Chromium(II) chemistry. Part 15. Synthesis and magnetic properties of piperazinium, hydrazinium, and monoaryl and other substituted ammonium tetrachlorochromatest

Abstract

The complex chlorides M₂[CrCl₄(OH₂)₂][M =½H₂pipz (pipz = piperazine) or NPhH₃] are magnetically dilute, high-spin chromium(II) compounds. On thermal dehydration antiferromagnetic [H₂pipz][CrCl₄] and ferromagnetic [NPhH₃]₂[CrCl₄] are obtained. The latter was also prepared from a mixture of glacial acetic acid and acetyl chloride, as was [NH₄]₂[CrCl₄], previously obtained by thermal dehydration. The complexes [N(o-CH₃C₆H₄)H₃]₂[CrCl₄] and [H₃N(CH₂)₃NH₃][CrCl₄] exhibit ferromagnetic behaviour, but [NEt₃H]₂[CrCl₄] and [N₂H₆]₂[CrCl₆] are antiferromagnetic. The reflectance spectra of the anhydrous tetrachlorochromates indicate tetragonal six-co-ordination and hence polymeric structures. The magnetic susceptibility data for the ferromagnetic complexes from room to liquid-nitrogen temperature have been fitted to a high-temperature series expansion formula for a sheet ferromagnet giving J ca. 6.5 cm^–1 and g ca. 1.94.