Crystal structure of cis-bis{4-phenyl-1-[(3R)-1,7,7-trimethyl-2-oxobicyclo[2.2.1]heptan-3-ylidene]thiosemicarbazidato-κ3 O,N 1,S}cadmium(II) with an unknown solvent molecule

The reaction between the racemic mixture of the camphor-4-phenylthiosemicarbazone derivative and cadmium acetate dihydrate yielded the title compound, [Cd(C17H20N3OS)2]. The CdII ion is six-coordinated in a distorted octahedral environment by two deprotonated thiosemicarbazone ligands acting as an O,N,S-donor in a tridentate chelating mode, forming five-membered chelate rings. In the crystal, the molecules are connected via pairs of N—H⋯S and C—H⋯S interactions, building centrosymmetric dimers. One of the ligands is disordered in the campher unit over two sets of sites with site-occupancy factors of 0.7 and 0.3. The structure contains additional solvent molecules, which are disordered and for which no reasonable split model was found. Therefore, the data were corrected for disordered solvent using the SQUEEZE routine [Spek (2015 ▸). Acta Cryst. C71, 9–18] in PLATON. Since the disordered solvents were removed by data processing, and the number of solvent entities was a suggestion only, they were not considered in the chemical formula and subsequent chemical or crystal information.

From the two crystallographically independent ligands in the asymmetric unit, one is disordered in the campher unit with S. O. F. = 0.7:0.3 (Fig. 2). The complex molecules are connected into centrosymmetric dimers via pairs of N-H···S and C-H···S intermolecurar interactions. The dimers are stacked along the crystallographic a-direction ( Fig. 3 and Table   1).

S2. Synthesis and crystallization
Starting materials were commercially available and were used without further purification. An R,S-camphor racemic mixture was oxidized with SeO 2 to the respective 1,2-diketone (Młochowski & Wójtowicz-Młochowska, 2015). The synthesis of the R,S-camphor-4-phenylthiosemicarbazone derivative was adapted from a procedure reported previously (Freund & Schander, 1902). The ligand (2 mmol) was dissolved in ethanol (20 mL) and deprotonated with 1 mL of a 1 M suitable for X-ray analysis, were obtained by recrystallization from an ethanol solution.

S3. Refinement
All non-hydrogen atoms except the disordered C atoms of lower occupancy were refined anisotropic. The C-H and N-H H atoms were positioned with idealized geometry and were refined isotropic with U iso (H) = 1.2 U eq (C,N) (1.5 for methyl H atoms) using a riding model.
The campher unit in one of the two independent ligands is disordered. This part was refined using a split model with S.
O. F. = 0.7:0.3 and with similarity restraints (SAME). The site occupation factors were selected in order that the disordered atoms exhibits similar isotropic displacement parameters based on the isotropic refinement. If the isotropic displacement parameters are fixed and the S. O. F. is refined, similar values are obtained. Finally, the disordered atoms of higher occupancy were refined anisotropic.
The refined structure contained additional disordered solvate molecules. Because no reasonable split model was found, the data were corrected for disordered solvent using the SQUEEZE option in PLATON (Spek, 2015). The void volume and void count electrons amount to 234 Å 3 and 55 e -·Å -3 . The void electrons count of 55 can be assigned to two solvent ethanol molecules (52 electrons in total). Ethanol was the synthesis solvent. Since the disordered solvents were removed by data processing, and the estimated number of two ethanol molecules was a suggestion only, they were not considered in the chemical formula and subsequent chemical or crystal informations.