Bis[2,6-bis(1H-benzimidazol-2-yl)pyridine]ruthenium(II) bis(hexafluoridophosphate) diethyl ether trisolvate

The cationic complex of the title salt, [Ru(C19H13N5)2](PF6)2·3C4H10O, has the Ru atom in a slightly distorted octahedral environment of two tridentate benzimdazolyl-pyridine ligands and displays extensive π–π and C—H⋯π interactions.


Structure description
Ruthenium(II) complexes that contain polypyridine ligands enjoy enormous popularity in the research community because of their interesting photochemical, electrochemical, and catalytic properties (Juris et al., 1988).Similar to what is found in 2,2 0 :6 0 ,2 00 terpyridine, the triimine structure, 2,6-bis(1H-benzimidazol-2-yl)pyridine (bimpy), offers a tridentate pocket for its coordination complexes; however, the imidazole units present a more convenient opportunity for tuning the electronics of donor-acceptor interactions (Groff et al., 2023).Our interest in bimpy complexes of ruthenium stems from reports of their activity in mediation of CO 2 by electrochemical reduction (Chen et al., 2011).This is the first crystal structure of a bis-bimpy complex of Ru II that we are aware of.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2.The data were first integrated to a resolution of 0.75 A ˚but during the final refinement, the data were cut at a resolution of 0.80 A ˚(� max = 26.37 � ) using a SHEL instruction to remove some of the noise.The unit cell was determined to be orthorhombic and it was found that the data reports   The structures of the molecular entities of the title compound with displacement ellipsoids at the 50% probability level.
structure could be refined in either the centrosymmetric space group Pbcn or in the non-centrosymmetric space group Pca2 1 .
Ultimately, the non-centrosymmetric space group was chosen, giving an asymmetric unit that contained one complete cation and two complete PF 6 anions.The crystal was also found to be solvated, containing three complete molecules of diethyl ether in the asymmetric unit.The Pca2 1 refinement had many atoms that had a tendency to become non-positive definite during the refinement, presumably because it was so close to being centrosymmetric.As a result, the displacement parameters of most atoms were restrained to be more isotropic during the refinement using global ISOR restraints.In addition, a rigid bond restraint was placed over all of the heavy atoms in the structure.The structure was treated as an inversion twin with the BASF parameter refining to 0.45 (12).The error is too large to say if this is different from the 0.50 expected for a centrosymmetric structure but it is possible to say it is not 0 or 1 (expected for a non-twinned non-centrosymmetric structure).Initial E statistics suggested that the correct space group was non-centrosymmetric and the best solution in SHELXT was also in a non-centrosymmetric space group.The structure was thus first refined in the non-centrosymmetric space group Pca2 1 .In this space group the final R-factor was high [R(reflections) = 0.0920 (9404) and wR2(reflections) = 0.1987 (11121)] and there was a level B checkCIF alert that the precision of the C-C bonds was low.A level G checkCIF alert suggested that there was an 89% fit to a centrosymmetric structure and that the alternative space group Pbcn should be used.Refinement in this space group was then carried out, but with much worse results overall.In the centrosymmetric space group, the central ring of the cation and the solvent molecules were all disordered (12% disorder in total).The statistics of the final refinement carried out under similar conditions to the non-centrosymmetric case were also much higher [R(reflections) = 0.1494 (5022) and wR2(reflections) = 0.3162 (5578)].For these reasons, refinement in the non-centrosymmetric space group was chosen and the Pca2 1 results are presented here.

Special details
Geometry.All esds (except the esd in the dihedral angle between two l.s.planes) are estimated using the full covariance matrix.The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry.An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s.planes.Refinement.Refined as a 2-component inversion twin.

Table 2
Experimental details.