cis-Bis(1,10-phenanthroline-κ2 N,N′)bis(pyridin-4-amine-κN 1)ruthenium(II) bis(hexafluoridophosphate)1

In the title complex, [Ru(C12H8N2)2(C5H6N2)2](PF6)2, the RuII atom is bonded to two α-diimine ligands, viz. 1,10-phenanthroline (phen), in a cis configuration, in addition with with two 4-aminopyridine (4Apy) ligands, resulting in a distorted octahedral coordination geometry. N—H⋯F hydrogen-bonding interactions play an important role in the crystal assembly: 21-screw-axis-related complex molecules and PF6 − counter-ions alternate in helical chains formed along the a axis by means of these contacts. N—H⋯π contacts (H⋯centroid = 3.45 Å) are responsible for cross-linking between the helical chains along [001].

Asymmetric units of complex (I) is shown in Fig. 1. As can be seen in this figure, each Ru atom is coordinated to six nitrogen atoms from four ligand molecules. Compound (I) crystallizes in the noncentrosymmetric orthorhombic space group P2 1 cn, with one Ru(II) atom, two 1,10-phenanthroline (phen) ligands, two 4-aminopyridine (4Apy) and two PF 6counterions in the asymmetric unit. Contacts of type N-H···F are also responsible for keeping coordinated ligands of (I) in contact with PF 6 counterions ( Fig. 2). In the packing of this compound, helical chains are formed along the a axis. 2 1 -Screw axis related complex molecules and PF 6 counterions are alternated into these chains, which are assembled through the N4A-H4A1···F1A and N4A-H4A2···F3A contacts. A same NH 2 group belonging to the 4Apy(2) moiety is hydrogen bonding donor in both interactions which have one of the two crystallographically independent PF 6 units as acceptor. The other PF 6 counterion is a hydrogen bonding acceptor from the other amine group of the 4Apy(1) moiety through the N4-H4A···F5 contact. This interaction in association with the non-classical C10A-H10A···F6 hydrogen bonding contributes to assemble the helical chains along the [100] direction. More specifically, PF 6 units acting as hydrogen bonding acceptors through their F5 and F6 atoms are connected to translation related complex molecules of the helical backbone. At last, the other NH 2 hydrogen of the 4Apy(1) moiety is involved in a N-H···π interaction with the πsystem of the 4Apy(2) ring. The occurrence of such intermolecular contact is supported on the basis of the moderate separation between H4B and the centroid of the 4Apy (2) (Stoyanov et al., 2002).
In the present structure, the α-diimine coordinated ligands are approximately planar with deviation from the least-square planes less than 2°. The two α-diimine ligands are nearly perpendicular, as indicated by the dihedral angle between their least square planes, 87.43 (9)° in (I).
The dihedral angles do not show any significant distortions in the structure of the complex to relieve the steric hindrance imposed by phenanthroline ligand. Fig. 1  to the planes of the phen ligands. The dihedral angles between the least-squares planes calculated through 4Apy and phen ligands are 86.9 (1)° [4Apy(1) and phen(1)] and 79.2 (1)° [4Apy(2) and phen (2)].

Experimental
The compound (I) was synthesized from the corresponding aquo-complex (Bonneson et al., 1983)

Refinement
The H atoms were located from the difference Fourier synthesis and refined using the riding model on their parent atoms with C-H = 0.93 Å for aromatic moieties or 0.96 Å for methyl group of acetonitrile, N-H = 0.86 Å and U iso (H) = 1.2U eq for phenyl and amine H atoms or 1.5U eq for methyl ones.