Variable coordination of tris(2-pyridyl)phosphine and its oxide toward M(hfac): a metal-specifiable switching between the formation of mono- and bis-scorpionate complexes.

An unexpected substitution of the anionic chelating ligands at the M centre by a neutral tripodal ligand has been observed in the reaction of Mn, Co, Ni and Cu hexafluoroacetylacetonates (hfac) with tris(2-pyridyl)phosphine (PyP) or its oxide (PyP = O). The nature of the metal ion in M(hfac) and the M/L ratio determine the degree of substitution of hfac-anions (partial vs. total) and therefore, the structure of the complex formed (scorpionate vs.