Positional and compositional disorder in a ruthenium(II) piano-stool complex

Abstract

In (η6-p-cymene)(difluorophosphinato-κO){2-[(1H-pyrazol-1-yl)methyl-κN2]pyridine-κN}ruthenium(II) 0.85-hexafluorophosphate 0.15-tetrafluoroborate, [Ru(PO2F2)(C10H14)(C9H9N3)](PF6)0.85(BF4)0.15, (I), the [PO2F2]−ligand exhibits positional disorder due to one F atom and one O atom sharing the same two positions related by a mirror reflection across the O—P—F plane. The correct composition of this coordinated anion was successfully determined to be [PO2F2]−by refining the complex with various tetrahedral anions in which terminal atoms have similar atomic form factors. The noncoordinated counter-ion is compositionally disordered between [PF6]−and [BF4]−. The difficulty in determining the correct composition of this anion illustrates the importance of a crystallographer remaining impartial and open to encountering unexpected moieties in the process of elucidating a structure.