Rhodamine 6G hexachloridostannate(IV) acetonitrile disolvate

In the title compound, bis({6-ethylamino-10-[2-(methoxycarbonyl)phenyl]-2,7-dimethylxanthen-3-ylidene}ethanaminium) hexachloridotin(IV) acetonitrile disolvate, (C27H29N2O3)2[SnCl6]·2C2H3N, the octahedral SnCl6 2− anion lies on an inversion center. The xanthene ring system is essentially planar, with an average deviation of 0.020 Å, and the substituent benzene ring forms a dihedral angle of 85.89 (2)° with it. The Sn—Cl distances are in the range 2.4237 (3)–2.4454 (3) Å. There are N—H⋯Cl hydrogen bonds between SnCl6 2− ions and rhodamine 6G cations as well as π–π stacking interactions between rhodamine 6G cations (interplanar distance of 3.827 Å).

The structure of (I) consists of discrete SnCl 6 2− anions lying on inversion centers, rhodamine 6 G cations and acetonitrile solvent molecules (Fig. 1). The xanthene ring of the cation is planar within an average deviation of 0.020 Å (maximum deviation is 0.045 (1) Å for C4), and the phenyl ring forms a dihedral angle of 85.89 (2)° with it. The C-N distances N1-C24 and N2-C26 are normal for this type of single bond, whereas C3-N1 and C11-N2 are much shorter, showing partial double-bond character; details are in the Table. A similar trend is observed in the other rhodamine 6 G cations (Wang et al., 1997;Liu et al., 1998).
Both hydrogen bonding between cations and anions and π-π stacking interactions between rhodamine 6 G cations exist.
Parallel rhodamine ions related by the inversion center have an interplanar distance of 3.827 Å (Fig. 2), and are slipped such that their O1-C13 bonds exactly overlap.

Experimental
Diphenyl tin dichloride (0.344 g, 1 mmol) was dissolved in 20 ml me thanol, and then 20 ml of methanol solution of rhodamine 6 G (0.479 g, 1 mmol) was added. The bright red solution was refluxed for 1 hr, whereafter red brown solid were obtained on cooling. Suitable size crystals were obtained by the recrystallization at room temperature from acetonitrile (yield ca 85%).

Refinement
H atoms were placed in idealized positions with C-H distances at 0.99, 0.98 and 0.95 Å for CH 2 , CH 3 and aromatic CH groups, respectively using a riding model. U iso for H was assigned as 1.2 times U eq of the attached C atoms (1.5 for methyl); a torsional parameter was refined for each methyl group. The largest positive and negative residual density peaks were located within 1 Å of the Sn1 position. sup-2 Crystal data (C 27