rac-{[2-(Diphenylthiophosphoryl)ferrocenyl]methyl}dimethylammonium diphenyldithiophosphinate

2-(Diphenylthiophosphino)dimethylaminomethylferrocene is a key intermediate in the synthesis of various ferrocenyl ligands. During one such synthesis, the title compound, [Fe(C5H5)(C20H22NPS)](C12H10PS2), was isolated as a by-product. It is built up by association of (2-(diphenylphosphino)ferrocenyl)methyl)dimethylammonium cations and diphenylphosphino dithioate anions. N—H⋯S, C—H⋯S and C—H⋯π interactions link the anions and cations. Each anion–cation pair is linked two by two through C—H⋯π interactions, forming pseudo dimers.

Cg1 and Cg2 are the centroids of the C111-C116 and C221-C226 phenyl rings, respectively.  (Routaboul et al., 2005;Mateus et al., 2006;Routaboul et al., 2007;Le Roux et al., 2007;Audin et al., 2010;), in our laboratories. The last step of the synthesis of 2-(diphenylthiophosphino)dimethylaminomethylferrocene is a sulfurization of 2-(diphenylphosphino)dimethylaminomethylferrocene without any purification with an excess of elemental sulfur (Mateus et al., 2006). During this synthesis, small amounts of dimethyl-(2-(diphenylthiophosphino)ferrocenyl)methylammonium diphenylphosphinodithioato can be observed in the crude materials. We were able to obtain pure salt fractions by flash chromatography on silicagel. Monocrystals suitable for X-ray diffraction analysis could be grown from a dichloromethane solution by slow diffusion of hexane.
Besides this rather strong hydrogen bond, there are weaker C-H···S and C-H···π hydrogen interactions. The anioncation couple are linked two by two through intermolecular C-H···π interactions ( Fig. 2; Table 1).
In the cation, the two Cp rings have roughly a staggered conformation with a twist angle of 20.6 (2)° and they are slightly bent with respect to each other making a dihedral angle of 4.72 (12)°. As observed in the related 2-(diphenylthiophosphino)-dimethylaminomethylferrocene (Mateus et al., 2006), the S atom is displaced undo towards the Fe atom by 1.149 (4) Å from the Cp ring. The C2-C21-N1 plane is making a dihedral angle of 58.9 (1)° with the corresponding Cp ring whereas in the above ferrocenylamine (Mateus et al., 2006) the corresponding angle was roughly 90°. The C21-N1 distance of 1.502 (2) Å is similar to the 1.526 (2) Å observed in the reported ferrocenylammonium cation, [FeCp 2 PPh 2 (CH 2 NMe 2 CH 2 Ph)] + (Štěpnička & Císařová, 2003).
The geometry of the anion fully agrees with related structures containing the same anion (Alison et al., 1971;Fackler et al., 1982;Silvestru et al., 1995).

Experimental
In a schlenk tube under argon 4gr of crude (2-diphenylphosphino) dimethylaminomethyl ferrocene (0,47 mmol) were dissolved in 100 ml of dichloromethane, 1,7gr of sulfur (53 mmol) were then added and the solution was heated to reflux for 2 h. The crude product was purified and crystallized at RT. Several days later, orange crystals suitable for X-ray analyses, were obtained.

Refinement
All H atoms attached to C atoms were fixed geometrically and treated as riding with C-H = 0.98 Å (methyl), 0.99 Å (methylene) and 0.95 Å (aromatic) with U iso (H) = 1.2U eq (C methylene , C aromatic ) and U iso (H) = 1.5U eq (C methyl  to nitrogen was freely refined with U iso (H) = 1.2U eq (N).

Figure 1
The asymmetric unit of (I) with the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability  [Symmetry code: (i) -x + 2, -y + 1, -z + 2]  Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.  (9) 0.0261 (9) −0.0017 (7) 0.0065 (7) −0.0037 (7) C4 0.0232 (9) 0.0320 (10) 0.0320 (9) −0.0003 (7) 0.0147 (7 (2)