Ferromagnetic tetrahalogenochromates(II) containing mixed halides (Cl and Br)

Abstract

Tetrahalogenochromates(II) containing mixed halides, [NRH₃]₂[CrCl_xBr_4–x](R = Me, Et, Prⁿ, Buⁿ, or n-C₈H₁₇), exhibit similar ferromagnetic behaviour to the homoleptic tetrahalogenochromates(II). Broad spin-allowed d–d absorption bands at ca.10 900 cm^–1 in their reflectance spectra indicate tetragonal six-co-ordination of chromium(II) and hence polymeric structures; the reflectance spectra also contain very sharp absorption bands at ca. 15 900 and 18 700 cm^–1 assigned to spinforbidden d–d transitions intensified by the magnetic coupling. Far-i.r. absorption bands near 290 and 245 cm^–1 are assigned to ν(Cr–Cl) and ν(Cr–Br) vibrations respectively.