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.