[2-(4-Methylpiperazin-1-ylmethyl)phenyl]diphenylphosphane

In the title compound, C24H27N2P, the P atom is bonded to three C atoms in a trigonal–pyramidal geometry. The overall Ψ-trigonal-bipyramidal coordination of the P atom is established when the contribution of the electron lone pair and of the N—P donor–acceptor distance of 3.051 (3)Å are considered. The 4-methylpiperazinyl ring adopts a chair conformation. Intra- and intermolecular C—H⋯π hydrogen bonding leads to the consolidation of the structure.


Comment
We report here on the preparation and structural characterization in solution and the crystalline state of an asymetric triphosphane, PPh 2 [C 6 H 4 {CH 2 N(CH 2 CH 2 ) 2 NMe}-2] (I).
In the structure of (I) the nitrogen atom bonded to the benzyl fragment is coordinated to the phosphorous atom trans to a phenyl group. This induces chirality at the Ψ-trigonal-bipyramidal phosphorus centre, in addition to the planar chirality (the nitrogen atom acts as the pilot atom and the phenyl group as the chiral plane). (I) crystallizes in the racemic form. The (R N A P ) isomer is shown in Fig. 1. The (S N C P ) isomer is generated by symmetry with respect to the inversion centre.
The P-C bond lengths and C-P-C angles (Table 1) are in the range of those of triclinic PPh 3 (Ziemer et al., 2000).
As expected, the P-C Ph bond in trans-position to the P-N bond is slightly longer than the other P-C bond. The length of the P-N bond donor···acceptor interaction is in the range of values found in P[C 6 H 4 (CH 2 NMe 2 )-2] 3 (Chandrasekaran et al., 2002).
The structure displays intramolecular C-H···π bonds between one hydrogen atom of the piperazinyl group and a phenyl group (Fig. 2). Four intermolecular C-H···π bonds are established between the hydrogen atoms of the phenyl groups and π electrons of the benzene rings of neighbouring molecules. Geometrical parameters of the hydrogen bonds are listed in Table 2.

Experimental
To a cooled solution of [2-{4-MeN(CH 2 CH 2 ) 2 NCH 2 }C 6 H 4 ]Li (2.55 g, 13 mmol) in tetrahydrofuran (thf) (203 K) was added dropwise a solution of PPh 2 Cl (2.40 ml, ρ = 1.23 g/ml, 13 mmol) in thf. The reaction mixture was stirred at 203 K for 2 h and was allowed to warm to room temperature. The solvent was removed under reduced pressure and over the resulting oily product was added dichloromethane. The obtained suspension was filtered and the dichloromethane was removed under reduced pressure. The remaining oily product solidified on addition of hexane. (I) was isolated as a colourless solid.
Colourless crystals were obtained by the diffusion method from a dichloromethane/hexane mixture. Yield: 2.87 g (59%).

Refinement
Hydrogen atoms were placed in calculated positions with isotropic displacement parameters set at 1.2 times of those of the parent carbon atoms for aromatic and methylene hydrogen atoms, and at 1.5 times for hydrogen atoms of the methyl group. Fig. 1. Graphical representation of the molecular structure of R N A P -I. Hydrogen atoms were omitted for clarity. Displacement ellipsoids are drawn at the 30% probability level. Fig. 2. Intramolecular H···π and N···P interactions in the structure of I (shown as dashed lines). All the hydrogen atoms, except for those involved in hydrogen bonds, were omitted for clarity. Cg2, Cg3, and Cg4 are the centroids of the benzene rings C1-C6, C13-C18, and C19-C24, respectively. Symmetry codes: (i) -x + 2, -y + 1, -z; (ii) -x + 3/2, y -1/2, -z + 1/2.