halogen and the actinide atoms on the structures, bonding nature and redox ability of a series of the tetravalent actinide halides with TREN ligand and facilitates our in-depth understanding of f-block elements, which could provide theoretical guidance for experimental work on actinide halides, especially for the synthetic chemistry of transuranic halides.

Combined experimental and theoretical studies towards mutual osmium-bismuth donor/acceptor bonding

Osmium(ii) PNP pincer complexes bearing a hemilabile pyridyl-pyrazolide (PyrPz) ligand have been synthesised, and their reactivity towards Lewis acidic bismuth compounds has been examined. Reactions with BiCl3 resulted in chlorine-atom-transfer to give an osmium(iii) species. Reactions with cationic bismuth species led to adduct formation through N → Bi bond formation via the PyrPz ligand. Theoretical analyses revealed that steric interactions hamper Os → Bi bond formation and indicate that such interactions are possible upon reducing the steric profile around the osmium atom. Analytical techniques include NMR, IR, and EPR spectroscopy, cyclic voltammetry, elemental analysis and DFT calculations.

Crystallographic structure and crystal field parameters in the [AnIV(DPA)3]2− series, An = Th, U, Np, Pu

The [An^IV(DPA)₃]²⁻ series with An = Th, U, Np, Pu has been synthesized and characterized using SC-XRD, vibrational spectroscopy, and first principles calculations.