Bis{1-[2-(diphenyl-phosphino)-ethyl]-3-ethylimidazol-2-yl-idene}palladium(II) bis-(hexa-fluoridophosphate) acetonitrile 2.85-solvate.

In the structure of the title compound, [Pd(C(19)H(21)N(2)P)(2)](PF(6))(2)·2.85CH(3)CN, the two six-membered NHC-phosphane chelate rings form a distorted square-planar coordination geometry around the Pd(II) atom, which lies 0.212 (1) Å above the coordination plane. The sum of the bond angles at Pd(II) is 358.3°, with C-Pd-P bite angles of 84.03 (10) and 83.54 (9)°. The structure includes three acetonitrile solvent mol-ecules, one with partial site occupation and one with severe disorder, which was eventually excluded from the refinement.

In the structure of the title compound, [Pd(C 19 H 21 N 2 P) 2 ]-(PF 6 ) 2 Á2.85CH 3 CN, the two six-membered NHC-phosphane chelate rings form a distorted square-planar coordination geometry around the Pd II atom, which lies 0.212 (1) Å above the coordination plane. The sum of the bond angles at Pd II is 358.3 , with C-Pd-P bite angles of 84.03 (10) and 83.54 (9) . The structure includes three acetonitrile solvent molecules, one with partial site occupation and one with severe disorder, which was eventually excluded from the refinement.

Experimental
To a solution of 3-[2-(diphenylphosphino)ethyl]-1-ethylimidazolium-hexafluoridophosphate (195 mg, 0.46 mmol) in THF (10 ml) was added KN(SiMe 3 ) 2 (118 mg, 0.46 mmol + 30%) and the mixture was stirred at room temperature under N 2 for 30 min. Then [Pd(COD)Cl 2 ] (66 mg, 0.230 mmol; COD = 1,5-cyclooctadiene) was added to the reaction mixture and the colour changed from pale yellow to yellow-orange. The reaction mixture was stirred for another 2 h and then the solvent was removed under vacuum. Yellow crystals were obtained from an acetonitrile solution by diethyl ether diffusion.

Refinement
For the final refinement, data were cut off at θ = 27.1° in order to get 99% completeness. H atoms were clearly identified in difference Fourier syntheses, idealized and refined at calculated positions riding on the C atoms with isotropic displacement parameters U iso (H) = 1.2U(C eq ) or 1.5U(-CH 3 ). All methyl H atoms were allowed to rotate but not to tip. There are three acetonitrile solvent molecules per asymmetric unit. Two of these could be refined easily, the N300 one with an occupation factor of 0.85 (1). It was, however, not possible to refine successfully the third heavily distorted acetonitrile molecule. After treatment of the data with the SQUEEZE facility of PLATON (Spek, 2009) refinement then proceeded smoothly. Fig. 1. Molecular structure of the title compound. Displacement ellipsoids are drawn at the 50% probability level. For clarity, the N300 solvent molecule with partial site occupation was omitted.

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds supplementary materials sup-3 in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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 Rfactors(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.