Bis(1,4,7-trithiacyclononane)nickel(II) bis(tetrafluoridoborate) nitromethane disolvate

The homoleptic thioether title complex, [Ni(C6H12S3)2](BF4)2·2CH3NO2, shows the expeced hexakis(thioether) octahedral environment around the NiII atom. It crystallized as two crystallographically independent complex cations, [Ni(9S3)2]2+ (9S3 = 1,4,7-trithiacyclononane), within the unit cell where each NiII lies on an inversion center. In addition to the complex cations, there are two crystallographically independent BF4 − anions present to balance the charge, and each shows disorder along a pseudo-C 3 axis with ratios of 0.53 (2):0.47 (2) and 0.55 (2):0.45 (2). Two nitromethane solvent molecules per complex cation are also present in the unit cell.


Comment
The coordination chemistry of 1,4,7-trithiacyclononane (9S3) has been well studied both by us as well as other groups (Grant et al., 1991;Helm et al., 2005;Helm et al., 2006;Setzer et al., 1990;Setzer et al., 1983;Cooper et al., 1990;Blake et al., 1990). The three sulfur atoms of the 9S3 ligand have been calculated to be all endodentate in the lowest energy conformation of the free ligand (Glass et al., 1980). The endodentate nature of the sulfur atoms of 9S3 provides facile facial coordination to metal centers, and 9S3 has been complexed, in a bis-homoleptic fashion {i.e., [M(9S3) 2 ] n+ }, to 26 transistion metals ions to give a total of 72 different structures in a recent search of the Cambridge Structural Database (Allen, 2002; Release with Feb. and May 2011 updates). The complex, bis(1,4,7-trithiacyclononane)nickel(II) tetrafluoroborate, has been previously synthesized and characterized, which includes a single-crystal X-ray crystal structure where the crystals were obtained from ethanol evaporation with exclusion of any solvent in the structure (Setzer et al., 1983). In addition, the structure of the dication [Ni(9S3) 2 ] 2+ has been crystallographically characterized using a number of different anions (Blake et al., 2007;Blake et al., 2001;Nishijo et al., 2003;Nishijo et al., 2004;Blake et al., 1992). Herein, we wish to report the structure of the coordination compound bis(1,4,7-trithiacyclononane)nickel(II)bistetrafluoroborate dinitromethane solvate to include with the previously reported [Ni(9S3) 2 ] 2+ complexes.
As can be seen in Figure 1, the title complex displays the expected hexakis (thioether) octahedral geometry around the Ni II center where each 9S3 ligand is coordinated to the face of the octahedron. Interestingly, the title complex crystallizes as two crystallographically independent complex cations within the unit cell where each Ni II cation lies at the inversion center ( Figure 2). In addition, both the tetrafluoroborate anion and nitromethane solvate crystallize as two crystallographically independent anions and solvent molecules, respectively. Out of the seven crystallographically characterized [Ni(9S3) 2 ] 2+ complex cations this is the first example where the unit cell contains two crystallographically different complex cations.
Packing within the monoclinic crystal lattice shows a face-centered array for the [Ni(9S3) 2 ] 2+ dication to give a total of four  (Setzer et al., 1983). However, there are several differences between the previously reported structure of the title complex crystallized from ethanol versus that reported herein from nitromethane. Most notably is the presence of two crystallographically different complex cations. This is likely due, at least in part, to differences in crystal packing in the two different solvents. Secondly, the incorporation of solvent in the crystal lattice is unique to this system, but not unprecedented for crystal growth of similar structures from nitromethane (Helm et al., 2006;Grant et al., 2005). Lastly, there is a difference in the tetrafluoroborate anions in the supplementary materials sup-2 structures. In the original report (Setzer et al., 1983), no disorder was observed in the BF 4 anions compared to the compound shown in Figure 2 where disorder in the B-F bonds along a C 3 axis is observed. Again, this could be attributed to different crystal packing in the two different solvents; however, temperature effects cannot be discounted as data collection on the Bruker SMART X2S was done at 203 K.

Experimental
Bis(1,4,7-trithiacyclononane)nickel(II) bistetrafluoroborate dinitromethane solvate was synthesized as previously reported (Setzer et al., 1983). Violet needle-like crystals were obtained by slow diffusion of diethyl ether into a concentrated CH 3 NO 2 solution of the title complex.

Refinement
All hydrogen atoms were set to calculated geometries and allowed to refine on the positions of the parent atoms.