Covalency is often considered to be an influential factor in driving An3+ vs. Ln3+ selectivity invoked by soft donor ligands. This is intensely debated, particularly the extent to which An3+/Ln3+ covalency differences prevail and manifest as the f‐block is traversed, and the effects of periodic breaks beyond Pu. Herein, two Am complexes, [Am{N(E=PPh2)2}3] (1‐Am, E=Se; 2‐Am, E=O) are compared to isoradial [Nd{N(E=PPh2)2}3] (1‐Nd, 2‐Nd) complexes. Covalent contributions are assessed and compared to U/La and Pu/Ce analogues. Through ab initio calculations grounded in UV‐vis‐NIR spectroscopy and single‐crystal X‐ray structures, we observe differences in f orbital involvement between Am–Se and Nd–Se bonds, which are not present in O‐donor congeners.
KSb and KSb Zintl ion precursors react with Pd(PPh) in ethylenediamine/toluene/PBu solutions to give crystals of Sb@Pd@Sb/PBu salts, where n = 3, 4. The clusters are structurally identical in the two charge states, with nearly perfect I point symmetry, and can be viewed as an Sb@Pd icosahedron centered inside of an Sb dodecahedron. The metric parameters suggest very weak Sb-Sb and Pd-Pd interactions with strong radial Sb-Pd bonds between the Sb and Pd shells. All-electron DFT analysis shows the 3- ion to be diamagnetic with I symmetry and a 1.33 eV HOMO-LUMO gap, whereas the 4- ion undergoes a Jahn-Teller distortion to an S = 1/2 D structure with a small 0.1 eV gap. The distortion is predicted to be small and is not discernible by crystallography. Laser desorption-ionization time-of-flight mass spectrometry (LDI-TOF MS) studies of the crystalline samples show intense parent Sb@Pd@Sb ions (negative ion mode) and Sb@Pd@Sb (positive ion mode) along with series of Sb@Pd@Sb ions. Ni(cyclooctadiene) reacts with KSb in en/tol/BuPBr solvent mixtures to give black precipitates of Sb@Ni@Sb salts that give similar Sb@Ni@Sb parent ions and Sb@Ni@Sb degradation series in the respective LDI-TOF MS studies. The solid-state and gas-phase studies of the icosahedral Sb@M@Sb ions show that the clusters can exist in the -4, -3, -1, +1 (M = Pd) and +1, -1 (M = Ni) oxidation states. These multiple-charge-state clusters are reminiscent of redox-active fullerenes (e.g., C, where n = +1, 0, -1, -2, -3, -4, -5, -6).
Californium (Cf) is currently the heaviest element accessible above microgram quantities. Cf isotopes impose severe experimental challenges due to their scarcity and radiological hazards. Consequently, chemical secrets ranging from the accessibility of 5f / 6d valence orbitals to engage in bonding, the role of spin-orbit coupling in electronic structure, and reactivity patterns compared to other f-elements, remain locked. Organometallic molecules were foundational in elucidating periodicity and bonding trends across the periodic table, 1-3 with a 21 st century renaissance of organometallic thorium (Th) through plutonium (Pu) chemistry [4][5][6][7][8][9][10][11][12] , and to a smaller extent americium (Am) 13 , transforming chemical understanding. Yet, analogous curium (Cm) -Cf chemistry has lain dormant since the 1970s. Here, we revive air-/moisture-sensitive Cf chemistry through the synthesis and characterization of [Cf(C5Me4H)2Cl2K(OEt2)]n from two milligrams of 249 Cf. This bent metallocene motif, not previously structurally authenticated beyond uranium (U) 14,15 , contains the first crystallographically characterized Cf-C bond. Analysis suggests the Cf-C bond is largely ionic with a small covalent contribution.Lowered Cf 5f orbital energy vs. Dy 4f in the colourless, isoelectronic, and isostructural [Dy(C5Me4H)2Cl2K(OEt2)]n results in an orange Cf compound, contrasting with light green typically associated with Cf compounds [16][17][18][19][20][21][22] . MainThe first actinide (An) metallocene, uranocene, [U(C8H8)2], reported in 1968 2,23 , featured two aromatic (C8H8) 2rings sandwiching the U 4+ ion and demonstrated that non-actinyl molecules are capable bonding that is intermediate between covalent transition metals and ionic lanthanide ions 24 . Recent organometallic and nonaqueous Th and U chemistry has exploded 12 , redrawing the boundaries of known oxidation states 25 , multiplybonded molecular motifs 26 , small molecule reactivity 4 , and covalency/electronic structure trends 5,8,24,27 .Analogous advances with the heaviest available transuranium actinides are limited, although there are some, such as the deep red putative CfCp3, that contrasted with the light green of most other Cf compounds 22 . While several AnCp3 (An = Th, U -Cf) 6,9,22,28,29 molecules have been synthesized and/or examined by theory 30,31 , none have been authenticated beyond Pu 6,9,11 . Related bent Th and U metallocenes like [M(C5R5)2Xn] (X = anion; n = 1, 2) have played a major role in improving our understanding of actinide electronic structure and
Accurate understanding of the subsurface production rate of the radionuclide 39 Ar is necessary for argon dating techniques and noble gas geochemistry of the shallow and the deep Earth, and is also of interest to the WIMP dark matter experimental particle physics community. Our new calculations of subsurface production of neutrons, 21 Ne, and 39 Ar take advantage of the state-of-the-art reliable tools of nuclear physics to obtain reaction cross sections and spectra (TALYS) and to evaluate neutron propagation in rock (MCNP6). We discuss our method and results in relation to previous studies and show the relative importance of various neutron, 21 Ne, and 39 Ar nucleogenic production channels. Uncertainty in nuclear reaction cross sections, which is the major contributor to overall calculation uncertainty, is estimated from variability in existing experimental and library data. Depending on selected rock composition, on the order of 10 7 -10 10 α particles are produced in one kilogram of rock per year (order of 1-10 3 kg −1 s −1 ); the number of produced neutrons is lower by ∼ 6 orders of magnitude, 21 Ne production rate drops by an additional factor of 15-20, and another one order of magnitude or more is dropped in production of 39 Ar. Our calculation yields a nucleogenic 21 Ne/ 4 He production ratio of (4.6 ± 0.6) × 10 −8 in Continental Crust and (4.2 ± 0.5) × 10 −8 in Oceanic Crust and Depleted Mantle. Calculated 39 Ar production rates span a great range from 29 ± 9 atoms kg-rock −1 yr −1 in the K-Th-U-enriched Upper Continental Crust to (2.6±0.8)×10 −4 atoms kg-rock −1 yr −1 in Depleted Upper Mantle. Nucleogenic 39 Ar production exceeds the cosmogenic production below ∼ 700 meters depth and thus, affects radiometric ages of groundwater. The 39 Ar chronometer, which fills in a gap between 3 H and 14 C, is particularly important given the need to tap deep reservoirs of ancient drinking water.
Reaction of the terphenyl bis(anilide) ligand [K(DME)2]2LAr (LAr = {C6H4[(2,6-iPrC6H3)NC6H4]2}2−) with trivalent chloride MCl3(THF)n salts (M = Ce, U, Np) yields two distinct products; neutral LArM(Cl)(THF) (1M) and the “-ate”...
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