Simple NUF₃ and PUF₃ Molecules with Triple Bonds to Uranium

Abstract

The chemical behavior of actinide elements must be understood to manage effectively the many uses of actinide materials in todays world. Considerable interest has developed in recent years in actinide (An) complexes with metalligand multiple bonds. Most of these investigations have centered on organometallic systems, [1] and molecular complexes containing metal nitride units have been prepared. [2][3][4][5][6] These compounds with U = N linkages and organoimido (An = NR) and phosphinidene (An = PR) groups [7,8] are representative. Matrix-isolation infrared spectroscopy has contributed to the short list of uranium compounds containing triple bonds with discovery of the NUN and CUO molecules and preparation the [NUO] + cation first detected by mass spectrometry. [9][10][11][12][13] The common first-row elements carbon, nitrogen, and oxygen form multiple bonds with their 2p valence orbitals, and these bonds are responsible for the chemical properties of many simple compounds, such as HCCH, NN, and O=O. However, heavier main group elements from the second, third, and fourth complete rows of the periodic table are much less inclined to form multiple bonds, and their chemistry markedly reflects this difference.[14] Although the heavier pblock elements are involved in double bonds, such triple bonds are seldom found. On the other hand f elements (lanthanides and actinides) with multiple bonds are not common, and the quest for such compounds with multiple bonds between two actinide metals and between actinide and main-group elements has evolved vigorously with computations leading the former [15][16][17][18][19][20] and synthesis the latter. [1][2][3][4][5][6][7][8] We recently reported the first examples of uranium methylidene and methylidyne molecules using laser-ablated uranium atoms as the reagent. These species include the CH 2 =UH 2 , CH 2 =UHF, CH 2 =UF 2 , HCUF 3 , and FCUF 3 molecules. [21][22][23][24] Analogous methylidene complexes are important reagents in organometallic chemistry, particularly for the early transition metals.[25] Although alkylidyne complexes are not as prevalent, a number of simple Group 6 methylidyne complexes have been prepared through metal-atom reactions with methyl halides. [25,26] Fluorine is a very important element in uranium chemistry because of its role in uranium-isotope separation using gaseous diffusion of the volatile uranium hexafluoride. Accordingly UF 6 has been the subject of considerable experimental and theoretical investigations. [27,28] The smaller UF n molecules have been studied less often, [28,29] but fluorine has demonstrated its ability to facilitate the participation of uranium in important chemical and physical processes. The strong inductive effect of fluorine was central to the stabilization of the first uranium methylidyne complex FCUF 3 , [24] and fluorine should be equally as useful in assisting other even heavier main-group elements to stabilize U VI and to form novel triple bonds to uranium. We report herein a combined experimental and theoretical inves...

Infrared Spectra and Electronic Structure Calculations for NN Complexes with U, UN, and NUN in Solid Argon, Neon, and Nitrogen

“…16 The subsequent reaction of U and NF 3 produced only the most stable NUF 3 product. 17 We have published a short description of the dinitrogen complexes of NUN and UN formed upon sample annealing in recent argon matrix investigations of U and N 2 reactions. 18 The most important new information on the terminal nitride UN is the observation of rotationally resolved optical transitions of supersonically cooled UN, which provided a ground-state UN bond length of 1.7650 (12) Å.…”

Triamidoamine uranium(IV)–arsenic complexes containing one-, two- and threefold U–As bonding interactions

“…Spurred on by previous matrix isolation experiments 54,55 37,43 . From a main group perspective, these species represent fundamental, metal-stabilized parent p-block fragments that are predominantly found as transient intermediates in the gas-phase or low-temperature matrices.…”

“…A thorium polyarsenide cluster is known 52 , but otherwise uranium-arsenic complexes are limited to computational investigations 53 or low-temperature matrix isolation experiments 54,55 . Spurred on by previous matrix isolation experiments 54,55 and the recent isolation of terminal uranium(V)-and (VI)-nitrides 38,39 , we reported that by using uranium(IV) precursors exemplified by [U(Tren TIPS )(THF)][BPh 4 ] [1, Tren TIPS = N(CH 2 CH 2 NSi i Pr 3 ) 3 ], parent uranium(IV) pnictide complexes [U(Tren TIPS )(EH 2 )] [E = N, 2a; E = P, 2b] can be accessed and converted to the corresponding uranium(IV) terminal parent imido and phosphinidene complexes [U(Tren TIPS )(EH)][K(L) 2 ] [E = N, L = 15-crown-5 ether (15C5), 3a; E = P, L = benzo-15-crown-5 ether (B15C5), 3b] 37,43 . From a main group perspective, these species represent fundamental, metal-stabilized parent p-block fragments that are predominantly found as transient intermediates in the gas-phase or low-temperature matrices.…”

“…Indeed, given that uranium comes into contact with a wide range of elements in nuclear fuel cycles, it is surprising that there are no structurally authenticated molecular uranium-arsenic bonds of any type under ambient conditions 50,51 . A thorium polyarsenide cluster is known 52 , but otherwise uranium-arsenic complexes are limited to computational investigations 53 or low-temperature matrix isolation experiments 54,55 .…”

Effects of density functionals and dispersion interactions on geometries, bond energies and harmonic frequencies of EUX3 (E=N, P, CH; X=H, F, Cl)

“…The isolation of terminal uranium nitride species [N"U@NH], [N"U@O] + , [N"U"N], and [N" UF 3 ] has been achieved by inert gas matrices at lower temperatures [1][2][3] [5]. A number of theoretical studies have been carried out for uranium compounds containing triple bonds between uranium and main group elements [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22]. The calculated U"E bond distances at various level of theory are summarized in Table 1 3 ] at CASPT2 level indicate that the more electronegative substituents lengthen the U"N bond distance.…”