(Furfurylamino)triphenylphosphonium bromide

In the title salt, C23H21NOP+·Br−, the dihedral angles between the phenyl rings are 70.41 (18), 73.6 (2) and 80.85 (19)°. In the crystal, neighboring molecules are linked through an N—H⋯Br hydrogen bond and four weak C—H⋯Br contacts, forming a three-dimensional network.


Experimental
A mixture of 630 mg of DABCO (5.65 mmol) and 1 ml of furfurylamine (11.31 mmol) in 10 ml of dry benzene was added dropwise through canula between 0 and 5 °C to a stirred suspension of Ph 3 PBr 2 (11.31 mmol) in 20 ml of dry benzene. After 3 h of stirring at ambient temperature, 10 ml of distilled water were added to the medium and the compound extracted with 20 ml of methylene chloride. The organic phase was further washed with 10 ml of water, dried over MgSO 4 and all volatiles were eliminated under vacuum. The off white powder obtained was suspended in Et 2 O and left under stirring overnight. After filtration of the suspension, the solid was crystallized from hot THF giving 4.05 g (81%) of colorless crystals of the title compound, which were suitable for X-ray crystal structure analysis and fully characterized by standard analytical methods. 31 P NMR (CH 2 Cl 2 ) 30.03 p.p.m.; m. p. 420 K.

Refinement
H atoms were positioned geometrically and constrained using the riding-model approximation [C-H aryl = 0.93 Å, U iso (H aryl )= 1.2 U eq (C); C-H methylene = 0.97 Å, U iso (H methylene ) = 1.2U eq (C)]. The hydrogen atom bonded to N1 was located in a difference Fourier map. Its coordinates were refined with a distance restraint N-H = 0.86 Å, and with U iso (H) = 1.2U eq (N).

Figure 1
The molecular structure of the title compound, showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as small spheres of arbitrary radius.  A view of the C-H···Br interactions (dashed lines), showing the R 2 4 (12), R 2 4 (18), R 2 4 (22) and R 2 4 (24) graph set motifs.
The furfuryl group and hydrogen atoms not involved in hydrogen bonding have been omitted for clarity.

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. 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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq