Chromium(V) Oxide Trichloride, and some Pentachlorido‐oxido‐chromate(V) Salts: Structures and Spectroscopic Characterization

Crystalline CrOCl 3 contains [Cl 2 OCr(μ‐Cl) 2 CrOCl 2 ] molecules with two square pyramidal CrOCl 4 units sharing a common edge and with the Cr–O arranged anti , a new structure type for transition metal M O X 3 compounds. Crystals are monoclinic with space group P 2 1 / c , Z = 4, with a = 5.735(5), b = 13.738(7), c = 11.318(4) Å, α = 90°, β = 98.346(6)°, γ = 90°. Its IR and UV/Vis spectra are reported and compared with those of the C 3 v monomer found in the gas phase. Structures are also reported for M 2 [CrOCl 5 ] ( M = Cs or Rb) and show a pseudo‐octahedral anion. Cs 2 [CrOCl 5 ] adopts a K 2 PtCl 6 ‐type structure with [CrOCl 5 ] 2– ions randomly orientated, but Rb 2 [CrOCl 5 ] is orthorhombic with space group Pnma with a = 13.6471(7), b = 9.9175(5), and c = 6.9562(4) Å. Rietveld refinement of the data on the rubidium salt gave Cr–O = 1.628(1), Cr–Cl transO = 2.652(7), Cr–Cl transCl = 2.239(8)–2.342(3) Å. Corresponding Cr V oxide bromide species do not form.