cis-Bis(2,2′-bipyridine-κ2 N,N′)bis(pyridin-4-amine-κN 1)ruthenium(II) bis(hexafluoridophosphate) acetonitrile monosolvate1

In the title complex, [Ru(C10H8N2)2(C5H6N2)2](PF6)2·CH3CN, the RuII atom is bonded to two α-diimine ligands, viz. 2,2′-bipyridine, in a cis configuration and to two 4-aminopyridine (4Apy) ligands in the expected distorted octahedral configuration. The compound is isostructural with [Ru(C10H8N2)2(C5H6N2)2](ClO4)2·CH3CN [Duan et al. (1999 ▶). J. Coord. Chem. 46, 301–312] and both structures are stabilized by classical hydrogen bonds between 4Apy ligands as donors and counter-ions and acetonitrile solvent molecules as acceptors. Indeed, N—H⋯F interactions give rise to an intermolecularly locked assembly of two centrosymmetric complex molecules and two PF6 − counter-ions, which can be considered as the building units of both crystal architectures. The building blocks are connected to one another through hydrogen bonds between 4Apy and the connecting pieces made up of two centrosymmetric motifs with PF6 − ions and acetonitrile molecules, giving rise to ribbons running parallel to [011]. 21-Screw-axis-related complex molecules and PF6 − counter-ions alternate in helical chains formed along the a axis by means of these contacts.

Asymmetric units of complex (I) is shown in Fig. 1 and each Ru atom is coordinated to six nitrogen atoms from four ligand molecules. The compound (I) crystallizes in the noncentrosymmetric orthorhombic space group P2 1 cn, with one Ru(II) atom, two 2,2-bipyridine (bpy) ligands, two 4-aminopyridine (4Apy) and two PF 6counterions in the asymmetric unit. The complex (I) is also present with one acetonitrile molecule in its asymmetric unit. Both compounds (I) and [Ru(C 10 Duan et al., 1999] are isostructural: they crystallize in the centrosymmetric triclinic space group with very similar cell parameters and crystal packing features. Their crystal assemblies are stabilized by van der Waals interactions and classical hydrogen bonds whose NH 2 groups of both 4Apy ligands are donors to either fluorine atoms (or oxygens of perchlorate in the antecedent isostructure) of the counterion or nitrogen one of acetonitrile solvent (Fig. 2). Indeed, four N-H···F interactions give rise to an intermolecularly-locked assembly of two centrosymmetric complex molecules and two PF 6 counterions ( Fig. 2). Two of them are related by a centrosymmetry to two independent ones, namely, the N4-H4A···F4 and N4A-H4A1···F5 contacts. These contacts involve both 4Apy moieties of (I) and one of the two crystallographically independent PF 6 units. Such an assembly can be considered as the building unit of both crystal architectures of (I) and the perchlorate analogue. However, in the former two oxygens of one perchlorate unit, which has occupancy sites of some oxygen atoms disordered over two positions, substitute for F4 and F5 fluorine atoms of (I). It is important to observe such a disorder as that reported for the perchlorate analogue can be related to this packing feature described above. In (I), the F4-P1-F5 angle is 89.7 (7)°, while tetrahedral geometry of the four oxygens around chlorine atom of the perchlorate counterion imposes O-Cl-O angles to be near to 109°. No disorder is found for the positions of the fluorine supramolecular functionalities in (I), which is in agreement with the favorable geometric orientation of both F4 and F5 atoms to accept the hydrogen bonding from two inversion-related coordination complexes. In contrast, the expected angle values for ClO 4 are much more enlarged than that of the cis-fluorine atoms acting as hydrogen bonding acceptors in N4-H4A···F4 and N4A-H4A1···F5, which clearly reveals the tendency for disordering the positions of the perchlorate oxygens in order to favor geometrically the formation of such contacts since the same intermolecular arrangement is kept in (I) and in the perchlorate analogue. No coordinates of the hydrogen atoms is available for the former structure, and therefore more bonding donation from both complex units of the centrosymmetric assembly to the other crystallographically independent PF 6 fragment and to the acetonitrile solvent through the N4-H4B···F6A and N4A-H4A2···N1S contacts, respectively.
In addition, there is a non-classical hydrogen bonding between this PF 6 counterion and the solvent molecule through the C2S-H1S···F6A contact. In fact, two centrosymmetric motifs made up of hydrogen-bonded PF 6 and acetonitrile molecules can be understood as the connecting pieces between the building units, giving rise to infinite one-dimensional ribbons running parallel to the [011] direction. Geometric parameters of the classical hydrogen bonding interactions are shown in Table 1.
The complex shows the Ru atom bonded to two bpy ligands in a cis configuration with the two 4Apy ligands in the (2.056 Å) (Stoyanov et al., 2002).
The dihedral angles do not show any significant distortions in the structure of the complex to relieve the steric hindrance imposed by bpy ligand. Fig. 1 shows a very neat twisted location of the 4Apy ligands with respect to the planes of the bpy ligands. The dihedral angles between the least-squares planes calculated through 4Apy and bpy ligands are 85.9 (1)° between [4Apy(1) and bpy (1)] and [4Apy(2) and bpy (2)].

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.

Figure 2
The crystal packing of (I). In this figure, three building units of (I) are shown on the left of the panel, which are joined together on the right along the [011] direction through hydrogen bonds with the connecting pieces (detached on the box).