Acetonyltriphenylphosphonium nitrate

Crystals of the title salt, C21H20OP+·NO3 −, are composed of acetonyltriphenylphosphonium cations and nitrate anions that mainly interact through electrostatic forces. The P atom in the cation has a slightly distorted tetrahedral environment, with C—P—C angles ranging from 104.79 (7) to 112.59 (6)°. The sum of O—N—O angles of the nitrate anion is 359.99°, reflecting its trigonal–planar character. C—H⋯O hydrogen bonds help to consolidate the crystal packing.

The title compound crystallizes with one phosphonium cation, C 21 H 20 OP + , and one nitrate anion in the asymmetric unit and 118.99 (12) °] of the nitrate anion is 359.99°, reflecting its trigonal-planar geometry. Between the C 21 H 20 OP + cations and the NO 3anions, the interactions are mainly of electrostatic nature. Such forces are also respondible for related salts like (3-chloropropyl)triphenylphosphonium bromide (Kavitha, 2012). The packing of the structure is shown in Fig. 2.
Weak C-H···O hydrogen bonds (Table 1) help to consolidate the crystal packing.

Experimental
All chemicals were purchased from Aldrich (Germany) and used without any further purification. Colourless crystals of the title compound, C 21 H 20 OP +. NO 3 -, have been obtained by the addition of a solution of Pb(NO 3 ) 2 (0.46 g,1.4 mmol) in water to a solution of CH 3 COCH 2 P(C 6 H 5 ) 3 Cl (0.5 g, 1.4 mmol) in water. The precipitated PbCl 2 was filtered off. Regular crystals were grown after slow solvent evaporation within few days.

Refinement
Hydrogen atoms, except H1c5 and H3c5, were kept in the geometrically correct positions with a C-H distance of 0.96 A. The tetrahedron around C5 contains phosphorus at one apex, therefore positions of H1C5 and H3C5 were refined with a C-H distance restraint of 0.96 Å (σ of the restraint 0.001). Isotropic temperature factors of all hydrogen atoms were calculated from U eq of the corresponding parent atom multiplied by 1.2.  The molecular entities of the title compound with displacement ellipsoids drawn at the 50% probability level.

Figure 2
The crystal packing of the title compound.  Special details Refinement. The refinement was carried out against all reflections. The conventional R-factor is always based on F. The goodness of fit as well as the weighted R-factor are based on F and F 2 for refinement carried out on F and F 2 , respectively. The threshold expression is used only for calculating R-factors etc. and it is not relevant to the choice of reflections for refinement. The program used for refinement, Jana2006, uses the weighting scheme based on the experimental expectations, see _refine_ls_weighting_details, that does not force S to be one. Therefore the values of S are usually larger than the ones from the SHELX program.