Cs[Cl3 F10 ]: A Propeller-Shaped [Cl3 F10 ]- Anion in a Peculiar A[5] B[5] Structure Type

[Br4F21]- - a unique molecular tetrahedral interhalogen ion containing a μ4-bridging fluorine atom surrounded by BrF5 molecules

The reaction of [NMe4][BrF6] with an excess of BrF5 leads to the compound [NMe4][Br4F21]·BrF5. It features molecular [(μ4-F)(BrF5)4]- anions of tetrahedron-like shape containing central μ4-bridging F atoms coordinated by four BrF5 molecules. It is the most BrF5-rich fluoridobromate anion by mass. Quantum-chemical calculations showed that the μ4-F-Br bonds within the anion are essentially ionic in nature. The compound is the first example where F atoms bridge μ4-like neither to metal nor to hydrogen atoms. It was characterized by Raman spectroscopy and by single-crystal X-ray diffraction. The latter showed surprisingly that its crystal structure is related to the intermetallic half-Heusler compound and structure type MgAgAs.

[(μ3 -F)(BrF5 )3 ]- - An Unprecedented Molecular Fluoridobromate(V) Anion in Cs[Br3 F16 ]

The reaction of Cs[BrF6 ] with BrF5 gave the compound Cs[Br3 F16 ] with the unprecedented propeller-shaped, C3 -symmetric [(μ3 -F)(BrF5 )3 ]- anion. All other currently known fluoridobromates(V) contain only octahedral [BrF6 ]- anions, which, unlike the related [IF6 ]- anions, never exhibited stereochemical activity of the lone pair on the Br atoms. Despite the same coordination number of six for the Br atom in the [BrF6 ]- and [(μ3 -F)(BrF5 )3 ]- anions, the longer μ3 -F-Br bonds provide additional space, allowing the lone pairs on the Br atoms to become stereochemically active. Cs[Br3 F16 ] was characterized by single-crystal X-ray diffraction, Raman spectroscopy, and quantum-chemical calculations for both the solid-state compound and the isolated anion at 0 K. Intrinsic bond orbital calculations show that the μ3 -F-Br bond is essentially ionic in nature and also underpin the stereochemical activity of the lone pairs of the Br(V) atoms.

Non-classical polyinterhalides of chlorine monofluoride: experimental and theoretical characterization of [F(ClF)3]. Chem Commun (Camb) 2021;57:4843-4846. [PMID: 33870378 PMCID: PMC8117328 DOI: 10.1039/d1cc01088c]

We present the synthesis and characterization of the first non-classical Cl(i) polyinterhalide [NMe4][F(ClF)3] as well as the homologous polychloride [NPr3Me][Cl7]. Both salts were obtained from the reaction of the corresponding ammonium chlorides with ClF or Cl2, respectively. Quantum-chemical investigations predict an unexpected planar structure for the [F(ClF)3]- anion.