trans-Iodido(pyrazinyl-κC 2)bis(triphenylphosphane-κP)palladium(II)

There are two independent molecules with similar configurations in the asymmetric unit of the title complex, [Pd(C4H3N2)I(C18H15P)2]. In each molecule, the geometry around the Pd atom is distorted square-planar, with the Pd atom displaced by 0.0549 (12) and 0.0734 (13) Å from the least-squares plane of the I—P—P—C atoms. The PPh3 ligands are in trans positions, with P—Pd—P angles of 173.12 (4) and 170.29 (4)°, while the pyrazinyl ligands and I atoms, also trans to each other, form C—Pd—I angles of 179.38 (12) and 178.44 (12)°. In the crystal, C—H⋯π interactions occur, resulting in a three-dimensional supramolecular architecture.

There are two independent molecules with similar configurations in the asymmetric unit of the title complex, [Pd(C 4 H 3 N 2 )I(C 18 H 15 P) 2 ]. In each molecule, the geometry around the Pd atom is distorted square-planar, with the Pd atom displaced by 0.0549 (12) and 0.0734 (13) Å from the least-squares plane of the I-P-P-C atoms. The PPh 3 ligands are in trans positions, with P-Pd-P angles of 173.12 (4) and 170.29 (4) , while the pyrazinyl ligands and I atoms, also trans to each other, form C-Pd-I angles of 179.38 (12) and 178.44 (12) . In the crystal, C-HÁ Á Á interactions occur, resulting in a three-dimensional supramolecular architecture.
For the synthesis of the pyrazinyl title compound, complex [Pd(PPh 3 ) 4 ] was used to react with 2-iodopyrazine in dichloromethane at room temperature. As a result, a two triphenylphosphine displaced complex [Pd(I)(C 4 H 3 N 2 )(PPh 3 ) 2 ] was isolated with 98% yield. The X-ray crystal structure analysis has been carried out to provide structural parameters.

Experimental
The synthesis of the title compound (I) was carried out as follows. CH 2 Cl 2 (20 ml) was added to a flask (100 ml) containing Pd(PPh 3 ) 4 (1.155 g, 1.0 mmol) and 2-iodiopyrazine (0.248 g, 1.2 mmol) at ambient temperature. The mixture was stirred for about 10 min. The solvent was concentrated to 10 ml, and 20 ml of diethyl ether was added to the solution.

Refinement
H atoms were positioned geometrically and refined using a riding model, with C-H = 0.95 Å and with U iso (H) = 1.2 times U eq (C).

Figure 1
The molecular structure of (I), showing the atom-numbering scheme and the 50% probability displacement ellipsoids.
Dashed lines represent the π-π interactions.  The molecular structure of (I), showing the intermolecular C-H···π hydrogen bond interactions.

(I)
Crystal data [Pd(C 4 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.