3.1. Sc Group 6772 3.2. Ti Group 6773 3.3. V Group 6775 3.4. Cr Group 6776 3.5. Mn Group 6777 3.6. Fe Group 6779 3.7. Co Group 6780 3.8. Ni Group 6782 3.9. Cu Group 6782 3.10. Zn Group 6784 3.11. Lanthanide Group 6784 3.12. Actinide Group 6785 3.13. Periodic Trends on Bonding and Reactivity 6785 4. Ionic Mononuclear Transition Metal Oxide Species 6787 4.1. Cations 6788 4.2. Anions 6790 4.2.1. Monoxide Anions 6790 4.2.2. Dioxide Anions 6791 4.2.3. Oxygen-Rich Anions 6792 5. Multinuclear Transition Metal Oxide Clusters 6792 5.1. Sc Group 6793 5.2. Ti Group 6793 5.3. V Group 6793 5.4. Cr Group 6797 5.5. Mn Group 6798 5.6. Fe Group 6798 5.7. Co Group 6798 5.8. Ni Group 6798 5.9. Cu Group 6799 6. Summary 6800 7. Acknowledgments 6800 8. References 6800

Spectroscopic and theoretical studies of transition metal oxides and dioxygen complexes.

Prior to the year 2000, non-aqueous uranium chemistry mainly involved metallocene and classical alkyl, amide, or alkoxide compounds as well as established carbene, imido, and oxo derivatives. Since then, there has been a resurgence of the area, and dramatic developments of supporting ligands and multiply bonded ligand types, small-molecule activation, and magnetism have been reported. This Review 1) introduces the reader to some of the specialist theories of the area, 2) covers all-important starting materials, 3) surveys contemporary ligand classes installed at uranium, including alkyl, aryl, arene, carbene, amide, imide, nitride, alkoxide, aryloxide, and oxo compounds, 4) describes advances in the area of single-molecule magnetism, and 5) summarizes the coordination and activation of small molecules, including carbon monoxide, carbon dioxide, nitric oxide, dinitrogen, white phosphorus, and alkanes.

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The Renaissance of Non-Aqueous Uranium Chemistry

In this critical review I describe fascinating experimental and theoretical advances in ‘noble gas’ chemistry during the last twenty years, and have taken a somewhat unexpected course since 2000. I also highlight perspectives for further development in this field, including the prospective synthesis of compounds containing as yet unknown Xe–element and element–Xe–element bridging bonds, peroxide species containing Xe, adducts of XeF2 with various metal fluorides, Xe–element alloys, and novel pressure-stabilized covalently bound and host–guest compounds of Xe. A substantial part of the essay is devoted to the—as yet experimentally unexplored—behaviour of the compounds of Xe under high pressure. The blend of science, history, and theoretical predictions, will be valued by inorganic and organic chemists, materials scientists, and the community of theoretical and experimental high-pressure physicists and chemists (151 references).

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Atypical compounds of gases, which have been called ‘noble’

Progress in the study of a new class of chemically bound compounds of noble-gas atoms is reviewed. The focus is on rare-gas molecules of the form HNgY, where Ng is a noble-gas atom and Y is an electronegative group, prepared by photolysis of HY in the rare-gas matrix. Other related types of new molecules of noble-gas atoms are discussed as well. Topics discussed in this review include: (a) The nature of bonding and the energetic stability of the compounds. (b) The vibrational spectroscopy of the molecules, and its role in identification of the species. (c) The mechanism and dynamics of photochemical formation of HNgY in the matrix, and the pathways for thermal and infrared (IR)-induced decomposition. Specifically, attention is given to the issue of "direct" formation following photolysis of HY versus "delayed" formation involving H atom diffusion. (d) Molecules of the lighter rare gases Ar, Ne, and He, focusing on the experimentally prepared HArF and on theoretical predictions suggesting the existence of other molecules. (e) The most-recently discovered photochemically induced insertion compounds of Ng into hydrocarbons, such as HXeCCH. (f) Clusters of HNgY with other molecules. The possible existence of neat aggregates and crystals of HNgY. The reviewed state-of-the-art suggests this field is at an early stage of development with major open questions bearing on the surprising properties of the molecules and on the formation mechanisms. These are part of the challenge for the future.

Formation of novel rare-gas molecules in low-temperature matrices

We report attempts to prepare uranyl(VI)- and uranium(VI) carbenes utilizing deprotonation and oxidation strategies. Treatment of the uranyl(VI)-methanide complex [(BIPMH)UO2Cl(THF)] [1, BIPMH = HC(PPh2NSiMe3)2] with benzyl-sodium did not afford a uranyl(VI)-carbene via deprotonation. Instead, one-electron reduction and isolation of di- and trinuclear [UO2(BIPMH)(μ-Cl)UO(μ-O){BIPMH}] (2) and [UO(μ-O)(BIPMH)(μ3-Cl){UO(μ-O)(BIPMH)}2] (3), respectively, with concomitant elimination of dibenzyl, was observed. Complexes 2 and 3 represent the first examples of organometallic uranyl(V), and 3 is notable for exhibiting rare cation–cation interactions between uranyl(VI) and uranyl(V) groups. In contrast, two-electron oxidation of the uranium(IV)-carbene [(BIPM)UCl3Li(THF)2] (4) by 4-morpholine N-oxide afforded the first uranium(VI)-carbene [(BIPM)UOCl2] (6). Complex 6 exhibits a trans-CUO linkage that represents a [R2C═U═O]2+ analogue of the uranyl ion. Notably, treatment of 4 with other oxidants such as Me3NO, C5...

Synthesis of a Uranium(VI)-Carbene: Reductive Formation of Uranyl(V)-Methanides, Oxidative Preparation of a [R2C?U?O]2+ Analogue of the [O?U?O]2+ Uranyl Ion (R = Ph2PNSiMe3), and Comparison of the Nature of UIV?C, UV?C, and UVI?C Double Bonds

Laser-ablated U atoms react with CO in excess argon to produce CUO, which is trapped in a triplet state in solid argon at 7 K, based on agreement between observed and relativistic density functional theory (DFT) calculated isotopic frequencies (12C16O, 13C16O, 12C18O). This observation contrasts a recent neon matrix investigation, which trapped CUO in a linear singlet state calculated to be about 1 kcal/mol lower in energy. Experiments with krypton and xenon give results analogous to those with argon. Similar work with dilute Kr and Xe in argon finds small frequency shifts in new four-band progressions for CUO in the same triplet states trapped in solid argon and provides evidence for four distinct CUO(Ar)4-n(Ng)n (Ng = Kr, Xe, n = 1, 2, 3, 4) complexes for each Ng. DFT calculations show that successively higher Ng complexes are responsible for the observed frequency progressions. This work provides the first evidence for noble gas−actinide complexes, and the first example of neutral complexes with four n...

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Noble gas-actinide complexes of the CUO molecule with multiple Ar, Kr, and Xe atoms in noble-gas matrices.

Laser-ablated U atoms react with CO in excess argon to produce CUO, which gives rise to 852.5 and 804.3 cm-1 infrared absorptions for the triplet state CUO(Ar)n complex in solid argon at 7 K. Relativistic density functional calculations show that the CUO(Ar) complex is stable and that up to four or five argon atoms can complex to CUO. When 1−3% Xe is added to the argon/CO reagent mixture, strong absorptions appear at 848.0 and 801.3 cm-1 and dominate new four-band progressions, which increase on annealing to 35−50 K as Xe replaces Ar in the intimate coordination sphere. Analogous spectra are obtained with 1−2% Kr added. This work provides evidence for eight distinct CUO(Ng)n(Ar)4-n (Ng = Kr, Xe, n = 1, 2, 3, 4) complexes and the first characterization of neutral complexes involving four noble-gas atoms on one metal center.

Binyong Liang

Papers

Noble gas-actinide complexes of the CUO molecule with multiple Ar, Kr, and Xe atoms in noble-gas matrices.

Noble gas-actinide compounds: Evidence for the formation of distinct CUO(Ar)(4-n)(Xe)(n) and CUO(Ar)(4-n)(Kr)(n) (n=1, 2, 3, 4) complexes