trans-Diaquabis(2,2′-bipyridine-κ2 N,N′)ruthenium(II) bis(trifluoromethanesulfonate)

The title compound, trans-[Ru(bpy)2(H2O)2](CF3SO3)2 (bpy = 2,2′-bipyridine, C10H8N2), crystallized from the decomposition of an aged aqueous solution of a dimeric complex of cis-Ru(bpy)2 in 0.1 M triflic acid. The RuII ion is located on a crystallographic inversion center and exhibits a distorted octahedral coordination with equivalent ligands trans to each other. The Ru—O distance is 2.1053 (16) Å and the Ru—N distances are 2.0727 (17) and 2.0739 (17) Å. The bpy ligands are bent, due to inter-ligand steric interactions between H atoms of opposite pyridyl units across the Ru center. The crystal structure exhibits an extensive hydrogen-bonding network involving the water ligands and the trifluoromethanesulfonate counter-ions within two-dimensional layers, although no close hydrogen-bond interactions exist between different layers.


Related literature
For the crystal structures of related compounds, see: Weathers et al. (1997); Durham et al. (1980); Klü fers & Zangl (2007). For a comparative discussion, see the Comment section in the Supplementary materials. For the preparation of the title compound, see: Jude et al. (2008); Sullivan et al. (1978). For related literature, see : Walsh & Durham (1982).

Experimental
Crystal data [Ru(C 10
The title compound trans-[Ru(bpy) 2 (H 2 O) 2 ](CF 3 SO 3 ) 2 , (I), was unintentionally obtained and crystallized from an acidic (0.1 M CF 3 SO 3 H) aqueous solution of [(bpy) 2 Ru(OMe)(pyz)Ru(bpy) 2 ](PF 6 ) 2 (Jude et al., 2008) that was left aging in ambient conditions for several weeks. Its crystal structure is shown in Figs. 1 and 2, and detailed structural information is available herein as supplementary materials as well as in the archived CIF.
The structure of the analogous compound as a hexafluorophosphate salt, i.e. trans-[Ru(bpy) 2 (H 2 O) 2 ](PF 6 ) 2 , (II), was previosuly reported (Weathers et al., 1997). In this case, the compound crystallized in the triclinic (P1) space group. The Ru-O distance of 2.116 (2) Å in the PF 6 salt is similar to that reported here for the CF 3 SO 3 analogue, and the mean Ru-N distance of 2.074 (2) Å in II is essentially identical to those observed for I. The dihedral angle between the pyridyl (C 5 N) ring planes in the distorted, non-planar bpy ligands is also similar in these compounds: 162.68 (12)° for II and 160.1 (1)° for I.
An extensive hydrogen bonding network exists within two-dimensional layers as a result of the hydrogen bonds between the water ligand molecules in the cationic complex and the sulfonate groups in the trifluoromethanesulfonate anions (Table   1 and Figure 2). However, no significant hydrogen-bond interactions are present between different layers.
Experimental cis-Ru(bpy) 2 Cl 2 was prepared as described by Sullivan et al. (1978). The title compound was a product of the decomposition of [(bpy) 2 Ru(OMe)(pyz)Ru(bpy) 2 ](PF 6 ) 2 (Jude et al., 2008) in a highly acidic (0.1 M CF 3 SO 3 H) aqueous solution that was supplementary materials sup-2 kept for several weeks in a sealed clear glass jar in ambient lighting and temperature conditions. Red-orange blocks suitable for single-crystal X-ray analysis were isolated from the mixture.

Refinement
Diffraction data for single crystals of I were collected for 2θ < 139.4° on a Bruker AXS SMART APEXII diffractometer.
The structure was solved by direct methods and hydrogen atoms were included in the final refinement cycles at predicted positions, with the exception of H1A and H1B which were refined isotropically. Fig. 1 as those based on F, and R-factors based on ALL data will be even larger.

Figures
Hydrogen atoms were placed in calculated positions with the exception of H1A and H1A, which were located in a difference synthesis and subsequently allowed to refine with isotropic thermal parameters.