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Octacarbonyl Ion Complexes of Actinides [An(CO)₈ ]^+/- (An=Th, U) and the Role of f Orbitals in Metal-Ligand Bonding.

ABSTRACT: The octacarbonyl cation and anion complexes of actinide metals [An(CO)₈ ]^+/- (An=Th, U) are prepared in the gas phase and are studied by mass-selected infrared photodissociation spectroscopy. Both the octacarbonyl cations and anions have been characterized to be saturated coordinated complexes. Quantum chemical calculations by using density functional theory show that the [Th(CO)₈ ]⁺ and [Th(CO)₈ ]^- complexes have a distorted octahedral (D_4h ) equilibrium geometry and a doublet electronic ground state. Both the [U(CO)₈ ]⁺ cation and the [U(CO)₈ ]^- anion exhibit cubic structures (O_h ) with a ⁶ A_1g ground state for the cation and a ⁴ A_1g ground state for the anion. The neutral species [Th(CO)₈ ] (O_h ; ¹ A_1g ) and [U(CO)₈ ] (D_4h ; ⁵ B_1u ) have also been calculated. Analysis of their electronic structures with the help on an energy decomposition method reveals that, along with the dominating 6d valence orbitals, there are significant 5f orbital participation in both the [An]?CO ? donation and [An]?CO ? back donation interactions in the cations and anions, for which the electronic reference state of An has both occupied and vacant 5f AOs. The trend of the valence orbital contribution to the metal-CO bonds has the order of 6d?5f>7s?7p, with the 5f orbitals of uranium being more important than the 5f orbitals of thorium.

SUBMITTER: Chi C

PROVIDER: S-EPMC6772027 | biostudies-literature | 2019 Sep

REPOSITORIES: biostudies-literature

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Octacarbonyl Ion Complexes of Actinides [An(CO)8 ]+/- (An=Th, U) and the Role of f Orbitals in Metal-Ligand Bonding.

Chi Chaoxian C Pan Sudip S Jin Jiaye J Meng Luyan L Luo Mingbiao M Zhao Lili L Zhou Mingfei M Frenking Gernot G

Chemistry (Weinheim an der Bergstrasse, Germany) 20190823 50

The octacarbonyl cation and anion complexes of actinide metals [An(CO)8 ]+/- (An=Th, U) are prepared in the gas phase and are studied by mass-selected infrared photodissociation spectroscopy. Both the octacarbonyl cations and anions have been characterized to be saturated coordinated complexes. Quantum chemical calculations by using density functional theory show that the [Th(CO)8 ]+ and [Th(CO)8 ]- complexes have a distorted octa ...[more]

PMID: 31276242

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Project description:Heterobimetallic complexes containing short uranium-group 10 metal bonds have been prepared from monometallic IU(IV)(OAr(P)-?(2)O,P)3 (2) {[Ar(P)O](-) = 2-tert-butyl-4-methyl-6-(diphenylphosphino)phenolate}. The U-M bond in IU(IV)(?-OAr(P)-1?(1)O,2?(1)P)3M(0), M = Ni (3-Ni), Pd (3-Pd), and Pt (3-Pt), has been investigated by experimental and DFT computational methods. Comparisons of 3-Ni with two further U-Ni complexes XU(IV)(?-OAr(P)-1?(1)O,2?(1)P)3Ni(0), X = Me3SiO (4) and F (5), was also possible via iodide substitution. All complexes were characterized by variable-temperature NMR spectroscopy, electrochemistry, and single crystal X-ray diffraction. The U-M bonds are significantly shorter than any other crystallographically characterized d-f-block bimetallic, even though the ligand flexes to allow a variable U-M separation. Excellent agreement is found between the experimental and computed structures for 3-Ni and 3-Pd. Natural population analysis and natural localized molecular orbital (NLMO) compositions indicate that U employs both 5f and 6d orbitals in covalent bonding to a significant extent. Quantum theory of atoms-in-molecules analysis reveals U-M bond critical point properties typical of metallic bonding and a larger delocalization index (bond order) for the less polar U-Ni bond than U-Pd. Electrochemical studies agree with the computational analyses and the X-ray structural data for the U-X adducts 3-Ni, 4, and 5. The data show a trend in uranium-metal bond strength that decreases from 3-Ni down to 3-Pt and suggest that exchanging the iodide for a fluoride strengthens the metal-metal bond. Despite short U-TM (transition metal) distances, four other computational approaches also suggest low U-TM bond orders, reflecting highly transition metal localized valence NLMOs. These are more so for 3-Pd than 3-Ni, consistent with slightly larger U-TM bond orders in the latter. Computational studies of the model systems (PH3)3MU(OH)3I (M = Ni, Pd) reveal longer and weaker unsupported U-TM bonds vs 3.

Dataset Information

Octacarbonyl Ion Complexes of Actinides [An(CO)₈ ]^+/- (An=Th, U) and the Role of f Orbitals in Metal-Ligand Bonding.

Publications

Octacarbonyl Ion Complexes of Actinides [An(CO)<sub>8</sub> ]<sup>+/-</sup> (An=Th, U) and the Role of f Orbitals in Metal-Ligand Bonding.

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