trans-Bis(4-aminopyridine-κN)bis(quinoxaline-2,3-dithiolato-κ2 S,S′)platinum(IV) dimethyl sulfoxide monosolvate

The title compound exhibits typical PtIV—S bond lengths. The packing of the complexes enable intermolecular interactions between the qdt ligands (qdt = quinoxaline-2,3-dithiolate) and an amine hydrogen atom (hydrogen bonding) or other qdt ligands (π–π stacking).


data reports
The chelating qdt ligands of this platinum(IV) complex are slightly canted relative to the platinum-sulfur atoms, with a 15.59 (11) angle between the plane of all the non-H atoms of the qdt ligand versus the plane containing Pt, S1, S2, S1 (1 À x, 1 À y, Àz) and S2 (1 À x, 1 À y, Àz). This tilt enables sandwich packing between intermolecular qdt ligands with a distance between centroids of the two qdt rings of 3.610 Å (Fig. 2), within the range ofinteractions (Sinnokrot et al., 2002). The basicity of the nitrogen atom on the coordinating qdt ligand (Cummings & Eisenberg, 1995b) makes it suitable for hydrogen bonding. This is observed between the amine hydrogen H4A and the N3 (x, y + 1, z) atom on a neighboring qdt ligand, with a distance of 2.23 Å (Table 1, Fig. 2). N-HÁ Á ÁO hydrogen bonding is observed between the complex and the O atom of the dmso solvent molecule.

Synthesis and crystallization
An orange solution of the anionic qdt ligand was prepared by combining 9.3 mg of 2,3-quinoxalinedithiol (Cummings & Eisenberg, 1995a) and 7.7 mg of NaHCO 3 with 25 ml of water and heating at 333 K for 5 h. Upon cooling to room temperature, the orange solution was added, via cannula, to a Schlenk flask containing 34.3 mg of [Pt(4-ap) 4 ](BF 4 ) 2 , prepared in a similar manner to [Pt(pyz) 4 ](BF 4 ) 2 (Derry et al., 2008), and 7.9 mg of NaHCO 3 . The solution was stirred for 7 d with the exclusion of light. The resulting orange-brown solid was collected via vacuum filtration in air and washed with 3 Â 10 ml of water and 15 ml of diethyl ether to give 7.4 mg (28% for [Pt(4-ap) 2 (qdt)]). Oxidation of platinum(II) to platinum(IV) likely occurred upon prolonged air exposure of the The packing of the complexes showing the hydrogen bonding between the H4A amine hydrogen atom and the N3 (x, y + 1, z) atom on a neighboring qdt ligand as well as the sandwich orientation between adjacent qdt ligands and the distance (Å ) between centroids of two qdt rings. Displacement ellipsoids are drawn at the 50% probability level; the dmso solvate is omitted for clarity. Table 1 Hydrogen-bond geometry (Å , ). Symmetry codes: (i) x; y þ 1; z; (ii) x À 1; y; z.

Figure 1
The molecular structure of the title complex drawn with displacement ellipsoids at the 50% probability level. Non-labeled atoms are generated by symmetry operation Àx + 1, Ày + 1, Àz. The disordered dmso solvate molecule is shown with only one orientation.
compound in solution (Geiger et al., 2001;Siddiqui et al., 2020). Light-yellow crystals of the title compound were grown by slow diffusion of water into a dmso solution of the platinum complex.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. The dmso solvent molecule is disordered about an inversion center and shows half occupancy.

Funding information
Funding for this research was provided by: National Science Foundation (grant No. 1726652 to UNT); Welch Foundation (grant No. AD-0007 to Austin College).