Precursor trichloroeth anoato-chromium (III) species in the formation of tris (2,4-pentanedionato) chromium (III)

Two precursor species have been identified as responsible for the catalyzing effect of the trichloroethanoate (TCE) anion on the formation of tris(2,4-pentanedionato)chromium(III), Cr(acac)₃. The first one is the green intermediate species (GIS) identified as tetrahydroxodecakis-μs-trichloroethanoato-trichloroethanoato-tetraaquopentachro-mium(III), Cr₅(OH)₄(CCl₃COO)₁₁(H₂)₄. This appears to be the first pentanuclear species reported among the polynuclear alkanoato metal complexes. It reacts at a rapid rate with the 2,4-penaanedtonate, acac, anion to produce a second precursor, the violet-green intermediate species (VGIS) identified as bis(2,4-pentanedionato)-trichloroethanoato-aquochromium(III), Cr(C₅H₇O₂)₂(CCl₃COO)(H₂O). This is attacked by the remainigg acac anion to ultimaelly produce the Cr(acac)₃. Thus the effect of the TCE anion in facilitating the formation of Cr(acac)₃ is through the ligand coordination catalytic mechanisms.