Noble-Gas Chemistry More than Half a Century after the First Report of the Noble-Gas Compound

Abstract

Recent development in the synthesis and characterization of noble-gas compounds is reviewed, i.e., noble-gas chemistry reported in the last five years with emphasis on the publications issued after 2017. XeF2 is commercially available and has a wider practical application both in the laboratory use and in the industry. As a ligand it can coordinate to metal centers resulting in [M(XeF2)x]n+ salts. With strong Lewis acids, XeF2 acts as a fluoride ion donor forming [XeF]+ or [Xe2F3]+ salts. Latest examples are [Xe2F3][RuF6]·XeF2, [Xe2F3][RuF6] and [Xe2F3][IrF6]. Adducts NgF2·CrOF4 and NgF2·2CrOF4 (Ng = Xe, Kr) were synthesized and structurally characterized at low temperatures. The geometry of XeF6 was studied in solid argon and neon matrices. Xenon hexafluoride is a well-known fluoride ion donor forming various [XeF5]+ and [Xe2F11]+ salts. A large number of crystal structures of previously known or new [XeF5]+ and [Xe2F11]+ salts were reported, i.e., [Xe2F11][SbF6], [XeF5][SbF6], [XeF5][Sb2F11], [XeF5][BF4], [XeF5][TiF5], [XeF5]5[Ti10F45], [XeF5][Ti3F13], [XeF5]2[MnF6], [XeF5][MnF5], [XeF5]4[Mn8F36], [Xe2F11]2[SnF6], [Xe2F11]2[PbF6], [XeF5]4[Sn5F24], [XeF5][Xe2F11][CrVOF5]·2CrVIOF4, [XeF5]2[CrIVF6]·2CrVIOF4, [Xe2F11]2[CrIVF6], [XeF5]2[CrV2O2F8], [XeF5]2[CrV2O2F8]·2HF, [XeF5]2[CrV2O2F8]·2XeOF4, A[XeF5][SbF6]2 (A = Rb, Cs), Cs[XeF5][BixSb1-xF6]2 (x = ~0.37–0.39), NO2XeF5(SbF6)2, XeF5M(SbF6)3 (M = Ni, Mg, Zn, Co, Cu, Mn and Pd) and (XeF5)3[Hg(HF)]2(SbF6)7. Despite its extreme sensitivity, many new XeO3 adducts were synthesized, i.e., the 15-crown adduct of XeO3, adducts of XeO3 with triphenylphosphine oxide, dimethylsulfoxide and pyridine-N-oxide, and adducts between XeO3 and N-bases (pyridine and 4-dimethylaminopyridine). [Hg(KrF2)8][AsF6]2·2HF is a new example of a compound in which KrF2 serves as a ligand. Numerous new charged species of noble gases were reported (ArCH2+, ArOH+, [ArB3O4]+, [ArB3O5]+, [ArB4O6]+, [ArB5O7]+, [B12(CN)11Ne]−). Molecular ion HeH+ was finally detected in interstellar space. The discoveries of Na2He and ArNi at high pressure were reported. Bonding motifs in noble-gas compounds are briefly commented on in the last paragraph of this review.

Stable Noble Gas Compounds Based on Superelectrophilic Anions [B12(BO)11]− and [B12(OBO)11]−

“…In addition, the Ngs located in a "crater" among the five ligands, and some other interactions such as dispersion and electrostatic interactions among surrounding ligands should also exist. [23][24][25]61] EDA was employed to partition the bonding interaction energy between the two binding fragments into orbital interactions, electrostatics, Pauli repulsion, and dispersion forces. Two different models have been considered for the EDA analysis.…”

XeF2 Coordination to La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy and Y in Rare‐Earth Metal(III) Tetrafluoridoborates

“…When the XeF 2 ligand interacts with metal cation only by one of its fluorine atoms, there is a slight elongation of Xe−F b (F b =bridging F atom interacting with M n+ ) bond, whereas the Xe−F t (F t =terminal F atom) bond is slightly shortened [12,30,37] . Such elongation (weakening) of Xe−F b and shortening (strengthening) of Xe−F t bond in [M x+ (XeF 2 ) n ][A − ] x salts is detectable by Raman spectroscopy.…”

“…When the XeF 2 ligand interacts with metal cation only by one of its fluorine atoms, there is a slight elongation of XeÀ F b (F b = bridging F atom interacting with M n + ) bond, whereas the XeÀ F t (F t = terminal F atom) bond is slightly shortened. [12,30,37] Such elongation (weakening) of XeÀ F b and shortening (strengthening) of XeÀ F t bond in [M x + (XeF 2 ) n ][A À ] x salts is 10) 775( 8) 776( 6) 777( 9) 779( 3) 779( 9) 778( 9) 779( 5) 779( 5) 780( 5 1) 537( 8) 538( 5) 539( 10) 542( 12) 541(sh) 541( 14) 542( 7) 541( 7) 542( 5) ν 4 (BF 4 ) 527 (3) 527( 1) 527( 5) 527( 4) 528( 8) 529( 4) 528( 3) 528( 6) 529( 4) 528( 5) 530( 5) ν 4 (BF 4 ) 509( 3) 509( 2) 509( 8) 510( 5) 510( 10) 508(sh) 511(sh) 511(sh) 506( 8) 509( 3) 506( 15) ν 4 (BF 4 ) 501 (12) 501( 25) 502( 14 366(br, < 1) ν 2 (BF 4 ) 254(< 1) 250(< 1) 257(< 1) 258(< 1) 260(< 1) 260(br, < 1) 260(br, < 1) 260(br, < 1) 265(br, < 1) 267(br, < 1)…”

“…There is an elongation of XeÀ F b bond, while the XeÀ F t (F t = terminal F atom) bond is shortened. [2,11,12] It can be argued that in [XeF] [MF 6 ] salts, the XeF 2 is also bound to the metal center. However, the elongation of XeÀ F b bond is much more pronounced than in [Ag(XeF 2 ) 2 ](AsF 6 ) and [XeF][MF 6 ] can be hardly described as coordination compound.…”

“…The XeF 2 interacts with MF 5 through Xe−F b ⋅⋅⋅M bridges (F b =bridge F atom). There is an elongation of Xe−F b bond, while the Xe−F t (F t =terminal F atom) bond is shortened [2,11,12] . It can be argued that in [XeF][MF 6 ] salts, the XeF 2 is also bound to the metal center.…”