Triethylammonium O-3β-cholest-5-en-3-yl (4-methoxyphenyl)dithiophosphonate

In the crystal structure of the title compound, C6H16N+·C34H52O2PS2 − or [(CH3CH2)3NH]+·[C34H52O2PS2]−, the cation and anion are paired via weak, intermolecular, bifurcated N—H⋯(S,S) hydrogen bonds. The cholesteryl units form an alternating (herringbone) motif as well as an infinitely stacked layered structure along the b axis. The P—S bond lengths [1.975 (2) and 1.981 (2) Å compared with ca 1.92 Å for a formal P=S double bond and with ca 2.01 Å for a P—S single bond] suggest delocalization of the negative charge between the P—S bonds. A distorted tetrahedral geometry around the P atom is revealed by non-ideal O—P—C and S—P—S bond angles of 96.7 (2) and 115.52 (11)°, respectively.

In the crystal structure of the title compound, C 6 H 16 N + Á-C 34 H 52 O 2 PS 2 À or [(CH 3 CH 2 ) 3 NH] + Á[C 34 H 52 O 2 PS 2 ] À , the cation and anion are paired via weak, intermolecular, bifurcated N-HÁ Á Á(S,S) hydrogen bonds. The cholesteryl units form an alternating (herringbone) motif as well as an infinitely stacked layered structure along the b axis. The P-S bond lengths [1.975 (2) and 1.981 (2) Å compared with ca 1.92 Å for a formal P S double bond and with ca 2.01 Å for a P-S single bond] suggest delocalization of the negative charge between the P-S bonds. A distorted tetrahedral geometry around the P atom is revealed by non-ideal O-P-C and S-P-S bond angles of 96.7 (2) and 115.52 (11) , respectively.

Related literature
For applications of dithiophosphonate derivatives, see: Beaton et al. (1991); Patnaik (1992); Roy (1990); Bromberg et al. (1993); Klaman (1984). For information on dithiophosphonate compounds, see: van Zyl et al. (1998van Zyl et al. ( , 2000van Zyl et al. ( , 2002; van Zyl et al. (2010). For P/S activation of steroids, see: Kvasnica et al. (2008). For related structures, see: Malenkovskaya et al. (2003); Cea-Olivares et al. (1999); Blaszczyk et al. (1996) Table 1 Hydrogen-bond geometry (Å , ). (7) 2.53 (7) 3.426 (7) 156 (5) N-H1Á Á ÁS2 i 0.96 (7) 2.78 (7) 3.437 (6) 126 (5) Symmetry code: (i) x; y À 1; z. The dithiophosphonato monoanion, [S 2 PR(OR')]may be described as a hybrid between the related dithiophosphato [S 2 P(OR) 2 ]and dithiophosphinato [S 2 PR 2 ]species. Of these, the dithiophosphonato version is of most interest for the following reasons: i) it can be considered rare in the chemical literature, particularly as a species that P/S activate natural products such as steroids (described in this study), and indeed for the majority of main-and transition metals simply nonexistent, ii) from the reaction between a common precursor (usually Lawesson's Reagent), and any compound that contains a 1° or 2° alcohol functionality, a tremendous number of new and varied derivatives can be obtained in a facile manner, iii) the synthetic methodology allows for control in the design of the compound to perform reactions and yield new products in both organic and aqueous phases, and iv) solution and solid state 31 P{ 1 H} NMR spectroscopy is a valuable tool to obtain mechanistic and structural information on these compounds (van Zyl et al., 2010). In terms of application, this class of compound has demonstrated use in a variety of technological areas such as oligonucleotide synthesis (Beaton et al., 1991), agricultural insecticides (Patnaik, 1992) and -pesticides (Roy, 1990), derivatives of metal ore extraction reagents (Bromberg et al., 1993) and antioxidant additives in the oil and petroleum industry (Klaman, 1984). In future, advances of these compounds as well as their metal complexes will be forthcoming in areas such as materials-and medicinal chemistry. General and convenient methods to dithiophosphonate salt derivatives have been reported (van Zyl et al., 2000).
In the title compound, (I) (Fig. 1), all bond lengths and angles are normal and comparable with those observed in the related structures (Malenkovskaya et al., 2003;Cea-Olivares et al., 1999;Blaszczyk et al., 1996). Aminium cations link cholesteryl moieties to form infinitely stacked layers along the b axis, supported by N-H···S interactions (see Fig. 2 and Table 1).
Only a few examples of the cholesteryl phosphate moiety exists (CSD show six hits with four usable results). Superimposing these (see Fig. 3) show large variations on the periphery of the molecules due to various packing arrangements found in each. Most notable of these interactions is the two different conformations adopted by the pentane tail of the cholesteryl moiety. The two configurations are differentiated by one group showing interactions to phosphate moieties of the neighbouring molecules.

Experimental
A 25-ml Schlenk tube was charged with commercially available (Aldrich) Lawesson's Reagent [(4-C 6 H 4 OMe)(P(S)S) 2 ] (6 mmol, 1 molar equivalent) and placed under vacuum for 30 minutes. The solid was then heated to approx. 70 °C and commercially available (Aldrich) cholesterol (12 mmol, 2 molar equivalents) was added in one portion together with 2 ml dry toluene. The temperature was maintained at 70-75 °C until dissolution of all solids were observed, and then stirred for a further 10-20 minutes. At this stage the dithiophosphonic acid had formed and no attempt was made to isolate it. The heat source was removed and the solution was cooled to room temperature. After 30 minutes it was cooled down further to 0 °C with the aid of an ice bath. The acid can be readily deprotonated by adding a few drops (12 mmol in theory, but a supplementary materials sup-2 slight excess is not detrimental) of triethylamine with vigorous agitation of the solution which led to formation of a white colored precipitate. The material was dried and consolidated with small additions of cold diethyl ether, and filtered on a frit. The isolated air-dried salt can be stored under a nitrogen atmosphere. The salt was dissolved in dichloromethane and layered with hexanes in a stoppered test-tube, but crystal growth proved slow and the test-tube stopper was subsequently removed, allowing the solvents to slowly evaporate at room temperature which led to the growth of a sufficient number of single crystals suitable for X-ray diffraction analysis.

Refinement
The aromatic, methine, methylene and methyl H atoms were placed in geometrically idealized positions (C-H = 0.97-0.98 Å) and constrained to ride on their parent atoms with U iso (H) = 1.2U eq (C) for the aromatic, methylene and methine H and U iso (H) = 1.5U eq (C) for the methyl H respectively. Torsion angles for the methyl H were refined from electron density. The aminium H was located in a Fourier difference map and refined isotropically.   Triethylammonium O-3β-cholest-5-en-3-yl (4-methoxyphenyl)dithiophosphonate

Special details
Experimental. The intensity data was collected on a Bruker SMART 1 K CCD diffractometer using an exposure time of 10 s/frame. A total of 1315 frames were collected with a frame width of 0.3° covering up to θ = 28.3° with 99.8% completeness accomplished.