Bis(1,10-phenanthroline-5,6-dione-κ2 N,N′)silver(I) tetrafluoridoborate

In the structure of the title compound, [Ag(C12H6N2O2)2]BF4 or [AgL 2]BF4 (L = phendione), the Ag and B atoms are located on twofold rotation axes. The dihedral angle between the two phendione ligands is 36.7 (2)°. The coordination about the AgI center is distorted tetrahedral (τ4 = 0.546). The crystal structure is consolidated by weak C—H⋯O(phendione) and C—H⋯F(BF4 −) interactions. The BF4 − counter-anion is strongly disordered and was modelled with two sets of idealized F atoms.


Experimental
Crystal data [Ag(C 12
The structure of (I), shown in Figure 1, is made up of an [Ag(L) 2 ] + cation and a tetrafluoridoborate anion. The silver atom is coordinated to the two nitrogen atoms of both phendione ligands. Both the Ag atom of the cation and the B atom of the anion lie on a crystallographic twofold rotation axes. The C═O bond lengths in the phendione ligands (1.210 (4) and 1.206 (3) Å) are comparable to those values found in other such complexes (Allen, 2002;Onuegbu et al., 2007). The  (2) and 2.357 (2) Å) are similar to those found in related phenanthroline derivatives of silver (Leschke et al., 2002;Paramonov et al., 2003;Pallenberg et al., 1997;Titze et al., 1997).
In (I), the silver cation is in a distorted tetrahedral environment. This is best illustrated by the dihedral angle between the planes of the coordinated ligands which in this case the angle is 36.7 (2)°. This compares with values of 36.8 (2)° found in the analogous perchlorate analog and the values of 32.4° and 70.5° found for other structurally characterized Ag complexes containing the bis(1,10-phenanthroline) core. Another recent parameter for 4-coordinate complexes (τ 4 , Yang et al., 2007) has been developed to place a structure on the continuum between square planar (0) and tetrahedral (1). For the present structure this value is 0.546.
Copper forms a similar complex with phendione. However, in this case the twofold axis passes between the phendione ligands with a dihedral angle of 44.5° between them.

Experimental
A flask containing 1,10-phenanthroline hydrate (1.00 g, 5.04 mmol) and potassium bromide (5.95 g, 50.0 mmol) was placed in an ice bath. Concentrated sulfuric acid (20 cm 3 ) was added in small portions, followed by drop-wise addition of concentrated nitric acid (10 cm 3 ). The resulting solution was heated for 2 h at 253-257 K and cooled to room temperature. The supplementary materials sup-2 solution was then poured into 400 cm 3 of water and neutralized with sodium bicarbonate, after which the phendione was extracted with dichloromethane, and recrystallized using a methanol-water mixture.
The title compound was synthesized in an atmosphere saturated with N 2 . To a solution of tetrakis(acetonitrile)silver(I)tetrafluoridoborate (0.0843 g) in 10 ml of CH 3 CN, was added drop-wise a solution (10 ml) of CH 3 CN containing 0.0492 g of phendione. The final yellowish solution was filtered and allowed to slowly evaporate yielding reddish brown crystals of the title compound suitable for X-ray studies.

Refinement
H atoms were placed in geometrically idealized positions and constrained to ride on their parent atoms with C-H distances of 0.95 Å and U iso (H) = 1.2U eq (C). The tetrafluoridoborate anion is disordered. Two sets of F atoms, constrained to meet the criteria for idealized tetrahedra, were used with occupancy factors of 0.406 (4) and 0.096 (4). The temperature factors for the major component were refined anisotropically and constrained by use of the SIMU and DELU instructions in SHELXL97 (Sheldrick, 2008). In the final difference Fourier there were positive and negative holes of +1.807 and -1.393 eA -3 near the disordered F atoms.  Bis(1,10-phenanthroline-5,6-dione-κ 2 N,N')silver(I) tetrafluoridoborate Crystal data [Ag(C 12   Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-supplementary materials sup-4 factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Occ. (